Real-time near IR (1310 nm) imaging of CO2 laser ablation of enamel.

PubMed

Darling, Cynthia L; Fried, Daniel

2008-02-18

The high-transparency of dental enamel in the near-IR (NIR) can be exploited for real-time imaging of ablation crater formation during drilling with lasers. NIR images were acquired with an InGaAs focal plane array and a NIR zoom microscope during drilling incisions in human enamel samples with a lambda=9.3-microm CO(2) laser operating at repetition rates of 50-300-Hz with and without a water spray. Crack formation, dehydration and thermal changes were observed during ablation. These initial images demonstrate the potential of NIR imaging to monitor laser-ablation events in real-time to provide information about the mechanism of ablation and to evaluate the potential for peripheral thermal and mechanical damage.

Fractional CO2 laser is as effective as Q-switched ruby laser for the initial treatment of a traumatic tattoo.

PubMed

Seitz, Anna-Theresa; Grunewald, Sonja; Wagner, Justinus A; Simon, Jan C; Paasch, Uwe

2014-12-01

Q-switched laser treatments are considered the standard method for removing both regular and traumatic tattoos. Recently, the removal of tattoo ink using ablative fractional lasers has been reported. Ablative fractional CO2 laser and q-switched ruby laser treatments were used in a split-face mode to compare the safety and efficacy of the two types of laser in removing a traumatic tattoo caused by the explosion of a firework. A male patient suffering from a traumatic tattoo due to explosive deposits in his entire face was subjected to therapy. A series of eleven treatments were performed. The right side of the face was always treated using an ablative fractional CO2 laser, whereas the left side was treated only using a q-switched ruby laser. After a series of eleven treatments, the patient demonstrated a significant lightening on both sides of his traumatic tattoo, with no clinical difference. After the first six treatments, the patient displayed greater lightening on the right side of his face, whereas after another five treatments, the left side of the patient's face appeared lighter. No side effects were reported. In the initial stage of removing the traumatic tattoo, the ablative fractional laser treatment appeared to be as effective as the standard ruby laser therapy. However, from the 6th treatment onward, the ruby laser therapy was more effective. Although ablative fractional CO2 lasers have the potential to remove traumatic tattoos, they remain a second-line treatment option.

Raman spectroscopy differentiates squamous cell carcinoma (SCC) from normal skin following treatment with a high-powered CO2 laser.

PubMed

Fox, Sara A; Shanblatt, Ashley A; Beckman, Hugh; Strasswimmer, John; Terentis, Andrew C

2014-12-01

The number of cases of non-melanoma skin cancer (NMSC), which include squamous cell carcinoma (SCC) and basal cell carcinoma (BCC), continues to rise as the aging population grows. Mohs micrographic surgery has become the treatment of choice in many cases but is not always necessary or feasible. Ablation with a high-powered CO2 laser offers the advantage of highly precise, hemostatic tissue removal. However, confirmation of complete cancer removal following ablation is difficult. In this study we tested for the first time the feasibility of using Raman spectroscopy as an in situ diagnostic method to differentiate NMSC from normal tissue following partial ablation with a high-powered CO2 laser. Twenty-five tissue samples were obtained from eleven patients undergoing Mohs micrographic surgery to remove NMSC tumors. Laser treatment was performed with a SmartXide DOT Fractional CO2 Laser (DEKA Laser Technologies, Inc.) emitting a wavelength of 10.6 μm. Treatment levels ranged from 20 mJ to 1200 mJ total energy delivered per laser treatment spot (350 μm spot size). Raman spectra were collected from both untreated and CO2 laser-treated samples using a 785 nm diode laser. Principal Component Analysis (PCA) and Binary Logistic Regression (LR) were used to classify spectra as originating from either normal or NMSC tissue, and from treated or untreated tissue. Partial laser ablation did not adversely affect the ability of Raman spectroscopy to differentiate normal from cancerous residual tissue, with the spectral classification model correctly identifying SCC tissue with 95% sensitivity and 100% specificity following partial laser ablation, compared with 92% sensitivity and 60% selectivity for untreated NMSC tissue. The main biochemical difference identified between normal and NMSC tissue was high levels of collagen in the normal tissue, which was lacking in the NMSC tissue. The feasibility of a combined high-powered CO2 laser ablation, Raman diagnostic procedure for the treatment of NMSC is demonstrated since CO2 laser treatment does not hinder the ability of Raman spectroscopy to differentiate normal from diseased tissue. This combined approach could be employed clinically to greatly enhance the speed and effectiveness of NMSC treatment in many cases. © 2014 Wiley Periodicals, Inc.

Fractional CO2 Laser: From Skin Rejuvenation to Vulvo-Vaginal Reshaping.

PubMed

Filippini, Maurizio; Del Duca, Ester; Negosanti, Francesca; Bonciani, Diletta; Negosanti, Luca; Sannino, Mario; Cannarozzo, Giovanni; Nisticò, Steven Paul

2017-03-01

The CO 2 laser has become the gold standard treatment in dermatologic surgery for the treatment of a large number of skin and mucosal lesions. The introduction of the fractional micro-ablative technology represented an integration to the ablative resurfacing technique, reducing the healing time and the side effects. Vaginal rejuvenation performed with this technique is a minimally invasive procedure that stimulates internal tissues of the female lower genital tract to regenerate the mucosa, improving tissue trophism and restoring the correct functionality. In our experience, 386 menopausal women affected with vulvo-vaginal atrophy (VVA) were treated with three section of fractional micro-ablative CO 2 laser. After three treatments, patients reported a complete improvement of the symptoms (59.94% dryness, 56.26% burn, sensation, 48.75% dyspareunia, 56.37% itch, 73.15% soreness, and 48.79% vaginal introitus pain). Fractional micro-ablative CO 2 laser seems to reduce symptoms related to vaginal atrophy. The beneficial effects were reported just after the first session and confirmed 12 months after the last session.

Influence of peak power in ablation rate of dental hard tissues: mathematical model

NASA Astrophysics Data System (ADS)

Colojoara, Carmen; Gabay, Shimon; van der Meulen, Freerk W.; van Gemert, Martin J. C.

1996-12-01

Pulsed Er:YAG and CO2 lasers should be suitable instruments for dentin and enamel ablation because both tissues have absorption peaks for radiation at 2.9 and 9.6 micrometers wavelengths. This is the context of our research that emphasizes the way in which the diameter and the depth of the crater made in enamel and dentin with the laser Er:YAG and CO2 is influenced in quantity and quality. Freshly extracted human third molar were used for this experiment. The laser source is Er:YAG Kavo Key dental model 1240 and CO2 Laser Sonics LS 860. The dimensions of the obtained craters were measured using the optical microscopy method. The obtained results were modelled experimentally with programs: GRAPHER and STATGRAPHICS. After the mathematical processing to the results what we obtain is relevant regarding the influence of the key parameters in the efficiency of the ablation according to the type of laser. On the whole, from our research results that both lasers ablate efficiently the dentin when the laser energy is between 200 and 300 mJ.

Co:MgF2 laser ablation of tissue: effect of wavelength on ablation threshold and thermal damage.

PubMed

Schomacker, K T; Domankevitz, Y; Flotte, T J; Deutsch, T F

1991-01-01

The wavelength dependence of the ablation threshold of a variety of tissues has been studied by using a tunable pulsed Co:MgF2 laser to determine how closely it tracks the optical absorption length of water. The Co:MgF2 laser was tuned between 1.81 and 2.14 microns, a wavelength region in which the absorption length varies by a decade. For soft tissues the ablation threshold tracks the optical absorption length; for bone there is little wavelength dependence, consistent with the low water content of bone. Thermal damage vs. wavelength was also studied for cornea and bone. Thermal damage to cornea has a weak wavelength dependence, while that to bone shows little wavelength dependence. Framing-camera pictures of the ablation of both cornea and liver show explosive removal of material, but differ as to the nature of the explosion.

New application of the long-pulsed Nd-YAG laser as an ablative resurfacing tool for skin rejuvenation: a 7-year study.

PubMed

Alshami, Mohammad Ali

2013-09-01

Carbon dioxide (CO2 ) and erbium-yttrium aluminum garnet (Er-YAG) lasers are the gold standards in ablative skin resurfacing. Neodymium-doped yttrium aluminum garnet (Nd-YAG) laser is considered a nonablative skin resurfacing laser whose usage is limited due to its high cost. To assess the efficacy and safety of Nd-YAG as an ablative resurfacing laser and to compare the results with those previously published for CO2 and Erbium-YAG lasers. A total of 296 patients (251 female and 45 male) with Fitzpatrick skin types III-IV and dermatological conditions amenable to ablative skin resurfacing participated in this study. Nd-YAG laser parameters assessed were wavelength (1064 nm), pulse duration (5 ms), fluence (10 J/cm(2) ), and spot size (8-10 mm). Efficacy of Nd-YAG laser was assessed by comparing pre- and posttreatment photographs. An improvement of 30-80% was observed in treated patients. The degree of improvement correlated positively with the number of laser sessions. The most common side effect was hyperpigmentation. Other side effects were less common and mild in intensity compared with published results for gold standard ablative lasers. Not only was the Nd-YAG laser found to be as effective as Er-YAG and CO2 lasers, but treated patients also had shorter recovery and treatment times, and at lower cost. © 2013 Wiley Periodicals, Inc.

High-speed scanning ablation of dental hard tissues with a λ=9.3-μm CO2 laser: heat accumulation and peripheral thermal damage

NASA Astrophysics Data System (ADS)

Nguyen, Daniel; Staninec, Michal; Lee, Chulsung; Fried, Daniel

2010-02-01

A mechanically scanned CO2 laser operated at high laser pulse repetition rates can be used to rapidly and precisely remove dental decay. This study aims to determine whether these laser systems can safely ablate enamel and dentin without excessive heat accumulation and peripheral thermal damage. Peripheral thermal damage can adversely impact the mechanical strength of the irradiated tissue, particularly for dentin, and reduce the adhesion characteristics of the modified surfaces. Samples were derived from noncarious extracted molars. Pulpal temperatures were recorded using microthermocouples situated at the pulp chamber roof of samples (n=12), which were occlusally ablated using a rapid-scanning, water-cooled 300 Hz CO2 laser over a two minute time course. The mechanical strength of facially ablated dentin (n=10) was determined via four-point bend test and compared to control samples (n=10) prepared with 320 grit wet sand paper to simulate conventional preparations. Composite-to-enamel bond strength was measured via single-plane shear test for ablated/non-etched (n=10) and ablated/acid-etched (n=8) samples and compared to control samples (n=9) prepared by 320 grit wet sanding. Thermocouple measurements indicated that the temperature remained below ambient temperature at 19.0°C (s.d.=0.9) if water-cooling was used. There was no discoloration of either dentin and enamel, the treated surfaces were uniformly ablated and there were no cracks observable on the laser treated surfaces. Fourpoint bend tests yielded mean mechanical strengths of 18.2 N (s.d.=4.6) for ablated dentin and 18.1 N (s.d.=2.7) for control (p>0.05). Shear tests yielded mean bond strengths of 31.2 MPa (s.d.=2.5, p<0.01) for ablated/acid-etched samples, 5.2 MPa (s.d.=2.4, p<0.001) for ablated/non-etched samples, and 37.0 MPa (s.d.=3.6) for control. The results indicate that a rapid-scanning 300 Hz CO2 laser can effectively ablate dentin and enamel without excessive heat accumulation and with minimal thermal damage. It is not clear whether the small (16%) but statistically significant reduction in the shear bond strength to enamel is clinically significant since the mean shear bond strength exceeded 30 MPa.

Optimized LWIR enhancement of nanosecond and femtosecond LIBS uranium emission

NASA Astrophysics Data System (ADS)

Akpovo, Codjo A.; Ford, Alan; Johnson, Lewis

2016-05-01

A carbon dioxide (CO2) transverse electrical breakdown in atmosphere (TEA), pulsed laser was used to enhance the laser-induced breakdown spectroscopy (LIBS) spectral signatures of uranium under nanosecond (ns) and femtosecond (fs) ablation. The peak areas of both ionic and neutral species increased by one order of magnitude for ns-ablation and two orders of magnitude for fs-ablation over LIBS when the CO2 TEA laser was used with samples of dried solutions of uranyl nitrate hexahydrate (UO2(NO3)2·6H2O) on silicon wafers. Electron temperature and density measurements show that the spectral emission improvement from using the TEA laser comes from plasma reheating.

Hypertrophic Scarring of the Neck Following Ablative Fractional Carbon Dioxide Laser Resurfacing

PubMed Central

Avram, Mathew M.; Tope, Whitney D.; Yu, Thomas; Szachowicz, Edward; Nelson, J. Stuart

2009-01-01

Background Ablative fractional carbon dioxide (CO2) laser treatments have gained popularity due to their efficacy, shortened downtime, and decreased potential for scarring in comparison to traditional ablative CO2 resurfacing. To date, scarring with fractional CO2 lasers has not been reported. Objective Five patients treated with the same fractional CO2 laser technology for photodamage of the neck were referred to our practices 1–3 months after treatment. Each patient developed scarring. Of the five cases, two are discussed in detail. The first was treated under general anesthesia on the face and anterior neck at a pulse energy of 30 mJ (859 μm depth) with 25% coverage. Eleven days after treatment, three non-healing areas along the horizontal skin folds of the anterior neck were noted. At 2 weeks after CO2 ablative fractional resurfacing, these areas had become thickened. These raised areas were treated with a non-ablative fractionated 1,550 nm laser to modify the wound healing milieu. One week later, distinct firm pale papules in linear arrays with mild hypopigmentation had developed along involved neck skin folds. Skin biopsy was performed. For the second patient, the neck was treated at a pulse energy of 20 mJ (630 μm depth) with 30% coverage of the exposed skin, with a total treatment energy of 5.0 kJ. Minimal crusting was noted on the neck throughout the initial healing phase of 2 weeks. She then experienced tightness on her neck. Approximately 3 weeks after treatment, she developed multiple vertical and horizontal hypertrophic scars (HS). Results Histopathology for the first case confirmed the presence of a hypertrophic scar. The papules in this case completely resolved with mild residual hypopigmentation after treatment with topical corticosteroids. HS failed to resolve in the second case to date after 1 month. Conclusion As with traditional ablative CO2 laser resurfacing, HS is a potential complication of ablative fractional CO2 laser resurfacing, particularly on the neck. With early diagnosis and appropriate treatment HS of neck skin may be reversible. We urge caution when treating the neck with this device and close attention to wound care in the post-operative period. PMID:19291746

Microsecond enamel ablation with 10.6μm CO2 laser radiation

NASA Astrophysics Data System (ADS)

Góra, W. S.; McDonald, A.; Hand, D. P.; Shephard, J. D.

2016-02-01

Lasers have been previously been used for dental applications, however there remain issues with thermally-induced cracking. In this paper we investigate the impact of pulse length on CO2 laser ablation of human dental enamel. Experiments were carried in vitro on molar teeth without any modification to the enamel surface, such as grinding or polishing. In addition to varying the pulse length, we also varied pulse energy and focal position, to determine the most efficient ablation of dental hard tissue and more importantly to minimize or eradicate cracking. The maximum temperature rise during the multi pulse ablation process was monitored using a set of thermocouples embedded into the pulpal chamber. The application of a laser device in dental surgery allows removal of tissue with higher precision, which results in minimal loss of healthy dental tissue. In this study we use an RF discharge excited CO2 laser operating at 10.6μm. The wavelength of 10.6 μm overlaps with a phosphate band (PO3-4) absorption in dental hard tissue hence the CO2 laser radiation has been selected as a potential source for modification of the tissue. This research describes an in-depth analysis of single pulse laser ablation. To determine the parameters that are best suited for the ablation of hard dental tissue without thermal cracking, a range of pulse lengths (10-200 μs), and fluences (0-100 J/cm2) are tested. In addition, different laser focusing approaches are investigated to select the most beneficial way of delivering laser radiation to the surface (divergent/convergent beam). To ensure that these processes do not increase the temperature above the critical threshold and cause the necrosis of the tissue a set of thermocouples was placed into the pulpal chambers. Intermittent laser radiation was investigated with and without application of a water spray to cool down the ablation site and the adjacent area. Results show that the temperature can be kept below the critical threshold either by using water spray or by decreasing the repetition rate. We demonstrate that CO2 laser pulses with pulse lengths in the regime of 10 μs can provide precise enamel tissue removal without introducing any unwanted thermal damage.

Selective mucosal ablation using CO2 laser for the development of novel endoscopic submucosal dissection: comparison of continuous wave and nanosecond pulsed wave

NASA Astrophysics Data System (ADS)

Ishii, K.; Watanabe, S.; Obata, D.; Hazama, H.; Morita, Y.; Matsuoka, Y.; Kutsumi, H.; Azuma, T.; Awazu, K.

2010-02-01

Endoscopic submucosal dissection (ESD) is accepted as a minimally invasive treatment technique for small early gastric cancers. Procedures are carried out using some specialized electrosurgical knifes with a submucosal injection solution. However it is not widely used because its procedure is difficult. The objective of this study is to develop a novel ESD method which is safe in principle and widely used by using laser techniques. In this study, we used CO2 lasers with a wavelength of 10.6 μm for mucosal ablation. Two types of pulse, continuous wave and pulsed wave with a pulse width of 110 ns, were studied to compare their values. Porcine stomach tissues were used as a sample. Aqueous solution of sodium hyaluronate (MucoUpR) with 50 mg/ml sodium dihydrogenphosphate is injected to a submucosal layer. As a result, ablation effect by CO2 laser irradiation was stopped because submucosal injection solution completely absorbed CO2 laser energy in the invasive energy condition which perforates a muscle layer without submucosal injection solution. Mucosal ablation by the combination of CO2 Laser and a submucosal injection solution is a feasible technique for treating early gastric cancers safely because it provides a selective mucosal resection and less-invasive interaction to muscle layer.

Skin Pretreatment With Conventional Non-Fractional Ablative Lasers Promote the Transdermal Delivery of Tranexamic Acid.

PubMed

Hsiao, Chien-Yu; Sung, Hsin-Ching; Hu, Sindy; Huang, Chun-Hsun

2016-07-01

Laser pretreatment of skin can be used to enable drugs used in dermatology to penetrate the skin to the depth necessary for their effect to take place. To compare the permeation of tranexamic acid after conventional non-fractionated ablative Er:YAG and CO2 laser pretreatment in a laser-aided transdermal delivery system. An erbium-doped yttrium aluminium garnet (Er:YAG) and a CO2 laser were used to pretreat dorsal porcine skin. Scanning electron microscopy was used to examine disruption of the skin surface. Confocal laser scanning microscopy was used to determine the depth of penetration of a reporter molecule (fluorescein isothiocyanate) into the skin. A Franz diffusion assembly was used to examine fluency-related increases in transdermal delivery of transexamic acid. Transdermal delivery of tranexamic acid increased as Er:YAG laser fluency increased. Transdermal delivery was higher when CO2 laser pretreatment was used than when Er:YAG laser pretreatment was used, but a "ceiling effect" was present and increasing the wattage did not cause a further increase in delivery. CO2 laser pretreatment also caused more extensive and deeper skin disruption than Er:YAG laser pretreatment. For conventional, non-fractionated ablative laser pretreatment, the Er:YAG laser would be an optimal choice to enhance transdermal penetration of transexamic acid.

High-speed scanning ablation of dental hard tissues with a λ = 9.3 μm CO2 laser: adhesion, mechanical strength, heat accumulation, and peripheral thermal damage

PubMed Central

Nguyen, Daniel; Chang, Kwang; Hedayatollahnajafi, Saba; Staninec, Michal; Chan, Kenneth; Lee, Robert; Fried, Daniel

2011-01-01

CO2 lasers can be operated at high laser pulse repetition rates for the rapid and precise removal of dental decay. Excessive heat accumulation and peripheral thermal damage is a concern when using high pulse repetition rates. Peripheral thermal damage can adversely impact the mechanical strength of the irradiated tissue, particularly for dentin, and reduce the adhesion characteristics of the modified surfaces. The interpulpal temperature rise was recorded using microthermocouples situated at the roof of the pulp chamber on teeth that were occlusally ablated using a rapidly-scanned CO2 laser operating at 9.3 μm with a pulse duration of 10 to 15 μs and repetition rate of 300 Hz over a 2 min time course. The adhesion strength of laser treated enamel and dentin surfaces was measured for various laser scanning parameters with and without post-ablation acid etching using the single-plane shear test. The mechanical strength of laser-ablated dentin surfaces were determined via the four-point bend test and compared to control samples prepared with 320 grit wet sand paper to simulate conventional preparations. Thermocouple measurements indicated that the temperature remained below ambient temperature if water-cooling was used. There was no discoloration of either dentin or enamel laser treated surfaces, the surfaces were uniformly ablated, and there were no cracks visible. Four-point bend tests yielded mean mechanical strengths of 18.2 N (s.d. = 4.6) for ablated dentin and 18.1 N (s.d. = 2.7) for control (p > 0.05). Shear tests yielded mean bond strengths approaching 30 MPa for both enamel and dentin under certain irradiation conditions. These values were slightly lower than nonirradiated acid-etched control samples. Additional studies are needed to determine if the slightly lower bond strength than the acid-etched control samples is clinically significant. These measurements demonstrate that enamel and dentin surfaces can be rapidly ablated by CO2 lasers with minimal peripheral thermal and mechanical damage and without excessive heat accumulation. PMID:21806256

High-speed scanning ablation of dental hard tissues with a λ = 9.3 μm CO2 laser: adhesion, mechanical strength, heat accumulation, and peripheral thermal damage

NASA Astrophysics Data System (ADS)

Nguyen, Daniel; Chang, Kwang; Hedayatollahnajafi, Saba; Staninec, Michal; Chan, Kenneth; Lee, Robert; Fried, Daniel

2011-07-01

CO2 lasers can be operated at high laser pulse repetition rates for the rapid and precise removal of dental decay. Excessive heat accumulation and peripheral thermal damage is a concern when using high pulse repetition rates. Peripheral thermal damage can adversely impact the mechanical strength of the irradiated tissue, particularly for dentin, and reduce the adhesion characteristics of the modified surfaces. The interpulpal temperature rise was recorded using microthermocouples situated at the roof of the pulp chamber on teeth that were occlusally ablated using a rapidly-scanned CO2 laser operating at 9.3 μm with a pulse duration of 10 to 15 μs and repetition rate of 300 Hz over a 2 min time course. The adhesion strength of laser treated enamel and dentin surfaces was measured for various laser scanning parameters with and without post-ablation acid etching using the single-plane shear test. The mechanical strength of laser-ablated dentin surfaces were determined via the four-point bend test and compared to control samples prepared with 320 grit wet sand paper to simulate conventional preparations. Thermocouple measurements indicated that the temperature remained below ambient temperature if water-cooling was used. There was no discoloration of either dentin or enamel laser treated surfaces, the surfaces were uniformly ablated, and there were no cracks visible. Four-point bend tests yielded mean mechanical strengths of 18.2 N (s.d. = 4.6) for ablated dentin and 18.1 N (s.d. = 2.7) for control (p > 0.05). Shear tests yielded mean bond strengths approaching 30 MPa for both enamel and dentin under certain irradiation conditions. These values were slightly lower than nonirradiated acid-etched control samples. Additional studies are needed to determine if the slightly lower bond strength than the acid-etched control samples is clinically significant. These measurements demonstrate that enamel and dentin surfaces can be rapidly ablated by CO2 lasers with minimal peripheral thermal and mechanical damage and without excessive heat accumulation.

High-speed scanning ablation of dental hard tissues with a λ = 9.3 μm CO2 laser: adhesion, mechanical strength, heat accumulation, and peripheral thermal damage.

PubMed

Nguyen, Daniel; Chang, Kwang; Hedayatollahnajafi, Saba; Staninec, Michal; Chan, Kenneth; Lee, Robert; Fried, Daniel

2011-07-01

CO(2) lasers can be operated at high laser pulse repetition rates for the rapid and precise removal of dental decay. Excessive heat accumulation and peripheral thermal damage is a concern when using high pulse repetition rates. Peripheral thermal damage can adversely impact the mechanical strength of the irradiated tissue, particularly for dentin, and reduce the adhesion characteristics of the modified surfaces. The interpulpal temperature rise was recorded using microthermocouples situated at the roof of the pulp chamber on teeth that were occlusally ablated using a rapidly-scanned CO(2) laser operating at 9.3 μm with a pulse duration of 10 to 15 μs and repetition rate of 300 Hz over a 2 min time course. The adhesion strength of laser treated enamel and dentin surfaces was measured for various laser scanning parameters with and without post-ablation acid etching using the single-plane shear test. The mechanical strength of laser-ablated dentin surfaces were determined via the four-point bend test and compared to control samples prepared with 320 grit wet sand paper to simulate conventional preparations. Thermocouple measurements indicated that the temperature remained below ambient temperature if water-cooling was used. There was no discoloration of either dentin or enamel laser treated surfaces, the surfaces were uniformly ablated, and there were no cracks visible. Four-point bend tests yielded mean mechanical strengths of 18.2 N (s.d. = 4.6) for ablated dentin and 18.1 N (s.d. = 2.7) for control (p > 0.05). Shear tests yielded mean bond strengths approaching 30 MPa for both enamel and dentin under certain irradiation conditions. These values were slightly lower than nonirradiated acid-etched control samples. Additional studies are needed to determine if the slightly lower bond strength than the acid-etched control samples is clinically significant. These measurements demonstrate that enamel and dentin surfaces can be rapidly ablated by CO(2) lasers with minimal peripheral thermal and mechanical damage and without excessive heat accumulation.

Rapid fabrication of poly(dimethylsiloxane)-based microchip capillary electrophoresis devices using CO2 laser ablation.

PubMed

Fogarty, Barbara A; Heppert, Kathleen E; Cory, Theodore J; Hulbutta, Kalonie R; Martin, R Scott; Lunte, Susan M

2005-06-01

The use of CO(2) laser ablation for the patterning of capillary electrophoresis (CE) microchannels in poly(dimethylsiloxane)(PDMS) is described. Low-cost polymer devices were produced using a relatively inexpensive CO(2) laser system that facilitated rapid patterning and ablation of microchannels. Device designs were created using a commercially available software package. The effects of PDMS thickness, laser focusing, power, and speed on the resulting channel dimensions were investigated. Using optimized settings, the smallest channels that could be produced averaged 33 microm in depth (11.1% RSD, N= 6) and 110 microm in width (5.7% RSD, N= 6). The use of a PDMS substrate allowed reversible sealing of microchip components at room temperature without the need for cleanroom facilities. Using a layer of pre-cured polymer, devices were designed, ablated, and assembled within minutes. The final devices were used for microchip CE separation and detection of the fluorescently labeled neurotransmitters aspartate and glutamate.

The role of mesoscopic modelling in understanding the response of dental enamel to mid-infrared radiation

NASA Astrophysics Data System (ADS)

Vila Verde, A.; Ramos, M. M. D.; Stoneham, A. M.

2007-05-01

Human dental enamel has a porous mesostructure at the nanometre to micrometre scales that affects its thermal and mechanical properties relevant to laser treatment. We exploit finite-element models to investigate the response of this mesostructured enamel to mid-infrared lasers (CO2 at 10.6 µm and Er:YAG at 2.94 µm). Our models might easily be adapted to investigate ablation of other brittle composite materials. The studies clarify the role of pore water in ablation, and lead to an understanding of the different responses of enamel to CO2 and Er:YAG lasers, even though enamel has very similar average properties at the two wavelengths. We are able to suggest effective operating parameters for dental laser ablation, which should aid the introduction of minimally-invasive laser dentistry. In particular, our results indicate that, if pulses of ap10 µs are used, the CO2 laser can ablate dental enamel without melting, and with minimal damage to the pulp of the tooth. Our results also suggest that pulses with 0.1-1 µs duration can induce high stress transients which may cause unwanted cracking.

Pulsed CO2 Laser Ablation of Superficial Basal Cell of Limbs and Trunk: A Comparative Randomized Clinical Trial With Cryotherapy and Surgical Ablation.

PubMed

Zane, Cristina; Facchinetti, Elena; Arisi, Mariachiara; Ortel, Bernhard; Calzavara-Pinton, Piergiacomo

2017-07-01

Pulsed CO2 laser is a treatment of superficial basal cell carcinoma (sBCC) although robust clinical evidence has not been reported so far. The authors investigated efficacy, safety, time to wound healing, cosmetic outcome, patient satisfaction, and cost-effectiveness ratio of pulsed CO2 laser in comparison to cryotherapy and surgery. BCCs of the trunk and extremities were randomized to one of the treatments. After 90 days, efficacy and cosmetic outcome were assessed. Patients recorded the time to complete healing of the wound and scored their overall satisfaction. Two hundred forty patients were randomized. After 3 months, complete remission (CR) rate with pulsed CO2 laser was 78.8%. This was significantly lower than surgery, whereas the CR rate with cryotherapy was not significantly different. Cosmetic result was better with surgery. High satisfaction was reported by 65.0% of patients treated with CO2 ablation. Time of wound healing was significantly shorter with CO2 laser. In comparison to cryotherapy, pulsed CO2 laser showed no statistically significant difference in efficacy, cosmetic outcome, and patient satisfaction. Time to healing was shorter; the cost and cost-effectiveness ratio were similar. Surgery had the greatest efficacy rate. The main limitation of this study was the short duration of follow-up (3 months).

Comparison of KTP, Thulium, and CO2 laser in stapedotomy using specialized visualization techniques: thermal effects.

PubMed

Kamalski, Digna M A; Verdaasdonk, Rudolf M; de Boorder, Tjeerd; Vincent, Robert; Trabelzini, Franco; Grolman, Wilko

2014-06-01

High-speed thermal imaging enables visualization of heating of the vestibule during laser-assisted stapedotomy, comparing KTP, CO2, and Thulium laser light. Perforation of the stapes footplate with laser bears the risk of heating of the inner ear fluids. The amount of heating depends on absorption of the laser light and subsequent tissue ablation. The ablation of the footplate is driven by strong water absorption for the CO2 and Thulium laser. For the KTP laser wavelength, ablation is driven by carbonization of the footplate and it might penetrate deep into the inner ear without absorption in water. The thermal effects were visualized in an inner ear model, using two new techniques: (1) high-speed Schlieren imaging shows relative dynamic changes of temperatures up to 2 ms resolution in the perilymph. (2) Thermo imaging provides absolute temperature measurements around the footplate up to 40 ms resolution. The high-speed Schlieren imaging showed minimal heating using the KTP laser. Both CO2 and Thulium laser showed heating below the footplate. Thulium laser wavelength generated heating up to 0.6 mm depth. This was confirmed with thermal imaging, showing a rise of temperature of 4.7 (±3.5) °C for KTP and 9.4 (±6.9) for Thulium in the area of 2 mm below the footplate. For stapedotomy, the Thulium and CO2 laser show more extended thermal effects compared to KTP. High-speed Schlieren imaging and thermal imaging are complimentary techniques to study lasers thermal effects in tissue.

Dentin ablation-rate measurements in endodontics witj HF and CO2 laser radiation

NASA Astrophysics Data System (ADS)

Makropoulou, Mersini I.; Serafetinides, Alexander A.; Khabbaz, Marouan; Sykaras, Sotirios; Tsikrikas, G. N.

1996-01-01

Recent studies focused on the ability of the laser light to enlarge the root canal during the endodontic therapy. The aim of this research is the experimental and theoretical study of the ablation rate of two infrared laser wavelengths on dentin. Thirty freshly extracted human teeth were longitudinally sectioned at thicknesses ranged from 0.5 to 2 mm, and irradiated on the root canal dentin. The measured ablation rates in dentinal wall of the root canal showed that the HF laser at 2.9 micrometer can more effectively penetrate into the tissue, whereas the carbon dioxide laser at 10.6 micrometer leads to high thermal damage of the ablation crater surroundings.

Stainless steel pinholes for fast fabrication of high-performance microchip electrophoresis devices by CO2 laser ablation.

PubMed

Yap, Yiing C; Guijt, Rosanne M; Dickson, Tracey C; King, Anna E; Breadmore, Michael C

2013-11-05

With the introduction of hobby laser engravers/cutters, the use of CO2 laser micromachining on poly(methyl methacrylate) (PMMA) has the potential for flexible, low cost, rapid prototyping of microfluidic devices. Unfortunately, the feature size created by most entry-level CO2 laser micromachining systems is too large to become a functional tool in analytical microfluidics. In this paper, we report a novel method to reduce the feature size of microchannels and the bulges formed at the rim of the channel during CO2 laser micromachining by passing the laser beam through a stainless steel pinhole. Without the pinhole, the channel width was typically 300 μm wide. However, when 50 or 35 μm diameter pinholes were used, channel widths of 60 and 25 μm, respectively, could be obtained. The height of the bulge deposited directly next to the channel was reduced to less than 0.8 μm with the pinhole during ablation. Separations of fluorescent dyes on devices ablated with and without the pinhole were compared. On devices fabricated with the pinhole, the number of theoretical plates/m was 2.2-fold higher compared to devices fabricated without the pinhole, and efficiencies comparable to embossed PMMA and laser ablated glass chips were obtained. A mass-produced commercial hobby laser (retailing at ∼$2500), when equipped with a $500 pinhole, represents a rapid and low-cost approach to the rapid fabrication of rigid plastic microchips including the narrow microchannels required for microchip electrophoresis.

Ablative skin resurfacing with a novel microablative CO2 laser.

PubMed

Gotkin, Robert H; Sarnoff, Deborah S; Cannarozzo, Giovanni; Sadick, Neil S; Alexiades-Armenakas, Macrene

2009-02-01

Carbon dioxide (CO2) laser skin resurfacing has been a mainstay of facial rejuvenation since its introduction in the mid 1990s. Recently, a new generation of fractional or microablative CO2 lasers has been introduced to the marketplace. According to the concept of fractional photothermolysis, these lasers ablate only a fraction of the epidermal and dermal architecture in the treatment area. An array of microscopic thermal wounds is created that ablates the epidermis and dermis within very tiny zones; adjacent to these areas, the epidermis and dermis are spared. This microablative process of laser skin resurfacing has proven safe and effective not only for facial rejuvenation, but elsewhere on the body as well. It is capable of improving wrinkles, acne scars, and other types of atrophic scars and benign pigmented lesions associated with elastotic, sun-damaged skin. Because of the areas of spared epidermis and dermis inherent in a procedure that employs fractional photothermolysis, healing is more rapid compared to fully ablative CO2 laser skin resurfacing and downtime is proportionately reduced. A series of 32 consecutive patients underwent a single laser resurfacing procedure with the a new microablative CO2 laser. All patients were followed for a minimum of 6 months and were asked to complete patient satisfaction questionnaires; a 6 month postoperative photographic evaluation by an independent physician, not involved in the treatment, was also performed. Both sets of data were graded and reported on a quartile scale. Results demonstrated greater than 50% improvement in almost all patients with those undergoing treatment for wrinkles, epidermal pigment or solar elastosis deriving the greatest change for the better (>75%).

CO2 and Er:YAG laser interaction with grass tissues

NASA Astrophysics Data System (ADS)

Kim, Jaehun; Ki, Hyungson

2013-01-01

Plant leaves are multi-component optical materials consisting of water, pigments, and dry matter, among which water is the predominant constituent. In this article, we investigate laser interaction with grass using CO2 and Er:YAG lasers theoretically and experimentally, especially targeting water in grass tissues. We have first studied the optical properties of light absorbing constituents of grass theoretically, and then have identified interaction regimes and constructed interaction maps through a systematic experiment. Using the interaction maps, we have studied how interaction regimes change as process parameters are varied. This study reveals some interesting findings concerning carbonization and ablation mechanisms, the effect of laser beam diameter, and the ablation efficiency and quality of CO2 and Er:YAG lasers.

Ultraviolet-Diode Pump Solid State Laser Removal of Titanium Aluminium Nitride Coating from Tungsten Carbide Substrate

NASA Astrophysics Data System (ADS)

See, Tian Long; Chantzis, Dimitrios; Royer, Raphael; Metsios, Ioannis; Antar, Mohammad; Marimuthu, Sundar

2017-09-01

This paper presents an investigation on the titanium aluminium nitride (TiAlN) coating removal from tungsten carbide (WC-Co) substrate using a diode pump solid state (DPSS) ultraviolet (UV) laser with maximum average power of 90 W, wavelength of 355 nm and pulse width of 50 ns. The TiAlN coating of 1.5 μm thickness is removed from the WC-Co substrate with laser fluence of 2.71 J/cm2 at 285.6 number of pulses (NOP) and with NOP of 117.6 at 3.38 J/cm2 fluence. Titanium oxide formation was observed on the ablated surface due to the re-deposition of ablated titanium residue and also attributed to the high temperature observed during the laser ablation process. Crack width of around 0.2 μm was observed over both TiAlN coating and WC-Co substrate. The crack depth ranging from 1 to 10 μm was observed and is related to the thickness of the melted carbide. The crack formation is a result of the thermal induced stresses caused by the laser beam interaction with the material as well as the higher thermal conductivity of cobalt compared to WC. Two cleaning regions are observed and is a consequence of the Gaussian distribution of the laser beam energy. The surface roughness of the ablated WC-Co increased with increasing laser fluence and NOP.

Interaction of graphite and ablative materials with CO2-laser, carbon-arc, and xenon-arc radiation. M.S. Thesis - George Washington Univ., Washington, D. C.

NASA Technical Reports Server (NTRS)

Brewer, W. D.

1975-01-01

The behavior of graphite and several charring ablators in a variety of high radiative heat flux environments was studied in various radiative environments produced by a CO2 laser and a carbon arc facility. Graphite was also tested in xenon arc radiation. Tests were conducted in air nitrogen, helium, and a mixture of CO2 and nitrogen, simulating the Venus atmosphere. The experimental results are compared with theoretical results obtained with a one dimensional charring ablator analysis and a two dimensional subliming ablator analysis. Photomicroscopy showed no significant differences in appearance or microstructure of the charring ablators or graphite after testing in the three different facilities, indicating that the materials respond fundamentally the same to the radiation of different frequencies. The performance of phenolic nylon and graphite was satisfactorily predicted with existing analyses and published material property data.

Near-infrared image-guided laser ablation of artificial caries lesions.

PubMed

Tao, You-Chen; Fan, Kenneth; Fried, Daniel

2007-01-01

Laser removal of dental hard tissue can be combined with optical, spectral or acoustic feedback systems to selectively ablate dental caries and restorative materials. Near-infrared (NIR) imaging has considerable potential for the optical discrimination of sound and demineralized tissue. The objective of this study was to test the hypothesis that two-dimensional NIR images of demineralized tooth surfaces can be used to guide CO(2) laser ablation for the selective removal of artificial caries lesions. Highly patterned artificial lesions were produced by submerging 5 × 5 mm(2) bovine enamel samples in demineralized solution for a 9-day period while sound areas were protected with acid resistant varnish. NIR imaging and polarization sensitive optical coherence tomography (PS-OCT) were used to acquire depth-resolved images at a wavelength of 1310-nm. An imaging processing module was developed to analyze the NIR images and to generate optical maps. The optical maps were used to control a CO(2) laser for the selective removal of the lesions at a uniform depth. This experiment showed that the patterned artificial lesions were removed selectively using the optical maps with minimal damage to sound enamel areas. Post-ablation NIR and PS-OCT imaging confirmed that demineralized areas were removed while sound enamel was conserved. This study successfully demonstrated that near-IR imaging can be integrated with a CO(2) laser ablation system for the selective removal of dental caries.

Near-infrared image-guided laser ablation of artificial caries lesions

PubMed Central

Tao, You-Chen; Fan, Kenneth; Fried, Daniel

2012-01-01

Laser removal of dental hard tissue can be combined with optical, spectral or acoustic feedback systems to selectively ablate dental caries and restorative materials. Near-infrared (NIR) imaging has considerable potential for the optical discrimination of sound and demineralized tissue. The objective of this study was to test the hypothesis that two–dimensional NIR images of demineralized tooth surfaces can be used to guide CO2 laser ablation for the selective removal of artificial caries lesions. Highly patterned artificial lesions were produced by submerging 5 × 5 mm2 bovine enamel samples in demineralized solution for a 9-day period while sound areas were protected with acid resistant varnish. NIR imaging and polarization sensitive optical coherence tomography (PS-OCT) were used to acquire depth-resolved images at a wavelength of 1310-nm. An imaging processing module was developed to analyze the NIR images and to generate optical maps. The optical maps were used to control a CO2 laser for the selective removal of the lesions at a uniform depth. This experiment showed that the patterned artificial lesions were removed selectively using the optical maps with minimal damage to sound enamel areas. Post-ablation NIR and PS-OCT imaging confirmed that demineralized areas were removed while sound enamel was conserved. This study successfully demonstrated that near-IR imaging can be integrated with a CO2 laser ablation system for the selective removal of dental caries. PMID:22866210

Ablative skin resurfacing.

PubMed

Agrawal, Nidhi; Smith, Greg; Heffelfinger, Ryan

2014-02-01

Ablative laser resurfacing has evolved as a safe and effective treatment for skin rejuvenation. Although traditional lasers were associated with significant thermal damage and lengthy recovery, advances in laser technology have improved safety profiles and reduced social downtime. CO2 lasers remain the gold standard of treatment, and fractional ablative devices capable of achieving remarkable clinical improvement with fewer side effects and shorter recovery times have made it a more practical option for patients. Although ablative resurfacing has become safer, careful patient selection and choice of suitable laser parameters are essential to minimize complications and optimize outcomes. This article describes the current modalities used in ablative laser skin resurfacing and examines their efficacy, indications, and possible side effects. Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.

Advanced film-forming gel formula vs spring thermal water and white petrolatum as primary dressings after full-face ablative fractional CO2 laser resurfacing: a comparative split-face pilot study.

PubMed

Marini, L

2018-01-01

Aesthetically pleasing results and fast, uneventful recovery are highly desirable after rejuvenating ablative laser procedures. Wound dressings following ablative laser procedures should ideally improve and optimize the wound healing environment. The purpose of this comparative split-face, single-blinded, prospective observational study was to assess the efficacy and acceptability of two primary wound dressings immediately after a full-face fractional CO 2 laser resurfacing procedure. The assessments of an innovative film-forming dressing called Stratacel (SC) vs spring thermal water + Vaseline (V+) were conducted after a standardized, single-pass, full-face ablative fractional CO 2 laser skin resurfacing procedure. Clinical parameters, such as haemoglobin - HB; surface temperature - ST; micro-textural modifications - MT; superficial melanin - M; intrafollicular porphyrins - P, were assessed at different phases of the healing process using standardized, non-invasive technologies. Five female volunteers were enrolled in this inpatient, controlled pilot study. Most of the clinical parameters considered, including 3D surface texture analysis, revealed a better performance of SC vs. V+ during the early, more delicate phases of the healing process. This preliminary study, even if performed on a small number of volunteers, confirmed a definite advantage of the tested semipermeable film-forming formula (SC) over a more conventional postoperative skin care regime (V+). Clinical results could be explained by a better uniformity of distribution of SC over the micro-irregularities induced by ablative fractional CO 2 laser resurfacing. Its thin, semipermeable film might, in fact, act as an efficient, perfectly biocompatible, full contact, temporary skin barrier, able to protect extremely delicate healing surfaces from potential environmental irritations. © 2017 European Academy of Dermatology and Venereology.

Ellipsometric study of YBa2Cu3O(7-x) laser ablated and co-evaporated films

NASA Technical Reports Server (NTRS)

Alterovitz, S. A.; Sieg, R. E.; Warner, J. D.; Stan, M. A.; Vitta, S.

1990-01-01

High temperature superconducting films of YBa2Cu3O(7-x) (YBCO were grown on SrTiO3, LaA1O3, and YSZ substrates using two techniques: excimer laser ablation with in situ annealing and co-evaporation of Y, Cu, and BaF2 with ex-situ annealing. Film thicknesses were typically 5000 A, with predominant c-axis alignment perpendicular to the substrate. Critical temperatures up to Tc(R=O)=90 K were achieved by both techniques. Ellipsometric measurements were taken in the range 1.6 to 4.3 eV using a variable angle spectroscopic ellipsometer. The complex dielectric function of the laser ablated films was reproducible from run to run, and was found to be within 10 percent of that previously reported for (001) oriented single crystals. A dielectric overlayer was observed in these films, with an index of refraction of approximately 1.55 and nearly zero absorption. For the laser ablated films the optical properties were essentially independent of substrate material. The magnitude of the dielectric function obtained for the co-evaported films was much lower than the value reported for single crystals, and was sample dependent.

Fractional CO2 Laser Resurfacing Complications

PubMed Central

Ramsdell, William M.

2012-01-01

Fractionated CO2 laser technology has allowed physicians to resurface patients with a lower rate of complications than nonfractionated ablative laser treatment. Unfortunately, adverse effects can still occur even with the best technology and physician care. Complication prevention, detection, and treatment are an important part of a physician's ability to provide the best result when treating a patient with fractionated CO2 resurfacing. PMID:23904822

CO2-laser ablation of Bi-Sr-Ca-Cu oxide by millisecond pulse lengths

NASA Astrophysics Data System (ADS)

Meskoob, M.; Honda, T.; Safari, A.; Wachtman, J. B.; Danforth, S.; Wilkens, B. J.

1990-03-01

We have achieved ablation of Bi-Sr-Ca-Cu oxide from single targets of superconducting pellets by CO2-laser pulses of l ms length to grow superconducting thin films. Upon annealing, the 6000-Å thin films have a Tc (onset) of 90 K and zero resistance at 78 K. X-ray diffraction patterns indicate the growth of single-phase thin films. This technique allows growth of uniform single-phase superconducting thin films of lateral area greater than 1 cm2.

The use of ablative lasers in the treatment of facial melasma.

PubMed

Morais, Orlando Oliveira de; Lemos, Érica Freitas Lima; Sousa, Márcia Carolline dos Santos; Gomes, Ciro Martins; Costa, Izelda Maria Carvalho; Paula, Carmen Déa Ribeiro de

2013-01-01

Melasma represents a pigmentary disorder that is difficult to treat. This study aims to broadly review the use of ablative lasers (Er:YAG and CO2) in the treatment of melasma, presenting the level of evidence of studies published to date. A total of 75 patients were enrolled in four case series studies (n=39), one controlled clinical trial (n=6) and one randomized controlled clinical trial (n=30). Studies on the Er:YAG laser showed better results with the use of short square-shaped pulses, which determined low rates of post-inflammatory hyperpigmentation and long-lasting maintenance of results. Likewise, studies on the CO2 laser proved the benefits of short pulse duration along with low-density energy. Post-treatment maintenance with the use of antipigmenting creams was necessary and effective to sustain long-term results. Ablative lasers may represent another useful and effective tool against melasma. Postinflammatory hyperpigmentation and difficulty in sustaining long-term results still represent the main limitations to a broader use of ablative lasers. Based on actual evidence, the use of this technology should be restricted to patients with recalcitrant disease. Further studies will help establish optimal laser parameters and treatment regimens.

The use of ablative lasers in the treatment of facial melasma*

PubMed Central

de Morais, Orlando Oliveira; Lemos, Érica Freitas Lima; Sousa, Márcia Carolline dos Santos; Gomes, Ciro Martins; Costa, Izelda Maria Carvalho; de Paula, Carmen Déa Ribeiro

2013-01-01

Melasma represents a pigmentary disorder that is difficult to treat. This study aims to broadly review the use of ablative lasers (Er:YAG and CO2) in the treatment of melasma, presenting the level of evidence of studies published to date. A total of 75 patients were enrolled in four case series studies (n=39), one controlled clinical trial (n=6) and one randomized controlled clinical trial (n=30). Studies on the Er:YAG laser showed better results with the use of short square-shaped pulses, which determined low rates of post-inflammatory hyperpigmentation and long-lasting maintenance of results. Likewise, studies on the CO2 laser proved the benefits of short pulse duration along with low-density energy. Post-treatment maintenance with the use of antipigmenting creams was necessary and effective to sustain long-term results. Ablative lasers may represent another useful and effective tool against melasma. Postinflammatory hyperpigmentation and difficulty in sustaining long-term results still represent the main limitations to a broader use of ablative lasers. Based on actual evidence, the use of this technology should be restricted to patients with recalcitrant disease. Further studies will help establish optimal laser parameters and treatment regimens. PMID:23739704

Possibilities of a metal surface radioactive decontamination using a pulsed CO2 laser

NASA Astrophysics Data System (ADS)

Milijanic, Scepan S.; Stjepanovic, Natasa N.; Trtica, Milan S.

2000-01-01

There is a growing interest in the laser radioactive decontamination of metal surfaces. It offers advantages over conventional methods: improved safety, reduction of secondary waste, reduced waste volume, acceptable cost. A main mechanism of cleaning in by lasers is ablation. In this work a pulsed TEA CO2 laser was used for surface cleaning, primarily in order to demonstrate that the ablation from metal surfaces with this laser is possible even with relatively low pulse energies, and secondary, that it could be competitive with other lasers because of much higher energy efficiencies. The laser pulse contains two parts, one strong and shot peak at the beginning, followed with a tail. The beam was focused onto a contaminated surface with a KBr lens. The surface was contaminated with 137Cs. Three different metals were used: stainless steel, copper and aluminum. The evaporated material was pumped out in air atmosphere and transferred to a filter. Presence of the activity on the filter was proved by a germanium detector-multichannel analyzer. Activity levels were measured by a GM counter. Calculated decontamination factors as well as collection factors have shown that ablation takes place with relatively high efficiency of decontamination. This investigation suggests that decontamination using the CO2 laser should be seriously considered.

CO2 laser ablation of external genital lesions with a SwiftLase flashscanner: treatment of extramammary Paget's disease of the vulva, penile condylomata, and other lesions

NASA Astrophysics Data System (ADS)

Sacknoff, Eric J.; Schweitzer, Jay; Slatkine, Michael; Mead, Douglass S.

1995-05-01

The ability to vaporize extremely thin layers of epithelial tissue without any char and with minimal thermal necrosis is extremely advantageous in the treatment of superficial lesions of the external genitalia. We present a novel CO2 laser `SwiftLase' flashscan technology capable of providing char free ablation of 3 mm diameter lesions with only 150 micron residual thermal necrosis depth at power level as low as 10 watts. These power levels are achievable with a small transportable CO2 laser. The SwiftLaser is a miniature opto- mechanical scanner which homogeneously covers a 3 mm diameter surface with a 0.1 mm spot size focused beam within 0.1 seconds. The instantaneous beam's dwelling time is 1 millisecond. The instantaneous power density level at the focal point is higher than the threshold for char free ablation, thus providing a large char free ablation crater. Since depth of each ablated layer is 0.1 mm, the depth of treatment can be precisely controlled. The SwiftLaser technology has extensively and successfully been used in the last two years for the treatment of HPV in female lower tracts (Vulvectomy). The same technique may be performed with extramammary Paget's disease of the vulva, penile condylomata, and other epithelial disorders of the external genitalia without damage to surrounding healthy tissue. Technique and clinical results will be discussed.

Deep pulse fractional CO2 laser combined with a radiofrequency system: results of a case series.

PubMed

Cannarozzo, Giovanni; Sannino, Mario; Tamburi, Federica; Chiricozzi, Andrea; Saraceno, Rosita; Morini, Cristiano; Nisticò, Steven

2014-07-01

The purpose of this study was evaluation of the safety and efficacy of this new combined technology that adds deep ablation to thermal stimulation. Minimally ablative or subablative lasers, such as fractional CO2 lasers, have been developed in an attempt to achieve the same clinical results observed with traditional ablative lasers, but with fewer side effects. Despite being an ablative laser, the system used in this study is able to produce a fractional supply of the beam of light. Fractional ablation of skin is performed through the development of microscopic vertical columns surrounded by spared areas of epidermis and dermis, ensuring rapid wound healing and minimum down time. Simultaneous synchronized delivery of a radiofrequency (RF) current to the deeper layers of the skin completes the therapeutic scenario, ensuring an effective skin tightening effect over the entire treated area. Nine adult patients were treated for wrinkles and acne scars using this new laser technology. An independent observer evaluated the improvement using a five point scale. All patients had good results in terms of improvement of skin texture, with mild and transitory side effects. This novel combined system produced improvement in wrinkles and acne scars, with progressive enhancement of skin tone and elasticity.

Reduction of post-surgical scarring with the use of ablative fractional CO2 lasers: A pilot study using a porcine model.

PubMed

Baca, Marissa E; Neaman, Keith C; Rapp, Derek A; Burton, Michael E; Mann, Robert J; Renucci, John D

2017-01-01

Wound healing inevitably leads to scarring, which leads to functional and cosmetic defects. It is the goal of this study to investigate the immediate use of ablative fractional CO 2 lasers to reduce post-operative scarring secondary to surgical wounds. In this prospective controlled study, 20 surgical incisions were created on each of three pigs. Fifteen of the incisions were treated with an ablative fractional CO 2 laser at one of three laser settings. The remaining five incisions served as a control. Punch biopsies were taken post-operatively over time. Digital photographs were taken of each incisional scar at each time period. Blinded evaluators used a previously verified scoring system to score photographs of the incisional scars taken at the 6 month time period. With regards to the comparison between the three individual laser treatment groups and the control, there were no statistically significant effects for treatment (P = 0.40), time (P = 0.48), or for the interaction of time and treatment (P = 0.57). With regards to the visual assessment tool, there were no statistically significant differences between treatments for Overall Appearance (P = 0.21) or for Total Score (P = 0.24). In the limited setting of this pilot study, treatment of surgical incisions with ablative fractional CO 2 lasers does not significantly lessen scar formation. In addition, photographic analysis was not able to demonstrate a significant difference. Future studies on this topic will need a larger sample size to better answer whether a statistically significant difference may exist. Lasers Surg. Med. 49:122-128, 2017. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Effects of pulsed CO2 laser in caries selective ablation

NASA Astrophysics Data System (ADS)

Colojoara, Carmen; David, Ion; Marinovici, Mariana

1995-03-01

We have evaluated the effect of pulsed carbon dioxide laser in the treatment for deep carious decay. The so called `caries profonda' is still a problem for conservative dentistry. A `Valvfivre' Master 20S carbon dioxide laser was pulsed to determine the effects on dentine and for testing the properties of softened dentine in selective ablation. Laser treatment parameters were from 1 to 2 W, 50 to 150 ms, 200 to 320 Hz. Fifteen human teeth samples were exposed to irradiation: extracted third molar were exposed to CO2 pulsed laser to determine in vitro the effects on pulp morphology. The tissue samples were analyzed histologically and by means of scanning electron microscopy for evidence of thermal damage. Next, we have evaluated the morphologic changes in vivo on 10 cases in patients with deep carious decay. Pulsed infrared lasers are capable of inducing physical and chemical changes in dentine structure. The results showed an artificially sclerosing and micro-hardness on the remaining dentine. CO2 laser can vaporized carious dentine.

The spectrum of laser skin resurfacing: nonablative, fractional, and ablative laser resurfacing.

PubMed

Alexiades-Armenakas, Macrene R; Dover, Jeffrey S; Arndt, Kenneth A

2008-05-01

The drive to attain cosmetic facial enhancement with minimal risk and rapid recovery has inspired the field of nonsurgical skin rejuvenation. Laser resurfacing was introduced in the 1980s with continuous wave carbon dioxide (CO(2)) lasers; however, because of a high rate of side effects, including scarring, short-pulse, high-peak power, and rapidly scanned, focused-beam CO(2) lasers and normal-mode erbium-doped yttrium aluminium garnet lasers were developed, which remove skin in a precisely controlled manner. The prolonged 2-week recovery time and small but significant complication risk prompted the development of non-ablative and, more recently, fractional resurfacing in order to minimize risk and shorten recovery times. Nonablative resurfacing produces dermal thermal injury to improve rhytides and photodamage while preserving the epidermis. Fractional resurfacing thermally ablates microscopic columns of epidermal and dermal tissue in regularly spaced arrays over a fraction of the skin surface. This intermediate approach increases efficacy as compared to nonablative resurfacing, but with faster recovery as compared to ablative resurfacing. Neither nonablative nor fractional resurfacing produces results comparable to ablative laser skin resurfacing, but both have become much more popular than the latter because the risks of treatment are limited in the face of acceptable improvement. At the completion of this learning activity, participants should be familiar with the spectrum of lasers and light technologies available for skin resurfacing, published studies of safety and efficacy, indications, methodologies, side effects, complications, and management.

Effects of Laser Wavelength on Ablator Testing

NASA Technical Reports Server (NTRS)

White, Susan M.

2014-01-01

Wavelength-dependent or spectral radiation effects are potentially significant for thermal protection materials. NASA atmospheric entry simulations include trajectories with significant levels of shock layer radiation which is concentrated in narrow spectral lines. Tests using two different high powered lasers, the 10.6 micron LHMEL I CO2 laser and the near-infrared 1.07 micron fiber laser, on low density ablative thermal protection materials offer a unique opportunity to evaluate spectral effects. Test results indicated that the laser wavelength can impact the thermal response of an ablative material, in terms of bond-line temperatures, penetration times, mass losses, and char layer thicknesses.

Rapid fibrin plug formation within cutaneous ablative fractional CO2 laser lesions.

PubMed

Kositratna, Garuna; Evers, Michael; Sajjadi, Amir; Manstein, Dieter

2016-02-01

Ablative fractional laser procedures have been shown to facilitate topical drug delivery into the skin. Past studies have mainly used ex vivo models to demonstrate enhanced drug delivery and in vivo studies have investigated laser created channels over a time course of days and weeks rather than within the first few minutes and hours after exposures. We have noticed rapid in vivo fibrin plug formation within ablative fractional laser lesions impairing passage through the laser created channels. In vivo laser exposures were performed in a porcine model. A fractional CO2 laser (AcuPulse™ system, AcuScan 120™ handpiece, Lumenis, Inc., Yokneam, Israel) was programmed in quasi-continuous wave (QCW) mode, at 40W, 50 mJ per pulse, 5% coverage, nominal 120 µm spot size, 8 × 8 mm square pattern, 169 MTZs per scan. Six millimeters punch biopsies were procured at 0, 2, 5, 10, 15, 30, 60, 90 minutes after completion of each scan, then fixed in 10% formalin. 12 repeats were performed of each time point. Skin samples were processed for serial vertically cut paraffin sections (5 μm collected every 25 μm) then H&E and special immunohistochemistry staining for fibrin and platelet. Dimensions of Microscopic Treatment Zones (MTZs) and extent of fibrin plug were assessed and quantified histologically. Ex vivo laser exposures of the identical laser parameter were performed on porcine and human skin at different storage conditions. Histology procured at various predetermined time intervals after in vivo fractional CO2 laser exposures revealed a rapidly forming fibrin plug initiating at the bottom of the MTZ lesions. At longer time intervals, the fibrin plug was extending towards the superficial sections. Within the first 5 minutes, more than 25% length of the entire laser-ablated channel was filled with a fibrin plug. With increased time intervals, the cavity was progressively filled with a fibrin plug. At 90 minutes, more than 90% length of the entire laser-ablated channel was occluded. Ex vivo exposures failed to produce any significant fibrin plug formation. The current study has demonstrated rapid fibrin plug formation after ablative fractional laser procedures. It was shown that the passage through laser created pathways is critically time dependent for in vivo exposures. In contrast, ex vivo exposures do not exhibit such time dependent passage capacity. In particular, drug, substance, and cell delivery studies for ablative fractional laser treatments should take early fibrin plug formation into consideration and further investigate the impact on transdermal delivery. © 2015 Wiley Periodicals, Inc.

CO{sub 2} Laser Ablation Propulsion Area Scaling With Polyoxymethylene Propellant

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sinko, John E.; Ichihashi, Katsuhiro; Ogita, Naoya

The topic of area scaling is of great importance in the laser propulsion field, including applications to removal of space debris and to selection of size ranges for laser propulsion craft in air or vacuum conditions. To address this issue experimentally, a CO{sub 2} laser operating at up to 10 J was used to irradiate targets. Experiments were conducted in air and vacuum conditions over a range of areas from about 0.05-5 cm{sup 2} to ablate flat polyoxymethylene targets at several fluences. Theoretical effects affecting area scaling, such as rarefaction waves, thermal diffusion, and diffraction, are discussed in terms ofmore » the experimental results. Surface profilometry was used to characterize the ablation samples. A CFD model is used to facilitate analysis, and key results are compared between experimental and model considerations. The dependence of key laser propulsion parameters, including the momentum coupling coefficient and specific impulse, are calculated based on experimental data, and results are compared to existing literature data.« less

Ablative fractional lasers (CO(2) and Er:YAG): a randomized controlled double-blind split-face trial of the treatment of peri-orbital rhytides.

PubMed

Karsai, Syrus; Czarnecka, Agnieszka; Jünger, Michael; Raulin, Christian

2010-02-01

Ablative fractional lasers were introduced for treating facial rhytides in an attempt to achieve results comparable to traditional ablative resurfacing but with fewer side effects. However, there is conflicting evidence on how well this goal has generally been achieved as well as on the comparative value of fractional CO(2) and Er:YAG lasers. The present study compares these modalities in a randomized controlled double-blind split-face study design. Twenty-eight patients were enrolled and completed the entire study. Patients were randomly assigned to receive a single treatment on each side of the peri-orbital region, one with a fractional CO(2) and one with a fractional Er:YAG laser. The evaluation included the profilometric measurement of wrinkle depth, the Fitzpatrick wrinkle score (both before and 3 months after treatment) as well as the assessment of side effects and patient satisfaction (1, 3, 6 days and 3 months after treatment). Both modalities showed a roughly equivalent effect. Wrinkle depth and Fitzpatrick score were reduced by approximately 20% and 10%, respectively, with no appreciable difference between lasers. Side effects and discomfort were slightly more pronounced after Er:YAG treatment in the first few days, but in the later course there were more complaints following CO(2) laser treatment. Patient satisfaction was fair and the majority of patients would have undergone the treatment again without a clear preference for either method. According to the present study, a single ablative fractional treatment session has an appreciable yet limited effect on peri-orbital rhytides. When fractional CO(2) and Er:YAG lasers are used in such a manner that there are comparable post-operative healing periods, comparable cosmetic improvement occurs. Multiple sessions may be required for full effect, which cancels out the proposed advantage of fractional methods, that is, fewer side effects and less down time.

Flexible CO2 laser and submucosal gel injection for safe endoluminal resection in the intestines.

PubMed

Au, Joyce T; Mittra, Arjun; Wong, Joyce; Carpenter, Susanne; Carson, Joshua; Haddad, Dana; Monette, Sebastien; Ezell, Paula; Patel, Snehal; Fong, Yuman

2012-01-01

The CO(2) laser's unique wavelength of 10.6 μm has the advantage of being readily absorbed by water but historically limited it to line-of-sight procedures. Through recent technological advances, a flexible CO(2) laser fiber has been developed and holds promise for endoluminal surgery. We examined whether this laser, along with injection of a water-based gel in the submucosal space, will allow safe dissection of the intestines and enhance the potential of this tool for minimally invasive surgery. Using an ex vivo model with porcine intestines, spot ablation was performed with the flexible CO(2) laser at different power settings until transmural perforation. Additionally, excisions of mucosal patches were performed by submucosal dissection with and without submucosal injection of a water-based gel. With spot ablation at 5 W, none of the specimens was perforated by 5 min, which was the maximum recorded time. The time to perforation was significantly shorter with increased laser power, and gel pretreatment protected the intestines against spot ablation, increasing the time to perforation from 6 to 37 s at 10 W and from 1 to 7 s at 15 W. During excision of mucosal patches, 56 and 83% of untreated intestines perforated at 5 and 10 W, respectively. Gel pretreatment prior to excision protected all intestines against perforation. These specimens were verified to be intact by inflation with air to over 100 mmHg. Furthermore, excision of the mucosal patch was complete in gel-pretreated specimens, whereas 22% of untreated specimens had residual islands of mucosa after excision. The flexible CO(2) laser holds promise as a precise dissection and cutting tool for endoluminal surgery of the intestines. Pretreatment with a submucosal injection of a water-based gel protects the intestines from perforation during ablation and mucosal dissection.

Selective laser ablation of carious lesions using simultaneous scanned near-IR diode and CO2 lasers

NASA Astrophysics Data System (ADS)

Chan, Kenneth H.; Fried, Daniel

2017-02-01

Previous studies have established that carious lesions can be imaged with high contrast using near-IR wavelengths coincident with high water absorption, namely 1450-nm, without the interference of stains. It has been demonstrated that computer-controlled laser scanning systems utilizing IR lasers operating at high pulse repetition rates can be used for serial imaging and selective removal of caries lesions. In this study, a point-to-point scanning system was developed integrating a 1450-nm diode laser with the CO2 ablation laser. This approach is advantageous since it does not require an expensive near-IR camera. In this pilot study, we demonstrate the feasibility of a combined NIR and IR laser system for the selective removal of carious lesions.

Selective Laser Ablation of Carious Lesions using Simultaneous Scanned Near-IR Diode and CO2 Lasers.

PubMed

Chan, Kenneth H; Fried, Daniel

2017-01-28

Previous studies have established that carious lesions can be imaged with high contrast using near-IR wavelengths coincident with high water absorption, namely 1450-nm, without the interference of stains. It has been demonstrated that computer-controlled laser scanning systems utilizing IR lasers operating at high pulse repetition rates can be used for serial imaging and selective removal of caries lesions. In this study, a point-to-point scanning system was developed integrating a 1450-nm diode laser with the CO 2 ablation laser. This approach is advantageous since it does not require an expensive near-IR camera. In this pilot study, we demonstrate the feasibility of a combined NIR and IR laser system for the selective removal of carious lesions.

Residual energy deposition in dental enamel during IR laser ablation at 2.79, 2.94, 9.6, and 10.6 μm

NASA Astrophysics Data System (ADS)

Ragadio, Jerome N.; Lee, Christian K.; Fried, Daniel

2000-03-01

The objective of this study was to measure the residual heat deposition during laser ablation at those IR laser wavelengths best suited for the removal of dental caries. The principal factor limiting the rate of laser ablation of dental hard tissue is the risk of excessive heat accumulation in the tooth, which has the potential for causing damage to the pulp. Optimal laser ablation systems minimize the residual energy deposition in the tooth by transferring deposited laser energy to kinetic and internal energy of ejected tissue components. The residual heat deposition in the tooth was measured at laser wavelengths of 2.79, 2.94, 9.6 and 10.6 micrometer and pulse widths of 150 ns - 150 microsecond(s) . The residual energy was at a minimum for fluences well above the ablation threshold where it saturates at values from 25 - 70% depending on pulse duration and wavelength for the systems investigated. The lowest values of the residual energy were measured for short (less than 20 microseconds) CO2 laser pulses at 9.6 micrometer and for Q-switched erbium laser pulses. This work was supported by NIH/NIDCR R29DE12091 and the Center for Laser Applications in Medicine, DOE DEFG0398ER62576.

Near-IR imaging of erbium laser ablation with a water spray

NASA Astrophysics Data System (ADS)

Darling, Cynthia L.; Maffei, Marie E.; Fried, William A.; Fried, Daniel

2008-02-01

Near-IR (NIR) imaging can be used to view the formation of ablation craters during laser ablation since the enamel of the tooth is almost completely transparent near 1310-nm1. Laser ablation craters can be monitored under varying irradiation conditions to assess peripheral thermal and transient-stress induced damage, measure the rate and efficiency of ablation and provide insight into the ablation mechanism. There are fundamental differences in the mechanism of enamel ablation using erbium lasers versus carbon dioxide laser systems due to the nature of the primary absorber and it is necessary to have water present on the tooth surface for efficient ablation at erbium laser wavelengths. In this study, sound human tooth sections of approximately 2-3-mm thickness were irradiated by free running and Q-switched Er:YAG & Er:YSGG lasers under varying conditions with and without a water spray. The incision area in the interior of each sample was imaged using a tungsten-halogen lamp with a band-pass filter centered at 1310-nm combined with an InGaAs area camera with a NIR zoom microscope. Obvious differences in the crater evolution were observed between CO2 and erbium lasers. Ablation stalled after a few laser pulses without a water spray as anticipated. Efficient ablation was re-initiated by resuming the water spray. Micro-fractures were continuously produced apparently driven along prism lines during multi-pulse ablation. These fractures or fissures appeared to merge together as the crater evolved to form the leading edge of the ablation crater. These observations support the proposed thermo-mechanical mechanisms of erbium laser involving the strong mechanical forces generated by selective absorption by water.

Near-infrared image-guided laser ablation of dental decay

NASA Astrophysics Data System (ADS)

Tao, You-Chen; Fried, Daniel

2009-09-01

Image-guided laser ablation systems are now feasible for dentistry with the recent development of nondestructive high-contrast imaging modalities such as near-IR (NIR) imaging and optical coherence tomography (OCT) that are capable of discriminating between sound and demineralized dental enamel at the early stages of development. Our objective is to demonstrate that images of demineralized tooth surfaces have sufficient contrast to be used to guide a CO2 laser for the selective removal of natural and artificial caries lesions. NIR imaging and polarization-sensitive optical coherence tomography (PS-OCT) operating at 1310-nm are used to acquire images of natural lesions on extracted human teeth and highly patterned artificial lesions produced on bovine enamel. NIR and PS-OCT images are analyzed and converted to binary maps designating the areas on the samples to be removed by a CO2 laser to selectively remove the lesions. Postablation NIR and PS-OCT images confirmed preferential removal of demineralized areas with minimal damage to sound enamel areas. These promising results suggest that NIR and PS-OCT imaging systems can be integrated with a CO2 laser ablation system for the selective removal of dental caries.

Near-infrared image-guided laser ablation of dental decay

PubMed Central

Tao, You-Chen; Fried, Daniel

2009-01-01

Image-guided laser ablation systems are now feasible for dentistry with the recent development of nondestructive high-contrast imaging modalities such as near-IR (NIR) imaging and optical coherence tomography (OCT) that are capable of discriminating between sound and demineralized dental enamel at the early stages of development. Our objective is to demonstrate that images of demineralized tooth surfaces have sufficient contrast to be used to guide a CO2 laser for the selective removal of natural and artificial caries lesions. NIR imaging and polarization-sensitive optical coherence tomography (PS-OCT) operating at 1310-nm are used to acquire images of natural lesions on extracted human teeth and highly patterned artificial lesions produced on bovine enamel. NIR and PS-OCT images are analyzed and converted to binary maps designating the areas on the samples to be removed by a CO2 laser to selectively remove the lesions. Postablation NIR and PS-OCT images confirmed preferential removal of demineralized areas with minimal damage to sound enamel areas. These promising results suggest that NIR and PS-OCT imaging systems can be integrated with a CO2 laser ablation system for the selective removal of dental caries. PMID:19895146

Near-infrared image-guided laser ablation of dental decay.

PubMed

Tao, You-Chen; Fried, Daniel

2009-01-01

Image-guided laser ablation systems are now feasible for dentistry with the recent development of nondestructive high-contrast imaging modalities such as near-IR (NIR) imaging and optical coherence tomography (OCT) that are capable of discriminating between sound and demineralized dental enamel at the early stages of development. Our objective is to demonstrate that images of demineralized tooth surfaces have sufficient contrast to be used to guide a CO(2) laser for the selective removal of natural and artificial caries lesions. NIR imaging and polarization-sensitive optical coherence tomography (PS-OCT) operating at 1310-nm are used to acquire images of natural lesions on extracted human teeth and highly patterned artificial lesions produced on bovine enamel. NIR and PS-OCT images are analyzed and converted to binary maps designating the areas on the samples to be removed by a CO(2) laser to selectively remove the lesions. Postablation NIR and PS-OCT images confirmed preferential removal of demineralized areas with minimal damage to sound enamel areas. These promising results suggest that NIR and PS-OCT imaging systems can be integrated with a CO(2) laser ablation system for the selective removal of dental caries.

Graphite and ablative material response to CO2 laser, carbon-arc, and xenon-arc radiation

NASA Technical Reports Server (NTRS)

Brewer, W. D.

1976-01-01

The behavior was investigated of graphite and several charring ablators in a variety of high-radiative heat-flux environments. A commercial-grade graphite and nine state-of-the-art charring ablators were subjected to various radiative environments produced by a CO2 laser and a carbon arc. Graphite was also tested in xenon-arc radiation. Heat-flux levels ranged from 10 to 47 MW/sq m. Tests were conducted in air, nitrogen, helium, and a CO2-N2 mixture which simulated the Venus atmosphere. The experimental results were compared with theoretical results obtained with a one-dimensional charring-ablator analysis and a two-dimensional subliming-ablator analysis. Neither the graphite nor the charring ablators showed significant differences in appearance or microstructure after testing in the different radiative environments. The performance of phenolic nylon and graphite was predicted satisfactorily with existing analyses and published material property data. Good agreement between experimental and analytical results was obtained by using sublimation parameters from a chemical nonequilibrium analysis of graphite sublimation. Some charring ablators performed reasonably well and could withstand radiative fluxes of the level encountered in certain planetary entries. Other materials showed excessive surface recession and/or large amounts of cracking and spalling, and appear to be unsuitable for severe radiative environments.

Dental hard tissue modification and removal using sealed transverse excited atmospheric-pressure lasers operating at lambda=9.6 and 10.6 um

NASA Astrophysics Data System (ADS)

Fried, Daniel; Ragadio, Jerome N.; Akrivou, Maria; Featherstone, John D.; Murray, Michael W.; Dickenson, Kevin M.

2001-04-01

Pulsed CO2 lasers have been shown to be effective for both removal and modification of dental hard tissue for the treatment of dental caries. In this study, sealed transverse excited atmospheric pressure (TEA) laser systems optimally tuned to the highly absorbed 9.6 micrometers wavelength were investigated for application on dental hard tissue. Conventional TEA lasers produce an initial high energy spike at the beginning of the laser pulse of submicrosecond duration followed by a long tail of about 1 - 4 microsecond(s) . The pulse duration is well matched to the 1 - 2 microsecond(s) thermal relaxation time of the deposited laser energy at 9.6 micrometers and effectively heats the enamel to the temperatures required for surface modification at absorbed fluences of less than 0.5 J/cm2. Thus, the heat deposition in the tooth and the corresponding risk of pulpal necrosis from excessive heat accumulation is minimized. At higher fluences, the high peak power of the laser pulse rapidly initiates a plasma that markedly reduces the ablation rate and efficiency, severely limiting applicability for hard tissue ablation. By lengthening the laser pulse to reduce the energy distributed in the initial high energy spike, the plasma threshold can be raised sufficiently to increase the ablation rate by an order of magnitude. This results in a practical and efficient CO2 laser system for caries ablation and surface modification.

Fractional CO2 laser resurfacing of photoaged facial and non-facial skin: histologic and clinical results and side effects.

PubMed

Sasaki, Gordon H; Travis, Heather M; Tucker, Barbara

2009-12-01

CO(2) fractional ablation offers the potential for facial and non-facial skin resurfacing with minimal downtime and rapid recovery. The purpose of this study was (i) to document the average depths and density of adnexal structures in non-lasered facial and non-facial body skin; (ii) to determine injury in ex vivo human thigh skin with varying fractional laser modes; and (iii) to evaluate the clinical safety and efficacy of treatments. Histologies were obtained from non-lasered facial and non-facial skin from 121 patients and from 14 samples of excised lasered thigh skin. Seventy-one patients were evaluated after varying energy (mJ) and density settings by superficial ablation, deeper penetration, and combined treatment. Skin thickness and adnexal density in non-lasered skin exhibited variable ranges: epidermis (47-105 mum); papillary dermis (61-105 mum); reticular dermis (983-1986 mum); hair follicles (2-14/ HPF); sebaceous glands (2-23/HPF); sweat glands (2-7/HPF). Histological studies of samples from human thigh skin demonstrated that increased fluencies in the superficial, deep and combined mode resulted in predictable deeper levels of ablations and thermal injury. An increase in density settings results in total ablation of the epidermis. Clinical improvement of rhytids and pigmentations in facial and non-facial skin was proportional to increasing energy and density settings. Patient assessments and clinical gradings by the Wilcoxon's test of outcomes correlated with more aggressive settings. Prior knowledge of normal skin depths and adnexal densities, as well as ex vivo skin laser-injury profiles at varying fluencies and densities, improve the safety and efficiency of fractional CO(2) for photorejuvenation of facial and non-facial skin.

Photorejuvenation: still not a fully established clinical tool for cosmetic treatment

NASA Astrophysics Data System (ADS)

Gong, Wei; Xie, Shusen; Li, Hui

2006-01-01

Several methods have been used to improve the esthetic appearance of photodamaged skin including dermabrasion, chemical peels and laser resurfacing using CO2 and Er:YAG laser. These procedures sacrifice epidermis, resulting in a long recuperation period and potential complications including persistent scarring, infection, hyperpigmentation, etc. Compared to ablative CO2 or Er:YAG laser resurfacing, non-ablative photorejuvenation technologies are playing an increasing role in the treatment of photodamaged skin. The clinical objective of which is to maximize thermal damage to upper dermis while minimizing injury to overlying skin. A variety of laser and non-laser systems have been used in the initial stage for this treatment. In our review, different treatment modalities have resulted in varying degrees of clinical effects. The basic mechanisms relate to improvement in employing non-ablative technologies are also discussed. Photorejuvenation is still not a fully established clinical tool for cosmetic treatment according to our review, therefore more research on basic mechanisms should be made.

In-vitro ablation of fibrocartilage by XeCl excimer laser

NASA Astrophysics Data System (ADS)

Buchelt, Martin; Papaioannou, Thanassis; Fishbein, Michael C.; Peters, Werner; Beeder, Clain; Grundfest, Warren S.

1991-07-01

A 308 nm excimer laser was employed for ablation of human fibrocartilage. Experiments were conducted in vitro. The tissue response was investigated with respect to dosimetry (ablation rate versus radiant exposure) and thermal effect (thermographic analysis). Irradiation was performed via a 600 um fiber, with radiant exposures ranging between 20mj/mm2 and 80mj/mm2, at 20Hz. The ablation rates were found to range from 3um/pulse to 80um/pulse depending on the radiant exposure and/or the applied pressure on the delivery system. Thermographic analysis, during ablation, revealed maximum average temperatures of about 65 degree(s)C. Similar measurements performed, for the purpose of comparison, with a CW Nd:YAG and a CW CO2 laser showed higher values, of the order of 200 degree(s)C.

Prevention of airway fires: testing the safety of endotracheal tubes and surgical devices in a mechanical model.

PubMed

Roy, Soham; Smith, Lee P

2015-01-01

This study was designed to assess the ability of carbon dioxide (CO2) lasers and radiofrequency ablation devices (Coblator) (ArthoCare Corporation, Sunnyvale, CA) to ignite either a non-reinforced (polyvinylchloride) endotracheal tube (ETT) or an aluminum and fluoroplastic wrapped silicon ("laser safe") ETT at varying titrations of oxygen in a mechanical model of airway surgery. Non-reinforced and laser safe ETTs were suspended in a mechanical model imitating endoscopic airway surgery. A CO2 laser set at 5-30 watts was fired at the ETT at oxygen concentrations ranging from 21% to 88%. The process was repeated using a radiofrequency ablation (RFA) device. All trials were repeated to ensure accuracy. The CO2 laser ignited a fire when contacting a non-reinforced ETT in under 2 seconds at oxygen concentrations as low as 44%. The CO2 laser could not ignite a laser safe ETT under any conditions, unless it struck the non-reinforced distal tip of the ETT. With the RFA, a fire could not be ignited with either reinforced or non-reinforced ETTs. RFA presents no risk of ignition in simulated airway surgery. CO2 lasers should be utilized with a reinforced ETT or no ETT, as fires can easily ignite when lasers strike a non-reinforced ETT. Decreasing the fraction of inspired oxygen reduces the risk of fire. Copyright © 2015 Elsevier Inc. All rights reserved.

CO laser angioplasty system: efficacy of manipulatable laser angioscope catheter

NASA Astrophysics Data System (ADS)

Arai, Tsunenori; Kikuchi, Makoto; Mizuno, Kyoichi; Sakurada, Masami; Miyamoto, Akira; Arakawa, Koh; Kurita, Akira; Nakamura, Haruo; Takeuchi, Kiyoshi; Utsumi, Atsushi; Akai, Yoshiro

1992-08-01

A percutaneous transluminal coronary angioplasty system using a unique combination of CO laser (5 micrometers ) and As-S infrared glass fiber under the guidance of a manipulatable laser angioscope catheter is described. The ablation and guidance functions of this system are evaluated. The angioplasty treatment procedure under angioscope guidance was studied by in vitro model experiment and in vivo animal experiment. The whole angioplasty system is newly developed. That is, a transportable compact medical CO laser device which can emit up to 10 W, a 5 F manipulatable laser angioscope catheter, a thin CO laser cable of which the diameter is 0.6 mm, an angioscope imaging system for laser ablation guidance, and a system controller were developed. Anesthetized adult mongrel dogs (n equals 5) with an artificial complete occlusion in the femoral artery and an artificial human vessel model including occluded or stenotic coronary artery were used. The manipulatability of the catheter was drastically improved (both rotation and bending), therefore, precise control of ablation to expand stenosis was obtained. A 90% artificial stenosis made of human yellow plaque in 4.0 mm diameter in the vessel was expanded to 70% stenosis by repetitive CO laser ablations of which total energy was 220 J. All procedures were performed and controlled under angioscope visualization.

Flexible CO2 laser and submucosal gel injection for safe endoluminal resection in the intestines

PubMed Central

Au, Joyce T.; Mittra, Arjun; Wong, Joyce; Carpenter, Susanne; Carson, Joshua; Haddad, Dana; Monette, Sebastien; Ezell, Paula; Patel, Snehal

2012-01-01

Background The CO2 laser’s unique wavelength of 10.6 µm has the advantage of being readily absorbed by water but historically limited it to line-of-sight procedures. Through recent technological advances, a flexible CO2 laser fiber has been developed and holds promise for endoluminal surgery. We examined whether this laser, along with injection of a water-based gel in the submucosal space, will allow safe dissection of the intestines and enhance the potential of this tool for minimally invasive surgery. Methods Using an ex vivo model with porcine intestines, spot ablation was performed with the flexible CO2 laser at different power settings until transmural perforation. Additionally, excisions of mucosal patches were performed by submucosal dissection with and without submucosal injection of a water-based gel. Results With spot ablation at 5 W, none of the specimens was perforated by 5 min, which was the maximum recorded time. The time to perforation was significantly shorter with increased laser power, and gel pretreatment protected the intestines against spot ablation, increasing the time to perforation from 6 to 37 s at 10 W and from 1 to 7 s at 15 W. During excision of mucosal patches, 56 and 83% of untreated intestines perforated at 5 and 10 W, respectively. Gel pretreatment prior to excision protected all intestines against perforation. These specimens were verified to be intact by inflation with air to over 100 mmHg. Furthermore, excision of the mucosal patch was complete in gel-pretreated specimens, whereas 22% of untreated specimens had residual islands of mucosa after excision. Conclusion The flexible CO2 laser holds promise as a precise dissection and cutting tool for endoluminal surgery of the intestines. Pretreatment with a submucosal injection of a water-based gel protects the intestines from perforation during ablation and mucosal dissection. PMID:21898027

120: THE CLINICAL EFFECTIVENESS AND COST-EFFECTIVENESS OF FRACTIONAL CO2 LASER IN ACNE SCARS AND SKIN REJUVENATION: A SYSTEMATIC REVIEW AND ECONOMIC EVALUATION

PubMed Central

Yaaghoobian, Barmak; Sadeghi-Ghyassi, Fatemeh; Hajebrahimi, Sakineh

2017-01-01

Background and aims Skin rejuvenation is one of high demand cosmetic interventions in Iran. Fractional CO2 Laser is a high power ablative laser which has variety of utilization in medicine including treatment of acne scars and rejuvenation. The aim of this study was to evaluate the safety, efficacy, and cost-effectiveness of Fractional CO2 Laser in comparison with other methods of rejuvenation and acne scar treatment. Methods A systematic database search including Medline (via OVID and PubMed), EMBASE, CINHAL, Cochrane Library, CRD, SCOPUS and Web of Science conducted. After screening search results, selected publications appraised by CASP and Cochrane Collaboration's tool for assessing risk of bias and eligible studies included in the systematic review. In economic evaluation, all costs and benefits analyzed from Iran ministry of health's perspective. Results From 2667 publications, two randomized control trials were eligible and included in the study. The affectivity and complications of Fractional CO2 laser were comparable with Er: YAG but Fractional CO2 laser was 14.7% (P=0.01) more effective than Q-Switched ND: YAG laser. Cost affectivity of this method was the same as other alternative lasers. Conclusions Fractional CO2 laser is an effective and safe method for curing several kinds of skin. Never the less there was not sufficient evidence to support its advantage. This device has equal or lower price in comparison to competent technologies except for the non- fractional ablative Co2 laser that has the same or lower price and comparable effects.

Thermal effects on pulp due to laser and handpiece usage.

PubMed

Penn, Christina; Beninati, Christopher; Mariano, Alissa; Dooley, Daniel; Harsono, Masly; Perry, Ronald; Kugel, Gerard

2014-01-01

The study was designed to compare changes in pulpal temperature during ablation of dental hard tissue while using two established erbium dental laser systems, a new CO2 laser system, and a conventional high-speed handpiece. Eighty non-carious human extracted molars were separated into four sample groups of 20 teeth each. Three laser systems were used, respectively, to ablate the occlusal surface of the teeth in three of the groups for 60 seconds each. The high-speed handpiece was used to drill the occlusal surface of the fourth group for 60 seconds. Pulpal temperatures were measured using thermocouples inserted into each tooth's pulpal chamber prior to ablation. None of the average temperature increases approached the threshold of 5.5°C at which pulpal damage begins. On average, the pulpal temperature of teeth ablated with the Waterlase MD system increased the most (3.56°C). The traditional handpiece caused the lowest average temperature increase (1.57°C), followed by the LightWalker DT system (3.20°C) and the Solea CO2 system (3.30°C).

Microscopically proven cure of actinic cheilitis by CO/sub 2/ laser

DOE Office of Scientific and Technical Information (OSTI.GOV)

Whitaker, D.C.

1987-01-01

Actinic cheilitis is a premalignant condition of the lip frequently seen in individuals with chronic sun exposure. Various surgical and ablative therapies have been employed, but microscopic outcome has not been well documented. In this study CO/sub 2/ laser ablation was performed on 16 patients with actinic cheilitis that involved 50% or greater of the lower lip. Pre- and post-treatment biopsies were performed to assess results of therapy. After treatment all 16 patients showed microscopic clearing of atypical cells and disorderly maturation characteristic of actinic cheilitis. One patient had clinical recurrence at 14 months, which was retreated with laser.

Thermal damage produced by high-irradiance continuous wave CO2 laser cutting of tissue.

PubMed

Schomacker, K T; Walsh, J T; Flotte, T J; Deutsch, T F

1990-01-01

Thermal damage produced by continuous wave (cw) CO2 laser ablation of tissue in vitro was measured for irradiances ranging from 360 W/cm2 to 740 kW/cm2 in order to investigate the extent to which ablative cooling can limit tissue damage. Damage zones thinner than 100 microns were readily produced using single pulses to cut guinea pig skin as well as bovine cornea, aorta, and myocardium. Multiple pulses can lead to increased damage. However, a systematic decrease in damage with irradiance, predicted theoretically by an evaporation model of ablation, was not observed. The damage-zone thickness was approximately constant around the periphery of the cut, consistent with the existence of a liquid layer which stores heat and leads to tissue damage, and with a model of damage and ablation recently proposed by Zweig et al.

Dental hard tissue modification and removal using sealed TEA lasers operating at λ=9.6 and 10.6 μm

NASA Astrophysics Data System (ADS)

Fried, Daniel; Murray, Michael W.; Featherstone, John D. B.; Akrivou, Maria; Dickenson, Kevin M.; Duhn, Clifford W.; Ojeda, Orlando P.

1999-05-01

Pulsed CO2 lasers have been shown to be effective for both removal and modification of dental hard tissue for the treatment of dental caries. In this study, sealed TEA laser systems optimally tuned to the highly absorbed 9.6 μm wavelength were investigated for application on dental hard tissue. Conventional TEA lasers produce a laser pulse wit a 100-200 ns gain switched spike followed by a long tail of about 1-4 μs in duration. the pulse duration is well matched to the 1-2 μs thermal relaxation time of the deposited laser energy at 9.6 μm and effectively heats the enamel to temperatures required for surface modification for caries prevention at absorbed fluences of less than 0.5 J/cm2. Thus, the heat deposition in the tooth and the corresponding risk, of pulpal necrosis form excessive heat accumulation is minimized. At higher fluences the high peak power of the gain-switched spike rapidly initiates a plasma that markedly reduces the ablation rate and efficiency, severely limiting applicability for hard tissue ablation. By slightly stretching the pulse to reduce the energy distributed in the initial 100-200 ns of the laser pulse, the plasma threshold can be raised sufficiently to increase the ablation rate by an order of magnitude. This results in a practical and efficient CO2 laser system for caries ablation and surface modification.

Carbon dioxide (CO2) laser treatment of cutaneous papillomas in a common snapping turtle, Chelydra serpentina.

PubMed

Raiti, Paul

2008-06-01

Carbon dioxide (CO2) laser was used to treat multiple cutaneous papillomas on an adult female common snapping turtle, Chelydra serpentina serpentina. A combination of excisional and ablative techniques provided excellent intraoperative visibility and postoperative results due to the laser's unique ability to incise and vaporize soft tissue.

Near-infrared image-guided laser ablation of artificial caries lesions

NASA Astrophysics Data System (ADS)

Tao, You-Chen; Fan, Kenneth; Fried, Daniel

2007-02-01

Laser removal of dental hard tissue can be combined with optical, spectral or acoustic feedback systems to selectively ablate dental caries and restorative materials. Near-infrared (NIR) imaging has considerable potential for the optical discrimination of sound and demineralized tissue. The objective of this study was to test the hypothesis that two-dimensional NIR images of demineralized tooth surfaces can be used to guide CO II laser ablation for the selective removal of artificial caries lesions. Highly patterned artificial lesions were produced by submerging 5 x 5 mm2 bovine enamel samples in demineralized solution for a 9-day period while sound areas were protected with acid resistant varnish. NIR imaging and polarization sensitive optical coherence tomography (PS-OCT) were used to acquire depth-resolved images at a wavelength of 1310-nm. An imaging processing module was developed to analyze the NIR images and to generate optical maps. The optical maps were used to control a CO II laser for the selective removal of the lesions at a uniform depth. This experiment showed that the patterned artificial lesions were removed selectively using the optical maps with minimal damage to sound enamel areas. Post-ablation NIR and PS-OCT imaging confirmed that demineralized areas were removed while sound enamel was conserved. This study successfully demonstrated that near-IR imaging can be integrated with a CO II laser ablation system for the selective removal of dental caries.

Selective removal of demineralized enamel using a CO2 laser coupled with near-IR reflectance imaging

NASA Astrophysics Data System (ADS)

Tom, Henry; Chan, Kenneth H.; Saltiel, Daniel; Fried, Daniel

2015-02-01

Detection and diagnosis of early dental caries lesions can be difficult due to variable tooth coloration, staining of the teeth and poor contrast between sound and demineralized enamel. These problems can be overcome by using near-infrared (NIR) imaging. Previous studies have demonstrated that lasers can be integrated with NIR imaging devices, allowing image-guided ablation. The aim of this study was to demonstrate that NIR light at 1500 - 1700 nm can be used to guide a 9.3-μm CO2 laser for the selective ablation of early demineralization on tooth occlusal surfaces. The occlusal surfaces of ten sound human molars were used in this in-vitro study. Shallow simulated caries lesions of varying depth and position were produced on tooth occlusal surfaces using a demineralization solution. Sequential NIR reflectance images at 1500 - 1700 nm were used to guide the laser for selective ablation of the lesion areas. Digital microscopy and polarization sensitive optical coherence tomography (PS-OCT) were used to assess the selectivity of removal. This study demonstrates that high contrast NIR reflectance images can be used for the image-guided laser ablation of early demineralization from tooth occlusal surfaces.

Carbon dioxide laser ablation with immediate autografting in a full-thickness porcine burn model.

PubMed Central

Glatter, R D; Goldberg, J S; Schomacker, K T; Compton, C C; Flotte, T J; Bua, D P; Greaves, K W; Nishioka, N S; Sheridan, R L

1998-01-01

OBJECTIVE: To compare the long-term clinical and histologic outcome of immediate autografting of full-thickness burn wounds ablated with a high-power continuous-wave CO2 laser to sharply débrided wounds in a porcine model. SUMMARY BACKGROUND DATA: Continuous-wave CO2 lasers have performed poorly as tools for burn excision because the large amount of thermal damage to viable subeschar tissues precluded successful autografting. However, a new technique, in which a high-power laser is rapidly scanned over the eschar, results in eschar vaporization without significant damage to underlying viable tissues, allowing successful immediate autografting. METHODS: Full-thickness paravertebral burn wounds measuring 36 cm2 were created on 11 farm swine. Wounds were ablated to adipose tissue 48 hours later using either a surgical blade or a 150-Watt continuous-wave CO2 laser deflected by an x-y galvanometric scanner that translated the beam over the tissue surface, removing 200 microm of tissue per scan. Both sites were immediately autografted and serially evaluated clinically and histologically for 180 days. RESULTS: The laser-treated sites were nearly bloodless. The mean residual thermal damage was 0.18+/-0.05 mm. The mean graft take was 96+/-11% in manual sites and 93+/-8% in laser sites. On postoperative day 7, the thickness of granulation tissue at the graft-wound bed interface was greater in laser-debrided sites. By postoperative day 180, the manual and laser sites were histologically identical. Vancouver scar assessment revealed no differences in scarring at postoperative day 180. CONCLUSIONS: Long-term scarring, based on Vancouver scar assessments and histologic evaluation, was equivalent at 6 months in laser-ablated and sharply excised sites. Should this technology become practical, the potential clinical implications include a reduction in surgical blood loss without sacrifice of immediate engraftment rates or long-term outcome. Images Figure 1. Figure 2. Figure 3. Figure 4. PMID:9712572

New technique for the direct analysis of food powders confined in a small hole using transversely excited atmospheric CO(2) laser-induced gas plasma.

PubMed

Khumaeni, Ali; Ramli, Muliadi; Deguchi, Yoji; Lee, Yong Inn; Idris, Nasrullah; Kurniawan, Koo Hendrik; Lie, Tjung Jie; Kagawa, Kiichiro

2008-12-01

Taking advantage of the differences between the interactions of transversely excited atmospheric (TEA) CO(2) lasers with metal and with organic powder, a new technique for the direct analysis of food powder samples has been developed. In this technique, the powder samples were placed into a small hole with a diameter of 2 mm and a depth of 3 mm and covered by a metal mesh. The TEA CO(2) laser (1500 mJ, 200 ns) was focused on the powder sample surfaces, passing through the metal mesh, at atmospheric pressure in nitrogen gas. It is hypothesized that the small hole functions to confine the powder particles and suppresses the blowing-off of sample, while the metal mesh works as the source of electrons to initiate the strong gas breakdown plasma. The confined powder particles are then ablated by laser irradiation and the ablated particles move into the strong gas breakdown plasma region to be atomized and excited; this method cannot be applied for the case of Nd:YAG lasers because in such case the metal mesh itself was ablated by the laser irradiation. A quantitative analysis of a milk powder sample containing different concentrations of Ca was successfully demonstrated, resulting in a good linear calibration curve with high precision.

SwiftLase: a new technology for char-free ablation in rectal surgery

NASA Astrophysics Data System (ADS)

Arnold, David A.

1995-05-01

We describe layer-by-layer char-free ablation of hemorrhoids and other rectal lesions at very low CO2 laser power levels with a miniature `SwiftLaser' optomechanical flashscanner. Increased speed with excellent control, very shallow thermal damage, and less postoperative pain are the main advantages of the flashscan technology in rectal surgery.

Carbon dioxide laser ablation of dermatosis papulosa nigra: high satisfaction and few complications in patients with pigmented skin.

PubMed

Ali, Faisal R; Bakkour, Waseem; Ferguson, Janice E; Madan, Vishal

2016-04-01

Dermatosis papulosa nigra (DPN) is a common condition of pigmented skin. Whilst lesions are benign, they may be symptomatic or cosmetically disfiguring. Ablative lasers have previously been reported as a useful therapeutic modality in DPN. We report the largest case series to date of patients with DPN ablated with the carbon dioxide (CO2) laser. A retrospective case note review was conducted of all patients with DPN treated in our laser clinic in the last five years, and a post-treatment telephone survey was undertaken to assess patient satisfaction. Forty-five patients were identified, with a median age of 41 years (range 25-74 years), of whom 37 (82%) were female. The median number of treatments undertaken was three (range 1-10). Of the 18 respondents to the telephone survey, when asked to grade their satisfaction with the procedure out of 10, median response was 9.5 (range 6-10) with nine patients citing the maximum score of 10. All patients replied that their confidence had improved following the procedure and that they would recommend the treatment to other patients. Five respondents (28%) reported recurrence of a few lesions following CO2 laser ablation; the remaining 13 respondents (72%) reported no recurrence of DPN. No respondents reported any other post-procedural complications (including scarring, hypopigmentation and hyperpigmentation). We advocate use of the CO2 laser as a safe, convenient means of treating DPN, with a high degree of patient satisfaction, low recurrence rate and few complications.

Outcomes of fractional CO2 laser application in aesthetic surgery: a retrospective review.

PubMed

Neaman, Keith C; Baca, Marissa E; Piazza, Rocco C; VanderWoude, Douglas L; Renucci, John D

2010-01-01

Despite the effectiveness of ablative CO(2) laser resurfacing for facial rejuvenation, its application has been limited owing to an undesirable side-effect profile, including prolonged hyperemia and potential pigmentary changes. However, newer fractional CO(2) laser technology has reduced the recovery time and led to decreases in postprocedural hypo- and hyperpigmentation. The authors investigate the application and outcomes of ablative fractional technology in a private cosmetic surgery practice. In this retrospective cohort study, the charts of patients who received fractional CO(2) laser resurfacing between March 2007 and May 2008 were reviewed. Data regarding patient demographics, pretreatment regimens, detailed operative data, and posttreatment findings were obtained. The length of hyperemia (less than five weeks, five to eight weeks, and more than eight weeks), complication rates, and revision rates were analyzed. A satisfaction survey was also sent to all patients. Throughout the 19-month study period, 97 patients received 101 treatments with an average follow-up of 4.5 months. Full-face laser resurfacing was performed in 81.1% of patients, with 64.3% receiving their treatment under local anesthesia without sedation. Length of hyperemia was less than five weeks in 93%, five to eight weeks in 5.9%, and more than eight weeks in 0.9% of patients. Hyperpigmentation (9.9%), milia (6.9%), acne breakout (5.9%), and transient ectropion (0.9%) were less common. Patient satisfaction surveys revealed that a majority of patients were satisfied with their results. New fractional CO(2) laser skin resurfacing is associated with shorter periods of hyperemia, resulting in shorter recovery time in comparison with older ablative technology. The side-effect profile is minor and infrequent. This new technology provides significant clinical improvement with high patient satisfaction.

Selective Removal of Natural Occlusal Caries by Coupling Near-infrared Imaging with a CO2 Laser

PubMed Central

Tao, You-Chen; Fried, Daniel

2011-01-01

Laser removal of dental hard tissue can be combined with optical, spectral or acoustic feedback systems to selectively ablate dental caries and restorative materials. Near-infrared (NIR) imaging has considerable potential for the optical discrimination of sound and demineralized tissue. Last year we successfully demonstrated that near-IR images can be used to guide a CO2 laser ablation system for the selective removal of artificial caries lesions on smooth surfaces. The objective of this study was to test the hypothesis that two-dimensional near-infrared images of natural occlusal caries can be used to guide a CO2 laser for selective removal. Two-dimensional NIR images were acquired at 1310-nm of extracted human molar teeth with occlusal caries. Polarization sensitive optical coherence tomography (PS-OCT) was also used to acquire depth-resolved images of the lesion areas. An imaging processing module was developed to analyze the NIR imaging output and generate optical maps that were used to guide a CO2 laser to selectively remove the lesions at a uniform depth. Post-ablation NIR images were acquired to verify caries removal. Based on the analysis of the NIR images, caries lesions were selectively removed with a CO2 laser while sound tissues were conserved. However, the removal rate varied markedly with the severity of decay and multiple passes were required for caries removal. These initial results are promising but indicate that the selective removal of natural caries is more challenging than the selective removal of artificial lesions due to varying tooth geometry, the highly variable organic/mineral ratio in natural lesions and more complicated lesion structure. PMID:21909225

Selective Removal of Natural Occlusal Caries by Coupling Near-infrared Imaging with a CO(2) Laser.

PubMed

Tao, You-Chen; Fried, Daniel

2008-03-01

Laser removal of dental hard tissue can be combined with optical, spectral or acoustic feedback systems to selectively ablate dental caries and restorative materials. Near-infrared (NIR) imaging has considerable potential for the optical discrimination of sound and demineralized tissue. Last year we successfully demonstrated that near-IR images can be used to guide a CO(2) laser ablation system for the selective removal of artificial caries lesions on smooth surfaces. The objective of this study was to test the hypothesis that two-dimensional near-infrared images of natural occlusal caries can be used to guide a CO(2) laser for selective removal. Two-dimensional NIR images were acquired at 1310-nm of extracted human molar teeth with occlusal caries. Polarization sensitive optical coherence tomography (PS-OCT) was also used to acquire depth-resolved images of the lesion areas. An imaging processing module was developed to analyze the NIR imaging output and generate optical maps that were used to guide a CO(2) laser to selectively remove the lesions at a uniform depth. Post-ablation NIR images were acquired to verify caries removal. Based on the analysis of the NIR images, caries lesions were selectively removed with a CO(2) laser while sound tissues were conserved. However, the removal rate varied markedly with the severity of decay and multiple passes were required for caries removal. These initial results are promising but indicate that the selective removal of natural caries is more challenging than the selective removal of artificial lesions due to varying tooth geometry, the highly variable organic/mineral ratio in natural lesions and more complicated lesion structure.

Laser treatment in gynecology

NASA Astrophysics Data System (ADS)

de Riese, Cornelia

2004-07-01

This presentation is designed as a brief overview of laser use in gynecology, for non-medical researchers involved in development of new laser techniques. The literature of the past decade is reviewed. Differences in penetration, absorption, and suitable delivery media for the beams dictate clinical application. The use of CO2 laser in the treatment of uterine cervical intraepithelial lesions is well established and indications as well as techniques have not changed over 30 years. The Cochrane Systematic Review from 2000 suggests no obviously superior technique. CO2 laser ablation of the vagina is also established as a safe treatment modality for VAIN. CO2 laser permits treatment of lesions with excellent cosmetic and functional results. The treatment of heavy menstrual bleeding by destruction of the endometrial lining using various techniques has been the subject of a 2002 Cochran Database Review. Among the compared treatment modalities are newer and modified laser techniques. Conclusion by reviewers is that outcomes and complication profiles of newer techniques compare favorably with the gold standard of endometrial resection. The ELITT diode laser system is one of the new successful additions. CO2 laser is also the dominant laser type used with laparoscopy for ablation of endometriotic implants. Myoma coagulation or myolysis with Nd:Yag laser through the laparoscope or hysteroscope is a conservative treatment option. Even MRI guided percutaneous approaches have been described. No long-term data are available.

Laser cutting of bone tissue under bulk water with a pulsed ps-laser at 532 nm.

PubMed

Tulea, Cristian-Alexander; Caron, Jan; Gehlich, Nils; Lenenbach, Achim; Noll, Reinhard; Loosen, Peter

2015-10-01

Hard-tissue ablation was already investigated for a broad variety of pulsed laser systems, which cover almost the entire range of available wavelengths and pulse parameters. Most effective in hard-tissue ablation are Er:YAG and CO2 lasers, both utilizing the effect of absorption of infrared wavelengths by water and so-called explosive vaporization, when a thin water film or water–air spray is supplied. The typical flow rates and the water layer thicknesses are too low for surgical applications where bleeding occurs and wound flushing is necessary. We studied a 20 W ps-laser with 532 nm wavelength and a pulse energy of 1 mJ to effectively ablate bones that are submerged 14 mm under water. For these laser parameters, the plasma-mediated ablation mechanism is dominant. Simulations based on the blow-off model predict the cut depth and cross-sectional shape of the incision. The model is modified considering the cross section of the Gaussian beam, the incident angle, and reflections. The ablation rate amounts to 0.2  mm3/s, corresponding to an increase by at least 50% of the highest values published so far for ultrashort laser ablation of hard tissue.

The Mixed Processing Models Development Of Thermal Fracture And Laser Ablation On Glass Substrate

NASA Astrophysics Data System (ADS)

Huang, Kuo-Cheng; Wu, Wen-Hong; Tseng, Shih-Feng; Hwang, Chi-Hung

2011-01-01

As the industries of cell phone and LCD TV were vigorously flourishing and the manufacturing requirements for LCD glass substrate were getting higher, the thermal fracture cutting technology (TFCT) has progressively become the main technology for LCD glass substrate cutting. Due to using laser as the heat source, the TFCT has many advantages, such as uniform heating, small heat effect zone, and high cutting speed, smooth cutting surface and low residual stress, etc. Moreover, a general laser ablation processing or traditional diamond wheel cutting does not have the last two advantages. The article presents a mixed processing of glass substrate, which consists of TFCT and laser ablation mechanisms, and how to enhance the cutting speed with little ablation laser energy. In this study, a 10W Nd:YAG laser and a 40W CO2 laser are used as the heat source of TFCT and laser ablation processing, respectively. The result indicates that the speed of the mixed processing is more than twice the speed of TFCT. Furthermore, after the mixed processing, the residual stresses in the glass substrates are also smaller.

Near-IR Imaging of Thermal Changes in Enamel during Laser Ablation.

PubMed

Maung, Linn H; Lee, Chulsung; Fried, Daniel

2010-03-05

The objective of this work was to observe the various thermal-induced optical changes that occur in the near-infrared (NIR) during drilling in dentin and enamel with the laser and the high-speed dental handpiece. Tooth sections of ~ 3 mm-thickness were prepared from extracted human incisors (N=60). Samples were ablated with a mechanically scanned CO(2) laser operating at a wavelength of 9.3-µm, a 300-Hz laser pulse repetition rate, and a laser pulse duration of 10-20 µs. An InGaAs imaging camera was used to acquire real-time NIR images at 1300-nm of thermal and mechanical changes (cracks). Enamel was rapidly removed by the CO(2) laser without peripheral thermal damage by mechanically scanning the laser beam while a water spray was used to cool the sample. Comparison of the peripheral thermal and mechanical changes produced while cutting with the laser and the high-speed hand-piece suggest that enamel and dentin can be removed at high speed by the CO(2) laser without excessive peripheral thermal or mechanical damage. Only 2 of the 15 samples ablated with the laser showed the formation of small cracks while 9 out of 15 samples exhibited crack formation with the dental hand-piece. The first indication of thermal change is a decrease in transparency due to loss of the mobile water from pores in the enamel which increase light-scattering. To test the hypothesis that peripheral thermal changes were caused by loss of mobile water in the enamel, thermal changes were intentionally induced by heating the surface. The mean attenuation coefficient of enamel increased significantly from 2.12 ± 0.82 to 5.08 ± 0.98 with loss of mobile water due to heating.

Near-IR imaging of thermal changes in enamel during laser ablation

NASA Astrophysics Data System (ADS)

Maung, Linn H.; Lee, Chulsung; Fried, Daniel

2010-02-01

The objective of this work was to observe the various thermal-induced optical changes that occur in the near-infrared (NIR) during drilling in dentin and enamel with the laser and the high-speed dental handpiece. Tooth sections of ~ 3 mm-thickness were prepared from extracted human incisors (N=60). Samples were ablated with a mechanically scanned CO2 laser operating at a wavelength of 9.3-μm, a 300-Hz laser pulse repetition rate, and a laser pulse duration of 10-20 μs. An InGaAs imaging camera was used to acquire real-time NIR images at 1300-nm of thermal and mechanical changes (cracks). Enamel was rapidly removed by the CO2 laser without peripheral thermal damage by mechanically scanning the laser beam while a water spray was used to cool the sample. Comparison of the peripheral thermal and mechanical changes produced while cutting with the laser and the high-speed hand-piece suggest that enamel and dentin can be removed at high speed by the CO2 laser without excessive peripheral thermal or mechanical damage. Only 2 of the 15 samples ablated with the laser showed the formation of small cracks while 9 out of 15 samples exhibited crack formation with the dental hand-piece. The first indication of thermal change is a decrease in transparency due to loss of the mobile water from pores in the enamel which increase lightscattering. To test the hypothesis that peripheral thermal changes were caused by loss of mobile water in the enamel, thermal changes were intentionally induced by heating the surface. The mean attenuation coefficient of enamel increased significantly from 2.12 +/- 0.82 to 5.08 +/- 0.98 with loss of mobile water due to heating.

Near-IR Imaging of Thermal Changes in Enamel during Laser Ablation

PubMed Central

Maung, Linn H.; Lee, Chulsung; Fried, Daniel

2011-01-01

The objective of this work was to observe the various thermal-induced optical changes that occur in the near-infrared (NIR) during drilling in dentin and enamel with the laser and the high-speed dental handpiece. Tooth sections of ~ 3 mm-thickness were prepared from extracted human incisors (N=60). Samples were ablated with a mechanically scanned CO2 laser operating at a wavelength of 9.3-µm, a 300-Hz laser pulse repetition rate, and a laser pulse duration of 10–20 µs. An InGaAs imaging camera was used to acquire real-time NIR images at 1300-nm of thermal and mechanical changes (cracks). Enamel was rapidly removed by the CO2 laser without peripheral thermal damage by mechanically scanning the laser beam while a water spray was used to cool the sample. Comparison of the peripheral thermal and mechanical changes produced while cutting with the laser and the high-speed hand-piece suggest that enamel and dentin can be removed at high speed by the CO2 laser without excessive peripheral thermal or mechanical damage. Only 2 of the 15 samples ablated with the laser showed the formation of small cracks while 9 out of 15 samples exhibited crack formation with the dental hand-piece. The first indication of thermal change is a decrease in transparency due to loss of the mobile water from pores in the enamel which increase light-scattering. To test the hypothesis that peripheral thermal changes were caused by loss of mobile water in the enamel, thermal changes were intentionally induced by heating the surface. The mean attenuation coefficient of enamel increased significantly from 2.12 ± 0.82 to 5.08 ± 0.98 with loss of mobile water due to heating. PMID:21935291

Selective removal of natural occlusal caries by coupling near-infrared imaging with a CO II laser

NASA Astrophysics Data System (ADS)

Tao, You-Chen; Fried, Daniel

2008-02-01

Laser removal of dental hard tissue can be combined with optical, spectral or acoustic feedback systems to selectively ablate dental caries and restorative materials. Near-infrared (NIR) imaging has considerable potential for the optical discrimination of sound and demineralized tissue. Last year we successfully demonstrated that near-IR images can be used to guide a CO2 laser ablation system for the selective removal of artificial caries lesions on smooth surfaces. The objective of this study was to test the hypothesis that two-dimensional near-infrared images of natural occlusal caries can be used to guide a CO2 laser for selective removal. Two-dimensional NIR images were acquired at 1310-nm of extracted human molar teeth with occlusal caries. Polarization sensitive optical coherence tomography (PS-OCT) was also used to acquire depth-resolved images of the lesion areas. An imaging processing module was developed to analyze the NIR imaging output and generate optical maps that were used to guide a CO2 laser to selectively remove the lesions at a uniform depth. Post-ablation NIR images were acquired to verify caries removal. Based on the analysis of the NIR images, caries lesions were selectively removed with a CO2 laser while sound tissues were conserved. However, the removal rate varied markedly with the severity of decay and multiple passes were required for caries removal. These initial results are promising but indicate that the selective removal of natural caries is more challenging than the selective removal of artificial lesions due to varying tooth geometry, the highly variable organic/mineral ratio in natural lesions and more complicated lesion structure.

First bite syndrome: our experience of laser tympanic plexus ablation.

PubMed

Amin, N; Pelser, A; Weighill, J

2014-02-01

First bite syndrome is a condition characterised by severe facial pain brought on by the first bite of each meal. This can severely affect the patient's ability to eat. We present a 70-year-old woman for whom we performed a laser ablation of the left ear tympanic plexus, as treatment of first bite syndrome. A permeatal approach was used to raise a tympanomeatal flap. The tympanic plexus was identified on the promontory and a 4 mm2 area of the plexus was ablated using CO2 laser. The flap was repositioned and a dressing was placed with topical antibiotics. At two-month follow up, there was full resolution of the patient's symptoms. First bite syndrome carries a high morbidity; treatment options are variable, and often unsuccessful. We describe the first documented case of laser tympanic plexus ablation, with a very effective initial response. This procedure represents a useful therapeutic option for first bite syndrome.

Ablative fractional laser treatment for hypertrophic scars: comparison between Er:YAG and CO2 fractional lasers.

PubMed

Choi, Jae Eun; Oh, Ga Na; Kim, Jong Yeob; Seo, Soo Hong; Ahn, Hyo Hyun; Kye, Young Chul

2014-08-01

Nonablative fractional photothermolysis has been reported to show early promise in the treatment of hypertrophic scars, but there are few reports on ablative fractional photothermolysis for the treatment of hypertrophic scars. To evaluate and compare the efficacy and safety of Er:YAG fractional laser (EYFL) and CO2 fractional laser (CO2FL) for treatment of hypertrophic scars. Thirteen patients with hypertrophic scars were treated with 2,940 nm EYFL, and ten were treated with 10,600 nm CO2FL. An independent physician evaluator assessed the treatment outcomes using Vancouver scar scale (VSS) and 5-point grading scale (grade 0, no improvement; grade 1, 1-25%; grade 2, 26-50%; grade 3, 51-75%; grade 4, 76-100% improvement). Patients are queried about their subjective satisfaction with the treatment outcomes. After the final treatment, average percentage changes of VSS were 28.2% for EYFL and 49.8% for CO2FL. Improvement was evident in terms of pliability, while insignificant in terms of vascularity and pigmentation. Based on physician's global assessment, mean grade of 1.8 for EYFL and 2.7 for CO2FL was achieved. Patient's subjective satisfaction scores paralleled the physician's objective evaluation. CO2FL is a potentially effective and safe modality for the treatment of hypertrophic scars, particularly in terms of pliability.

Comparative analysis of the effects of CO2 fractional laser and sonophoresis on human skin penetration with 5-aminolevulinic acid.

PubMed

Choi, J H; Shin, E J; Jeong, K H; Shin, M K

2017-11-01

Successful delivery of a photosensitizer into the skin is an important factor for effective photodynamic therapy (PDT). The effective method to increase drug penetration within short incubation time overcoming skin barrier have been investigated. This study was performed to analyze and compare the effectiveness of ablative fractional laser (FXL) pretreatment and/or sonophoresis for enhancing the penetration of 5-aminolevulinic acid (ALA) into human skin in vivo. Twenty-four identical 1 × 1 cm 2 treatment areas were mapped on the backs of ten healthy male subjects. Each area received FXL pretreatment and/or sonophoresis with different energy settings and ALA incubation times. After treatments, porphyrin fluorescence reflecting the ALA penetration were measured. Application of ablative CO 2 FXL pretreatment resulted to higher fluorescence intensities than the non-treatment group. Incubation times were positively correlated with the increments of ALA penetration. However, increasing pulse energy or combining with sonophoresis did not show additional positive effects on ALA penetration. Ablative CO 2 FXL pretreatment effectively facilitated ALA penetration in human skin in vivo. Ablative CO 2 FXL alone without sonophoresis setting pulse energy of 10 and 20 mJ with more than 60 min of ALA incubation time could be an ideal setting for ALA penetration.

Flash scanning the CO2 laser: a revival of the CO2 laser in plastic surgery

NASA Astrophysics Data System (ADS)

Lach, Elliot

1994-09-01

The CO2 laser has broad clinical application yet also presents a number of practical disadvantages. These drawbacks have limited the success and utilization of this laser in plastic surgery. Flashscanner technology has recently been used for char-free CO2 laser surgery of the oropharynx, the external female genital tract, and perirectal mucosa. A commercially available optomechanical flashscanner unit `Swiftlase,' was adapted to a CO2 laser and used for treatment in numerous plastic surgical applications. Conditions and situations that were treated in this study included generalized neurofibromatosis, tuberous sclerosis, rhinophyma, viral warts, breast reconstruction, and deepithelialization prior to microsurgery or local flap transfer and/or skin graft placement. There were no significant wound healing complications. Some patients previously sustained undue scarring from conventional CO2 laser surgery. Conservative, primarily ablative CO2 laser surgery with the Swiftlase has usefulness for treatment of patients in plastic surgery including those that were previously unsuccessfully treated.

Near-IR Image-Guided Laser Ablation of Demineralization on Tooth Occlusal Surfaces

PubMed Central

Tom, Henry; Chan, Kenneth H.; Darling, Cynthia L.; Fried, Daniel

2016-01-01

Introduction Studies have shown that reflectance images at near-IR wavelengths coincident with higher water absorption are well-suited for image-guided laser ablation of carious lesions since the contrast between sound and demineralized enamel is extremely high and interference from stains is minimized. The objective of this study was to demonstrate that near-IR reflectance images taken at a wavelength range of 1,500–1,700 nm can be used to guide a 9.3 μm CO2 laser for the selective ablation of early demineralization on tooth occlusal surfaces. Methods The occlusal surfaces of ten sound human molars were used in this in vitro study. Shallow simulated caries lesions with random patterns and varying depth and position were produced on tooth occlusal surfaces. Sequential near-IR reflectance images at 1,500–1,700 nm were used to guide the laser for the selective removal of the demineralized enamel. Digital microscopy and polarization sensitive optical coherence tomography (PS-OCT) were used to assess selectivity. Results Images taken before and after lesion removal suggest that the demineralized areas were removed with high selectivity. Although the estimated volume of tissue ablated was typically higher than the initial lesion volume measured with PS-OCT, the volume of enamel removed by the laser correlated well with the initial lesion volume. Conclusion Sequential near-IR reflectance images at 1,500–1,700 nm can be used to guide a 9.3 μm CO2 laser for the selective ablation of early demineralization on tooth occlusal surfaces. PMID:26763111

Fs-laser ablation of teeth is temperature limited and provides information about the ablated components.

PubMed

de Menezes, Rebeca Ferraz; Harvey, Catherine Malinda; de Martínez Gerbi, Marleny Elizabeth Márquez; Smith, Zachary J; Smith, Dan; Ivaldi, Juan C; Phillips, Alton; Chan, James W; Wachsmann-Hogiu, Sebastian

2017-10-01

The goal of this work is to investigate the thermal effects of femtosecond laser (fs-laser) ablation for the removal of carious dental tissue. Additional studies identify different tooth tissues through femtosecond laser induced breakdown spectroscopy (fsLIBS) for the development of a feedback loop that could be utilized during ablation in a clinical setting. Scanning Election Microscope (SEM) images reveal that minimal morphological damages are incurred at repetition rates below the carbonization threshold of each tooth tissue. Thermal studies measure the temperature distribution and temperature decay during laser ablation and after laser cessation, and demonstrate that repetition rates at or below 10kHz with a laser fluence of 40 J/cm 2 would inflict minimal thermal damage on the surrounding nerve tissues and provide acceptable clinical removal rates. Spectral analysis of the different tooth tissues is also conducted and differences between the visible wavelength fsLIBS spectra are evident, though more robust classification studies are needed for clinical translation. These results have initiated a set of precautionary recommendations that would enable the clinician to utilize femtosecond laser ablation for the removal of carious lesions while ensuring that the solidity and utility of the tooth remain intact. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Properties of Laser Ablation Products of Delrin with CO2 Laser

DTIC Science & Technology

2004-07-01

was then measured with the fast detector. Optical observation in air shows that a jet of luminous gas exits the hole to the rear side of the 16 probe...g) Ab la te Pressure (mbar) Diagramm 12 Ablated mass per pulse at a pulse energy of 280 J vs. pressure 34 independent of the metal...m itt ed P ul se (µ s) Incident Laser Pulse Energy (J) Diagramm 32 Pulse duration shortening effect with incident pulse energy in tr

Highly efficient nonthermal ablation of bone under bulk water with a frequency-doubled Nd:YVO4 picosecond laser

NASA Astrophysics Data System (ADS)

Tulea, C.; Caron, J.; Wahab, H.; Gehlich, N.; Hoefer, M.; Esser, D.; Jungbluth, B.; Lenenbach, A.; Noll, R.

2013-03-01

Several laser systems in the infrared wavelength range, such as Nd:YAG, Er:YAG or CO2 lasers are used for efficient ablation of bone tissue. Here the application of short pulses in coaction with a thin water film results in reduced thermal side effects. Nonetheless up to now there is no laser-process for bone cutting in a clinical environment due to lack of ablation efficiency. Investigations of laser ablation rates of bone tissue using a rinsing system and concerning bleedings have not been reported yet. In our study we investigated the ablation rates of bovine cortical bone tissue, placed 1.5 cm deep in water under laminar flow conditions, using a short pulsed (25 ps), frequency doubled (532 nm) Nd:YVO4 laser with pulse energies of 1 mJ at 20 kHz repetition rate. The enhancement of the ablation rate due to debris removal by an additional water flow from a well-directed blast pipe as well as the negative effect of the admixture of bovine serum albumin to the water were examined. Optical Coherence Tomography (OCT) was used to measure the ablated volume. An experimental study of the depth dependence of the ablation rate confirms a simplified theoretical prediction regarding Beer-Lambert law, Fresnel reflection and a Gaussian beam profile. Conducting precise incisions with widths less than 1.5 mm the maximum ablation rate was found to be 0.2 mm3/s. At depths lower than 100 μm, while the maximum depth was 3.5 mm.

[The use of lasers in dermatology].

PubMed

Lecocq, C; Pirard, D; del Marmol, V; Berlingin, E

2013-01-01

Albert Einstein is undoubtedly the father of lasers. But it is not until 1964 that the first dermatological lasers were introduced. The Nd-YAG laser, the CO2 laser were developed by Kumar Patel. In a 40 year period lasers not only were diversified but have also become safer and miniaturized. This article hopes to strengthen general practionners' and specialist's knowledge of the different categories of available lasers. The most frequently used ones are ablative lasers (CO2-Erbium), vascular lasers (Nd-YAG, KTP, pulsed dye laser) and the pigment lasers (Q-Switched Nd-YAG, Alexandrite). A description of these lasers and their indications in dermatology will be discussed.

Femtosecond laser ablation of enamel

NASA Astrophysics Data System (ADS)

Le, Quang-Tri; Bertrand, Caroline; Vilar, Rui

2016-06-01

The surface topographical, compositional, and structural modifications induced in human enamel by femtosecond laser ablation is studied. The laser treatments were performed using a Yb:KYW chirped-pulse-regenerative amplification laser system (560 fs and 1030 nm) and fluences up to 14 J/cm2. The ablation surfaces were studied by scanning electron microscopy, grazing incidence x-ray diffraction, and micro-Raman spectroscopy. Regardless of the fluence, the ablation surfaces were covered by a layer of resolidified material, indicating that ablation is accompanied by melting of hydroxyapatite. This layer presented pores and exploded gas bubbles, created by the release of gaseous decomposition products of hydroxyapatite (CO2 and H2O) within the liquid phase. In the specimen treated with 1-kHz repetition frequency and 14 J/cm2, thickness of the resolidified material is in the range of 300 to 900 nm. The micro-Raman analysis revealed that the resolidified material contains amorphous calcium phosphate, while grazing incidence x-ray diffraction analysis allowed detecting traces of a calcium phosphate other than hydroxyapatite, probably β-tricalcium phosphate Ca3), at the surface of this specimen. The present results show that the ablation of enamel involves melting of enamel's hydroxyapatite, but the thickness of the altered layer is very small and thermal damage of the remaining material is negligible.

Investigation of ultrashort-pulsed laser on dental hard tissue

NASA Astrophysics Data System (ADS)

Uchizono, Takeyuki; Awazu, Kunio; Igarashi, Akihiro; Kato, Junji; Hirai, Yoshito

2007-02-01

Ultrashort-pulsed laser (USPL) can ablate various materials with precious less thermal effect. In laser dentistry, to solve the problem that were the generation of crack and carbonized layer by irradiating with conventional laser such as Er:YAG and CO II laser, USPL has been studied to ablate dental hard tissues by several researchers. We investigated the effectiveness of ablation on dental hard tissues by USPL. In this study, Ti:sapphire laser as USPL was used. The laser parameter had the pulse duration of 130 fsec, 800nm wavelength, 1KHz of repetition rate and the average power density of 90~360W/cm2. Bovine root dentin plates and crown enamel plates were irradiated with USPL at 1mm/sec using moving stage. The irradiated samples were analyzed by SEM, EDX, FTIR and roughness meter. In all irradiated samples, the cavity margin and wall were sharp and steep, extremely. In irradiated dentin samples, the surface showed the opened dentin tubules and no smear layer. The Ca/P ratio by EDX measurement and the optical spectrum by FTIR measurement had no change on comparison irradiated samples and non-irradiated samples. These results confirmed that USPL could ablate dental hard tissue, precisely and non-thermally. In addition, the ablation depths of samples were 10μm, 20μm, and 60μm at 90 W/cm2, 180 W/cm2, and 360 W/cm2, approximately. Therefore, ablation depth by USPL depends on the average power density. USPL has the possibility that can control the precision and non-thermal ablation with depth direction by adjusting the irradiated average power density.

Outcomes of radiofrequency ablation (RFA) and CO2 laser for early glottic cancer.

PubMed

Shuang, Yu; Li, Chao; Zhou, Xuan; Huang, Yongwang; Zhang, Lun

2016-01-01

In the present study, the voice and functional outcomes of radiofrequency ablation (RFA) and CO2 laser for early glottic cancer were evaluated. One hundred sixty eight patients with early glottic cancer from October 2007 to June 2015 were included. Ninety-seven patients underwent RFA and seventy-one patients underwent CO2 laser. The operation time and score of visual analog scale (VAS) for pain on the second day after surgery were recorded. The electronic laryngoscopy was performed at one week, one month and three months of postoperation. The operation time in RFA was shorter than that in CO2 laser (8.52±1.43min vs. 11.76±1.67min, P<0.05). There was no statistical difference in VAS scores between two operation methods (2.86±0.52 vs. 2.89±0.68, P>0.05). One month after operation, the mucosal recovery in RFA group was better than that in CO2 laser group (P<0.05). The alterations of acoustic parameters Jitter, Shimmer and HNR at three time points after operation showed statistical significances in both RFA and CO2 laser groups (P<0.05). The significant differences in acoustic parameters between two groups were also observed (P<0.05). There were no differences in three-year survival rate, local recurrence rate, recurrence rate with anterior commissure involvement and postoperative adhesion rate with anterior commissure between the patients with RFA and CO2 laser (P>0.05). No patient underwent tracheotomy and had symptoms of bucking, dyspnea, severe pain, hemoptysis and other serious complications. Both RFA and CO2 laser are safe and effective for the treatment of early glottic cancer. RFA has the advantage of quick voice recovery, low mucosa injury and short operation time, which is worthy for wide clinical application. Copyright © 2016 Elsevier Inc. All rights reserved.

CTE:YAG laser applications in dentistry

NASA Astrophysics Data System (ADS)

Shori, Ramesh K.; Fried, Daniel; Featherstone, John D. B.; Kokta, Milan R.; Duhn, Clifford W.

1998-04-01

The suitability of CTE:YAG laser radiation was investigated for caries preventive laser treatments and caries ablation. Although, CTE:YAG laser radiation at 2.69 micrometer is less highly absorbed by dental hard tissues than other erbium laser wavelengths, namely 2.79 and 2.94 micrometer, it can readily be transmitted through a conventional low hydroxyl fiber with minimal loss. These studies show that reasonable ablation rates and efficiencies are obtainable with both free running (200 microseconds) and Q-switched (100 ns) laser pulses on both dentin and enamel with the application of a relatively thick layer of water to the tissue surface. The water served to remove tissue char and debris from the ablation site leaving a clean crater. However, mechanical forces produced during the energetic ablative process resulted in peripheral mechanical damage to the tissue. Surface dissolution studies on enamel indicated that CTE:YAG radiation inhibited surface dissolution by organic acid by 60 - 70% compared to unirradiated controls, albeit, at fluences an order of magnitude higher than those required for CO2 laser radiation. This layer system may be suitable for dental hard tissue applications if mechanical damage can be mitigated. This work was supported by NIH/NIDR Grants R29DE12091 and R01DE09958.

Femtosecond laser ablation of cemented carbides: properties and tribological applications

NASA Astrophysics Data System (ADS)

Dumitru, G.; Romano, V.; Weber, H. P.; Gerbig, Y.; Haefke, H.; Bruneau, S.; Hermann, J.; Sentis, M.

Laser ablation with fs laser pulses was performed in air on cobalt cemented tungsten carbide by means of a Ti : sapphire laser (800 nm, 100 fs). Small and moderate fluences (2, 5, 10 J/cm2) and up to 5×104 pulses per irradiated spot were used to drill holes with aspect ratios up to 10. Cross-section cuts from laser-irradiated samples were produced and they were analysed with optical microscopy and SEM. EDX analyses were carried out on selected zones. Quasi-cylindrical holes were found for 2 J/cm2, whereas for 5 and 10 J/cm2 irregular shapes (lobes, bottoms wider than hole entrances) were found to occur after a given number of incident pulses. Layers with modified structure were evidenced at pore walls. SEM revealed a denser structure, while EDX analyses showed uniform and almost similar contents of W, C, and Co in these layers. As a direct application, patterning of coated WC-Co was carried out with 2 J/cm2 and 100 pulses per pore. The resulted surfaces were tribologically tested and these tests revealed an improved friction and wear behaviour.

Pulpal Effects of Enamel Ablation With a Microsecond Pulsed λ=9.3-μm CO2 Laser

PubMed Central

Staninec, Michal; Darling, Cynthia L.; Goodis, Harold E.; Pierre, Daniel; Cox, Darren P.; Fan, Kenneth; Larson, Michael; Parisi, Renaldo; Hsu, Dennis; Manesh, Saman K.; Ho, Chi; Hosseini, Mehran; Fried, Daniel

2011-01-01

Background and Objectives In vitro studies have shown that CO2 lasers operating at the highly absorbed 9.3 and 9.6-μm wavelengths with a pulse duration in the range of 10–20-microsecond are well suited for the efficient ablation of enamel and dentin with minimal peripheral thermal damage. Even though these CO2 lasers are highly promising, they have yet to receive FDA approval. Clinical studies are necessary to determine if excessive heat deposition in the tooth may have any detrimental pulpal effects, particularly at higher ablative fluencies. The purpose of this study was to evaluate the pulpal safety of laser irradiation of tooth occlusal surfaces under the conditions required for small conservative preparations confined to enamel. Study Design/Materials and Methods Test subjects requiring removal of third molar teeth were recruited and teeth scheduled for extraction were irradiated using a pulsed CO2 laser at a wavelength of 9.3 μm operating at 25 or 50 Hz using a incident fluence of 20 J/cm2 for a total of 3,000 laser pulses (36 J) for both rates with water cooling. Two control groups were used, one with no treatment and one with a small cut made with a conventional high-speed hand-piece. No anesthetic was used for any of the procedures and tooth vitality was evaluated prior to treatment by heat, cold and electrical testing. Short term effects were observed on teeth extracted within 72 hours after treatment and long term effects were observed on teeth extracted 90 days after treatment. The pulps of the teeth were fixed with formalin immediately after extraction and subjected to histological examination. Additionally, micro-thermocouple measurements were used to estimate the potential temperature rise in the pulp chamber of extracted teeth employing the same irradiation conditions used in vivo. Results Pulpal thermocouple measurements showed the internal temperature rise in the tooth was within safe limits, 3.3±4°C without water cooling versus 1.7±6°C with water-cooling, n=25, P<0.05. None of the control or treatment groups showed any deleterious effects on pulpal tissues and none of the 29 test-subjects felt pain or discomfort after the procedure. Only two test-subjects felt discomfort from “cold sensitivity” during the procedure caused by the water-spray. Conclusion It appears that this CO2 laser can ablate enamel safely without harming the pulp under the rate of energy deposition employed in this study. Lasers Surg. PMID:19347946

Understanding the tissue interaction of new treatment modalities in laparoscopic surgery in view of safe and effective application (Conference Presentation)

NASA Astrophysics Data System (ADS)

Grimbergen, Matthijs C. M.; Klaessens, John H.; van der Veen, Albert J.; Verdaasdonk, Rudolf M.

2016-03-01

During laparoscopic surgery, devices are require to either cut, ablate or coagulate tissue and veins with high precision and controlled lateral damage preferably in an one-for-all modality. The tissue interactions of 3 new treatment modalities were studied using special imaging techniques to obtain a better understanding the working mechanism in view of effective and safe application. The Plasmajet produces a high temperature ionized gas 'flame' directed to the tissue surface at the tip of a 4 mm diameter rigid hand piece. The Lumenis DUO CO2 laser enables endoscopic laser energy delivery through a 1 mm outer diameter flexible hollow waveguide. The 2 µm 'Thulium' laser is delivered by (standard) 400 µm diameter optical fiber. Thermal imaging and Schlieren techniques were used to assess the superficial ablative and coagulation effects these surgical instruments scanning at preset velocities and distances from the surface of biological tissues and phantoms . The CO2 was very effective in tissue ablation even at a distance up to 10 mm due to a very small diverging beam from the hollow waveguide. In contrast, the Thulium laser showed less ablation and increasing coagulation at larger distance to the tissue. The gas 'flame' of the Plasmajet spread the thermal energy over the surface for effective superficial ablation and coagulation. However, the pressure of the gas flow is substantial on the tissue surface creating turbulence and even indirect cooling. The specific ablation and coagulation effects of the three treatment modalities have to be appreciate and the effective and safe application will depend on the preference and skills of the surgeon

Laser ablation of surgical margins after excisional partial vulvectomy for VIN: Effect on recurrence.

PubMed

Brown, John V; Goldstein, Bram H; Rettenmaier, Mark A; Aylward, Michelle M; Graham, Cheri L; Micha, John P

2005-05-01

To determine the recurrence rates in patients who underwent different surgical treatments for vulvar intraepithelial neoplasia (VIN) 2 and 3. Data on every patient who underwent surgical treatment for VIN 2 or 3 between January 1994 and December 2002 by a single gynecologic oncologist were retrospectively reviewed. The recurrence rates for 3 different surgical therapies were analyzed using Fischer's exact test. Thirty-three patients, who had a median age of 46 years (range, 31-80), were identified. The preoperative biopsy demonstrated VIN 2 or 3 in 9.1% and 90.9% of the patients, respectively. The following primary surgical procedures were employed: 16 patients (48.4%) underwent excisional partial vulvectomy with CO2 laser ablation of the margins, 10 patients (30.3%) had CO2 laser ablation alone, 6 patients (18.2%) had an excisional partial vulvectomy, and 1 patient (3.0%) was. treated with the ultrasonic surgical aspirator. No patient had invasive disease. Recurrent disease was seen in 7 patients (70.0%) treated by laser alone, 3 patients (50.0%) who had an excisional partial vulvectomy and 1 patient (6.25%) who underwent a combined laser and excisional partial vulvectomy (p = 0.0016). The results of this small study suggest that laser and excisional partial vulvectomy for the treatment of VIN 2 and 3 may be associated with a lower recurrence rate than either modality alone. A larger study will be needed to confirm these results.

A new sealed RF-excited CO2 laser for enamel ablation operating at 9.4-μm with a pulse duration of 26-μs

PubMed Central

Chan, Kenneth H.; Jew, Jamison M.; Fried, Daniel

2016-01-01

Several studies over the past 20 years have shown that carbon dioxide lasers operating at wavelengths between 9.3 and 9.6-μm with pulse durations near 20-μs are ideal for hard tissue ablation. Those wavelengths are coincident with the peak absorption of the mineral phase. The pulse duration is close to the thermal relaxation time of the deposited energy of a few microseconds which is short enough to minimize peripheral thermal damage and long enough to minimize plasma shielding effects to allow efficient ablation at practical rates. The desired pulse duration near 20-μs has been difficult to achieve since it is too long for transverse excited atmospheric pressure (TEA) lasers and too short for radio-frequency (RF) excited lasers for efficient operation. Recently, Coherent Inc. (Santa Clara, CA) developed the Diamond J5-V laser for microvia drilling which can produce laser pulses greater than 100-mJ in energy at 9.4-μm with a pulse duration of 26-μs and it can achieve pulse repetition rates of 3 KHz. We report the first results using this laser to ablate dental enamel. Efficient ablation of dental enamel is possible at rates exceeding 50-μm per pulse. This laser is ideally suited for the selective ablation of carious lesions. PMID:27006521

Histologic comparison of the CO2 laser and Nd:YAG with and without water/air surface cooling on tooth root structure

NASA Astrophysics Data System (ADS)

Cobb, Charles M.; Spencer, Paulette; McCollum, Mark H.

1995-05-01

Specimens consisted of 18 extracted single rooted teeth unaffected by periodontal disease. After debriding roots, specimens were randomly divided into 4 treatment groups and subjected to a single pass, at varying energy densities, of a CO2, Nd:YAG, and Nd:YAG with air/water surface cooling (Nd:YAG-C). The rate of exposure was controlled at 4 mm/sec. Approximate energy densities were: CO2, 138, 206, 275, and 344 J/cm2; Nd:YAG, 114, 171, 229, and 286 J/cm2; Nd:YAG-C, 286, 343, 514, and 571 J/cm2. The CO2 laser was used both in continuous and pulsed beam modes (20 Hz, 0.01 sec pulse length and 0.8 mm dia spot size) whereas the Nd:YAG and Nd:YAG-C were preset at 50 Hz, 0.08 sec pulse length and 0.6 mm dia spot size. Specimen examination by SEM revealed, for all lasers, a direct correlation between increasing energy densities and depth of tissue ablation and width of tissue damage. However, to achieve the same relative dept of tissue ablation, the Nd:YAG-C required higher energy densities than either the CO2 or Nd:YAG lasers. The Nd:YAG-C generated a cavitation with sharply defined margins. Furthermore, regardless of energy density, and in contrast with other laser types, areas treated with the Nd:YAG-C did not exhibit collateral zones of heat damaged surface tissue.

Histological evaluation of vertical laser channels from ablative fractional resurfacing: an ex vivo pig skin model.

PubMed

Skovbølling Haak, Christina; Illes, Monica; Paasch, Uwe; Hædersdal, Merete

2011-07-01

Ablative fractional resurfacing (AFR) represents a new treatment potential for various skin conditions and new laser devices are being introduced. It is important to gain information about the impact of laser settings on the dimensions of the created laser channels for obtaining a safe and efficient treatment outcome. The aim of this study was to establish a standard model to document the histological tissue damage profiles after AFR and to test a new laser device at diverse settings. Ex vivo abdominal pig skin was treated with a MedArt 620, prototype fractional carbon dioxide (CO(2)) laser (Medart, Hvidovre, Denmark) delivering single microbeams (MB) with a spot size of 165 μm. By using a constant pulse duration of 2 ms, intensities of 1-18 W, single and 2-4 stacked pulses, energies were delivered in a range from 2-144 mJ/MB. Histological evaluations included 3-4 high-quality histological measurements for each laser setting (n = 28). AFR created cone-shaped laser channels. Ablation depths varied from reaching the superficial dermis (2 mJ, median 41 μm) to approaching the subcutaneous fat (144 mJ, median 1,943 μm) and correlated to the applied energy levels in an approximate linear relation (r(2) = 0.84, p < 0.001). The dermal ablation width increased slightly within the energy range of 4-144 mJ (median 163 μm). The thickness of the coagulation zone reached a plateau around 65 μm at energies levels above 16 mJ. The calculated volumes of ablated tissue increased with increasing energies. We suggest this ex vivo pig skin model to characterize AFR laser channels histologically.

Fractional CO2 Laser Treatment of the Vestibule for Patients with Vestibulodynia and Genitourinary Syndrome of Menopause: A Pilot Study.

PubMed

Murina, Filippo; Karram, Mickey; Salvatore, Stefano; Felice, Raffaele

2016-12-01

Chronic vulvar pain and burning remains one of the most perplexing problems faced by practicing gynecologists. To evaluate the effectiveness and safety of the application of micro-ablative fractional CO 2 laser to the vulvar vestibule in the management of patients with vulvar pain from vestibulodynia or genitourinary syndrome of menopause. Patients (N = 70) underwent fractional micro-ablative CO 2 laser treatment for vestibular pain plus vestibulodynia (n = 37) or genitourinary syndrome of menopause (n = 33). Inclusion criteria were the existence of vestibular atrophic changes and the absence of moderate or severe pelvic floor hypertonic dysfunction. A visual analog scale of pain and the Marinoff score of dyspareunia were chosen to evaluate improvement. Grading of vestibular health also was quantified using a four-point scoring system (0 = no atrophy, 3 = severe atrophy). Data were collected at baseline, at weeks 4, 8, and 12, and 4 months after the final treatment. For visual analog scale and dyspareunia scoring and for the overall vestibular health index scoring, statistically significant improvement was noted after three sessions of vestibular fractional CO 2 laser treatment. Improvement gradually increased throughout the study period and was maintained through the 4-month follow-up visit. There was no statistically significant difference in outcomes between the two study groups. No adverse events from fractional CO 2 laser treatment were noted. Overall, 67.6% of patients stated significant improvement from the laser procedure. This preliminary case series showed encouraging results using fractional CO 2 laser treatment of the vestibule in women with vestibulodynia and genitourinary syndrome of menopause. Copyright © 2016 International Society for Sexual Medicine. Published by Elsevier Inc. All rights reserved.

Carbon Nanotube Synthesis in a Flame with Independently Prepared Laser-Ablated Catalyst Particles

NASA Technical Reports Server (NTRS)

VanderWal, Randall L.; Berger, Gordon M.; Ticich, Thomas M.

2003-01-01

Laser ablation has been used ex situ to create metal nanoparticles for introduction into a reactive pyrolysis flame. By prior synthesis of the metal nanoparticles, the effects of the reactive gases can be clearly separated from the pyrolysis chemistry of a solvent carrier, as when nebulized solutions are used. Moreover, varying reactivity issues associated with particle growth and size are bypassed. Our results show that Fe selectively reacts with CO to produce nanotubes, whereas Ni selectively reacts with C2H2 to produce nanofibers. These observations are interpreted through the donation and withdrawal of electron density between the adsorbate's molecular orbitals and surface atoms of the metal nanoparticle. The rate of reaction of Ni with only C2H2 is found to be greater than the rate with C2H2 and CO. This suggests that CO inhibits the Ni-catalyzed reaction.

Laser radiation at various wavelengths for decompression of intervertebral disk. Experimental observations on human autopsy specimens.

PubMed

Choy, D S; Altman, P A; Case, R B; Trokel, S L

1991-06-01

The interaction of laser radiation with the nucleus pulposus from autopsy specimens of human intervertebral disks was evaluated at different wavelengths (193 nm, 488 nm & 514 nm, 1064 nm, 1318 nm, 2150 nm, 2940 nm, and 10600 nm). A significant correlation of linear least squares fit of the mass ablated as a function of incident energy was found for all lasers used except the Excimer at 193 nm. The 2940-nm Erbium:YAG laser was most efficient in terms of mass of disk ablated per joule in the limited lower range where this wavelength was observed. At higher energy levels, the CO2 laser in the pulsed mode was most efficient. However, the Nd:YAG 1064-nm and 1318-nm lasers are currently best suited for percutaneous laser disk decompression because of the availability of usable waveguides. Carbonization of tissue with the more penetrating Nd:YAG 1064-nm laser increases the efficiency of tissue ablation and makes it comparable to the Nd:YAG 1318-nm laser.

Ablation velocity and thermal damage of myocardial tissue using a CO2 laser for transmyocardial laser revascularization

NASA Astrophysics Data System (ADS)

Sachinopoulou, Anna; Beek, Johan F.; van Leeuwen, Ton G. J. M.; Beek, W. J.

1999-02-01

Transmyocardial Laser Revascularization (TMLR) is a new experimental method for relief of angina pectoris in patients with severe coronary artery disease. TMLR aims at revascularizing chronic hibernating myocardium by creating transmural channels. One of the working mechanism hypotheses is that the endocardial side of the channels remains open, enabling perfusion of the hibernating myocardium directly from the left ventricle. Although the working mechanism of TMLR is still unknown (perfusion through patent channels, induction of angiogenesis, relief of angina through destruction of sympatic innervation, others?), first clinical studies are successful. Currently, the Heart LaserTM and other CO2 lasers, XeCl Excimer laser and Ho:YAG laser are under investigation for TMLR. The initial attempts of TMR with needles were soon replaced by laser induced channels. Efforts were focused on developing a CO2 laser that could penetrate a beating heart during its relaxation phase. Later, the position of the beam could be fixed in the myocardial wall using lasers with fiber delivery systems and perforation was achieved within multiple cycles. Various researchers reported on both patent and non-patent channels after TMLR. Our belief is that the extent of laser induced thermal damage is one of the factors that determine the clinical outcome and the extent of angiogenesis (and, possibly, the patency of the channel). The purpose of this study is to present a simple theoretical model to predict the extent of thermal damage around a transmyocardial channel. In vitro experiments were performed on myocardial bovine tissue and damage was assessed. The results were used to determine the final parameters of the approximating theoretical equation. To evaluate our results, we compared our results to in vitro data using the Heart LaserTM from the literature. Ablation velocities were also measured and the results were compared to ablation velocity calculations using a model described by Ostegar et al.

Selective ablation of carious lesions using an integrated near-IR imaging system and a novel 9.3-μm CO2 Laser

NASA Astrophysics Data System (ADS)

Chan, Kenneth H.; Fried, Nathaniel M.; Fried, Daniel

2018-02-01

Previous studies have shown that reflectance imaging at wavelengths greater than 1200-nm can be used to image demineralization on tooth occlusal surfaces with high contrast and without the interference of stains. In addition, these near-IR imaging systems can be integrated with laser ablation systems for the selective removal of carious lesions. Higher wavelengths, such as 1950-nm, yield higher lesion contrast due to higher water absorption and lower scattering. In this study, a point-to-point scanning system employing diode and fiber lasers operating at 1450, 1860, 1880, and 1950-nm was used to acquire reflected light images of the tooth surface. Artificial lesions were imaged at these wavelengths to determine the highest lesion contrast. Near-IR images at 1880-nm were used to demarcate lesion areas for subsequent selective carious lesion removal using a new compact air-cooled CO2 laser prototype operating at 9.3-μm. The highest lesion contrast was at 1950-nm and the dual NIR/CO2 laser system selectively removed the simulated lesions with a mean loss of only 12-μm of sound enamel.

Influence of water layer thickness on hard tissue ablation with pulsed CO2 laser

NASA Astrophysics Data System (ADS)

Zhang, Xianzeng; Zhan, Zhenlin; Liu, Haishan; Zhao, Haibin; Xie, Shusen; Ye, Qing

2012-03-01

The theory of hard tissue ablation reported for IR lasers is based on a process of thermomechanical interaction, which is explained by the absorption of the radiation in the water component of the tissue. The microexplosion of the water is the cause of tissue fragments being blasted from hard tissue. The aim of this study is to evaluate the influence of the interdependence of water layer thickness and incident radiant exposure on ablation performance. A total of 282 specimens of bovine shank bone were irradiated with a pulse CO2 laser. Irradiation was carried out in groups: without a water layer and with a static water layer of thickness ranging from 0.2 to 1.2 mm. Each group was subdivided into five subgroups for different radiant exposures ranging from 18 to 84 J/cm2, respectively. The incision geometry, surface morphology, and microstructure of the cut walls as well as thermal injury were examined as a function of the water layer thickness at different radiant exposures. Our results demonstrate that the additional water layer is actually a mediator of laser-tissue interaction. There exists a critical thickness of water layer for a given radiant exposure, at which the additional water layer plays multiple roles, not only acting as a cleaner to produce a clean cut but also as a coolant to prevent bone heating and reduce thermal injury, but also helping to improve the regularity of the cut shape, smooth the cut surface, and enhance ablation rate and efficiency. The results suggest that desired ablation results depend on optimal selection of both water layer thickness and radiant exposure.

Skin graft take and healing following 193-nm excimer, continuous-wave carbon dioxide (CO2), pulsed CO2, or pulsed holmium: YAG laser ablation of the graft bed.

PubMed

Green, H A; Burd, E E; Nishioka, N S; Compton, C C

1993-08-01

Ablative lasers have been used for cutaneous surgery for greater than two decades since they can remove skin and skin lesions bloodlessly and efficiently. Because full-thickness skin wounds created after thermal laser ablation may require skin grafting in order to heal, we have examined the effect of the residual laser-induced thermal damage in the wound bed on subsequent skin graft take and healing. In a pig model, four different pulsed and continuous-wave lasers with varying wavelengths and radiant energy exposures were used to create uniform fascial graft bed thermal damage of approximately 25, 160, 470, and 1100 microns. Meshed split-thickness skin graft take and healing on the thermally damaged fascial graft beds were examined on a gross and microscopic level on days 3 and 7, and then weekly up to 42 days. Laser-induced thermal damage on the graft bed measuring greater than 160 +/- 60 microns in depth significantly decreased skin graft take. Other deleterious effects included delayed graft revascularization, increased inflammatory cell infiltrate at the graft-wound bed interface, and accelerated formation of hypertrophied fibrous tissue within the graft bed and underlying muscle. Ablative lasers developed for cutaneous surgery should create less than 160 +/- 60 microns of residual thermal damage to permit optimal skin graft take and healing. Pulsed carbon dioxide and 193-nm excimer lasers may be valuable instruments for the removal of full-thickness skin, skin lesions, and necrotic tissue, since they create wound beds with minimal thermal damage permitting graft take comparable to that achieved with standard surgical techniques.

The effect of CO2 laser treatment on skin tissue.

PubMed

Baleg, Sana Mohammed Anayb; Bidin, Noriah; Suan, Lau Pik; Ahmad, Muhammad Fakarruddin Sidi; Krishnan, Ganesan; Johari, Abd Rahman; Hamid, Asma

2015-09-01

The aim of this study was to evaluate the effects of multiple pulses on the depth of injury caused by CO2 laser in an in vivo rat model. A 10 600-nm CO2 laser was applied to rat skin, with one side of the rat dorsal skin being exposed, leaving the other side as a control. All of the various laser pulses tested led to gradual loss of epidermal thickness as well as a dramatic increase in thermal damage depth. Collagen coagulation was most effective with ten pulses of CO2 laser, while the strength of irradiated skin tissue increased as the influence of the laser increased. Fundamental laser-skin interaction effects were studied using a CO2 laser. The photodamaged areas obtained from laser interaction were recorded via couple charge device video camera and analyzed via ImageJ software. Photodamage induced by CO2 laser is due to photothermal effects, which involve burning and vaporizing mechanisms to ablate the epidermis layer. The burning area literally expands and penetrates deep into the dermis layer, subsequently causing collagen coagulation. This fundamental study shows in detail the effect of CO2 laser interaction with skin. The CO2 attributed severe burning, producing deep coagulation, and induced strength to treated skin. © 2015 Wiley Periodicals, Inc.

Pulpal effects of enamel ablation with a microsecond pulsed lambda = 9.3-microm CO2 laser.

PubMed

Staninec, Michal; Darling, Cynthia L; Goodis, Harold E; Pierre, Daniel; Cox, Darren P; Fan, Kenneth; Larson, Michael; Parisi, Renaldo; Hsu, Dennis; Manesh, Saman K; Ho, Chi; Hosseini, Mehran; Fried, Daniel

2009-04-01

In vitro studies have shown that CO2 lasers operating at the highly absorbed 9.3 and 9.6-microm wavelengths with a pulse duration in the range of 10-20-microsecond are well suited for the efficient ablation of enamel and dentin with minimal peripheral thermal damage. Even though these CO2 lasers are highly promising, they have yet to receive FDA approval. Clinical studies are necessary to determine if excessive heat deposition in the tooth may have any detrimental pulpal effects, particularly at higher ablative fluencies. The purpose of this study was to evaluate the pulpal safety of laser irradiation of tooth occlusal surfaces under the conditions required for small conservative preparations confined to enamel. Test subjects requiring removal of third molar teeth were recruited and teeth scheduled for extraction were irradiated using a pulsed CO2 laser at a wavelength of 9.3 microm operating at 25 or 50 Hz using a incident fluence of 20 J/cm(2) for a total of 3,000 laser pulses (36 J) for both rates with water cooling. Two control groups were used, one with no treatment and one with a small cut made with a conventional high-speed hand-piece. No anesthetic was used for any of the procedures and tooth vitality was evaluated prior to treatment by heat, cold and electrical testing. Short term effects were observed on teeth extracted within 72 hours after treatment and long term effects were observed on teeth extracted 90 days after treatment. The pulps of the teeth were fixed with formalin immediately after extraction and subjected to histological examination. Additionally, micro-thermocouple measurements were used to estimate the potential temperature rise in the pulp chamber of extracted teeth employing the same irradiation conditions used in vivo. Pulpal thermocouple measurements showed the internal temperature rise in the tooth was within safe limits, 3.3+/-1.4 degrees C without water cooling versus 1.7+/-1.6 degrees C with water-cooling, n = 25, P<0.05. None of the control or treatment groups showed any deleterious effects on pulpal tissues and none of the 29 test-subjects felt pain or discomfort after the procedure. Only two test-subjects felt discomfort from "cold sensitivity" during the procedure caused by the water-spray. It appears that this CO2 laser can ablate enamel safely without harming the pulp under the rate of energy deposition employed in this study.

Widely tunable asymmetric long-period fiber grating with high sensitivity using optical polymer on laser-ablated cladding.

PubMed

Chen, Nan-Kuang; Hsu, Der-Yi; Chi, Sien

2007-08-01

We demonstrate high-efficiency, wideband-tunable, laser-ablated long-period fiber gratings that use an optical polymer overlay. Portions of the fiber cladding are periodically removed by CO(2) laser pulses to induce periodic index changes for coupling the core mode into cladding modes. An optical polymer with a high thermo-optic coefficient with a dispersion distinct from that of silica is used on a deep-ablated cladding structure so that the effective indices of cladding modes become dispersive and the resonant wavelengths can be efficiently tuned. The tuning efficiency can be as high as 15.8 nm/ degrees C, and the tuning range can be wider than 105 nm (1545-1650 nm).

Molecular effects of fractional carbon dioxide laser resurfacing on photodamaged human skin.

PubMed

Reilly, Michael J; Cohen, Marc; Hokugo, Akishige; Keller, Gregory S

2010-01-01

Objective To elucidate the sequential changes in protein expression that play a role in the clinically beneficial results seen with fractional carbon dioxide (CO(2)) laser resurfacing of the face and neck. Methods Nine healthy volunteers were recruited for participation from the senior author's facial plastic surgery practice. After informed consent was obtained, each volunteer underwent a 2-mm punch biopsy from a discrete area of infra-auricular neck skin prior to laser treatment. Patients then immediately underwent laser resurfacing of photodamaged face and neck skin at a minimal dose (30 W for 0.1 second) with the Pixel Perfect fractional CO(2) laser. On completion of the treatment, another biopsy specimen was taken adjacent to the first site. Additional biopsy specimens were subsequently taken from adjacent skin at 2 of 3 time points (day 7, day 14, or day 21). RNA was extracted from the specimens, and reverse transcriptase-polymerase chain reaction and protein microarray analysis were performed. Comparisons were then made between time points using pairwise comparison testing. Results We found statistically significant changes in the gene expression of several matrix metalloproteinases (MMPs). The data demonstrate a consistent up-regulation of MMPs 1, 3, 9, and 13, all of which have been previously reported for fully ablative CO(2) laser resurfacing. There was also a statistically significant increase in MMP-10 and MMP-11 levels in this data set. Conclusion This study suggests that the molecular mechanisms of action are similar for both fractional and fully ablative CO(2) laser resurfacing.

Improving the ablation efficiency of excimer laser systems with higher repetition rates through enhanced debris removal and optimized spot pattern.

PubMed

Arba-Mosquera, Samuel; Klinner, Thomas

2014-03-01

To evaluate the reasons for the required increased radiant exposure for higher-repetition-rate excimer lasers and determine experimentally possible compensations to achieve equivalent ablation profiles maintaining the same single-pulse energies and radiant exposures for laser repetition rates ranging from 430 to 1000 Hz. Schwind eye-tech-solutions GmbH and Co. KG, Kleinostheim, Germany. Experimental study. Poly(methyl methacrylate) (PMMA) plates were photoablated. The pulse laser energy was maintained during all experiments; the effects of the flow of the debris removal, the shot pattern for the correction, and precooling the PMMA plates were evaluated in terms of achieved ablation versus repetition rate. The mean ablation performance ranged from 88% to 100%; the variability between the profile measurements ranged from 1.4% to 6.2%. Increasing the laser repetition rate from 430 Hz to 1000 Hz reduced the mean ablation performance from 98% to 91% and worsened the variability from 1.9% to 4.3%. Increasing the flow of the debris removal, precooling the PMMA plates to -18°C, and adapting the shot pattern for the thermal response of PMMA to excimer ablation helped stabilize the variability. Only adapting the shot pattern for the thermal response of PMMA to excimer ablation helped stabilize the mean ablation performance. The ablation performance of higher-repetition-rate excimer lasers on PMMA improved with improvements in the debris removal systems and shot pattern. More powerful debris removal systems and smart shot patterns in terms of thermal response improved the performance of these excimer lasers. Copyright © 2014 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

Inflammatory responses, matrix remodeling, and re-epithelialization after fractional CO2 laser treatment of scars.

PubMed

DeBruler, Danielle M; Blackstone, Britani N; Baumann, Molly E; McFarland, Kevin L; Wulff, Brian C; Wilgus, Traci A; Bailey, J Kevin; Supp, Dorothy M; Powell, Heather M

2017-09-01

Fractional CO 2 laser therapy has been used to improve scar pliability and appearance; however, a variety of treatment protocols have been utilized with varied outcomes. Understanding the relationship between laser power and extent of initial tissue ablation and time frame for remodeling could help determine an optimum power and frequency for laser treatment. The characteristics of initial injury caused by fractional CO 2 laser treatment, the rates of dermal remodeling and re-epithelialization, and the extent of inflammation as a function of laser stacking were assessed in this study in a porcine scar model. Full-thickness burn wounds were created on female Red Duroc pigs followed by immediate excision of the eschar and split-thickness autografting. Three months after injury, the resultant scars were treated with a fractional CO 2 laser with 70 mJ of energy delivered as either a single pulse or stacked for three consecutive pulses. Immediately prior to laser treatment and at 1, 24, 96, and 168 hours post-laser treatment, transepidermal water loss (TEWL), erythema, and microscopic characteristics of laser injury were measured. In addition, markers for inflammatory cytokines, extracellular matrix proteins, and re-epithelialization were quantified at all time points using qRT-PCR. Both treatments produced erythema in the scar that peaked 24 hours after treatment then decreased to basal levels by 168 hours. TEWL increased after laser treatment and returned to normal levels between 24 and 96 hours later. Stacking of the pulses did not significantly increase the depth of ablated wells or extend the presence of erythema. Interleukin 6 and monocyte chemoattractant protein-1 were found to increase significantly 1 hour after treatment but returned to baseline by 24 hours post laser. In contrast, expression of transforming growth factor β1 and transforming growth factor β3 increased slowly after treatment with a more modest increase than interleukin 6 and monocyte chemoattractant protein-1. In the current study, the properties of the ablative zones were not directly proportional to the total amount of energy applied to the porcine scars with the use of triple stacking, resulting in only minor increases to microthermal zone (MTZ) depth and width versus a single pulse. Re-epithelialization and re-establishment of epidermal barrier function were observed in laser treated scars by 48 hours post therapy. Finally, many of the inflammatory genes up-regulated by the laser ablation returned to baseline within 1 week. As a whole, these results suggest that microthermal zones created by FXCO 2 treatment re-epithelialize rapidly with the inflammatory response to the laser induced injury largely resolved within 1 week post treatment. Further study is needed to understand the relationship between laser stacking and MTZ properties in human scars in order to evaluate the clinical applicability of the stacking technique. Lasers Surg. Med. 49:675-685, 2017. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

Influence of the shielding effect on the formation of a micro-texture on the cermet with nanosecond pulsed laser ablation.

PubMed

Yuan, Jiandong; Liang, Liang; Jiang, Lelun; Liu, Xin

2018-04-01

The degree of laser pulse overlapping in a laser scanning path has a significant impact on the ablation regime in the laser machining of a micro-texture. In this Letter, a nanosecond pulsed laser is used to prepare the micro-scaled groove on WC-8Co cermet under different scanning speeds. It is observed that as the scanning speed increases, the ablated trace morphology in the first scanning pass transits from a succession of intermittent deep dimples to the consecutive overlapped shallow pits. The test result also indicates that ablated trace morphology with respect to the low scanning speed stems from a plume shielding effect. Moreover, the ablation regime considering the shielding effect in micro-groove formation process is clarified. The critical scanning speed that can circumvent the shielding effect is also summarized with respect to different laser powers.

Clinical applications of CO2 laser resurfacing in the treatment of various pathologic skin disorders

NASA Astrophysics Data System (ADS)

Giler, Shamai

1997-12-01

CO2 laser skin resurfacing devices are widely used in cosmetic surgery for the treatment of facial rhytides, acne scars and aging skin. This technique is also useful in the treatment of various benign and premalignant or multiple pathological skin conditions and disorders originating in the epidermal, dermal and skin appendages, vascular lesions, epidermal nevi, infected wounds and ulcers, and keloids. Various surgical techniques have been developed in our clinic using laser resurfacing in the treatment of more than 2,000 patients with various skin pathologic disorders. We describe our experience with the various techniques used. The precise depth control and ablation properties combined with the hemostatic and sterilizing effects of the CO2 laser beam, reduction of the possibility of bleeding, infection and damage to healthy tissues, make the CO2 laser resurfacing techniques the treatment of choice for cosmetic surgery and treatment of benign, premalignant and multiple pathologic skin conditions.

Comparison of different laser systems in the treatment of hypertrophic and atrophic scars and keloids

NASA Astrophysics Data System (ADS)

Scharschmidt, D.; Algermissen, Bernd; Willms-Jones, J.-C.; Philipp, Carsten M.; Berlien, Hans-Peter

1997-12-01

Different laser systems and techniques are used for the treatment of hypertrophic scars, keloids and acne scars. Significant criteria in selecting a suitable laser system are the scar's vascularization, age and diameter. Flashlamp- pumped dye-lasers, CO2-lasers with scanner, Argon and Nd:YAG-lasers are used. Telangiectatic scars respond well to argon lasers, erythematous scars and keloids to dye-laser treatment. Using interstitial Nd:YAG-laser vaporization, scars with a cross-section over 1 cm can generally be reduced. For the treatment of atrophic and acne scars good cosmetic results are achieved with a CO2-laser/scanner system, which allows a precise ablation of the upper dermis with low risk of side-effects.

Role of dual-laser ablation in controlling the Pb depletion in epitaxial growth of Pb(Zr0.52Ti0.48)O3 thin films with enhanced surface quality and ferroelectric properties

NASA Astrophysics Data System (ADS)

Mukherjee, Devajyoti; Hyde, Robert; Mukherjee, Pritish; Srikanth, Hariharan; Witanachchi, Sarath

2012-03-01

Pb depletion in Pb(Zr0.52Ti0.48)O3 (PZT) thin films has remained as a major setback in the growth of defect-free PZT thin films by pulsed laser ablation techniques. At low excimer (KrF) laser fluences, the high volatility of Pb in PZT leads to non-congruent target ablation and, consequently, non-stoichiometric films, whereas, at high laser fluences, the inherent ejection of molten droplets from the target leads to particulate laden films, which is undesirable in heterostructure growth. To overcome these issues, a dual-laser ablation (PLDDL) process that combines an excimer (KrF) laser and CO2 laser pulses was used to grow epitaxial PZT films on SrTiO3 (100) and MgO (100) substrates. Intensified-charge-coupled-detector (ICCD) images and optical emission spectroscopy of the laser-ablated plumes in PLDDL revealed a broader angular expansion and enhanced excitation of the ablated species as compared to those for single-laser ablation (PLDSL). This led to the growth of particulate-free PZT films with higher Pb content, better crystallinity, and lower surface roughness as compared to those deposited using PLDSL. For FE measurements, PZT capacitors were fabricated in situ using the latticed-matched metallic oxide, La0.7Sr0.3MnO3, as the top and bottom electrodes. PZT films deposited using PLDDL exhibited enhanced polarization for all driving voltages as compared to those deposited using PLDSL. A highest remanent polarization (Pr) of ˜91 μC/cm2 and low coercive field of ˜40 kV/cm was recorded at 9 V driving voltage. Fatigue characterization revealed that PZT films deposited using PLDDL showed unchanging polarization, even after 109 switching cycles.

Low-pressure, high-temperature thermal bonding of polymeric microfluidic devices and their applications for electrophoretic separation

NASA Astrophysics Data System (ADS)

Sun, Yi; Chian Kwok, Yien; Nguyen, Nam-Trung

2006-08-01

A new method for thermally bonding poly(methyl methacrylate) (PMMA) substrates has been demonstrated. PMMA substrates are first engraved by CO2-laser micromachining to form microchannels. Both channel width and depth can be adjusted by varying the laser power and scanning speed. Channel depths from 50 µm to 1500 µm and widths from 150 µm to 400 µm are attained. CO2 laser is also used for drilling and dicing of the PMMA parts. Considering the thermal properties of PMMA, a novel thermal bonding process with high temperature and low bonding pressure has been developed for assembling PMMA sheets. A high bonding strength of 2.15 MPa is achieved. Subsequent inspection of the cross sections of several microdevices reveals that the dimensions of the channels are well preserved during the bonding process. Electroosmotic mobility of the ablated channel is measured to be 2.47 × 10-4 cm2 V-1 s-1. The functionality of these thermally bonded microfluidic substrates is demonstrated by performing rapid and high-resolution electrophoretic separations of mixture of fluorescein and carboxyfluorescein as well as double-stranded DNA ladders (ΦX174-Hae III dsDNA digest). The performance of the CO2 laser ablated and thermally bonded PMMA devices compares favorably with those fabricated by other professional means.

Paint removal from aluminum and composite substrate of aircraft by laser ablation using TEA CO2 lasers

NASA Astrophysics Data System (ADS)

Tsunemi, Akira; Endo, Akira; Ichishima, Daiji

1998-09-01

A high power TEA CO2 laser was applied to strip paints from the surface of aircraft. For our experimental samples, aluminum and fiber-reinforced composite substrate were painted as the completely same way as normal aircraft. As a result of delicate control of the irradiation parameters, the surfaces of not only aluminum substrate but also composite substrate were clearly exposed without any damages. Removed materials were found out to be effectively collected by a combination of a micro filter and activated carbon powder.

Thrust Measurements in Ballistic Pendulum Ablative Laser Propulsion Experiments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brazolin, H.; Rodrigues, N. A. S.; Minucci, M. A. S.

This paper describes a setup for thrust measurement in ablative laser propulsion experiments, based on a simple ballistic pendulum associated to an imaging system, which is being assembled at IEAv. A light aluminium pendulum holding samples is placed inside a 100 liters vacuum chamber with two optical windows: the first (in ZnSe) for the laser beam and the second (in fused quartz) for the pendulum visualization. A TEA-CO{sub 2} laser beam is focused to the samples providing ablation and transferring linear moment to the pendulum as a whole. A CCD video camera captures the oscillatory movement of the pendulum andmore » the its trajectory is obtained by image processing. By fitting the trajectory of the pendulum to a dumped sinusoidal curve is possible to obtain the amplitude of the movement which is directly related to the momentum transfered to the sample.« less

Serial removal of caries lesions from tooth occlusal surfaces using near-IR image-guided IR laser ablation

NASA Astrophysics Data System (ADS)

Chan, Kenneth H.; Tom, Henry; Darling, Cynthia L.; Fried, Daniel

2015-02-01

Previous studies have established that caries lesions can be imaged with high contrast without the interference of stains at near-IR wavelengths greater than 1300-nm. It has been demonstrated that computer controlled laser scanning systems utilizing IR lasers operating at high pulse repetition rates can be used for serial imaging and selective removal of caries lesions. In this study, we report our progress towards the development of algorithms for generating rasterized ablation maps from near-IR reflectance images for the removal of natural lesions from tooth occlusal surfaces. An InGaAs camera and a filtered tungsten-halogen lamp producing near-IR light in the range of 1500-1700-nm were used to collect crosspolarization reflectance images of tooth occlusal surfaces. A CO2 laser operating at a wavelength of 9.3- μm with a pulse duration of 10-15-μs was used for image-guided ablation.

Histologic comparison of microscopic treatment zones induced by fractional lasers and radiofrequency.

PubMed

Shin, Min-Kyung; Choi, Jeong Hwee; Ahn, Soo Beom; Lee, Mu Hyoung

2014-12-01

Fractional photothermolysis induces microscopic, localized thermal injury in the skin surrounded by undamaged viable tissue in order to promote wound healing. This study evaluated acute histologic changes following each single pass of various fractional lasers and radiofrequency (RF). Three male domestic swine were used. We used fractional Erbium:glass (Er:glass), Erbium:yttrium-aluminum-garnet (Er:YAG), CO2 lasers, and fractional ablative microplasma RF. We analyzed features and average values of the diameter, depth, and vertical sectional areas treated with each kind of laser and RF. The microscopic treatment zone (MTZ) of fractional Er:glass resulted in separation of dermoepidermal junction with no ablative zone. Fractional Er:YAG provided the most superficial and broad MTZ with little thermal collateral damage. Fractional CO2 resulted in a narrow and deep "cone"-like MTZ. Fractional RF resulted in a superficial and broad "crater"-like MTZ. This study provides the first comparison of MTZs induced by various fractional lasers and RF. These data provide basic information on proper laser and RF options. We think that these findings could be a good reference for information about fractional laser-assisted drug delivery.

Review of Laser Ablation Process for Single Wall Carbon Nanotube Production

NASA Technical Reports Server (NTRS)

Arepalli, Sivaram

2003-01-01

Different types of lasers are now routinely used to prepare single wall carbon nanotubes (SWCNTs). The original method developed by researchers at Rice University utilized a "double pulse laser oven" process. A graphite target containing about 1 atomic percent of metal catalysts is ablated inside a 1473K oven using laser pulses (10 ns pulse width) in slow flowing argon. Two YAG lasers with a green pulse (532 nm) followed by an IR pulse (1064 nm) with a 50 ns delay are used for ablation. This set up produced single wall carbon nanotube material with about 70% purity having a diameter distribution peaked around 1.4 nm. The impurities consist of fullerenes, metal catalyst clusters (10 to 100 nm diameter) and amorphous carbon. The rate of production with the initial set up was about 60 mg per hour with 10Hz laser systems. Several researchers have used variations of the lasers to improve the rate, consistency and study effects of different process parameters on the quality and quantity of SWCNTs. These variations include one to three YAG laser systems (Green, Green and IR), different pulse widths (nano to microseconds as well as continuous) and different laser wavelengths (Alexandrite, CO, CO2, free electron lasers in the near to far infrared). It is noted that yield from the single laser (Green or IR) systems is only a fraction of the two laser systems. The yield seemed to scale up with the repetition rate of the laser systems (10 to 60 Hz) and depended on the beam uniformity and quality of the laser pulses. The shift to longer wavelength lasers (free electron, CO and CO2) did not improve the quality, but increased the rate of production because these lasers are either continuous (CW) or high repetition rate pulses (kHz to MHz). The average power and the peak power of the lasers seem to influence the yields. Very high peak powers (MegaWatts per square centimeter) are noted to increase ablation of bigger particles with reduced yields of SWCNTs. Increased average powers seem to help the conversion of the carbon from target into vapor phase to improve formation of nanotubes. The use of CW far infrared lasers reduced the need for the oven, at the expense of controlled ablation. Some of these variations are tried with different combinations and concentrations of metal catalysts (Nickel with Cobalt, Iron, Palladium and Platinum) different buffer gases (e.g. Helium); with different oven temperatures (Room temperature to 1473K); under different flow conditions (1 to 1000 kPa) and even different porosities of the graphite targets. It is to be noted that the original Cobalt and Nickel combination worked best, possibly because of improved carbonization with stable crystalline phases. The mean diameter and yield seemed to increase with increasing oven temperatures. Thermal conductivity of the buffer gas and flow conditions dictate the quality as well as quantity of the SWCNTs. Faster flows, lower pressures and heavier gases seem to increase the yields. This review will attempt to cover all these variations and their relative merits. Possible growth mechanisms under these different conditions will also be discussed.

Reactions of laser-ablated Fe, Co, and Ni with NO: Infrared spectra and density functional calculations of MNO{sup +} and M(NO){sub x} (M = Fe, Co, x = 1--3; M = Ni, x = 1,2), and M(NO){sub x}{sup {minus}} (M = Co, Ni; x = 1,2)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhou, M.; Andrews, L.

2000-05-04

Laser-ablated iron, cobalt, and nickel atoms, cations, and electrons have been reacted with NO molecules during condensation in excess neon and argon. The end-on bonded Fe(NO){sub 1-3}, Co(NO){sub 1-3}, and Ni(NO){sub 1-2} nitrosyls and side-bonded Fe-({eta}{sup 2}-NO), Co-({eta}{sup 2}-NO), and Ni-({eta}{sup 2}-NO) species are formed during sample deposition or on annealing. The FeNO{sup +}, CoNO{sup +}, and NiNO{sup +} mononitrosyl cations are also produced via metal cation reactions with NO. Evidence is also presented for the Ni(NO){sub 1,2}{sup {minus}} and Co(NO){sub 1,2}{sup {minus}} anions. The product absorptions are identified by isotopic substitution ({sup 15}N{sup 16}O, {sup 15}N{sup 18}O, and mixtures),more » electron trapping with added CCl{sub 4}, and density functional calculations of isotopic frequencies. This work provides the first vibrational spectroscopic characterization of Fe, Co, and Ni nitrosyl cations and anions.« less

Thermoplastic microchannel fabrication using carbon dioxide laser ablation.

PubMed

Wang, Shau-Chun; Lee, Chia-Yu; Chen, Hsiao-Ping

2006-04-14

We report the procedures of machining microchannels on Vivak co-polyester thermoplastic substrates using a simple industrial CO(2) laser marker. To avoid overheating the substrates, we develop low-power marking techniques in nearly anaerobic environment. These procedures are able to machine microchannels at various aspect ratios. Either straight or serpent channel can be easily marked. Like the wire-embossed channel walls, the ablated channel surfaces become charged after alkaline hydrolysis treatment. Stable electroosmotic flow in the charged conduit is observed to be of the same order of magnitude as that in fused silica capillary. Typical dynamic coating protocols to alter the conduit surface properties are transferable to the ablated channels. The effects of buffer acidity on electroosmotic mobility in both bare and coated channels are similar to those in fused silica capillaries. Using video microscopy we also demonstrate that this device is useful in distinguishing the electrophoretic mobility of bare and latex particles from that of functionalized ones.

Comparative study of excimer and erbium:YAG lasers for ablation of structural components of the knee

NASA Astrophysics Data System (ADS)

Vari, Sandor G.; Shi, Wei-Qiang; van der Veen, Maurits J.; Fishbein, Michael C.; Miller, J. M.; Papaioannou, Thanassis; Grundfest, Warren S.

1991-05-01

This study was designed to compare the efficiency and thermal effect of a 135 ns pulsed-stretched XeCl excimer laser (308 nm) and a free-running Erbium:YAG laser (2940 nm) with 200 microsecond(s) pulse duration for ablation of knee joint structures (hyaline and fibrous cartilage, tendon and bone). The radiant exposure used for tissue ablation ranged from 2 to 15 J/cm2 for the XeCl excimer and from 33 to 120 J/cm2 for Er:YAG. The excimer and Er:YAG lasers were operated at 4 and 5 Hz respectively. The ablative laser energy was delivered to tissue through fibers. Ablation rates of soft tissues (hyaline and fibrous cartilage, tendon) varied from 8.5 to 203 micrometers /pulse for excimer and from 8.2 to 273 micrometers /pulse for Er:YAG lasers. Ablation rates of soft tissues are linearly dependent on the radiant exposure. Within the range of parameters tested all the tissues except the bone could be rapidly ablated by both lasers. Bone ablation was much less efficient, requiring 15 J/cm2 and 110 J/cm2 radiant exposure for excimer and Er:YAG lasers to ablate 9.5 and 8.2 micrometers tissue per pulse. However, excimer laser ablation produced less thermal damage in the tissues studied compared to Er:YAG at the same laser parameters. The authors conclude that both lasers are capable of efficient knee joint tissue ablation. XeCl excimer laser requires an order of magnitude less energy than Er:YAG laser for comparable tissue ablation.

Standard guidelines of care: CO2 laser for removal of benign skin lesions and resurfacing.

PubMed

Krupashankar, D S

2008-01-01

Resurfacing is a treatment to remove acne and chicken pox scars, and changes in the skin due to ageing. MACHINES: Both ablative and nonablative lasers are available for use. CO 2 laser is the gold standard in ablative lasers. Detailed knowledge of the machines is essential. INDICATIONS FOR CO 2 LASER: Therapeutic indications: Actinic and seborrheic keratosis, warts, moles, skin tags, epidermal and dermal nevi, vitiligo blister and punch grafting, rhinophyma, sebaceous hyperplasia, xanthelasma, syringomas, actinic cheilitis angiofibroma, scar treatment, keloid, skin cancer, neurofibroma and diffuse actinic keratoses. CO 2 laser is not recommended for the removal of tattoos. AESTHETIC INDICATIONS: Resurfacing for acne, chicken pox and surgical scars, periorbital and perioral wrinkles, photo ageing changes, facial resurfacing. PHYSICIANS' QUALIFICATIONS: Any qualified dermatologist (DVD or MD) may practice CO 2 laser. The dermatologist should possess postgraduate qualification in dermatology and should have had specific hands-on training in lasers either during postgraduation or later at a facility which routinely performs laser procedures under a competent dermatologist/plastic surgeon, who has experience and training in using lasers. For the use of CO 2 lasers for benign growths, a full day workshop is adequate. As parameters may vary in different machines, specific training with the available machine at either the manufacturer's facility or at another centre using the machine is recommended. CO 2 lasers can be used in the dermatologist's minor procedure room for the above indications. However, when used for full-face resurfacing, the hospital operation theatre or day care facility with immediate access to emergency medical care is essential. Smoke evacuator is mandatory. Detailed counseling with respect to the treatment, desired effects, possible postoperative complications, should be discussed with the patient. The patient should be provided brochures to study and also given adequate opportunity to seek information. Detailed consent forms need to be completed by the patients. Consent forms should include information on the machine used; possible postoperative course expected and postoperative complications. Preoperative photography should be carried out in all cases of resurfacing. Choice of the machine and the parameters depends on the site, type of lesion, result needed, and the physician's experience. Localized lesions can be treated under eutectic mixture of local anesthesia (EMLA) cream anesthesia or local infiltration anesthesia. Full-face resurfacing can be performed under general anesthesia. Proper postoperative care is important to avoid complications.

Cutaneous resurfacing with CO2 and erbium: YAG lasers: preoperative, intraoperative, and postoperative considerations.

PubMed

Alster, T S

1999-02-01

The development and integration of pulsed and scanned CO2 and erbium:YAG laser systems into mainstream surgical practice over the past years has revolutionized cutaneous resurfacing. These lasers are capable of delivering to skin high peak fluences to effect controlled tissue vaporization, while leaving an acceptably narrow zone of residual thermal damage. The inherent technological differences that exist between the two distant laser systems in terms of ablation depths, degree of thermal coagulation, and postoperative side-effects and complications guide patient selection and management. This article reviews the basic principles of CO2 and erbium:YAG laser resurfacing, including preoperative, intraoperative, and postoperative patient considerations. Side-effects and complications encountered after laser resurfacing are discussed with specific guidelines provided on their appropriate management. Anticipated future developments and cutting-edge research endeavors in cutaneous laser resurfacing are also briefly outlined.

A comparative evaluation: Oral leukoplakia surgical management using diode laser, CO2 laser, and cryosurgery.

PubMed

Natekar, Madhukar; Raghuveer, Hosahallli-Puttaiah; Rayapati, Dilip-Kumar; Shobha, Eshwara-Singh; Prashanth, Nagesh-Tavane; Rangan, Vinod; Panicker, Archana G

2017-06-01

The comparatively evaluate the three surgical treatment modalities namely cryosurgery, diode and CO2 laser surgery in terms of healing outcomes on the day of surgery, first and second week post operatively and recurrence at the end of 18 months was assessed. Thirty selected patients were divided randomly into three groups. Each group comprising of ten patients were subjected to one of the three modalities of treatment namely cryosurgery, diode laser or CO2 laser surgery for ablation of OL. Obtained data was analyzed using mainly using Chi-square and Anova tests. Study showed statistical significant differences (p > 0.05) for evaluation parameters like pain, edema and scar. The parameters like infection, recurrence, bleeding showed no statistical significance. Pain was significantly higher in CO2 laser surgery group as compared with diode laser group. There was no recurrence observed at the end of the 6 months follow up period in all the three study groups. Observations from the study highlights that all three surgical modalities used in this study were effective for treatment of OL, and the overall summation of the results of the study showed that laser therapy (CO2 and Diode) seems to offer better clinically significant results than cryotherapy. Key words: Oral premalignant lesion, leukoplakia, cryosurgery, CO2 laser surgery, diode laser surgery.

The clinical effectiveness and cost-effectiveness of fractional CO2 laser in acne scars and skin rejuvenation: A meta-analysis and economic evaluation.

PubMed

Ansari, Fereshteh; Sadeghi-Ghyassi, Fatemeh; Yaaghoobian, Barmak

2018-01-31

Fractional CO 2 has many indications in medicine including in treatment of acne scars and rejuvenation. The aim of this study was to evaluate the safety, efficacy, and cost-effectiveness of Fractional CO 2 Laser in comparison with other methods of rejuvenation and acne scar treatment. Several databases including Medline, OVID, EMBASE, CINHAL, SCOPUS, Web of science, CRD, and Cochrane were searched. After conducting the search and evaluation of selected publications, critical appraisal was done and eligible studies were accepted for inclusion in the systematic review. From 2667 identified publications two of the trials were eligible. The effectiveness and complications of Fractional CO 2 laser were comparable with Er:YAG but Fractional CO 2 laser was 14.7% (p = 0.01) more effective than Q-Switched ND:YAG laser. Cost affectivity of this method was the same as other alternative lasers. In conclusion Fractional CO 2 laser is an effective and safe method for curing of several kinds of skin diseases. Nevertheless there was not sufficient evidence to support its advantage. This device has equal or lower price in comparison to competent technologies except for the non- fractional ablative CO 2 laser that has the same or lower price and comparable effects.

Myocardium tissue ablation with high-peak-power nanosecond 1,064- and 532-nm pulsed lasers: influence of laser-induced plasma.

PubMed

Ogura, Makoto; Sato, Shunichi; Ishihara, Miya; Kawauchi, Satoko; Arai, Tunenori; Matsui, Takemi; Kurita, Akira; Kikuchi, Makoto; Ashida, Hiroshi; Obara, Minoru

2002-01-01

We investigated the mechanism and characteristics of porcine myocardium tissue ablation in vitro with nanosecond 1,064- and 532-nm pulsed lasers at laser intensities up to approximately 5.0 GW/cm(2). Particular attention was paid to study the influence of the laser-induced plasma on the ablation characteristics. The applicability of these two lasers to transmyocardial laser revascularization (TMLR) was discussed. Porcine myocardium tissue samples were irradiated with 1,064- and 532-nm, Q-switched Nd:YAG laser pulses, and the ablation depths were measured. The temporal profiles of the laser-induced optical emissions were measured with a biplanar phototube. For the ablated tissue samples, histological analysis was performed with an optical microscope and a polarization microscope. The ablation efficiency at 1,064 nm was higher than that at 532 nm. The ablation threshold at 1,064 nm (approximately 0.8 GW/cm(2)) was lower than that at 532 nm (approximately 1.6 GW/cm(2)), in spite of the lower absorption coefficient being expected at 1,064 nm. For the 1,064-nm laser-ablated tissues, thermal damage was very limited, while damage presumably caused by the mechanical effect was observed in most of the cases. For the 1,064-nm laser ablation, the ablation threshold was equal to the threshold of the laser-induced optical emission (approximately 0.8 GW/cm(2)), while for the 532-nm laser ablation, the optical emission threshold ( approximately 2.4 GW/cm(2)) was higher than the ablation threshold. We considered that for the 1,064-nm laser ablation, the tissue removal was achieved through a photodisruption process at laser intensities of > approximately 0.8 GW/cm(2). At laser intensities of > 3.0 GW/cm(2), however, the ablation efficiency decreased; this can be attributed to the absorption of incoming laser pulses by the plasma. For the 532-nm laser ablation, the tissue removal was achieved through a photothermal process at laser intensities of > approximately 1.6 GW/cm(2). At laser intensities of > 2.4 GW/cm(2), a photodisruption process may also contribute to the tissue removal, in addition to a photothermal process. With regard to the ablation rates, the 1,064-nm laser was more suitable for TMLR than the 532-nm laser. We concluded that the 1,064-nm Q-switched Nd:YAG laser would be a potential candidate for a laser source for TMLR because of possible fiber-based beam delivery, its compact structure, cost effectiveness, and easy maintenance. Animal trials, however, have to be carried out to evaluate the influence of the tissue damage. Copyright 2002 Wiley-Liss, Inc.

Effect of laser on pain relief and wound healing of recurrent aphthous stomatitis: a systematic review.

PubMed

Suter, Valerie G A; Sjölund, Sophia; Bornstein, Michael M

2017-05-01

The aim of this systematic review was to assess a potential benefit of laser use in the treatment of recurrent aphthous stomatitis (RAS). The primary outcome variables were pain relief, duration of wound healing and reduction in episode frequency. A PICO approach was used as a search strategy in Medline, Embase and Cochrane databases. After scanning and excluding titles, abstracts and full texts, 11 studies (ten RCTs and one non-randomised controlled trial) were included. Study selection and data extraction was done by two observers. Study participants varied between 7-90 for the laser and 5-90 for the control groups. Laser treatment included Nd:YAG laser ablation, CO 2 laser applied through a transparent gel (non-ablative) and diode laser in a low-level laser treatment (LLLT) mode. Control groups had placebo, no therapy or topical corticosteroid treatment. Significant pain relief immediately after treatment was found in five out of six studies. Pain relief in the days following treatment was recorded in seven studies. The duration of RAS wound healing was also reduced in five studies. However, criteria of evaluation differed between the studies. The episode frequency was not evaluated as only one study addressed this outcome parameter, but did not discriminate between the study (LLLT) and control (corticosteroid) groups. Jadad scores (ranging from 0 to 5) for quality assessment of the included studies range between 0 and 2 (mean = 1.0) for studies analysing pain relief and between 0 and 3 (mean = 1.1) for studies evaluating wound healing. The use of lasers (CO 2 laser, Nd:YAG laser and diode laser) to relieve symptoms and promote healing of RAS is a therapeutic option. More studies for laser applications are necessary to demonstrate superiority over topical pharmaceutical treatment and to recommend a specific laser type, wavelength, power output and applied energy (ablative versus photobiomodulation).

Combined fractional resurfacing (10600 nm/1540 nm): Tridimensional imaging evaluation of a new device for skin rejuvenation.

PubMed

Mezzana, Paolo; Valeriani, Maurizio; Valeriani, Roberto

2016-11-01

In this study were described the results, by tridimensional imaging evaluation, of the new "Combined Fractional Resurfacing" technique with the first fractional laser that overtakes the limits of traditional ablative, nonablative fractional resurfacing by combining CO 2 ablative and GaAs nonablative lasers. These two wavelengths can work separately or in a mixed modality to give the best treatment choice to all the patients. In this study, it is demonstrated that the simultaneous combination of the CO 2 wavelength (10600 nm) and GaAs wavelength (1540 nm) reduced the downtime, reduced pain during the treatment, and produced better results on fine wrinkles reduction and almost the same results on pigmentation as seen with 3D analysis by Antera (Miravex).

Mesoscopic modeling of the response of human dental enamel to mid-infrared radiation

NASA Astrophysics Data System (ADS)

Vila Verde, Ana; Ramos, Marta; Stoneham, A. M.

2006-03-01

Ablation of human dental enamel, a composite biomaterial with water pores, is of significant importance in minimally invasive laser dentistry but progress in the area is hampered by the lack of optimal laser parameters. We use mesoscopic finite element models of this material to study its response to mid-infrared radiation. Our results indicate that the cost-effective, off-the-shelf CO2 laser at λ = 10.6 μm may in fact ablate enamel precisely, reproducibly and with limited unwanted side effects such as cracking or heating, provided that a pulse duration of 10 μs is used. Furthermore, our results also indicate that the Er:YAG laser (λ = 2.94 μm), currently popular for laser dentistry, may in fact cause unwanted deep cracking in the enamel when regions with unusually high water content are irradiated, and also provide an explanation for the large range of ablation threshold values observed for this material. The model may be easily adapted to study the response of any composite material to infrared radiation and thus may be useful for the scientific community.

Rapid and high-resolution stable isotopic measurement of biogenic accretionary carbonate using an online CO2 laser ablation system: Standardization of the analytical protocol.

PubMed

Sreemany, Arpita; Bera, Melinda Kumar; Sarkar, Anindya

2017-12-30

The elaborate sampling and analytical protocol associated with conventional dual-inlet isotope ratio mass spectrometry has long hindered high-resolution climate studies from biogenic accretionary carbonates. Laser-based on-line systems, in comparison, produce rapid data, but suffer from unresolvable matrix effects. It is, therefore, necessary to resolve these matrix effects to take advantage of the automated laser-based method. Two marine bivalve shells (one aragonite and one calcite) and one fish otolith (aragonite) were first analysed using a CO 2 laser ablation system attached to a continuous flow isotope ratio mass spectrometer under different experimental conditions (different laser power, sample untreated vs vacuum roasted). The shells and the otolith were then micro-drilled and the isotopic compositions of the powders were measured in a dual-inlet isotope ratio mass spectrometer following the conventional acid digestion method. The vacuum-roasted samples (both aragonite and calcite) produced mean isotopic ratios (with a reproducibility of ±0.2 ‰ for both δ 18 O and δ 13 C values) almost identical to the values obtained using the conventional acid digestion method. As the isotopic ratio of the acid digested samples fall within the analytical precision (±0.2 ‰) of the laser ablation system, this suggests the usefulness of the method for studying the biogenic accretionary carbonate matrix. When using laser-based continuous flow isotope ratio mass spectrometry for the high-resolution isotopic measurements of biogenic carbonates, the employment of a vacuum-roasting step will reduce the matrix effect. This method will be of immense help to geologists and sclerochronologists in exploring short-term changes in climatic parameters (e.g. seasonality) in geological times. Copyright © 2017 John Wiley & Sons, Ltd.

The use of sunscreen starting on the first day after ablative fractional skin resurfacing.

PubMed

Wanitphakdeedecha, R; Phuardchantuk, R; Manuskiatti, W

2014-11-01

The most common side-effect of ablative fractional skin resurfacing in Asians is post inflammatory hyperpigmentation (PIH). Various attempts have been made to reduce the occurrence of PIH after laser treatment including sun avoidance, the use of preoperative and postoperative treatment regimens, and treatment using conservative energy settings and epidermal protection. To determine whether the use of broad-spectrum sunscreen with anti-inflammatory agents starting on the first day after fractional CO2 laser skin resurfacing reduces the incidence of post laser PIH. Thirty patients were treated with ablative fractional CO2 resurfacing on both sides of their faces at 10 mJ and 10% density. Each subject was randomly treated on one side of the face with petrolatum ointment four times a day for the first week after laser treatment and on the other side of the face with petrolatum ointment four times a day plus broad-spectrum sunscreen with anti-inflammatory agents in the morning starting on the first day after laser treatment. Transepidermal water loss was recorded at baseline and every day for 1 week. Melanin and erythema indexes were measured at baseline, 1-, 2-week, 1-, 2- and at 3-month post treatment. Of the 30 patients involved in the study, 26 received the treatment and attended 1-, 2-week, 1-, 2- and 3-month post-treatment visits. Four patients were withdrawn from the study because they could not attend every follow-up visit. There was no statistically significant difference in transepidermal water loss at baseline, immediately after laser treatment, or at the D1 to D7 follow-up visits. Erythema index had no significantly statistical difference at baseline, 1-, 2- and at 3-month after laser treatment. Furthermore, there was a statistically significant difference in melanin index at 1-week post laser treatment between both sides (P = 0.001). Melanin index at the 1-week follow-up visit on the side treated with broad-spectrum sunscreen with anti-inflammatory agents starting on the first day after laser treatment was significantly less than the control side. The use of broad-spectrum sunscreen with anti-inflammatory agents starting on the first day after ablative fractional skin resurfacing can decrease the incidence of PIH after laser treatment at 1-week postoperatively. © 2013 European Academy of Dermatology and Venereology.

Structuring by field enhancement of glass, Ag, Au, and Co thin films using short pulse laser ablation

NASA Astrophysics Data System (ADS)

Ulmeanu, M.; Zamfirescu, M.; Rusen, L.; Luculescu, C.; Moldovan, A.; Stratan, A.; Dabu, R.

2009-12-01

Single pulse laser ablation of glass, Ag, Au, and Co thin films was experimentally investigated with a laser pulse width of 400 ps at a wavelength of 532 nm both in the far and near fields. In the far-field regime, the electromagnetic field results from a focused laser beam, while the near-field regime is realized by a combination of the focused laser beam incident on a spherical colloidal particle. For the near-field experiments we have used polystyrene colloidal particles of 700 nm diameter self-assembled or spin coated on top of the surfaces. Laser fluences applied are in the range of 0.01-10 J/cm2. The diameter and the morphologies of the ablated holes were investigated by optical microscopy, profilometry, scanning electron microscopy, and atomic force microscopy. The dependence of the shape of the holes reflects the fluence regime and the thermophysical properties, i.e., melting temperature and thermal diffusivity of the surfaces involved in the experiments. We give quantitative data about the fluence threshold, diameter, and depth ablation dependence for the far and near fields and discuss their values with respect to the enhancement factor of the intensity of the electromagnetic field due to the use of the colloidal particles. Theoretical estimations of the intensity enhancement were done using the finite-difference time-domain method by using the RSOFT software. The application of near fields allows structuring of the surfaces with structure dimension in the order of 100 nm and even below.

All fiber cladding mode stripper with uniform heat distribution and high cladding light loss manufactured by CO2 laser ablation

NASA Astrophysics Data System (ADS)

Jebali, M. A.; Basso, E. T.

2018-02-01

Cladding mode strippers are primarily used at the end of a fiber laser cavity to remove high-power excess cladding light without inducing core loss and beam quality degradation. Conventional manufacturing methods of cladding mode strippers include acid etching, abrasive blasting or laser ablation. Manufacturing of cladding mode strippers using laser ablation consist of removing parts of the cladding by fused silica ablation with a controlled penetration and shape. We present and characterize an optimized cladding mode stripper design that increases the cladding light loss with a minimal device length and manufacturing time. This design reduces the localized heat generation by improving the heat distribution along the device. We demonstrate a cladding mode stripper written on a 400um fiber with cladding light loss of 20dB, with less than 0.02dB loss in the core and minimal heating of the fiber and coating. The manufacturing process of the designed component is fully automated and takes less than 3 minutes with a very high throughput yield.

Ultrashort pulse laser ablation of dielectrics: Thresholds, mechanisms, role of breakdown

PubMed Central

Mirza, Inam; Bulgakova, Nadezhda M.; Tomáštík, Jan; Michálek, Václav; Haderka, Ondřej; Fekete, Ladislav; Mocek, Tomáš

2016-01-01

In this paper, we establish connections between the thresholds and mechanisms of the damage and white-light generation upon femtosecond laser irradiation of wide-bandgap transparent materials. On the example of Corning Willow glass, evolution of ablation craters, their quality, and white-light emission were studied experimentally for 130-fs, 800-nm laser pulses. The experimental results indicate co-existence of several ablation mechanisms which can be separated in time. Suppression of the phase explosion mechanism of ablation was revealed at the middle of the irradiation spots. At high laser fluences, air ionization was found to strongly influence ablation rate and quality and the main mechanisms of the influence are analysed. To gain insight into the processes triggered by laser radiation in glass, numerical simulations have been performed with accounting for the balance of laser energy absorption and its distribution/redistribution in the sample, including bremsstrahlung emission from excited free-electron plasma. The simulations have shown an insignificant role of avalanche ionization at such short durations of laser pulses while pointing to high average energy of electrons up to several dozens of eV. At multi-pulse ablation regimes, improvement of crater quality was found as compared to single/few pulses. PMID:27991543

Ultrashort pulse laser ablation of dielectrics: Thresholds, mechanisms, role of breakdown

NASA Astrophysics Data System (ADS)

Mirza, Inam; Bulgakova, Nadezhda M.; Tomáštík, Jan; Michálek, Václav; Haderka, Ondřej; Fekete, Ladislav; Mocek, Tomáš

2016-12-01

In this paper, we establish connections between the thresholds and mechanisms of the damage and white-light generation upon femtosecond laser irradiation of wide-bandgap transparent materials. On the example of Corning Willow glass, evolution of ablation craters, their quality, and white-light emission were studied experimentally for 130-fs, 800-nm laser pulses. The experimental results indicate co-existence of several ablation mechanisms which can be separated in time. Suppression of the phase explosion mechanism of ablation was revealed at the middle of the irradiation spots. At high laser fluences, air ionization was found to strongly influence ablation rate and quality and the main mechanisms of the influence are analysed. To gain insight into the processes triggered by laser radiation in glass, numerical simulations have been performed with accounting for the balance of laser energy absorption and its distribution/redistribution in the sample, including bremsstrahlung emission from excited free-electron plasma. The simulations have shown an insignificant role of avalanche ionization at such short durations of laser pulses while pointing to high average energy of electrons up to several dozens of eV. At multi-pulse ablation regimes, improvement of crater quality was found as compared to single/few pulses.

Ultrashort pulse laser ablation of dielectrics: Thresholds, mechanisms, role of breakdown.

PubMed

Mirza, Inam; Bulgakova, Nadezhda M; Tomáštík, Jan; Michálek, Václav; Haderka, Ondřej; Fekete, Ladislav; Mocek, Tomáš

2016-12-19

In this paper, we establish connections between the thresholds and mechanisms of the damage and white-light generation upon femtosecond laser irradiation of wide-bandgap transparent materials. On the example of Corning Willow glass, evolution of ablation craters, their quality, and white-light emission were studied experimentally for 130-fs, 800-nm laser pulses. The experimental results indicate co-existence of several ablation mechanisms which can be separated in time. Suppression of the phase explosion mechanism of ablation was revealed at the middle of the irradiation spots. At high laser fluences, air ionization was found to strongly influence ablation rate and quality and the main mechanisms of the influence are analysed. To gain insight into the processes triggered by laser radiation in glass, numerical simulations have been performed with accounting for the balance of laser energy absorption and its distribution/redistribution in the sample, including bremsstrahlung emission from excited free-electron plasma. The simulations have shown an insignificant role of avalanche ionization at such short durations of laser pulses while pointing to high average energy of electrons up to several dozens of eV. At multi-pulse ablation regimes, improvement of crater quality was found as compared to single/few pulses.

Use of a compact fiber optic spectrometer for spectral feedback during the laser ablation of dental hard tissues and restorative materials

NASA Astrophysics Data System (ADS)

Cheng, Joyce Y.; Fan, Kenneth; Fried, Daniel

2006-02-01

One perceived disadvantage of caries removal using lasers is the loss of the tactile feedback associated with the handpiece. However, alternative methods of acoustic and optical feedback become available with the laser that can be exploited to provide information about the chemical composition of the material ablated, the ablation efficiency and rate, the depth of the incision, and the surface and plume temperature during ablation. Such information can be used to increase the selectivity of ablation, avoid peripheral thermal damage and excessive heat deposition in the tooth, and provide a mechanism of robotic automation. The objective of this study was to test the hypothesis that a compact fiberoptic spectrometer could be used to differentiate between the ablation of sound and carious enamel and dentin and between dental hard tissues and composite. Sound and carious tooth surfaces along with composite restorative materials were scanned with λ=0.355, 2.79 and 9.3 μm laser pulses at irradiation intensities ranging from 0.5-100 J/cm2 and spectra were acquired from λ=250-900-nm using a compact fiber-optic spectrometer. Emission spectra varied markedly with the laser wavelength and pulse duration. Optical feedback was not successful in differentiating between sound and carious enamel and dentin even with the addition of various chromophores to carious lesion areas. However, the spectral feedback was successfully used to differentiate between composites and sound enamel and dentin enabling the selective removal of composite from tooth surfaces using a computer controlled λ=9.3-μm pulsed CO II laser and scanning system.

Carbon dioxide laser versus erbium:YAG laser in treatment of epidermal verrucous nevus: a comparative randomized clinical study.

PubMed

Osman, Mai Abdel Raouf; Kassab, Ahmed Nazmi

2017-08-01

A verrucous epidermal nevus (VEN) is a skin disorder that has been treated using different treatment modalities with varying results. Ablative lasers such as carbon dioxide laser (CO 2 ) and erbium:yttrium-aluminum-garnet (Er:YAG) laser have been considered as the gold standard for the treatment of epidermal nevi. To evaluate and compare the efficacy, postoperative wound healing and side effects of pulsed CO 2 laser and Er:YAG laser for the treatment of verrucous epidermal nevi. Twenty patients with localized VEN were randomly divided into two groups. Group 1 was administered CO 2 laser and group 2 underwent Er:YAG laser treatment. A blinded physician evaluated the photographs and dermoscopic photomicrographs for the efficacy and possible side effects. All patients received one treatment session and were followed up over a 6-month period. Both lasers induced noticeable clinical improvement, but there were no significant differences between two lasers in treatment response, patient satisfaction, duration of erythema and side effects. The average time to re-epithelialization was 13.5 days with CO 2 and 7.9 days with Er:YAG laser (p< .0005). No scarring was observed in Er:YAG laser group and no lesional recurrence was detected in CO 2 laser group since treatment. Apart from re-epithelialization, both lasers showed equivalent outcomes with respect to treatment response, patient satisfaction, side effects and complications.

DEVELOPMENT OF LiCo0.90Mg0.05Al0.05O2 THIN FILMS BY PULSED LASER DEPOSITION TECHNIQUE

NASA Astrophysics Data System (ADS)

Vasanthi, R.; Ruthmangani, I.; Manoravi, P.; Joseph, M.; Kesavamoorthy, R.; Sundar, C.; Selladurai, S.

LiCo0.90Mg0.05Al0.05O2 bulk powders are synthesized using combustion process and made into a thin film by depositing on silicon wafer using a pulsed laser ablation technique. A comparative study by SEM (Scanning Electron Microscope) XRD (X-ray diffraction), Infrared spectroscopy and Raman Spectroscopy is performed on both bulk and PLD thin films.

Monitoring the inhibition of erosion by a CO2 laser with OCT

NASA Astrophysics Data System (ADS)

Chan, Kenneth H.; Tom, Henry; Fried, Daniel

2014-02-01

Since optical coherence tomography (OCT) is well suited for measuring small dimensional changes on tooth surfaces, OCT has great potential for monitoring tooth erosion. Previous studies have shown that enamel areas ablated by a carbon dioxide laser manifested lower rates of erosion compared to the nonablated areas. The purpose of this study was to develop a model to monitor erosion in vitro that could potentially be used in vivo. Teeth surfaces were irradiated with a carbon dioxide laser at low sub-ablative fluence to create an acid-resistant reference layer without damaging the enamel. The laser treated areas were compared with the unprotected areas using OCT during exposure to a pH cycling model for up to 6 days. The laser treated areas markedly reduced the rate of erosion.

Nanosecond laser-metal ablation at different ambient conditions

NASA Astrophysics Data System (ADS)

Elsied, Ahmed M.; Dieffenbach, Payson C.; Diwakar, Prasoon K.; Hassanein, Ahmed

2018-05-01

Ablation of metals under different ambient conditions and laser fluences, was investigated through series of experiments. A 1064 nm, 6 ns Nd:YAG laser was used to ablate 1 mm thick metal targets with laser energy ranging from 2 mJ to 300 mJ. The experiments were designed to study the effect of material properties, laser fluence, ambient gas, and ambient pressure on laser-metal ablation. The first experiment was conducted under vacuum to study the effect of laser fluence and material properties on metal ablation, using a wide range of laser fluences (2 J/cm2 up to 300 J/cm2) and two different targets, Al and W. The second experiment was conducted at atmospheric pressure using two different ambient gases air and argon, to understand the effect of ambient gas on laser-metal ablation process. The third experiment was conducted at two different pressures (10 Torr and 760 Torr) using the same ambient gas to investigate the effect of ambient pressure on laser-metal ablation. To compare the different ablation processes, the amount of mass ablated, ablation depth, crater profile and melt formation were measured using White Light Profilometer (WLP). The experimental results show that at low laser fluence: the ablated mass, ablation depth, and height of molten layer follow a logarithmic function of the incident laser fluence. While, at high laser fluence they follow a linear function. This dependence on laser fluence was found to be independent on ambient conditions and irradiated material. The effect of ambient pressure was more pronounced than the effect of ambient gas type. Plasma shielding effect was found to be very pronounced in the presence of ambient gas and led to significant reduction in the total mass ablation.

Direct solid analysis of powdered tungsten carbide hardmetal precursors by laser-induced argon spark ablation with inductively coupled plasma atomic emission spectrometry.

PubMed

Holá, Markéta; Kanický, Viktor; Mermet, Jean-Michel; Otruba, Vítezslav

2003-12-01

The potential of the laser-induced argon spark atomizer (LINA-Spark atomizer) coupled with ICP-AES as a convenient device for direct analysis of WC/Co powdered precursors of sintered hardmetals was studied. The samples were presented for the ablation as pressed pellets prepared by mixing with powdered silver binder containing GeO2 as internal standard. The pellets were ablated with the aid of a Q-switched Nd:YAG laser (1064 nm) focused 16 mm behind the target surface with a resulting estimated power density of 5 GW cm(-2). Laser ablation ICP-AES signals were studied as a function of ablation time, and the duration of time prior to measurement (pre-ablation time) which was necessary to obtain reliable results was about 40 s. Linear calibration plots were obtained up to 10% (m/m) Ti, 9% Ta and 3.5% Nb both without internal standardization and by using germanium as an added internal standard or tungsten as a contained internal standard. The relative uncertainty at the centroid of the calibration line was in the range from +/- 6% to +/- 11% for Nb, Ta and Ti both with and without internal standardisation by Ge. A higher spread of points about the regression was observed for cobalt for which the relative uncertainty at the centroid was in the range from +/- 9% to +/- 14%. Repeatability of results was improved by the use of both Ge and W internal standards. The lowest determinable quantities calculated for calibration plots were 0.060% Co, 0.010% Nb, 0.16% Ta and 0.030% Ti with internal standardization by Ge. The LA-ICP-AES analyses of real samples led to good agreement with the results obtained by solution-based ICP determination with a relative bias not exceeding 10%. The elimination of the dissolution procedure of powdered tungsten (Nb, Ta, Ti) carbide is the principal advantage of the developed LA-ICP-AES method.

Transepidermal drug delivery: a new treatment option for areata alopecia?

PubMed

Issa, Maria Claudia Almeida; Pires, Marianna; Silveira, Priscilla; Xavier de Brito, Esther; Sasajima, Cristiane

2015-02-01

Transepidermal drug delivery (TED) is a new potential method in dermatology. Permeability alterations induced by ablative fractional resurfacing have been described with the aim to increasing the delivery of different substances into the skin. To evaluate clinical response and side effects of TED in areata alopecia (AA) treatment using ablative fractional methods associated with acoustic pressure ultrasound (US) to deliver triamcinolone solution into the skin. Five cases of AA underwent treatment which comprised of 3 steps: 1) Ablative fractioned RF or CO2 laser 2) topical application of triamcinolone 3) acoustic pressure wave US. The number of sessions varied according to the clinical response, ranging from one to six sessions. All patients had complete recovery of the area treated. Two of them treated with ablative fractional RF + triamcinolone + US had complete response after three and six sessions. The other two treated with ablative fractional CO2 + triamcinolone + US had complete response after one session. Fractioned ablative resurfacing associated with acoustic pressure wave US is a new option to areata alopecia treatment with good clinical result and low incidence of side effects.

Perspective on One Decade of Laser Propulsion Research at Air Force Research Laboratory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Larson, C. William

The Air Force Laser Propulsion Program spanned nearly 10-years and included about 35-weeks of experimental research with the Pulsed Laser Vulnerability Test System of the High Energy Laser Systems Test Facility at White Sands Missile Range, New Mexico, WSMR/HELSTF/PLVTS. PLVTS is a pulsed CO2 laser that produces up to 10 kW of power in {approx}10 cm{sup 2} spot at wavelength of 10.6 microns. The laser is capable of a pulse repetition rate up to 25 Hz, with pulse durations of about 20 microseconds. During the program basic research was conducted on the production of propulsion thrust from laser energy throughmore » heating of air and ablation of various candidate rocket propellant fuels. Flight tests with an ablation fuel (Delrin) and air were accomplished with a model Laser Lightcraft vehicle that was optimized for propulsion by the PLVTS at its maximum power output, 10 kW at 25 Hz, 400 J/pulse. Altitudes exceeding 200-feet were achieved with ablation fuels. The most recent contributions to the technology included development of a mini-thruster standard for testing of chemically enhanced fuels and theoretical calculations on the performance of formulations containing ammonium nitrate and Delrin. Results of these calculations will also be reported here.« less

Perspective on One Decade of Laser Propulsion Research at Air Force Research Laboratory

NASA Astrophysics Data System (ADS)

Larson, C. William

2008-04-01

The Air Force Laser Propulsion Program spanned nearly 10-years and included about 35-weeks of experimental research with the Pulsed Laser Vulnerability Test System of the High Energy Laser Systems Test Facility at White Sands Missile Range, New Mexico, WSMR/HELSTF/PLVTS. PLVTS is a pulsed CO2 laser that produces up to 10 kW of power in ˜10 cm2 spot at wavelength of 10.6 microns. The laser is capable of a pulse repetition rate up to 25 Hz, with pulse durations of about 20 microseconds. During the program basic research was conducted on the production of propulsion thrust from laser energy through heating of air and ablation of various candidate rocket propellant fuels. Flight tests with an ablation fuel (Delrin) and air were accomplished with a model Laser Lightcraft vehicle that was optimized for propulsion by the PLVTS at its maximum power output, 10 kW at 25 Hz, 400 J/pulse. Altitudes exceeding 200-feet were achieved with ablation fuels. The most recent contributions to the technology included development of a mini-thruster standard for testing of chemically enhanced fuels and theoretical calculations on the performance of formulations containing ammonium nitrate and Delrin. Results of these calculations will also be reported here.

Cutting and skin-ablative properties of pulsed mid-infrared laser surgery.

PubMed

Kaufmann, R; Hartmann, A; Hibst, R

1994-02-01

Pulsed mid-infrared lasers allow a precise removal of soft tissues with only minimal thermal damage. To study the potential dermatosurgical usefulness of currently available systems at different wavelengths (2010-nm Thulium:YAG laser, 2100-nm Holmium:YAG laser, 2790-nm Erbium:YSGG laser, and 2940-nm Erbium:YAG laser) in vivo on pig skin. Immediate effects and wound healing of superficial laser-abrasions and incisions were compared with those of identical control lesions produced by dermabrasion, scalpel incisions, or laser surgery performed by a 1060-nm Nd:YAG and a 1060-nm CO2 laser (continuous and superpulsed mode). Best efficiency and least thermal injury was found for the pulsed Erbium:YAG laser, leading to ablative and incisional lesions comparable to those obtained by dermabrasion or superficial scalpel incisions, respectively. In contrast to other mid-infrared lasers tested, the 2940-nm Erbium:YAG laser thus provides a potential instrument for future applications in skin surgery, especially when aiming at a careful ablative removal of delicate superficial lesions with maximum sparing of adjacent tissue structures. However, in the purely incisional application mode pulsed mid-infrared lasers, though of potential usefulness in microsurgical indications (eg, surgery of the cornea), do not offer a suggestive alternative to simple scalpel surgery of the skin.

Iron doped LiCoPO4 thin films for lithium-ion microbatteries obtained by ns pulsed laser deposition

NASA Astrophysics Data System (ADS)

Smaldone, A.; Brutti, S.; De Bonis, A.; Ciarfaglia, N.; Santagata, A.; Teghil, R.

2018-07-01

Well crystallized and homogeneous iron doped LiCoPO4 (LCfP) thin films have been grown by ns Pulsed Laser Ablation, at ambient temperature without any substrate heating or post-annealing treatments. The films have been deposited in vacuum and in the presence of buffer gases (O2, Ar) and it has been found that their crystallinity, structure and morphology depend on pressure conditions. The films have been studied by Scanning Electron Microscopy and X Ray Diffraction, while their first steps of growth have been characterized by Transmission Electron Microscopy. A study of the plasma produced by the laser ablation in the different pressure conditions has been carried out with the aim of elucidate the mechanisms involved in the films deposition. LCfP thin films have been also tested as microelectrodes in lithium cells in galvanostatic condition for analyzing the reversibility of the lithium-ion battery.

Ablation mass features in multi-pulses femtosecond laser ablate molybdenum target

NASA Astrophysics Data System (ADS)

Zhao, Dongye; Gierse, Niels; Wegner, Julian; Pretzler, Georg; Oelmann, Jannis; Brezinsek, Sebastijan; Liang, Yunfeng; Neubauer, Olaf; Rasinski, Marcin; Linsmeier, Christian; Ding, Hongbin

2018-03-01

In this study, the ablation mass features related to reflectivity of bulk Molybdenum (Mo) were investigated by a Ti: Sa 6 fs laser pulse at central wavelength 790 nm. The ablated mass removal was determined using Confocal Microscopy (CM) technique. The surface reflectivity was calibrated and measured by a Lambda 950 spectrophotometer as well as a CCD camera during laser ablation. The ablation mass loss per pulse increase with the increasing of laser shots, meanwhile the surface reflectivity decrease. The multi-pulses (100 shots) ablation threshold of Mo was determined to be 0.15 J/cm2. The incubation coefficient was estimated as 0.835. The reflectivity change of the Mo target surface following multi-pulses laser ablation were studied as a function of laser ablation shots at various laser fluences from 1.07 J/cm2 to 36.23 J/cm2. The results of measured reflectivity indicate that surface reflectivity of Mo target has a significant decline in the first 3-laser pulses at the various fluences. These results are important for developing a quantitative analysis model for laser induced ablation and laser induced breakdown spectroscopy for the first wall diagnosis of EAST tokamak.

Characterization of SrTiO3 target doped with Co ions, SrCoxTi1-xO3-δ, and their thin films prepared by pulsed laser ablation (PLA) in water for visible light response

NASA Astrophysics Data System (ADS)

Ichihara, Fumihiko; Murata, Yuma; Ono, Hiroshi; Choo, Cheow-keong; Tanaka, Katsumi

2017-10-01

SrTiO3 (STO) and Co-doped SrTiO3 (Co-STO) sintered targets were synthesized and were Ar+ sputtered to elucidate the charge compensation effect between Sr, Ti and Co cations following the reduction by oxygen desorption. Following exposure of the Ar+-sputtered target to the air, charge transfer reactions occurred among Co2+, Ti3+, O2- and Sr2+ species which were studied by their XPS spectra. Pulsed laser ablation (PLA) of these targets was carried out in water to prepare the nanoparticles which could be supplied to the thin films with much higher surface reactivity expected for photocatalytic reactions. The roles of Co ions were studied for the stoichiometry and crystallinity of the nanoparticles which constituted the thin films. Photo-degradation of methylene blue was carried out on the PLA thin films under very weak visible light at 460 nm. The PLA thin films showed the photocatalytic activities, which were enhanced by the presence of Co ions. Such the effect of Co ions was considered from viewpoint of the d-d transition and the charge-transfer between Co ions and the ligand oxygen.

CO2 laser therapy of rhinophyma

NASA Astrophysics Data System (ADS)

Voigt, Peggy; Jovanovic, Sergije; Sedlmaier, Benedikt W.

2000-06-01

Laser treatment of skin changes has become common practice in recent years. High absorption of the CO2 laser wavelength in water is responsible for its low penetration dpt in biological tissue. Shortening the tissue exposure time minimizes thermic side effects of laser radiation such as carbonization and coagulation. This can be achieved with scanner systems that move the focused laser beam over a defined area by microprocessor-controlled rapidly rotating mirrors. This enables controlled and reliable removal of certain dermal lesions, particularly hypertrophic scars, scars after common acne, wrinkles and rhinophyma. Laser ablation of rhinophyma is a stress-minimizing procedure for the surgeon and the patient, since it is nearly bloodless and can be performed under local anaesthesia. Cosmetically favorable reepithelization of the lasered surfaces is achieved within a very short period of time.

Transversely Excited Atmospheric CO2 Laser-Induced Plasma Spectroscopy for the Detection of Heavy Metals in Soil

NASA Astrophysics Data System (ADS)

Khumaeni, A.; Sugito, H.; Setia Budi, W.; Yoyo Wardaya, A.

2018-01-01

A rapid detection of heavy metals in soil was presented by the metal-assisted gas plasma method using specific characteristics of a pulsed, transversely excited atmospheric (TEA) CO2 laser. The soil particles were placed in a hole made of acrylic plate. The sample was covered by a to prevent the soil particles from being blown off. The mesh also functioned to initiate a luminous plasma. When a TEA CO2 laser (1500 mJ, 200 ns) was focused on the soil sample, passing through the metal mesh, some of the laser energy was used to generate the gas plasma on the mesh surface, and the remaining laser energy was employed to ablate the soil particles. The fine, ablated soil particles moved into the gas plasma region to be dissociated and excited. Using this technique, analysis can be made with reduced sample pretreatment, and therefore a rapid analysis can be performed efficiently. The results proved that the signal to noise ratio (S/N) of the emission spectral lines is much better for the case of the present method (mesh method) compared to the case of standard laser-induced breakdown spectroscopy using the pellet method. Rapid detection of heavy metal elements in soil has been successfully carried out. The detection limits of Cu and Hg in soil were estimated to be 3 and 10 mg/kg, respectively. The present method has good potential for rapid and sensitive detection of heavy metals in soil samples.

Femtosecond laser ablation of dentin and enamel: relationship between laser fluence and ablation efficiency.

PubMed

Chen, Hu; Liu, Jing; Li, Hong; Ge, Wenqi; Sun, Yuchun; Wang, Yong; Lü, Peijun

2015-02-01

The objective was to study the relationship between laser fluence and ablation efficiency of a femtosecond laser with a Gaussian-shaped pulse used to ablate dentin and enamel for prosthodontic tooth preparation. A diode-pumped thin-disk femtosecond laser with wavelength of 1025 nm and pulse width of 400 fs was used for the ablation of dentin and enamel. The laser spot was guided in a line on the dentin and enamel surfaces to form a groove-shaped ablation zone under a series of laser pulse energies. The width and volume of the ablated line were measured under a three-dimensional confocal microscope to calculate the ablation efficiency. Ablation efficiency for dentin reached a maximum value of 0.020 mm3∕J when the laser fluence was set at 6.51 J∕cm2. For enamel, the maximum ablation efficiency was 0.009 mm3∕J at a fluence of 7.59 J∕cm2.Ablation efficiency of the femtosecond laser on dentin and enamel is closely related to the laser fluence and may reach a maximum when the laser fluence is set to an appropriate value. © 2015 Society of Photo-Optical Instrumentation Engineers (SPIE)

Photoacoustic characterization of radiofrequency ablation lesions

NASA Astrophysics Data System (ADS)

Bouchard, Richard; Dana, Nicholas; Di Biase, Luigi; Natale, Andrea; Emelianov, Stanislav

2012-02-01

Radiofrequency ablation (RFA) procedures are used to destroy abnormal electrical pathways in the heart that can cause cardiac arrhythmias. Current methods relying on fluoroscopy, echocardiography and electrical conduction mapping are unable to accurately assess ablation lesion size. In an effort to better visualize RFA lesions, photoacoustic (PA) and ultrasonic (US) imaging were utilized to obtain co-registered images of ablated porcine cardiac tissue. The left ventricular free wall of fresh (i.e., never frozen) porcine hearts was harvested within 24 hours of the animals' sacrifice. A THERMOCOOLR Ablation System (Biosense Webster, Inc.) operating at 40 W for 30-60 s was used to induce lesions through the endocardial and epicardial walls of the cardiac samples. Following lesion creation, the ablated tissue samples were placed in 25 °C saline to allow for multi-wavelength PA imaging. Samples were imaged with a VevoR 2100 ultrasound system (VisualSonics, Inc.) using a modified 20-MHz array that could provide laser irradiation to the sample from a pulsed tunable laser (Newport Corp.) to allow for co-registered photoacoustic-ultrasound (PAUS) imaging. PA imaging was conducted from 750-1064 nm, with a surface fluence of approximately 15 mJ/cm2 maintained during imaging. In this preliminary study with PA imaging, the ablated region could be well visualized on the surface of the sample, with contrasts of 6-10 dB achieved at 750 nm. Although imaging penetration depth is a concern, PA imaging shows promise in being able to reliably visualize RF ablation lesions.

Influence of irradiation by a novel CO2 9.3-μm short-pulsed laser on sealant bond strength.

PubMed

Rechmann, P; Sherathiya, K; Kinsel, R; Vaderhobli, R; Rechmann, B M T

2017-04-01

The objective of this in vitro study was to evaluate whether irradiation of enamel with a novel CO 2 9.3-μm short-pulsed laser using energies that enhance caries resistance influences the shear bond strength of composite resin sealants to the irradiated enamel. Seventy bovine and 240 human enamel samples were irradiated with a 9.3-μm carbon dioxide laser (Solea, Convergent Dental, Inc., Natick, MA) with four different laser energies known to enhance caries resistance or ablate enamel (pulse duration from 3 μs at 1.6 mJ/pulse to 43 μs at 14.9 mJ/pulse with fluences between 3.3 and 30.4 J/cm 2 , pulse repetition rate between 4.1 and 41.3 Hz, beam diameter of 0.25 mm and 1-mm spiral pattern, and focus distance of 4-15 mm). Irradiation was performed "freehand" or using a computerized, motor-driven stage. Enamel etching was achieved with 37% phosphoric acid (Scotchbond Universal etchant, 3M ESPE, St. Paul, MN). As bonding agent, Adper Single Bond Plus was used followed by placing Z250 Filtek Supreme flowable composite resin (both 3M ESPE). After 24 h water storage, a single-plane shear bond test was performed (UltraTester, Ultradent Products, Inc., South Jordan, UT). All laser-irradiated samples showed equal or higher bond strength than non-laser-treated controls. The highest shear bond strength values were observed with the 3-μs pulse duration/0.25-mm laser pattern (mean ± SD = 31.90 ± 2.50 MPa), representing a significant 27.4% bond strength increase over the controls (25.04 ± 2.80 MPa, P ≤ 0.0001). Two other caries-preventive irradiation (3 μs/1 mm and 7 μs/0.25 mm) and one ablative pattern (23 μs/0.25 mm) achieved significantly increased bond strength compared to the controls. Bovine enamel also showed in all test groups increased shear bond strength over the controls. Computerized motor-driven stage irradiation did not show superior bond strength values over the clinically more relevant freehand irradiation. Enamel that is made caries-resistant with CO 2 9.3-μm short-pulsed laser irradiation showed at least equal or significantly higher shear bond strength to pit and fissure sealants than non-laser-irradiated enamel. The risk of a sealant failure due to CO 2 9.3-μm short-pulsed laser irradiation appears reduced. If additional laser ablation is required before placing a sealant, the CO 2 9.3-μm enamel laser-cut showed equivalent or superior bond strength to a flowable sealant.

Enhancing hair growth in male androgenetic alopecia by a combination of fractional CO2 laser therapy and hair growth factors.

PubMed

Huang, Yue; Zhuo, Fenglin; Li, Linfeng

2017-11-01

Laser therapy and growth factors have been used as alternative treatments for male androgenetic alopecia (MAA). The aim of this study is to determine the efficacy and safety of hair growth factors alone or combined with ablative carbon dioxide (CO 2 ) fractional laser therapy in MAA. Twenty-eight men were enrolled in this randomized half-split study based on a left-head to right-head pattern. Fractional CO 2 laser treatment was unilaterally performed; hair growth factors were bilaterally applied. Six sessions with 2-week intervals were performed. Global photographs and dermoscopy assessments were performed at the baseline and 4 months after first treatment. Global photographs underwent blinded review by three independent dermatologists. Scanning electron microscopy was used to compare changes in hair-follicle phase and hair-shaft diameter. Twenty-seven participants completed the 4-month treatment schedule. One patient was lost. Mean hair density increased from 114 ± 27 to 143 ± 25/cm 2 (P < 0.001) in the combined group and from 113 ± 24 to 134 ± 19/cm 2 in the growth factor group (P < 0.001). The mean change from baseline between two groups was also compared (P = 0.003). Global photographs showed improvement in 93% (25/27) patients in the combined group and 67% (18/27) patients in the growth factor group. Under scanning electron microscopy, hair follicles appeared to transition from telogen to anagen, and hair-shaft diameter increased in five randomly selected patients. Ablative fractional CO 2 laser combined with hair growth factors may serve as an alternative treatment for MAA in individuals unwilling/unable to undergo medical or surgical treatment.

Design of co-existence parallel periodic surface structure induced by picosecond laser pulses on the Al/Ti multilayers

NASA Astrophysics Data System (ADS)

Petrović, Suzana; Peruško, D.; Kovač, J.; Panjan, P.; Mitrić, M.; Pjević, D.; Kovačević, A.; Jelenković, B.

2017-09-01

Formation of periodic nanostructures on the Ti/5x(Al/Ti)/Si multilayers induced by picosecond laser pulses is studied in order to better understand the formation of a laser-induced periodic surface structure (LIPSS). At fluence slightly below the ablation threshold, the formation of low spatial frequency-LIPSS (LSFL) oriented perpendicular to the direction of the laser polarization is observed on the irradiated area. Prolonged irradiation while scanning results in the formation of a high spatial frequency-LIPSS (HSFL), on top of the LSFLs, creating a co-existence parallel periodic structure. HSFL was oriented parallel to the incident laser polarization. Intermixing between the Al and Ti layers with the formation of Al-Ti intermetallic compounds was achieved during the irradiation. The intermetallic region was formed mostly within the heat affected zone of the sample. Surface segregation of aluminium with partial ablation of the top layer of titanium was followed by the formation of an ultra-thin Al2O3 film on the surface of the multi-layered structure.

Direct biological effects of fractional ultrapulsed CO2 laser irradiation on keratinocytes and fibroblasts in human organotypic full-thickness 3D skin models.

PubMed

Schmitt, L; Huth, S; Amann, P M; Marquardt, Y; Heise, R; Fietkau, K; Huth, L; Steiner, T; Hölzle, F; Baron, J M

2018-05-01

Molecular effects of various ablative and non-ablative laser treatments on human skin cells-especially primary effects on epidermal keratinocytes and dermal fibroblasts-are not yet fully understood. We present the first study addressing molecular effects of fractional non-sequential ultrapulsed CO 2 laser treatment using a 3D skin model that allows standardized investigations of time-dependent molecular changes ex vivo. While histological examination was performed to assess morphological changes, we utilized gene expression profiling using microarray and qRT-PCR analyses to identify molecular effects of laser treatment. Irradiated models exhibited dose-dependent morphological changes resulting in an almost complete recovery of the epidermis 5 days after irradiation. On day 5 after laser injury with a laser fluence of 100 mJ/cm 2 , gene array analysis identified an upregulation of genes associated with tissue remodeling and wound healing (e.g., COL12A1 and FGF7), genes that are involved in the immune response (e.g., CXCL12 and CCL8) as well as members of the heat shock protein family (e.g., HSPB3). On the other hand, we detected a downregulation of matrix metalloproteinases (e.g., MMP3), differentiation markers (e.g., LOR and S100A7), and the pro-inflammatory cytokine IL1α.Overall, our findings substantiate the understanding of time-dependent molecular changes after CO 2 laser treatment. The utilized 3D skin model system proved to be a reliable, accurate, and reproducible tool to explore the effects of various laser settings both on skin morphology and gene expression during wound healing.

Current status of lasers in soft tissue dental surgery.

PubMed

Pick, R M; Colvard, M D

1993-07-01

The aims of this paper are to briefly describe laser physics, the types of lasers currently available for use on soft tissues focusing primarily on CO2 and Nd:YAG laser energies, the histological effects of lasers on oral tissues, laser safety, the clinical applications of lasers on oral soft tissues, and future directions. Of the two types of lasers currently available for dental applications, both the CO2 and Nd:YAG lasers can be used for frenectomies, ablation of lesions, incisional and excisional biopsies, gingivectomies, gingivoplasties, soft tissue tuberosity reductions, operculum removal, coagulation of graft donor sites, and certain crown lengthening procedures. The advantages of lasers include a relatively bloodless surgical and post-surgical course, minimal swelling and scarring, coagulation, vaporization, and cutting, minimal or no suturing, reduction in surgical time, and, in a majority of cases, much less or no post-surgical pain. CO2 lasers, compared to Nd:YAG are faster for most procedures, with less depth of tissue penetration and a well-documented history. There have been recent reports on the use of the Nd:YAG laser for periodontal scaling, gingival curettage, and root desensitization, but further research needs to be conducted. Both the CO2 and the Nd:YAG laser have limited use in conventional flap therapy.

Spatially resolved δ13C analysis using laser ablation isotope ratio mass spectrometry

NASA Astrophysics Data System (ADS)

Moran, J.; Riha, K. M.; Nims, M. K.; Linley, T. J.; Hess, N. J.; Nico, P. S.

2014-12-01

Inherent geochemical, organic matter, and microbial heterogeneity over small spatial scales can complicate studies of carbon dynamics through soils. Stable isotope analysis has a strong history of helping track substrate turnover, delineate rhizosphere activity zones, and identifying transitions in vegetation cover, but most traditional isotope approaches are limited in spatial resolution by a combination of physical separation techniques (manual dissection) and IRMS instrument sensitivity. We coupled laser ablation sampling with isotope measurement via IRMS to enable spatially resolved analysis over solid surfaces. Once a targeted sample region is ablated the resulting particulates are entrained in a helium carrier gas and passed through a combustion reactor where carbon is converted to CO2. Cyrotrapping of the resulting CO2 enables a reduction in carrier gas flow which improves overall measurement sensitivity versus traditional, high flow sample introduction. Currently we are performing sample analysis at 50 μm resolution, require 65 ng C per analysis, and achieve measurement precision consistent with other continuous flow techniques. We will discuss applications of the laser ablation IRMS (LA-IRMS) system to microbial communities and fish ecology studies to demonstrate the merits of this technique and how similar analytical approaches can be transitioned to soil systems. Preliminary efforts at analyzing soil samples will be used to highlight strengths and limitations of the LA-IRMS approach, paying particular attention to sample preparation requirements, spatial resolution, sample analysis time, and the types of questions most conducive to analysis via LA-IRMS.

Investigation of the differentiation of ex vivo nerve and fat tissues using laser-induced breakdown spectroscopy (LIBS): Prospects for tissue-specific laser surgery.

PubMed

Mehari, Fanuel; Rohde, Maximillian; Kanawade, Rajesh; Knipfer, Christian; Adler, Werner; Klämpfl, Florian; Stelzle, Florian; Schmidt, Michael

2016-10-01

In the present study, the elemental compositions of fat and nerve tissue during their plasma mediated laser ablation are studied in the context of tissue differentiation for laser surgery applications by using Laser-Induced Breakdown Spectroscopy (LIBS). Tissue samples of porcine fat and nerve were prepared as ex vivo experimental objects. Plasma mediated laser ablation is performed using an Nd : YAG laser in open air and under normal stray light conditions. The performed measurements suggest that the two tissue types show a high similarity in terms of qualitative elemental composition while at the same time revealing a distinct difference in the concentration of the constituent elements. Different analysis approaches are evaluated and discussed to optimize the tissue-differentiation performance of the LIBS approach. Plasma mediated laser tissue ablation. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Visual servoing of a laser ablation based cochleostomy

NASA Astrophysics Data System (ADS)

Kahrs, Lüder A.; Raczkowsky, Jörg; Werner, Martin; Knapp, Felix B.; Mehrwald, Markus; Hering, Peter; Schipper, Jörg; Klenzner, Thomas; Wörn, Heinz

2008-03-01

The aim of this study is a defined, visually based and camera controlled bone removal by a navigated CO II laser on the promontory of the inner ear. A precise and minimally traumatic opening procedure of the cochlea for the implantation of a cochlear implant electrode (so-called cochleostomy) is intended. Harming the membrane linings of the inner ear can result in damage of remaining organ functions (e.g. complete deafness or vertigo). A precise tissue removal by a laser-based bone ablation system is investigated. Inside the borehole the pulsed laser beam is guided automatically over the bone by using a two mirror galvanometric scanner. The ablation process is controlled by visual servoing. For the detection of the boundary layers of the inner ear the ablation area is monitored by a color camera. The acquired pictures are analyzed by image processing. The results of this analysis are used to control the process of laser ablation. This publication describes the complete system including image processing algorithms and the concept for the resulting distribution of single laser pulses. The system has been tested on human cochleae in ex-vivo studies. Further developments could lead to safe intraoperative openings of the cochlea by a robot based surgical laser instrument.

Bone Ablation at 2.94 mm Using the Free-Electron Laser and Er:YAG Laser

NASA Astrophysics Data System (ADS)

Ivanov, Borislav; Hakimian, Arman; Peavy, G. M.; Haglund, Richard

2002-03-01

Bone Ablation at 2.94 microns Using the Free-Electron Laser and Er:YAG Laser in Perfluorocarbon Compounds B. Ivanov^1, A. M. Hakimian^1, G. M. Peavy^2, R. F. Haglund, Jr.1 1Department of Physics and Astronomy, W. M. Keck Foundation Free-Electron Laser Center, Vanderbilt University, Nashville, TN 37235 2Beckman Laser Institute and Medical Clinic, College of Medicine, University of California, Irvine, CA 92612 We report studies on the efficiency of mid-IR laser ablation of cow cortical bone using the Vanderbilt free-electron laser (FEL), when irrigating the ablation zone with an inert and biocompatible perfluorocarbon compounds (PFC). At 2.94 microns, the bone matrix (mainly by water) absorbs the radiation while the PFCs transmit this wavelength, dissipate heat and acoustical stress, and prevent carbonization of the bone sample. The ablation rate, as a function of laser fluence, scanning speed and the type of PFC, was investigated. The laser fluence was estimated to be 5 J/cm^2 - 100 J/cm^2 with a laser focal spot diameter of 160 microns 500 microns and a scanning speed of 40 microns/s 2960 microns/s. The ablation rate was estimated from scanning electron microscopy to be 0.5 mm/s 2.4 mm/s. Comparisons of ablation rates with the FEL and a Er:YAG laser at 2.94 microns are being evaluated.

Rovibronically selected and resolved two-color laser photoionization and photoelectron study of cobalt carbide cation.

PubMed

Huang, Huang; Chang, Yih Chung; Luo, Zhihong; Shi, Xiaoyu; Lam, Chow-Shing; Lau, Kai-Chung; Ng, C Y

2013-03-07

We have conducted a two-color visible-ultraviolet (VIS-UV) resonance-enhanced laser photoionization efficiency and pulsed field ionization-photoelectron (PFI-PE) study of gaseous cobalt carbide (CoC) near its ionization onset in the total energy range of 61,200-64,510 cm(-1). The cold gaseous CoC sample was prepared by a laser ablation supersonically cooled beam source. By exciting CoC molecules thus generated to single N' rotational levels of the intermediate CoC∗((2)Σ(+); v') state using a VIS dye laser prior to UV laser photoionization, we have obtained N(+) rotationally resolved PFI-PE spectra for the CoC(+)(X(1)Σ(+); v(+) = 0 and 1) ion vibrational bands free from interference by impurity species except Co atoms produced in the ablation source. The rotationally selected and resolved PFI-PE spectra have made possible unambiguous rotational assignments, yielding accurate values for the adiabatic ionization energy of CoC(X(2)Σ(+)), IE(CoC) = 62,384.3 ± 0.6 cm(-1) (7.73467 ± 0.00007 eV), the vibrational frequency ωe (+) = 985.6 ± 0.6 cm(-1), the anharmonicity constant ωe (+)χe (+) = 6.3 ± 0.6 cm(-1), the rotational constants (Be (+) = 0.7196 ± 0.0005 cm(-1), αe (+) = 0.0056 ± 0.0008 cm(-1)), and the equilibrium bond length re (+) = 1.534 Å for CoC(+)(X(1)Σ(+)). The observation of the N(+) = 0 level in the PFI-PE measurement indicates that the CoC(+) ground state is of (1)Σ(+) symmetry. Large ΔN(+) = N(+) - N' changes up to 6 are observed for the photoionization transitions CoC(+)(X(1)Σ(+); v(+) = 0-2; N(+)) ← CoC∗((2)Σ(+); v'; N' = 6, 7, 8, and 9). The highly precise energetic and spectroscopic data obtained in the present study have served as a benchmark for testing theoretical predictions based on state-of-the-art ab initio quantum calculations at the CCSDTQ∕CBS level of theory as presented in the companion article.

Comparison of four different lasers for acne scars: Resurfacing and fractional lasers.

PubMed

You, Hi-Jin; Kim, Deok-Woo; Yoon, Eul-Sik; Park, Seung-Ha

2016-04-01

Acne scars are common and cause cosmetic problems. There is a multitude of treatment options for acne scars, including dermabrasion, chemical peeling, and fillers, but the advent of laser technology has greatly improved the treatment of acne scars. Although several laser systems are available, studies comparing their efficacy are limited. This study compares the results of treatments using resurfacing (carbon dioxide, CO2; erbium-doped yttrium aluminum garnet, Er:YAG) versus fractional (nonablative fractional laser, NAFL; ablative fractional laser, AFL) lasers. A retrospective photographic analysis of 58 patients who underwent laser treatment for facial atrophic acne scars was performed. Clinical improvement was assessed by six blinded investigators with a scale graded from 0 to 10. Adverse events were also noted. Mean improvement scores of the CO2, Er:YAG, NAFL, and AFL groups were 6.0, 5.8, 2.2, and 5.2, respectively. The NAFL group showed a significantly lower score than the other groups. The mean number of treatments was significantly greater in the fractional laser groups than in the resurfacing laser groups. The resurfacing laser groups had a prolonged recovery period and high risk of complications. The Er:YAG laser caused less erythema or pigmentation compared to the CO2 laser. Although the CO2 laser, Er:YAG laser, and AFL improved the acne scars, the CO2 laser had a greater downtime. Three consecutive AFL treatments are as effective as a single treatment with resurfacing lasers, with shorter social downtime periods and less adverse effects. Copyright © 2016 British Association of Plastic, Reconstructive and Aesthetic Surgeons. Published by Elsevier Ltd. All rights reserved.

Modelling the influence of pore size on the response of materials to infrared lasers An application to human enamel

NASA Astrophysics Data System (ADS)

Vila Verde, A.; Ramos, Marta M. D.

2005-07-01

We present an analytical model for a ceramic material (hydroxyapatite, HA) containing nanometre-scale water pores, and use it to estimate the pressure at the pore as a function of temperature at the end of a single 0.35 μs laser pulse by Er:YAG (2.94 μm) and CO 2 (10.6 μm) lasers. Our results suggest that the pressure at the pore is directly related to pore temperature, and that very high pressures can be generated simply by the thermal expansion of liquid water. Since the temperature reached in the pores at the end of the laser pulse is a strong function of pore size for Er:YAG lasers, but is independent of pore size for CO 2 lasers, our present results provide a possible explanation for the fact that human dental enamel threshold ablation fluences vary more for Er:YAG lasers than for CO 2 lasers. This suggests that experimentalists should analyse their results accounting for factors, like age or type of tooth, that may change the pore size distribution in their samples.

The treatment of sulphur mustard burns with laser debridement.

PubMed

Evison, D; Brown, R F R; Rice, P

2006-01-01

The chemical warfare agent, sulphur mustard (SM), is a potent blistering agent in man. Skin exposure can produce partial-thickness burns which take up to three months to heal. The aim of this study was to investigate the use of early laser ablation as a means of accelerating this exceptionally slow rate of healing. Four circular partial-thickness SM burns were induced on the dorsum of nine large white pigs (under general anaesthesia). At 72 h post-exposure, three burns per animal were ablated with a single pass of an UltraPulse 5000C CO(2) laser, at a fluence of 5-6 J cm(-2). All the burns were dressed with silver sulphadiazine and a semi-occlusive dressing. At one, two and three weeks post-surgery three animals were culled and all lesions excised for histological analysis. Burn depth was confirmed and measurements of the radii of regenerative epithelium were performed allowing the area of the zone of re-epithelialisation in each lesion to be calculated. Laser-treated lesions showed a significant increase (350%) in healing rates compared to controls (p<0.005). At two weeks, the laser-treated sites were 95% healed in comparison with control sites (28% healed). These data suggest that laser ablation may be effective in the treatment of partial-thickness SM-induced skin injury.

Laser micromachining of cadmium tungstate scintillator for high energy X-ray imaging

NASA Astrophysics Data System (ADS)

Richards, Sion Andreas

Pulsed laser ablation has been investigated as a method for the creation of thick segmented scintillator arrays for high-energy X-ray radiography. Thick scintillators are needed to improve the X-ray absorption at high energies, while segmentation is required for spatial resolution. Monte-Carlo simulations predicted that reflections at the inter-segment walls were the greatest source of loss of scintillation photons. As a result of this, fine pitched arrays would be inefficient as the number of reflections would be significantly higher than in large pitch arrays. Nanosecond and femtosecond pulsed laser ablation was investigated as a method to segment cadmium tungstate (CdWO_4). The effect of laser parameters on the ablation mechanisms, laser induced material changes and debris produced were investigated using optical and electron microscopy, energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy for both types of lasers. It was determined that nanosecond ablation was unsuitable due to the large amount of cracking and a heat affected zone created during the ablation process. Femtosecond pulsed laser ablation was found to induce less damage. The optimised laser parameters for a 1028 nm laser was found to be a pulse energy of 54 μJ corresponding to a fluence of 5.3 J cm. -2 a pulse duration of 190 fs, a repetition rate of 78.3 kHz and a laser scan speed of 707 mm s. -1 achieving a normalised pulse overlap of 0.8. A serpentine scan pattern was found to minimise damage caused by anisotropic thermal expansion. Femtosecond pulsed ablation was also found to create a layer of tungsten and cadmium sub-oxides on the surface of the crystals. The CdWO_4 could be cleaned by immersing the CdWO_4 in ammonium hydroxide at 45°C for 15 minutes. However, XPS indicated that the ammonium hydroxide formed a thin layer of CdCO_3 and Cd(OH)_2 on the surface. Prototype arrays were shown to be able to resolve features as small as 0.5 mm using keV energy X-rays. The most efficient prototype showed low detective quantum efficiency of 0.08±0.01 at 0 lp/mm using a tube voltage of 160 kVp.

PHOTONICS AND NANOTECHNOLOGY Laser synthesis and modification of composite nanoparticles in liquids

NASA Astrophysics Data System (ADS)

Tarasenko, N. V.; Butsen, A. V.

2010-12-01

The works devoted to the formation and modification of nanoparticles using laser ablation of solid targets in liquids are reviewed. Several approaches to implement laser ablation in liquids, aimed at synthesising nanoparticles of complex composition, are considered: direct laser ablation of a target of corresponding composition, laser ablation of a combined target composed of two different metals, laser irradiation of a mixture of two or more colloidal solutions, and laser ablation in reactive liquids. The properties of two-component bimetallic systems (Ag — Cu, Ag — Au), semiconductor nanocrystals (ZnO, CdSe), chalcopyrite nanoparticles, and doped oxide nanoparticles (ZnO:Ag, Gd2O2:Tb3+) formed as a result of single- and double-pulse laser ablation in different liquids (water, ethanol, acetone, solutions of polysaccharides) are discussed.

Selective removal of esthetic composite restorations with spectral guided laser ablation

NASA Astrophysics Data System (ADS)

Yi, Ivana; Chan, Kenneth H.; Tsuji, Grant H.; Staninec, Michal; Darling, Cynthia L.; Fried, Daniel

2016-02-01

Dental composites are used for a wide range of applications such as fillings for cavities, adhesives for orthodontic brackets, and closure of gaps (diastemas) between teeth by esthetic bonding. Anterior restorations are used to replace missing, diseased and unsightly tooth structure for both appearance and function. When these restorations must be replaced, they are difficult to remove mechanically without causing excessive removal or damage to enamel because dental composites are color matched to teeth. Previous studies have shown that CO2 lasers have high ablation selectivity and are well suited for removal of composite on occlusal surfaces while minimizing healthy tissue loss. A spectral feedback guidance system may be used to discriminate between dental composite and dental hard tissue for selective ablation of composite material. The removal of composite restorations filling diastemas is more challenging due to the esthetic concern for anterior teeth. The objective of this study is to determine if composite spanning a diastema between anterior teeth can be removed by spectral guided laser ablation at clinically relevant rates with minimal damage to peripheral healthy tissue and with higher selectivity than a high speed dental handpiece.

Using synchrotron X-ray phase-contrast micro-computed tomography to study tissue damage by laser irradiation.

PubMed

Robinson, Alan M; Stock, Stuart R; Soriano, Carmen; Xiao, Xianghui; Richter, Claus-Peter

2016-11-01

The aim of this study was to determine if X-ray micro-computed tomography could be used to locate and characterize tissue damage caused by laser irradiation and to describe its advantages over classical histology for this application. A surgical CO 2 laser, operated in single pulse mode (100 milliseconds) at different power settings, was used to ablate different types of cadaveric animal tissues. Tissue samples were then harvested and imaged with synchrotron X-ray phase-contrast and micro-computed tomography to generate stacks of virtual sections of the tissues. Subsequently, Fiji (ImageJ) software was used to locate tissue damage, then to quantify volumes of laser ablation cones and thermal coagulation damage from 3D renderings of tissue image stacks. Visual comparisons of tissue structures in X-ray images with those visible by classic light microscopy histology were made. We demonstrated that micro-computed tomography could be used to rapidly identify areas of surgical laser ablation, vacuolization, carbonization, and thermally coagulated tissue. Quantification and comparison of the ablation crater, which represents the volume of ablated tissue, and the thermal coagulation zone volumes were performed faster than we could by classical histology. We demonstrated that these procedures can be performed on fresh hydrated and non-sectioned plastic embedded tissue. We demonstrated that the application of non-destructive micro-computed tomography to the visualization and analysis of laser induced tissue damage without tissue sectioning is possible. This will improve evaluation of new surgical lasers and their corresponding effect on tissues. Lasers Surg. Med. 48:866-877, 2016. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Laser assisted drug delivery: a review of an evolving technology.

PubMed

Sklar, Lindsay R; Burnett, Christopher T; Waibel, Jill S; Moy, Ronald L; Ozog, David M

2014-04-01

Topically applied drugs have a relatively low cutaneous bioavailability. This article reviews the existing applications of laser assisted drug delivery, a means by which the permeation of topically applied agents can be enhanced into the skin. The existing literature suggests that lasers are a safe and effective means of enhancing the delivery of topically applied agents through the skin. The types of lasers most commonly studied in regards to drug delivery are the carbon dioxide (CO2 ) and erbium:yttrium-aluminum-garnet (Er:YAG) lasers. Both conventional ablative and fractional ablative modalities have been utilized and are summarized herein. The majority of the existing studies on laser assisted drug delivery have been performed on animal models and additional human studies are needed. Laser assisted drug delivery is an evolving technology with potentially broad clinical applications. Multiple studies demonstrate that laser pretreatment of the skin can increase the permeability and depth of penetration of topically applied drug molecules for both local cutaneous and systemic applications. © 2014 Wiley Periodicals, Inc.

Hair regrowth through wound healing process after ablative fractional laser treatment in a murine model.

PubMed

Bae, Jung Min; Jung, Han Mi; Goo, Boncheol; Park, Young Min

2015-07-01

Alopecia is one of the most common dermatological problems in the elderly; however, current therapies for it are limited by low efficacy and undesirable side effects. Although clinical reports on fractional laser treatment for various alopecia types are increasing, the exact mechanism remains to be clarified. The purposes of this study were to demonstrate the effect of ablative fractional laser treatment on hair follicle regrowth in vivo and investigate the molecular mechanism after laser treatment. Ablative CO2 fractional laser was applied to the shaved dorsal skin of 7-week-old C57BL/6 mice whose hair was in the telogen stage. After 12 mice were treated at various energy (10-40 mJ/spot) and density (100-400 spots/cm(2) ) settings to determine the proper dosage for maximal effect. Six mice were then treated at the decided dosage and skin specimens were sequentially obtained by excision biopsy from the dorsal aspect of each mouse. Tissue samples were used for the immunohistochemistry and reverse transcription polymerase chain reaction assays to examine hair follicle status and their related molecules. The most effective dosage was the 10 mJ/spot and 300 spots/cm(2) setting. The anagen conversion of hair was observed in the histopathological examination, while Wnt/β-catenin expression was associated with hair regrowth in the immunohistochemistry and molecular studies. Ablative fractional lasers appear to be effective for inducing hair regrowth via activation of the Wnt/β-catenin pathway in vivo. Our findings indicate that fractional laser treatment can potentially be developed as new treatment options for stimulating hair regrowth. © 2015 Wiley Periodicals, Inc.

Optical ridge waveguides in Er3+/Yb3+ co-doped phosphate glass produced by ion irradiation combined with femtosecond laser ablation for guided-wave green and red upconversion emissions

NASA Astrophysics Data System (ADS)

Chen, Chen; He, Ruiyun; Tan, Yang; Wang, Biao; Akhmadaliev, Shavkat; Zhou, Shengqiang; de Aldana, Javier R. Vázquez; Hu, Lili; Chen, Feng

2016-01-01

This work reports on the fabrication of ridge waveguides in Er3+/Yb3+ co-doped phosphate glass by the combination of femtosecond laser ablation and following swift carbon ion irradiation. The guiding properties of waveguides have been investigated at 633 and 1064 nm through end face coupling arrangement. The refractive index profile on the cross section of the waveguide has been constructed. The propagation losses can be reduced considerably after annealing treatment. Under the optical pump laser at 980 nm, the upconversion emission of both green and red fluorescence has been realized through the ridge waveguide structures.

193 nm ArF laser ablation and patterning of chitosan thin films

NASA Astrophysics Data System (ADS)

Aesa, A. A.; Walton, C. D.

2018-06-01

This paper reports laser ablation studies on spin-coated biopolymer chitosan films, β-l,4-1inked 2-amino-2-deoxy- d-glucopyranose. Chitosan has been irradiated using an ArF laser emitting at 193 nm. An ablation threshold of F T = 85±8 mJ cm-2 has been determined from etch rate measurements. Laser-ablated chitosan is characterised using white light interferometry, scanning electron microscopy, and thermo-gravimetric analysis. Laser ablation of chitosan is discussed in terms of thermal and photoacoustic mechanisms. Heat transfer is simulated to assist in the understanding of laser-irradiated chitosan using a finite-element method and the software package COMSOL Multi-Physics™. As a demonstrator, a micro-array of square structures in the form of a crossed grating has been fabricated by laser ablation using a mask projection scanning method. The initial investigations show no evidence of thermal damage occurring to the adjacent chitosan when operating at a moderately low laser fluence of 110 mJ cm-2.

Soft tissue effects of the THC:YAG laser on canine vocal cords.

PubMed

Kay, S L; Oz, M C; Haber, M; Blitzer, A; Treat, M R; Trokel, S L

1992-09-01

Recently, a laser based on a thulium-holmium-chromium (THC) doped Yttrium-aluminum-garnet (YAG) rod has been developed that produces light of 2.15 microns wavelength and can be transmitted through a low OH- silica fiberoptic cable. This wavelength falls on one of the peaks of the energy absorption spectrum of water. Thus, the THC:YAG laser eliminates the disadvantage of a cumbersome delivery system found in the CO2 laser while still providing precise cutting and minimal tissue injury inherent in lasers emitting light absorbed by water. We evaluated the soft tissue effects of this laser on canine vocal cords. Ablative lesions were produced by the THC:YAG laser and histologically examined on postoperative days 1, 7, and 28. Results indicate that the depth of tissue penetration is easily controlled and the healing response to tissue injury is comparable to that of the CO2 laser. The THC:YAG laser should prove to be a superior laser for use in otorhinolaryngology, especially when adapted to a flexible endoscope.

Laser fractional photothermolysis of the skin: numerical simulation of microthermal zones.

PubMed

Marqa, Mohamad Feras; Mordon, Serge

2014-04-01

Laser Fractional Photothermolysis (FP) is one of the innovative techniques for skin remodeling and resurfacing. During treatment, the control of the Microscopic Thermal Zones' (MTZs) dimensions versus pulse energy requires detailed knowledge of the various parameters governing the heat transfer process. In this study, a mathematical model is devised to simulate the effect of pulse energy variations on the dimensions of MTZs. Two series of simulations for ablative (10.6 μm CO2) and non-ablative (1.550 μm Er:Glass) lasers systems were performed. In each series, simulations were carried for the following pulses energies: 5, 10, 15, 20, 25, 30, 35, and 40 mJ. Results of simulations are validated by histological analysis images of MTZs sections reported in works by Hantash et al. and Bedi et al. MTZs dimensions were compared between histology and those achieved using our simulation model using fusion data technique for both ablative FP and non-ablative FP treatment methods. Depths and widths from simulations are usually deeper (21 ± 2%) and wider (12 ± 2%) when compared with histological analysis data. When accounting for the shrinkage effect of excision of cutaneous tissues, a good correlation can be established between the simulation and the histological analysis results.

Laser-assisted delivery of vitamin C, vitamin E, and ferulic acid formula serum decreases fractional laser postoperative recovery by increased beta fibroblast growth factor expression.

PubMed

Waibel, Jill S; Mi, Qing-Sheng; Ozog, David; Qu, Le; Zhou, Li; Rudnick, Ashley; Al-Niaimi, Firas; Woodward, Julie; Campos, Valerie; Mordon, Serge

2016-03-01

Laser-assisted drug delivery is an emerging technology to achieve greater penetration by existing topical medications to reach desired targets in the tissue. The objective of this research was to study whether laser-assisted delivery of Vitamin C, E, and Ferulic immediately postoperatively of fractional ablative laser could improve wound healing. Secondary objectives were to evaluate the potential molecular markers involved in this wound-healing process. A double blinded, prospective, single center, randomized split face trial of Vitamin C, E, and Ferulic topical formula #740019 to decrease postoperative recovery time in fractional ablative laser resurfacing for photo damage. Fifteen healthy men and women of ages 30-55 years were treated with the Vitamin C, E, and Ferulic acid serum to one side of face and vehicle to the other side of face, within 2 minutes immediately after fractional ablative CO2 laser surgery and daily during the healing process. Patients were evaluated daily on days 1-7 using photographs, patient questionnaires, and molecular evaluation. Clinically, postoperative Vitamin C, E, and Ferulic delivery resulted in decreased edema versus vehicle on postoperative day 7 and decreased erythema versus vehicle on postoperative days 3 and 5. Molecularly, the expression of basic fibroblast growth factor (bFGF) was significantly increased at day 5 on the lesion treated with Vitamin C, E, and Ferulic acid serum compared to vehicle control on the other side. This is first study to show that Vitamin C, E, and Ferulic acid correlate with more rapid wound healing post-fractional ablative laser. Elevated bFGF could be involved in the Vitamin C, E, and Ferulic acid-induced rapid wound healing. © 2015 Wiley Periodicals, Inc.

Effect of ZrO2 Powders on the Pyrolysis of Polycarbosilanes Coating Under Laser Ablation

NASA Astrophysics Data System (ADS)

Cheng, Han; Chen, Zhaofeng; Tao, Jie; Yan, Bo; Li, Cong; Wang, Liangbing; Zhang, Ying; Fang, Dan; Wan, Shuicheng; Wu, Wangping

Aircrafts hold the outstanding mastery of the sky in modern wars, however the laser beam weapons can carry out laser attacking to aircrafts. The purpose of the present paper is to research on a new type laser protective material. Polycarbosilanes (PCS)/divinylbenzene mixtures containing ZrO2 powders were brushed to the surface of the aluminum alloy plates and then cured at 150°C for 6 h. The PCS-coated plates were ablated by laser for 3 s. The phase identification of as-ablated powders was examined by X-ray diffraction. The results indicated that the as-ablated powders of cured PCS were composed of major phase β-SiC and smaller amounts of free carbon. The PCS composite coating played a certain role of laser ablation resistance. The effect of added ZrO2 powders on the pyrolysis of PCS-coating under laser ablation is conspicuous.

Infrared spectra of the CO2- and C2O4- anions isolated in solid argon

NASA Astrophysics Data System (ADS)

Zhou, Mingfei; Andrews, Lester

1999-02-01

Laser ablation of transition metal targets with concurrent 11 to 12 K condensation of CO2-Ar mixtures produces a sharp metal independent infrared absorption at 1657.0 cm-1 due to CO2-, which is formed from the capture of ablated electrons by CO2 molecules during the condensation process. Two additional metal independent absorptions are produced at 1856.7 and 1184.7 cm-1 on matrix annealing to 25 K to allow diffusion and reaction of CO2 and CO2-. Isotopic substitution (13CO2, C18O2, C16,18O2, and mixtures) shows that these two vibrations involve two equivalent CO2 subunits. The excellent agreement with frequencies, intensities, and isotopic frequency ratios from density-functional calculations supports assignment to the symmetrical C2O4- anion with D2d symmetry. Photodissociation (470-580 nm) and failure to observe these absorptions in identical experiments doped with the electron trapping molecule CCl4 further support the molecular anion assignments. Although absorptions were observed for weak (CO2)(CO2-) complexes, no evidence was found for the asymmetric O2CṡOCO- molecule-anion complex characterized by calculations.

Comprehensive studies of ultrashort laser pulse ablation of tin target at terawatt power

NASA Astrophysics Data System (ADS)

Elsied, Ahmed M.; Diwakar, Prasoon K.; Hassanein, Ahmed

2018-01-01

The fundamental properties of ultrashort laser interactions with metals using up to terawatt power were comprehensively studied, i.e., specifically mass ablation, nanoparticle formation, and ion dynamics using multitude of diagnostic techniques. Results of this study can be useful in many fields of research including spectroscopy, micromachining, thin film fabrication, particle acceleration, physics of warm dense matter, and equation-of-state determination. A Ti:Sapphire femtosecond laser system (110 mJ maximum energy, 40 fs, 800 nm, P-polarized, single pulse mode) was used, which delivered up to 3 terawatt laser power to ablate 1 mm tin film in vacuum. The experimental analysis includes the effect of the incident laser fluence on the ablated mass, size of the ablated area, and depth of ablation using white light profilometer. Atomic force microscope was used to measure the emitted particles size distribution at different laser fluence. Faraday cup (FC) detector was used to analyze the emitted ions flux by measuring the velocity, and the total charge of the emitted ions. The study shows that the size of emitted particles follows log-normal distribution with peak shifts depending on incident laser fluence. The size of the ablated particles ranges from 20 to 80 nm. The nanoparticles deposited on the wafer tend to aggregate and to be denser as the incident laser fluence increases as shown by AFM images. Laser ablation depth was found to increase logarithmically with laser fluence then leveling off at laser fluence > 400 J/cm2. The total ablated mass tends to increase logarithmically with laser fluence up to 60 J/cm2 while, increases gradually at higher fluence due to the increase in the ablated area. The measured ion emitted flux shows a linear dependence on laser fluence with two distinct regimes. Strong dependence on laser fluence was observed at fluences < 350 J/cm2. Also, a slight enhancement in ion velocity was observed with increasing laser fluence up to 350 J/cm2.

Preparation of graphite dispersed copper composite on copper plate with CO2 laser

NASA Astrophysics Data System (ADS)

Yokoyama, S.; Ishikawa, Y.; Muizz, M. N. A.; Hisyamudin, M. N. N.; Nishiyama, K.; Sasano, J.; Izaki, M.

2018-01-01

It was tried in this work to prepare the graphite dispersed copper composite locally on a copper plate with a CO2 laser. The objectives of this study were to clear whether copper graphite composite was prepared on a copper plate and how the composite was prepared. The carbon content at the laser spot decreased with the laser irradiation time. This mainly resulted from the elimination by the laser trapping. The carbon content at the outside of the laser spot increased with time. Both the laser ablation and the laser trapping did not act on the graphite particles at the outside of the laser spot. Because the copper at the outside of the laser spot melted by the heat conduction from the laser spot, the particles were fixed by the wetting. However, the graphite particles were half-floated on the copper plate. The Vickers hardness decreased with an increase with laser irradiation time because of annealing.

Clinical effects of non-ablative and ablative fractional lasers on various hair disorders: a case series of 17 patients.

PubMed

Cho, Suhyun; Choi, Min Ju; Zheng, Zhenlong; Goo, Boncheol; Kim, Do-Young; Cho, Sung Bin

2013-04-01

Both ablative and non-ablative fractional lasers have been applied to various uncommon hair disorders. The purpose of this study was to demonstrate the clinical effects of fractional laser therapy on the course of primary follicular and perifollicular pathologies and subsequent hair regrowth. A retrospective review of 17 patients with uncommon hair disorders - including ophiasis, autosomal recessive woolly hair/hypotrichosis, various secondary cicatricial alopecias, pubic hypotrichosis, frontal fibrosing alopecia, and perifolliculitis abscedens et suffodiens - was conducted. All patients had been treated with non-ablative and/or ablative fractional laser therapies. The mean clinical improvement score in these 17 patients was 2.2, while the mean patient satisfaction score was 2.5. Of the 17 subjects, 12 (70.6%) demonstrated a clinical response to non-ablative and/or ablative fractional laser treatments, including individuals with ophiasis, autosomal recessive woolly hair/hypotrichosis, secondary cicatricial alopecia (scleroderma and pressure-induced alopecia), frontal fibrosing alopecia, and perifolliculitis abscedens et suffodiens. Conversely, patients with long-standing ophiasis, surgical scar-induced secondary cicatricial alopecia, and pubic hypotrichosis did not respond to fractional laser therapy. Our findings demonstrate that the use of non-ablative and/or ablative fractional lasers promoted hair growth in certain cases of uncommon hair disorders without any remarkable side effects.

An observation of ablation effect of soft biotissue by pulsed Er:YAG laser

NASA Astrophysics Data System (ADS)

Zhang, Xianzeng; Xie, Shusen; Ye, Qing; Zhan, Zhenlin

2007-02-01

Because of the unique properties with regard to the absorption in organic tissue, pulsed Er:YAG laser has found most interest for various application in medicine, such as dermatology, dentistry, and cosmetic surgery. However, consensus regarding the optimal parameters for clinical use of this tool has not been reached. In this paper, the laser ablation characteristics of soft tissue by Er:YAG laser irradiation was studied. Porcine skin tissue in vitro was used in the experiment. Laser fluences ranged from 25mJ/mm2 to 200mJ/mm2, repetition rates was 5Hz, spot sizes on the tissue surface was 2mm. The ablation effects were assessed by the means of optical microscope, ablation diameters and depths were measured with reading microscope. It was shown that the ablation of soft biotissue by pulsed Er:YAG laser was a threshold process. With appropriate choice of irradiation parameters, high quality ablation with clean, sharp cuts following closely the spatial contour of the incident beam can be achieved. The curves of ablation crater diameter and depth versus laser fluence were obtained, then the ablation threshold and ablation yield were calculated subsequently, and the influence of the number of pulses fired into a crater on ablation crater depth was also discussed.

Bond strength of etch-and-rinse and self-etch adhesive systems to enamel and dentin irradiated with a novel CO2 9.3 μm short-pulsed laser for dental restorative procedures.

PubMed

Rechmann, Peter; Bartolome, N; Kinsel, R; Vaderhobli, R; Rechmann, B M T

2017-12-01

The objective of this study was to evaluate the influence of CO 2 9.3 μm short-pulsed laser irradiation on the shear bond strength of composite resin to enamel and dentin. Two hundred enamel and 210 dentin samples were irradiated with a 9.3 µm carbon dioxide laser (Solea, Convergent Dental, Inc., Natick, MA) with energies which either enhanced caries resistance or were effective for ablation. OptiBond Solo Plus [OptiBondTE] (Kerr Corporation, Orange, CA) and Peak Universal Bond light-cured adhesive [PeakTE] (Ultradent Products, South Jordan, UT) were used. In addition, Scotchbond Universal [ScotchbondSE] (3M ESPE, St. Paul, MN) and Peak SE self-etching primer with Peak Universal Bond light-cured adhesive [PeakSE] (Ultradent Products) were tested. Clearfil APX (Kuraray, New York, NY) was bonded to the samples. After 24 h, a single plane shear bond test was performed. Using the caries preventive setting on enamel resulted in increased shear bond strength for all bonding agents except for self-etch PeakSE. The highest overall bond strength was seen with PeakTE (41.29 ± 6.04 MPa). Etch-and-rinse systems achieved higher bond strength values to ablated enamel than the self-etch systems did. PeakTE showed the highest shear bond strength with 35.22 ± 4.40 MPa. OptiBondTE reached 93.8% of its control value. The self-etch system PeakSE presented significantly lower bond strength. The shear bond strength to dentin ranged between 19.15 ± 3.49 MPa for OptiBondTE and 43.94 ± 6.47 MPa for PeakSE. Etch-and-rinse systems had consistently higher bond strength to CO 2 9.3 µm laser-ablated enamel. Using the maximum recommended energy for dentin ablation, the self-etch system PeakSE reached the highest bond strength (43.9 ± 6.5 MPa).

In situ diagnosis of pulsed UV laser surface ablation of tungsten carbide hardmetal by using laser-induced optical emission spectroscopy

NASA Astrophysics Data System (ADS)

Li, Tiejun; Lou, Qihong; Wei, Yunrong; Huang, Feng; Dong, Jingxing; Liu, Jingru

2001-12-01

Surface ablation of cobalt cemented tungsten carbide hardmetal with pulsed UV laser has been in situ diagnosed by using the technique of laser-induced optical emission spectroscopy. The dependence of emission intensity of cobalt lines on number of laser shots was investigated at laser fluence of 2.5 J/cm 2. As a comparison, the reliance of emission intensity of cobalt lines as a function of laser pulse number by using pure cobalt as ablation sample was also studied at the same laser condition. It was found that for surface ablation of tungsten carbide hardmetal at laser fluence of 2.5 J/cm 2, the intensities of cobalt lines fell off dramatically in the first 300 consecutive laser shots and then slowed down to a low stable level with even more shots. For surface ablation of pure cobalt at the same laser condition, the intensities of cobalt lines remained constant more or less even after 500 laser shots and then reduced very slowly with even more shots. It was concluded that selective evaporation of cobalt at this laser fluence should be responsible for the dramatic fall-off of cobalt lines with laser shots accumulation for surface ablation of tungsten carbide hardmetal. In contrast, for surface ablation of pure cobalt, the slow reduction of cobalt lines with pulse number accumulation should be due to the formation of laser-induced crater effect.

Nd:YAG and CO2 laser therapy of oral mucosal lesions.

PubMed

White, J M; Chaudhry, S I; Kudler, J J; Sekandari, N; Schoelch, M L; Silverman, S

1998-12-01

Experiences gained in the management of oral mucosal lesions by CO2 and Nd:YAG laser therapy in an outpatient clinic treated over an 80-year period are described. Lasers have indications for use in dentistry for incision, excision, and coagulation of intraoral soft tissue. Advances in laser technology have provided delivery systems for site-specific delivery of laser energy with short interaction items on tissue to be ablated. This study retrospectively evaluates a series of clinical case studies. Sixty-four patients with a variety of benign oral soft tissue lesions were treated by laser excision. Thirty-five patients were treated by a pulsed fiberoptic delivered Nd:YAG contact laser, and 29 by a continuous free-beam CO2 non-contact laser. The largest group of lesions treated were leukoplakia (39 cases). Other lesions excised and biopsied were lichen planus, squamous papilloma, pyogenic granuloma, focal melanosis, nonhealing traumatic ulceration, hemangioma, and lymphangioma. All patients were followed postoperatively (mean 6.8 months, range 1-36 months). Laser excision was well tolerated by patients with no intraoperative or postoperative adverse effects. All patients healed postsurgically with no loss of function. CO2 and Nd:YAG lasers are successful surgical options when performing excision of benign intraoral lesions. Advantages of laser therapy include minimal postoperative pain, conservative site-specific minimally invasive surgeries, and elimination of need for sutures.

Performance of Er:YAG laser ablation of hard bone under different irrigation water cooling conditions

NASA Astrophysics Data System (ADS)

Beltrán Bernal, Lina M.; Shayeganrad, Gholamreza; Kosa, Gabor; Zelechowski, Marek; Rauter, Georg; Friederich, Niklaus; Cattin, Philippe C.; Zam, Azhar

2018-02-01

The biological applicability of the Erbium-doped Yttrium Aluminum Garnet (Er:YAG) laser in surgical processes is so far limited to hard dental tissues. Using the Er:YAG laser for bone ablation is being studied since it has shown good performance for ablating dental hard tissues at the wavelength 2.94 μm, which coincides with the absorption peak of water, one of the main components of hard tissue, like teeth and bone. To obtain a decent performance of the laser in the cutting process, we aim at examining the influence of sequenced water jet irrigation on both, the ablation rate and the prevention of carbonization while performing laser ablation of bone with fixed laser parameters. An Er:YAG laser at 2.94 μm wavelength, 940 mJ energy per pulse, 400 μs pulse width, and 10 Hz repetition rate is used for the ablation of a porcine femur bone under different pulsed water jet irrigation conditions. We used micro-computed tomography (micro-CT) scans to determine the geometry of the ablated areas. In addition, scanning electron microscopy (SEM) is used for qualitative observations for the presence of carbonization and micro-fractures on the ablated surfaces. We evaluate the performance of the laser ablation process for the different water jet conditions in terms of the ablation rate, quantified by the ablated volume per second and the ablation efficiency, calculated as the ablated volume per pulse energy. We provide an optimized system for laser ablation which delivers the appropriate amount of water to the bone and consequently, the bone is ablated in the most efficient way possible without carbonization.

Partial ablation of stratum corneum by UV (193-nm) or IR (2.94-μm) pulsed lasers to enhance transdermal drug delivery rate

NASA Astrophysics Data System (ADS)

Fujiwara, Ai; Hinokitani, Toshihiro; Goto, Kenichi; Arai, Tsunenori

2004-07-01

To develop the noninvasive transdermal drug delivery system, pulsed lasers (argon-fluoride excimer laser (ArF laser) and erbium:yittrium aluminum garnet laser (Er:YAG laser)) were used to partially ablate the stratum corneum (SC), the upper layer of the skin. Because of the barrier function of the SC to drug permeation, the number of drugs especially macromolecules used in transdermal drug delivery system without skin irritation has been limited. Ultrastructural changes on the SC surface of ablated Yucatan micropig skin in vitro were observed with Environmental Scanning Electron Microscope. The result indicated that the structural changes varied according to each laser sources and irradiation conditions (laser fluences and numbers of pulses). Many granular structures of about 2 μm in diameter were observed in the ablated sites on ArF laser with lower fluence exposure (30 mJ/cm2, 200 pulses), and plane structures in the sites with higher fluence exposure (80 mJ/cm2, 80 pulses). In contrast, the ablation of Er:YAG laser created some pores of about 20 μm across on the surface of the SC. Under the irradiation condition of partial ablation, the skin permeability of macromolecule compound was enhanced. This partial SC ablation by pulsed laser could be possible candidate of the noninvasive transdermal drug delivery system with good physiological conditions of skin.

Structural modifications induced in dentin by femtosecond laser

NASA Astrophysics Data System (ADS)

Le, Quang-Tri; Bertrand, Caroline; Vilar, Rui

2016-12-01

The structural and chemical modifications induced in dentin by ultrafast laser ablation were studied. The laser experiments were performed with a Yb:KYW chirped-pulse-regenerative amplification laser system (560-fs pulse duration, 1030-nm radiation wavelength), fluences in the range 2 to 14 J/cm2, 1-kHz pulse repetition rate, and 5-mm/s scanning speed. The ablation surfaces were characterized by scanning electron microscopy and Fourier transform infrared spectroscopy. The ablation surfaces produced with 2 J/cm2 presented an irregular morphology with exposed dentinal tubules and no evidence of thermal effects. For 7 and 14 J/cm2, the ablation surfaces were covered by a layer of redeposited ablation debris, consisting mainly of amorphous calcium phosphate. This layer is weakly adherent to the underlying tissue and can be easily removed by ultrasonication, revealing a surface with a morphology similar to the one obtained with 2 J/cm2. The constitution of the dentin ablation surfaces is similar to the constitution of pristine dentin, showing that, within this fluence range, the laser treatment does not significantly modify the structure and constitution of dentin. The results achieved suggest an ablation mechanism where collagen is preferentially decomposed by the laser radiation, reducing the tissue cohesive strength and leading, ultimately, to its ablation.

The threshold of vapor channel formation in water induced by pulsed CO2 laser

NASA Astrophysics Data System (ADS)

Guo, Wenqing; Zhang, Xianzeng; Zhan, Zhenlin; Xie, Shusen

2012-12-01

Water plays an important role in laser ablation. There are two main interpretations of laser-water interaction: hydrokinetic effect and vapor phenomenon. The two explanations are reasonable in some way, but they can't explain the mechanism of laser-water interaction completely. In this study, the dynamic process of vapor channel formation induced by pulsed CO2 laser in static water layer was monitored by high-speed camera. The wavelength of pulsed CO2 laser is 10.64 um, and pulse repetition rate is 60 Hz. The laser power ranged from 1 to 7 W with a step of 0.5 W. The frame rate of high-speed camera used in the experiment was 80025 fps. Based on high-speed camera pictures, the dynamic process of vapor channel formation was examined, and the threshold of vapor channel formation, pulsation period, the volume, the maximum depth and corresponding width of vapor channel were determined. The results showed that the threshold of vapor channel formation was about 2.5 W. Moreover, pulsation period, the maximum depth and corresponding width of vapor channel increased with the increasing of the laser power.

Comparison of separation performance of laser-ablated and wet-etched microfluidic devices

PubMed Central

Baker, Christopher A.; Bulloch, Rayford; Roper, Michael G.

2010-01-01

Laser ablation of glass allows for production of microfluidic devices without the need of hydrofluoric acid and photolithography. The goal of this study was to compare the separation performance of microfluidic devices produced using a low-cost laser ablation system and conventional wet etching. During laser ablation, cracking of the glass substrate was prevented by heating the glass to 300°C. A range of laser energy densities was found to produce channel depths ranging from 4 – 35 μm and channel widths from 118 – 162 μm. The electroosmotic flow velocity was lower in laser-ablated devices, 0.110 ± 0.005 cm s−1, as compared to wet-etched microfluidic chips, 0.126 ± 0.003 cm s−1. Separations of both small and large molecules performed on both wet- and laser-ablated devices were compared by examining limits of detection, theoretical plate count, and peak asymmetry. Laser-induced fluorescence detection limits were 10 pM fluorescein for both types of devices. Laser-ablated and wet-etched microfluidic chips had reproducible migration times with ≤ 2.8% RSD and peak asymmetries ranging from 1.0 – 1.8. Numbers of theoretical plates were between 2.8- and 6.2-fold higher on the wet-etched devices compared to laser-ablated devices. Nevertheless, resolution between small and large analytes was accomplished, which indicates that laser ablation may find an application in pedagogical studies of electrophoresis or microfluidic devices, or in settings where hydrofluoric acid cannot be used. PMID:20827468

Lasers as an approach for promoting drug delivery via skin.

PubMed

Lin, Chih-Hung; Aljuffali, Ibrahim A; Fang, Jia-You

2014-04-01

Using lasers can be an effective drug permeation-enhancement approach for facilitating drug delivery into or across the skin. The controlled disruption and ablation of the stratum corneum (SC), the predominant barrier for drug delivery, is achieved by the use of lasers. The possible mechanisms of laser-assisted drug permeation are the direct ablation of the skin barrier, optical breakdown by a photomechanical wave and a photothermal effect. It has been demonstrated that ablative approaches for enhancing drug transport provide some advantages, including increased bioavailability, fast treatment time, quick recovery of SC integrity and the fact that skin surface contact is not needed. In recent years, the concept of using laser techniques to treat the skin has attracted increasing attention. This review describes recent developments in using nonablative and ablative lasers for drug absorption enhancement. This review systematically introduces the concepts and enhancement mechanisms of lasers, highlighting the potential of this technique for greatly increasing drug absorption via the skin. Lasers with different wavelengths and types are employed to increase drug permeation. These include the ruby laser, the erbium:yttrium-gallium-garnet laser, the neodymium-doped yttrium-aluminum-garnet laser and the CO2 laser. Fractional modality is a novel concept for promoting topical/transdermal drug delivery. The laser is useful in enhancing the permeation of a wide variety of permeants, such as small-molecule drugs, macromolecules and nanoparticles. This potential use of the laser affords a new treatment for topical/transdermal application with significant efficacy. Further studies using a large group of humans or patients are needed to confirm and clarify the findings in animal studies. Although the laser fluence or output energy used for enhancing drug absorption is much lower than for treatment of skin disorders and rejuvenation, the safety of using lasers is still an issue. Caution should be used in optimizing the feasible conditions of the lasers in balancing the effectiveness of permeation enhancement and skin damage.

Reflectivity and laser ablation of ZrB2/Cu ultra high temperature ceramic

NASA Astrophysics Data System (ADS)

Yan, Zhenyu; Ma, Zhuang; Zhu, Shizhen; Liu, Ling; Xu, Qiang

2013-05-01

Ultra high temperature ceramics (UHTCs) were thought to be candidates for laser protective materials due to their high melting point, thermal shock and ablation resistance. The ablation behaviors of UHTCs like ZrB2 and its composite had been intensely investigated by the means of arc, plasma, oxyacetylene ablation. However, the ablation behavior under laser irradiation was still unknown by now. In this paper, the dense bulk composites of ZrB2/Cu were successfully sintered by spark plasma sintering (SPS) at 1650 degree C for 3min. The reflectivity of the composites measured by spectrophotometry achieved 60% in near infrared range and it decreased with the increasing wavelength of incident light. High intensity laser ablation was carried out on the ZrB2/Cu surface. The phase composition and microstructure changes before and after laser irradiation were characterized by X-ray diffraction and SEM respectively. The results revealed that the oxidation and melting were the main mechanisms during the ablation processing.

Comparison of Q-switched Nd: YAG laser and fractional carbon dioxide laser for the treatment of solar lentigines in Asians.

PubMed

Vachiramon, Vasanop; Panmanee, Wikanda; Techapichetvanich, Thanya; Chanprapaph, Kumutnart

2016-04-01

Solar lentigines are benign pigmented lesions that occur mostly on sun-exposed areas. Q-switched and ablative lasers are effective for removing these lesions but the high incidence of postinflammatory hyperpigmentation raises concern in darker skin types. The objective of this study is to compare the efficacy and degree of postinflammatory hyperpigmentation with the Q-switched Nd:YAG and fractional carbon dioxide (CO2 ) laser for treatment of solar lentigines in Asians. Twenty-five Thai patients (skin phototype III-IV) with at least two lesions of solar lentigines on upper extremities were enrolled in this study. Two lesions were randomly selected for the treatment with a single session of Q-switched Nd:YAG or fractional CO2 laser. Outcomes were evaluated using physician grading scale, colorimeter, and patient self-assessment at 6 and 12 weeks after treatment. Side effects were recorded. A total of 532 nm Q-switched Nd:YAG laser showed significant improvement of pigmentation over fractional CO2 laser at 6th and 12th week by both colorimeter assessment and physician grading scale (P < 0.05). No significant difference in postinflammatory hyperpigmentation from both lasers was observed. In terms of patient self-assessment, 80% of the patients treated with 532 nm Q-switched Nd:YAG laser had excellent results compared to 8% in fractional CO2 laser group. However, fractional CO2 laser treatment had faster healing time and less pain score compared to Q-switched Nd:YAG laser. Q-switched Nd:YAG is superior to fractional CO2 laser for treatment of solar lentigines but requires longer healing time and produces more pain. The incidence of postinflammatory hyperpigmentation was not significantly different with both lasers. Further studies are needed to obtain the proper parameter and the treatment frequency of fractional CO2 laser in solar lentigines. © 2016 Wiley Periodicals, Inc.

Long-wave plasma radiofrequency ablation for treatment of xanthelasma palpebrarum.

PubMed

Baroni, Adone

2018-03-01

Xanthelasma palpebrarum is the most common type of xanthoma affecting the eyelids. It is characterized by asymptomatic soft yellowish macules, papules, or plaques over the upper and lower eyelids. Many treatments are available for management of xanthelasma palpebrarum, the most commonly used include surgical excision, ablative CO 2 or erbium lasers, nonablative Q-switched Nd:YAG laser, trichloroacetic acid peeling, and radiofrequency ablation. This study aims to evaluate the effectiveness of RF ablation in the treatment of xanthelasma palpebrarum, with D.A.S. Medical portable device (Technolux, Italia), a radiofrequency tool working with long-wave plasma energy and without anesthesia. Twenty patients, 15 female and 5 male, affected by xanthelasma palpebrarum, were enrolled for long-wave plasma radiofrequency ablation treatment. The treatment consisted of 3/4 sessions that were carried out at intervals of 30 days. Treatments were well tolerated by all patients with no adverse effects and optimal aesthetic results. The procedure is very fast and can be performed without anesthesia because of the low and tolerable pain stimulation. Long-wave plasma radiofrequency ablation is an effective option for treatment of xanthelasma palpebrarum and adds an additional tool to the increasing list of medical devices for aesthetic treatments. © 2018 Wiley Periodicals, Inc.

Optical Coherence Tomography Guided Laser Cochleostomy: Towards the Accuracy on Tens of Micrometer Scale

PubMed Central

Weller, Marcel; Wieser, Wolfgang; Huber, Robert; Raczkowsky, Jörg; Schipper, Jörg; Wörn, Heinz; Klenzner, Thomas

2014-01-01

Lasers have been proven to be precise tools for bone ablation. Applying no mechanical stress to the patient, they are potentially very suitable for microsurgery on fragile structures such as the inner ear. However, it remains challenging to control the laser-bone ablation without injuring embedded soft tissue. In this work, we demonstrate a closed-loop control of a short-pulsed CO2 laser to perform laser cochleostomy under the monitoring of an optical coherence tomography (OCT) system. A foresighted detection of the bone-endosteum-perilymph boundary several hundred micrometers before its exposure has been realized. Position and duration of the laser pulses are planned based on the residual bone thickness distribution. OCT itself is also used as a highly accurate tracking system for motion compensation between the target area and the optics. During ex vivo experimental evaluation on fresh porcine cochleae, the ablation process terminated automatically when the thickness of the residual tissue layer uniformly reached a predefined value. The shape of the resulting channel bottom converged to the natural curvature of the endosteal layer without injuring the critical structure. Preliminary measurements in OCT scans indicated that the mean absolute accuracy of the shape approximation was only around 20 μm. PMID:25295253

Thermodynamic and Spectroscopic Properties of Nd:YAG-CO2 Double-Pulse Laser-Induced Iron Plasmas

DTIC Science & Technology

2009-01-01

S. Palanco, L.M. Cabalín, D. Romero, J.J. Laserna, Infrared laser ablation and atomic emission spectrometry of stainless steel at high temperatures, J...is given from thepreparation of the sample by thefirst pulse (smoothing,first crater , onset ofmelt) to the energy couplingwith the plasma (ion yield...duration is 5 ns as measured with a fast photodiode (Thorlabs) placed behind a dielectric turning mirror. The laser is focused with a 13.5 cm focal length

Verruca plana as a complication of CO2 laser treatment: a case report.

PubMed

Winn, Aubrey E; Kentosh, Joshua; Bingham, Jonathan L

2015-04-01

Carbon dioxide (CO2) laser treatment is a common therapeutic modality for many dermatologic conditions. It uses a high energy, infrared beam of light, which selectively targets water-containing tissue resulting in controlled ablative resurfacing. This modality, however, can manifest significant cosmetic side effects. Here we report a case of verruca plana manifesting as a response to CO2 laser treatment. A 74-year-old female with recent Mohs surgery for a basal cell carcinoma, presented for full-face-fractionated CO2 treatment to address her surgical scars in addition to treating her mild diffuse actinic damage. Six weeks post treatment, the patient developed erythematous thin plaques over the areas that had been treated. Histology was consistent with verruca plana. Lesions showed mild improvement with topical tretinoin. Verruca plana are benign and typically self-limited; however, they can present a significant cosmetic burden to patients and are an important complication to consider when performing elective cosmetic procedures.

Hydrogen cyanide production due to mid-size impacts in a redox-neutral N2-rich atmosphere.

PubMed

Kurosawa, Kosuke; Sugita, Seiji; Ishibashi, Ko; Hasegawa, Sunao; Sekine, Yasuhito; Ogawa, Nanako O; Kadono, Toshihiko; Ohno, Sohsuke; Ohkouchi, Naohiko; Nagaoka, Yoichi; Matsui, Takafumi

2013-06-01

Cyanide compounds are amongst the most important molecules of the origin of life. Here, we demonstrate the importance of mid-size (0.1-1 km in diameter) hence frequent meteoritic impacts to the cyanide inventory on the early Earth. Subsequent aerodynamic ablation and chemical reactions with the ambient atmosphere after oblique impacts were investigated by both impact and laser experiments. A polycarbonate projectile and graphite were used as laboratory analogs of meteoritic organic matter. Spectroscopic observations of impact-generated ablation vapors show that laser irradiation to graphite within an N2-rich gas can produce a thermodynamic environment similar to that produced by oblique impacts. Thus, laser ablation was used to investigate the final chemical products after this aerodynamic process. We found that a significant fraction (>0.1 mol%) of the vaporized carbon is converted to HCN and cyanide condensates, even when the ambient gas contains as much as a few hundred mbar of CO2. As such, the column density of cyanides after carbon-rich meteoritic impacts with diameters of 600 m would reach ~10 mol/m(2) over ~10(2) km(2) under early Earth conditions. Such a temporally and spatially concentrated supply of cyanides may have played an important role in the origin of life.

Efficacy of fractional lasers in treating alopecia: a literature review.

PubMed

Perper, Marina; Aldahan, Adam S; Fayne, Rachel A; Emerson, Christopher P; Nouri, Keyvan

2017-11-01

Hair loss stemming from different types of alopecia, such as androgenic alopecia and alopecia areata, negatively affects over half the population and, in many circumstances, causes serious psychosocial distress. Current treatment options for alopecia, such as minoxidil, anthralin, and intralesional corticosteroids, vary efficacy and side effect profiles. It is known that low-level laser/light therapies (LLLT), or photobiomodulations, such as the US FDA-cleared HairMax Lasercomb®, He-Ne laser, and excimer laser, are relatively affordable, user-friendly, safe, and effective forms of treatment for hair loss. While less is known about the effectiveness of fractional lasers for combating hair loss, research suggests that by creating microscopic thermal injury zones, fractional lasers may cause an increase in hair growth from a wound healing process, making them potential therapeutic options for alopecia. A literature review was performed to evaluate the effectiveness of fractional lasers on hair regrowth. The specific fractional laser therapies include the 1550-nm nonablative fractional erbium-glass laser, the ablative fractional 2940-nm erbium:YAG laser, and the ablative fractional CO 2 fractional laser. Additional randomized controlled trials are necessary to further evaluate the effectiveness of the lasers, as well as to establish appropriate parameters and treatment intervals.

Real-time near-IR imaging of laser-ablation crater evolution in dental enamel

NASA Astrophysics Data System (ADS)

Darling, Cynthia L.; Fried, Daniel

2007-02-01

We have shown that the enamel of the tooth is almost completely transparent near 1310-nm in the near-infrared and that near-IR (NIR) imaging has considerable potential for the optical discrimination of sound and demineralized tissue and for observing defects in the interior of the tooth. Lasers are now routinely used for many applications in dentistry including the ablation of dental caries. The objective of this study was to test the hypothesis that real-time NIR imaging can be used to monitor laser-ablation under varying conditions to assess peripheral thermal and transient-stress induced damage and to measure the rate and efficiency of ablation. Moreover, NIR imaging may have considerable potential for monitoring the removal of demineralized areas of the tooth during cavity preparations. Sound human tooth sections of approximately 3-mm thickness were irradiated by a CO II laser under varying conditions with and without a water spray. The incision area in the interior of each sample was imaged using a tungsten-halogen lamp with band-pass filter centered at 131--nm combined with an InGaAs focal plane array with a NIR zoom microscope in transillumination. Due to the high transparency of enamel at 1310-nm, laser-incisions were clearly visible to the dentin-enamel junction and crack formation, dehydration and irreversible thermal changes were observed during ablation. This study showed that there is great potential for near-IR imaging to monitor laser-ablation events in real-time to: assess safe laser operating parameters by imaging thermal and stress-induced damage, elaborate the mechanisms involved in ablation such as dehydration, and monitor the removal of demineralized enamel.

Comparison of laser ablation and dried solution aerosol as sampling systems in inductively coupled plasma mass spectrometry.

PubMed

Coedo, A G; Padilla, I; Dorado, M T

2004-12-01

This paper describes a study designed to determine the possibility of using a dried aerosol solution for calibration in laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The relative sensitivities of tested materials mobilized by laser ablation and by aqueous nebulization were established, and the experimentally determined relative sensitivity factors (RSFs) were used in conjunction with aqueous calibration for the analysis of solid steel samples. To such a purpose a set of CRM carbon steel samples (SS-451/1 to SS-460/1) were sampled into an ICP-MS instrument by solution nebulization using a microconcentric nebulizer with membrane desolvating (D-MCN) and by laser ablation (LA). Both systems were applied with the same ICP-MS operating parameters and the analyte signals were compared. The RSF (desolvated aerosol response/ablated solid response) values were close to 1 for the analytes Cr, Ni, Co, V, and W, about 1.3 for Mo, and 1.7 for As, P, and Mn. Complementary tests were carried out using CRM SS-455/1 as a solid standard for one-point calibration, applying LAMTRACE software for data reduction and quantification. The analytical results are in good agreement with the certified values in all cases, showing that the applicability of dried aerosol solutions is a good alternative calibration system for laser ablation sampling.

Ablation of dermal and mucosal lesions with a new CO2 laser application system

NASA Astrophysics Data System (ADS)

Jovanovic, Sergije; Sedlmaier, Benedikt W.; Fuehrer, Ariane

1997-05-01

Laser treatment of skin changes has become common practice in recent years. The high absorption of the wavelength of the carbon-dioxide laser (10600 nm) is responsible for its low penetration depth in biological tissue. Shortening the exposure time minimizes thermic side effects such as carbonization and coagulation. This effect can be achieved with the SilkTouchTM scanner 767, since the focused laser beam is moved over a defined area by rapidly rotating mirrors. This enables controlled and reliable removal of certain dermal lesions, particularly hypertrophic scars, scars after common acne, wrinkles, rhinophyma and benign neoplasms like verruca vulgaris. Cosmetically favorable reepithelialization of the lasered surfaces results within a very short period of time. Benign mucosal changes of the upper aerodigestive tract can also be treated. Ablation is less traumatic for papillomas, fibromas, hyperplasias in the area of Waldeyer's tonsillar ring and certain laryngotracheal pathologies. Clinical examples demonstrate the advantages of this new mode of application.

Pulsed and CW adjustable 1942 nm single-mode all-fiber Tm-doped fiber laser system for surgical laser soft tissue ablation applications.

PubMed

Huang, Yize; Jivraj, Jamil; Zhou, Jiaqi; Ramjist, Joel; Wong, Ronnie; Gu, Xijia; Yang, Victor X D

2016-07-25

A surgical laser soft tissue ablation system based on an adjustable 1942 nm single-mode all-fiber Tm-doped fiber laser operating in pulsed or CW mode with nitrogen assistance is demonstrated. Ex vivo ablation on soft tissue targets such as muscle (chicken breast) and spinal cord (porcine) with intact dura are performed at different ablation conditions to examine the relationship between the system parameters and ablation outcomes. The maximum laser average power is 14.4 W, and its maximum peak power is 133.1 W with 21.3 μJ pulse energy. The maximum CW power density is 2.33 × 10⁶ W/cm² and the maximum pulsed peak power density is 2.16 × 10⁷ W/cm². The system parameters examined include the average laser power in CW or pulsed operation mode, gain-switching frequency, total ablation exposure time, and the input gas flow rate. The ablation effects were measured by microscopy and optical coherence tomography (OCT) to evaluate the ablation depth, superficial heat-affected zone diameter (HAZD) and charring diameter (CD). Our results conclude that the system parameters can be tailored to meet different clinical requirements such as ablation for soft tissue cutting or thermal coagulation for future applications of hemostasis.

Comparison of Q-switched Nd:YAG laser alone versus its combination with ultrapulse CO2 laser for the treatment of black tattoo.

PubMed

Vanarase, Mithila; Gautam, Ram Krishan; Arora, Pooja; Bajaj, Sonali; Meena, Neha; Khurana, Ananta

2017-10-01

Q-switched lasers are conventionally used for the treatment of black tattoo. However, they require multiple sittings, and the response may be slow due to competing epidermal pigment in dark skin. To compare the efficacy of Q-switched Nd:YAG laser alone with its combination with ultrapulse CO 2 for the removal of black tattoo. Sixty patients with black tattoo were randomized into two groups viz., group A and group B. Group A was treated with QS Nd:YAG laser (1064 nm) alone, and group B received combination of ablative ultrapulse CO 2 followed by fixed-dose QS Nd:YAG laser (1064 nm), at 6-week interval for a maximum of 6 sittings. After each sitting, 3 independent physicians noted percentage of improvement that was evaluated using visual analogue scale (VAS) and grading system for tattoo ink lightening (TIL). Combination laser (group B) showed statistically significant improvement in mean VAS score in the last 2 noted visits as compared to 1st session (p < 0.007, p < 0.001) and TIL mean score in last three noted visits as compared to 1st session (p < 0.008, p < 0.020, and p < 0.004). There was no statistically significant difference in the side effect profile of both the groups. For refractory professional tattoos, combination of ultrapulse CO 2 laser and QS Nd:YAG laser is superior to QS Nd:YAG laser alone.

A spectroscopic approach to monitor the cut processing in pulsed laser osteotomy.

PubMed

Henn, Konrad; Gubaidullin, Gail G; Bongartz, Jens; Wahrburg, Jürgen; Roth, Hubert; Kunkel, Martin

2013-01-01

During laser osteotomy surgery, plasma arises at the place of ablation. It was the aim of this study to explore whether a spectroscopic analysis of this plasma would allow identification of the type of tissue that was affected by the laser. In an experimental setup (Rofin SCx10, CO(2) Slab Laser, wavelength 10.6 μm, pulse duration 80 μs, pulse repetition rate 200 Hz, max. output in cw-mode 100 W), the plasma spectra evoked by a pulsed laser, cutting 1-day postmortem pig and cow bones, were recorded. Spectra were compared to the reference spectrum of bone via correlation analysis. Our measurements show a clear differentiation between the plasma spectra when cutting either a bone or a soft tissue. The spectral changes could be detected from one to the next spectrum within 200 ms. Continuous surveillance of plasma spectra allows us to differentiate whether bone or soft tissue is hit by the last laser pulse. With this information, it may be possible to stop the laser when cutting undesired soft tissue and to design an automatic control of the ablation process.

Fe(+) chemical ionization of peptides.

PubMed

Speir, J P; Gorman, G S; Amster, I J

1993-02-01

Laser-desorbed peptide neutral molecules were allowed to react with Fe(+) in a Fourier transform mass spectrometer, using the technique of laser desorption/chemical ionization. The Fe(+) ions are formed by laser ablation of a steel target, as well as by dissociative charge-exchange ionization of ferrocene with Ne(+). Prior to reaction with laser-desorbed peptide molecules, Fe(+) ions undergo 20-100 thermalizin collisions with xenon to reduce the population of excited-state metal ion species. The Fe(+) ions that have not experienced thermalizing collisions undergo charge exchange with peptide molecules. Iron ions that undergo thermalizing collisions before they are allowed to react with peptides are found to undergo charge exchange and to form adduct species [M + Fe(+)] and fragment ions that result from the loss of small, stable molecules, such as H2O, CO, and CO2, from the metal ion-peptide complex.

Pulsed Tm:YAG laser ablation of knee joint tissues

NASA Astrophysics Data System (ADS)

Shi, Wei-Qiang; Vari, Sandor G.; Duffy, J. T.; Miller, J. M.; Weiss, Andrew B.; Fishbein, Michael C.; Grundfest, Warren S.

1992-06-01

We investigated the effect of a free-running 2.01 micron pulsed Tm:YAG laser on bovine knee joint tissues. Ablation rates of fresh fibrocartilage, hyaline cartilage, and bone were measured in saline as a function of laser fluence (160 - 640 J/cm2) and fiber core size (400 and 600 microns). All tissues could be effectively ablated and the ablation rate increased linearly with the increasing fluence. Use of fibers of different core sizes, while maintaining constant energy fluence, did not result in significant difference in ablation rate. Histology analyses of the ablated tissue samples reveal average Tm:YAG radiation induced thermal damage (denatunalization) zones ranging between 130 and 540 microns, depending on the laser parameters and the tissue type.

Efficacy and safety of fractional CO2 laser versus fractional Er:YAG laser in the treatment of facial skin wrinkles.

PubMed

Robati, Reza M; Asadi, Elmira

2017-02-01

Ablative fractional lasers were introduced for treating facial rhytides. Few studies have compared fractional CO 2 and Er:YAG lasers on cutaneous photodamages by a split trial. The aim of the present study was to compare these modalities in a randomized controlled double-blind split-face design with multiple sessions and larger sample size compared to previous studies done before. Forty patients with facial wrinkles were enrolled. Patients were randomly assigned to receive three monthly treatments on each side of the face, one with a fractional CO 2 and one with a fractional Er:YAG laser. The evaluations included investigating clinical outcome determined by two independent dermatologists not enrolled in the treatment along with measuring skin biomechanical property of cheeks using a sensitive biometrologic device with the assessment of cutaneous resonance running time (CRRT). Moreover, possible side effects and patients' satisfaction have been recorded at baseline, 1 month after each treatment, and 3 months after the last treatment session. Clinical assessment showed both modalities significantly reduce facial wrinkles (p value < 0.05), with no appreciable difference between two lasers. Mean CRRT values also decreased significantly after the laser treatment compared to the baseline in both laser groups. There was no serious long-standing adverse effect after both laser treatments, but the discomfort was more pronounced by the participants after CO 2 laser treatment. According to the present study, both fractional CO 2 and fractional Er:YAG lasers show considerable clinical improvement of facial skin wrinkles with no serious adverse effects, but post-treatment discomfort seems to be lower with Er:YAG laser.

Novel two-step laser ablation and ionization mass spectrometry (2S-LAIMS) of actor-spectator ice layers: Probing chemical composition of D{sub 2}O ice beneath a H{sub 2}O ice layer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Rui, E-mail: ryang73@ustc.edu; Gudipati, Murthy S., E-mail: gudipati@jpl.nasa.gov

2014-03-14

In this work, we report for the first time successful analysis of organic aromatic analytes imbedded in D{sub 2}O ices by novel infrared (IR) laser ablation of a layered non-absorbing D{sub 2}O ice (spectator) containing the analytes and an ablation-active IR-absorbing H{sub 2}O ice layer (actor) without the analyte. With these studies we have opened up a new method for the in situ analysis of solids containing analytes when covered with an IR laser-absorbing layer that can be resonantly ablated. This soft ejection method takes advantage of the tenability of two-step infrared laser ablation and ultraviolet laser ionization mass spectrometry,more » previously demonstrated in this lab to study chemical reactions of polycyclic aromatic hydrocarbons (PAHs) in cryogenic ices. The IR laser pulse tuned to resonantly excite only the upper H{sub 2}O ice layer (actor) generates a shockwave upon impact. This shockwave penetrates the lower analyte-containing D{sub 2}O ice layer (spectator, a non-absorbing ice that cannot be ablated directly with the wavelength of the IR laser employed) and is reflected back, ejecting the contents of the D{sub 2}O layer into the vacuum where they are intersected by a UV laser for ionization and detection by a time-of-flight mass spectrometer. Thus, energy is transmitted from the laser-absorbing actor layer into the non-absorbing spectator layer resulting its ablation. We found that isotope cross-contamination between layers was negligible. We also did not see any evidence for thermal or collisional chemistry of PAH molecules with H{sub 2}O molecules in the shockwave. We call this “shockwave mediated surface resonance enhanced subsurface ablation” technique as “two-step laser ablation and ionization mass spectrometry of actor-spectator ice layers.” This method has its roots in the well-established MALDI (matrix assisted laser desorption and ionization) method. Our method offers more flexibility to optimize both the processes—ablation and ionization. This new technique can thus be potentially employed to undertake in situ analysis of materials imbedded in diverse media, such as cryogenic ices, biological samples, tissues, minerals, etc., by covered with an IR-absorbing laser ablation medium and study the chemical composition and reaction pathways of the analyte in its natural surroundings.« less

Structure and properties of nanoparticles fabricated by laser ablation of Zn metal targets in water and ethanol

NASA Astrophysics Data System (ADS)

Svetlichnyi, V. A.; Lapin, I. N.

2013-10-01

Size characteristics, structure, and spectral and luminescent properties of nanoparticles fabricated by laser ablation of zinc metal targets in water and ethanol are experimentally investigated upon excitation by Nd:YAG-laser radiation (1064 nm, 7 ns, and 15 Hz). It is demonstrated that zinc oxide nanoparticles with average sizes of 10 nm (in water) and 16 nm (in ethanol) are formed in the initial stage as a result of ablation. The kinetics of the absorption and luminescence spectra, transmission electron microscopy, and x-ray structural analysis demonstrate that during long storage of water dispersions and their drying, nanoparticles efficiently interact with carbon dioxide gas of air that leads to the formation of water-soluble Zn(CO3)2(OH)6. In ethanol, Zn oxidation leads to the formation of stable dispersions of ZnO nanoparticles with 99% of the wurtzite phase; in this case, the fluorescence spectra of ZnO nanoparticles change with time, shifting toward longer wavelength region from 550 to 620 nm, which is caused by the changed nature of defects.

Photoactive dye enhanced tissue ablation for endoscopic laser prostatectomy

NASA Astrophysics Data System (ADS)

Ahn, Minwoo; Nguyen, Trung Hau; Nguyen, Van Phuc; Oh, Junghwan; Kang, Hyun Wook

2015-02-01

Laser light has been widely used as a surgical tool to treat benign prostate hyperplasia with high laser power. The purpose of this study was to validate the feasibility of photoactive dye injection to enhance light absorption and eventually to facilitate tissue ablation with low laser power. The experiment was implemented on chicken breast due to minimal optical absorption Amaranth (AR), black dye (BD), hemoglobin powder (HP), and endoscopic marker (EM), were selected and tested in vitro with a customized 532-nm laser system with radiant exposure ranging from 0.9 to 3.9 J/cm2. Light absorbance and ablation threshold were measured with UV-VIS spectrometer and Probit analysis, respectively, and compared to feature the function of the injected dyes. Ablation performance with dye-injection was evaluated in light of radiant exposure, dye concentration, and number of injection. Higher light absorption by injected dyes led to lower ablation threshold as well as more efficient tissue removal in the order of AR, BD, HP, and EM. Regardless of the injected dyes, ablation efficiency principally increased with input parameter. Among the dyes, AR created the highest ablation rate of 44.2+/-0.2 μm/pulse due to higher absorbance and lower ablation threshold. Preliminary tests on canine prostate with a hydraulic injection system demonstrated that 80 W with dye injection yielded comparable ablation efficiency to 120 W with no injection, indicating 33 % reduced laser power with almost equivalent performance. In-depth comprehension on photoactive dye-enhanced tissue ablation can help accomplish efficient and safe laser treatment for BPH with low power application.

An investigation on 800 nm femtosecond laser ablation of K9 glass in air and vacuum

NASA Astrophysics Data System (ADS)

Xu, Shi-zhen; Yao, Cai-zhen; Dou, Hong-qiang; Liao, Wei; Li, Xiao-yang; Ding, Ren-jie; Zhang, Li-juan; Liu, Hao; Yuan, Xiao-dong; Zu, Xiao-tao

2017-06-01

Ablation rates of K9 glass were studied as a function of femtosecond laser fluences. The central wavelength was 800 nm, and pulse durations of 35 fs and 500 fs in air and vacuum were employed. Ablation thresholds of 0.42 J/cm2 and 2.1 J/cm2 were obtained at 35 fs and 500 fs, respectively, which were independent with the ambient conditions and depend on the incident pulse numbers due to incubation effects. The ablation rate of 35 fs pulse laser increased with the increasing of laser fluence in vacuum, while in air condition, it slowly increased to a plateau at high fluence. The ablation rate of 500 fs pulse laser showed an increase at low fluence and a slow drop of ablation rate was observed at high fluence in air and vacuum, which may due to the strong defocusing effects associated with the non-equilibrium ionization of air, and/or the shielding effects of conduction band electrons (CBEs) produced by multi-photon ionization and impact ionization in K9 glass surface. The typical ablation morphologies, e.g. smooth zone and laser-induced periodic surface structures (LIPSS) were also presented and illustrated.

Investigation of the wavelength dependence of laser stratigraphy on Cu and Ni coatings using LIBS compared to a pure thermal ablation model

NASA Astrophysics Data System (ADS)

Paulis, Evgeniya; Pacher, Ulrich; Weimerskirch, Morris J. J.; Nagy, Tristan O.; Kautek, Wolfgang

2017-12-01

In this study, galvanic coatings of Cu and Ni, typically applied in industrial standard routines, were investigated. Ablation experiments were carried out using the first two harmonic wavelengths of a pulsed Nd:YAG laser and the resulting plasma spectra were analysed using a linear Pearson correlation method. For both wavelengths the absorption/ablation behaviour as well as laser-induced breakdown spectroscopy (LIBS) depth profiles were studied varying laser fluences between 4.3-17.2 J/cm^2 at 532 nm and 2.9-11.7 J/cm^2 at 1064 nm. The LIBS-stratigrams were compared with energy-dispersive X-ray spectroscopy of cross-sections. The ablation rates were calculated and compared to theoretical values originating from a thermal ablation model. Generally, higher ablation rates were obtained with 532 nm light for both materials. The light-plasma interaction is suggested as possible cause of the lower ablation rates in the infrared regime. Neither clear evidence of the pure thermal ablation, nor correlation with optical properties of investigated materials was obtained.

Temperature monitoring by infrared radiation measurements during ArF excimer laser ablation with cornea

NASA Astrophysics Data System (ADS)

Ishihara, Miya; Arai, Tsunenori; Sato, Shunichi; Nakano, Hironori; Obara, Minoru; Kikuchi, Makoto

1999-06-01

We measured infrared thermal radiation from porcine cornea during various fluences ArF excimer laser ablations with 1 microsecond(s) rise time. To obtain absolute temperature by means of Stefan-Boltzman law of radiation, we carried out a collection efficiency and detective sensitivity by a pre-experiment using panel heater. We measured the time course of the thermal radiation intensity with various laser fluences. We studied the relation between the peak cornea temperature during the ablation and irradiation fluences. We found the ablation situations, i.e., sub-ablation threshold, normal thermal ablation, and over-heated ablation, may be judged by both of the measured temperature transient waveforms and peak temperature. The boundary fluences corresponding to normal thermal ablation were 90 and 160 mJ/cm2. Our fast remote temperature monitoring during cornea ablation might be useful to control ablation quality/quantity of the cornea ArF laser ablation, that is PRK.

Experimental scaling law for mass ablation rate from a Sn plasma generated by a 1064 nm laser

NASA Astrophysics Data System (ADS)

Burdt, Russell A.; Yuspeh, Sam; Sequoia, Kevin L.; Tao, Yezheng; Tillack, Mark S.; Najmabadi, Farrokh

2009-08-01

The ablation depth in planar Sn targets irradiated with a pulsed 1064 nm laser was investigated over laser intensities from 3×1011 to 2×1012 W/cm2. The ablation depth was measured by irradiating a thin layer of Sn evaporated onto a Si wafer, and looking for signatures of Si ions in the expanding plasma with spectroscopic and particle diagnostics. It was found that ablation depth scales with laser intensity to the (5/9)th power, which is consistent with analytical models of steady-state laser ablation, as well as empirical formulae from previous studies of mass ablation rate in overlapping parameter space. In addition, the scaling of mass ablation rate with atomic number of the target as given by empirical formulae in previous studies using targets such as C and Al, are shown to remain valid for the higher atomic number of the target (Z =50) used in these experiments.

The application of robotics to microlaryngeal laser surgery.

PubMed

Buckmire, Robert A; Wong, Yu-Tung; Deal, Allison M

2015-06-01

To evaluate the performance of human subjects, using a prototype robotic micromanipulator controller in a simulated, microlaryngeal operative setting. Observational cross-sectional study. Twenty-two human subjects with varying degrees of laser experience performed CO2 laser surgical tasks within a simulated microlaryngeal operative setting using an industry standard manual micromanipulator (MMM) and a prototype robotic micromanipulator controller (RMC). Accuracy, repeatability, and ablation consistency measures were obtained for each human subject across both conditions and for the preprogrammed RMC device. Using the standard MMM, surgeons with >10 previous laser cases performed superior to subjects with fewer cases on measures of error percentage and cumulative error (P = .045 and .03, respectively). No significant differences in performance were observed between subjects using the RMC device. In the programmed (P/A) mode, the RMC performed equivalently or superiorly to experienced human subjects on accuracy and repeatability measures, and nearly an order of magnitude better on measures of ablation consistency. The programmed RMC performed significantly better for repetition error when compared to human subjects with <100 previous laser cases (P = .04). Experienced laser surgeons perform better than novice surgeons on tasks of accuracy and repeatability using the MMM device but roughly equivalently using the novel RMC. Operated in the P/A mode, the RMC performs equivalently or superior to experienced laser surgeons using the industry standard MMM for all measured parameters, and delivers an ablation consistency nearly an order of magnitude better than human laser operators. NA. © 2014 The American Laryngological, Rhinological and Otological Society, Inc.

Laser ablation system, and method of decontaminating surfaces

DOEpatents

Ferguson, Russell L.; Edelson, Martin C.; Pang, Ho-ming

1998-07-14

A laser ablation system comprising a laser head providing a laser output; a flexible fiber optic cable optically coupled to the laser output and transmitting laser light; an output optics assembly including a nozzle through which laser light passes; an exhaust tube in communication with the nozzle; and a blower generating a vacuum on the exhaust tube. A method of decontaminating a surface comprising the following steps: providing an acousto-optic, Q-switched Nd:YAG laser light ablation system having a fiber optically coupled output optics assembly; and operating the laser light ablation system to produce an irradiance greater than 1.times.10.sup.7 W/cm.sup.2, and a pulse width between 80 and 170 ns.

Fiber-delivered mid-infrared (6-7) laser ablation of retinal tissue under perfluorodecalin

NASA Astrophysics Data System (ADS)

Mackanos, Mark A.; Joos, Karen M.; Jansen, E. Duco

2003-07-01

The Er:YAG laser (l=2.94mm) is an effective tool in vitreo-retinal surgery. Pulsed mid-infrared (l=6.45 mm) radiation from the Free Electron Laser has been touted as a potentially superior cutting tool. To date, use of this laser has been limited to applications in an air environment. The goal of this study was: 1) determine feasibility of fiberoptic delivery of 6.45mm using silverhalide fibers (d=700mm); 2) use infrared transparent vitreous substitute (perfluorodecalin) to allow non-contact ablation of the retina at 6.45mm. Fiber damage threshold=7.8J/cm2 (0.54GW/cm2) while transmission loss=0.54dB/m, allowing supra-ablative radiant exposures to the target. FTIR measurements of perfluorodecalin at 6.45mm yielded ma=3mm-1. Pump-probe imaging of ablation of a tissue-phantom through perfluorodecalin showed feasibility of non-contact ablation at l=6.45mm. Ablation of the retinal membranes of enucleated pig eyes was carried out under perfluorodecalin (5 Hz, 1.3 J/cm2). Each eye was cut along its equator to expose the retina. Vitreous was replaced by perfluorodecalin and laser radiation was delivered to the retina via the silverhalide fiber. The eye was rotated (at 2 rpm) using a stepper motor (0.9o/step) to create an ablation circle around the central axis of the retina (50% spot-to-spot overlap). Histological analysis of ablation yield and collateral damage will be presented. We have shown that using l=6.45mm delivered via silver halide fibers through perfluorodecalin allowed non-contact laser ablation. Remote structures are shielded, as the radiant exposure falls below the ablation threshold owing non-negligible absorption of perfluorodecalin at 6.45mm. This may optimize efficacy and safety of laser-based vitreoretinal surgery.

Through-the-thickness selective laser ablation of ceramic coatings on soda-lime glass

NASA Astrophysics Data System (ADS)

Romoli, L.; Khan, M. M. A.; Valentini, M.

2017-05-01

This paper investigates through-thickness laser ablation characteristics of ceramic coating deposited on the bottom surface of the soda-lime glass substrate. Experimental studies were focused on determining the effects of energy density, hatch distance and coating color on the ablation completion index. Effect of glass thickness was also tested to verify the robustness of the designed process. Up to a certain threshold limit, the ablation completion index is energy-limited and has an inverse U-shape relationship with the energy density input. Since greater hatch distance means faster ablation and lesser ablation completion index, there must be a tradeoff between ablation completion index and hatch distance. During through-thickness laser ablation of ceramic coating, energy density input should be in the range of 0.049 J/mm2 - 0.251 J/mm2 for black ceramic coating and 0.112 J/mm2 - 0.251 J/mm2 for other coatings. Finally, the designed process is capable of ablating the ceramic coating effectively through varied thickness.

An experimental study on laser drilling and cutting of composite materials for the aerospace industry using excimer and CO2 sources

NASA Astrophysics Data System (ADS)

dell'Erba, M.; Galantucci, L. M.; Miglietta, S.

This paper reports on the results of research which investigated the potential for the application of an excimer laser in the field of composite material drilling and cutting, by comparing this technology with that using CO2 sources. In particular, the scope of the work was to check whether the interaction between excimer lasers and composite materials, whose characteristic feature is the absence of thermal transfer, could yield better results than those obtainable with CO2 sources once heat transfer-induced difficulties had been eliminated. The materials selected for the experiments were multilayer composites having an epoxy resin matrix (65 percent in volume), with aramid fiber (Kevlar), carbon fiber and glass fiber as reinforcing materials, all of considerable interest for the aerospace industry. Optimal operational parameters were identified in relation to each source with a view to obtaining undersize holes or through cuts exhibiting severed areas of good quality. A comparison between the two types of processing carried out show that rims processed by excimer lasers are of better quality - particularly so with Kevlar - whereas the ablation rate is undoubtedly rather low compared with the CO2 technology.

Mathematical modeling of laser based potato cutting and peeling.

PubMed

Ferraz, A Carlos O; Mittal, Gauri S; Bilanski, Walter K; Abdullah, Hussein A

2007-01-01

A mathematical model is developed and validated to predict the depth of cut in potato tuber slabs as a function of laser power and travel speed. The model considers laser processing parameters such as input power, spot size and exposure time as well as the properties of the material being cut such as specific heat, thermal conductivity, surface reflectance, etc. The model also considers the phase change of water in potato and the ignition temperature of the solid portion. The composition of the potato tuber is assumed to be of water and solid. The model also assumes that the ablation process is accomplished through ejection of liquid water, debris and water vapour, and combustion of solid. A CO(2) laser operating in c.w. mode was chosen for the experimental work because water absorbs laser energy highly at 10.6 microm, and CO(2) laser units with relatively high output power are available. Slabs of potato tuber were chosen to be laser processed since potato contains high moisture and large amounts of relatively homogeneous tissue. The results of the preliminary calculations and experiments concluded that the model is able to predict the depth of cut in potato tuber parenchyma when subjected to a CO(2) laser beam.

Fractional carbon dioxide laser versus low-dose UVA-1 phototherapy for treatment of localized scleroderma: a clinical and immunohistochemical randomized controlled study.

PubMed

Shalaby, S M; Bosseila, M; Fawzy, M M; Abdel Halim, D M; Sayed, S S; Allam, R S H M

2016-11-01

Morphea is a rare fibrosing skin disorder that occurs as a result of abnormal homogenized collagen synthesis. Fractional ablative laser resurfacing has been used effectively in scar treatment via abnormal collagen degradation and induction of healthy collagen synthesis. Therefore, fractional ablative laser can provide an effective modality in treatment of morphea. The study aimed at evaluating the efficacy of fractional carbon dioxide laser as a new modality for the treatment of localized scleroderma and to compare its results with the well-established method of UVA-1 phototherapy. Seventeen patients with plaque and linear morphea were included in this parallel intra-individual comparative randomized controlled clinical trial. Each with two comparable morphea lesions that were randomly assigned to either 30 sessions of low-dose (30 J/cm 2 ) UVA-1 phototherapy (340-400 nm) or 3 sessions of fractional CO 2 laser (10,600 nm-power 25 W). The response to therapy was then evaluated clinically and histopathologically via validated scoring systems. Immunohistochemical analysis of TGF-ß1 and MMP1 was done. Patient satisfaction was also assessed. Wilcoxon signed rank test for paired (matched) samples and Spearman rank correlation equation were used as indicated. Comparing the two groups, there was an obvious improvement with fractional CO 2 laser that was superior to that of low-dose UVA-1 phototherapy. Statistically, there was a significant difference in the clinical scores (p = 0.001), collagen homogenization scores (p = 0.012), and patient satisfaction scores (p = 0.001). In conclusion, fractional carbon dioxide laser is a promising treatment modality for cases of localized morphea, with proved efficacy of this treatment on clinical and histopathological levels.

Ablation experiment and threshold calculation of titanium alloy irradiated by ultra-fast pulse laser

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zheng, Buxiang; Jiang, Gedong; Wang, Wenjun, E-mail: wenjunwang@mail.xjtu.edu.cn

The interaction between an ultra-fast pulse laser and a material's surface has become a research hotspot in recent years. Micromachining of titanium alloy with an ultra-fast pulse laser is a very important research direction, and it has very important theoretical significance and application value in investigating the ablation threshold of titanium alloy irradiated by ultra-fast pulse lasers. Irradiated by a picosecond pulse laser with wavelengths of 1064 nm and 532 nm, the surface morphology and feature sizes, including ablation crater width (i.e. diameter), ablation depth, ablation area, ablation volume, single pulse ablation rate, and so forth, of the titanium alloymore » were studied, and their ablation distributions were obtained. The experimental results show that titanium alloy irradiated by a picosecond pulse infrared laser with a 1064 nm wavelength has better ablation morphology than that of the green picosecond pulse laser with a 532 nm wavelength. The feature sizes are approximately linearly dependent on the laser pulse energy density at low energy density and the monotonic increase in laser pulse energy density. With the increase in energy density, the ablation feature sizes are increased. The rate of increase in the feature sizes slows down gradually once the energy density reaches a certain value, and gradually saturated trends occur at a relatively high energy density. Based on the linear relation between the laser pulse energy density and the crater area of the titanium alloy surface, and the Gaussian distribution of the laser intensity on the cross section, the ablation threshold of titanium alloy irradiated by an ultra-fast pulse laser was calculated to be about 0.109 J/cm{sup 2}.« less

Investigations on laser hard tissue ablation under various environments

NASA Astrophysics Data System (ADS)

Kang, H. W.; Oh, J.; Welch, A. J.

2008-06-01

The purpose of this study was to investigate the effect of liquid environments upon laser bone ablation. A long-pulsed Er,Cr:YSGG laser was employed to ablate bovine bone tibia at various radiant exposures under dry, wet (using water or perfluorocarbon) and spray environmental conditions. Energy loss by the application of liquid during laser irradiation was evaluated, and ablation performance for all conditions was quantitatively measured by optical coherence tomography (OCT). Microscope images were also used to estimate thermal side effects in tissue after multiple-pulse ablation. Wet using water and spray conditions equally attenuated the 2.79 µm wavelength laser beam. Higher transmission efficiency was obtained utilizing a layer of perfluorocarbon. Dry ablation exhibited severe carbonization due to excessive heat accumulation. Wet condition using water resulted in similar ablation volume to the dry case without carbonization. The perfluorocarbon layer produced the largest ablation volume but some carbonization due to the poor thermal conductivity. Spray induced clean cutting with slightly reduced efficiency. Liquid-assisted ablation provided significant beneficial effects such as augmented material removal and cooling/cleaning effects during laser osteotomy.

Selective femtosecond laser structuring of dielectric thin films with different band gaps: a time-resolved study of ablation mechanisms

NASA Astrophysics Data System (ADS)

Rapp, Stephan; Schmidt, Michael; Huber, Heinz P.

2016-12-01

Ultrashort pulse lasers have been increasingly gaining importance for the selective structuring of dielectric thin films in industrial applications. In a variety of works the ablation of thin SiO2 and SiNx films from Si substrates has been investigated with near infrared laser wavelengths with photon energies of about 1.2 eV where both dielectrics are transparent (E_{{gap,SiO2}}≈ 8 eV; E_{{gap,SiN}x}≈ 2.5 eV). In these works it was found that few 100 nm thick SiO2 films are selectively ablated with a "lift-off" initiated by confined laser ablation whereas the SiN_{{x}} films are ablated by a combination of confined and direct laser ablation. In the work at hand, ultrafast pump-probe imaging was applied to compare the laser ablation dynamics of the two thin film systems directly with the uncoated Si substrate—on the same setup and under identical parameters. On the SiO2 sample, results show the pulse absorption in the Si substrate, leading to the confined ablation of the SiO2 layer by the expansion of the substrate. On the SiN_{{x}} sample, direct absorption in the layer is observed leading to its removal by evaporation. The pump-probe measurements combined with reflectivity corrected threshold fluence investigations suggest that melting of the Si substrate is sufficient to initiate the lift-off of an overlaying transparent film—evaporation of the substrate seems not to be necessary.

Delivery of Methotrexate and Characterization of Skin Treated by Fabricated PLGA Microneedles and Fractional Ablative Laser.

PubMed

Nguyen, Hiep X; Banga, Ajay K

2018-02-21

This study investigated in vitro transdermal delivery of methotrexate through dermatomed porcine ear and cadaver human skin treated with poly (D,L-lactide-co-glycolide) acid microneedles or fractional ablative laser. PLGA microneedles were fabricated and characterized using scanning electron microscopy and mechanical assessment techniques. The integrity of treated skin was evaluated by rheometer, transepidermal water loss, and skin electrical resistance measurements. Successful skin microporation was demonstrated by dye binding, histology, pore uniformity, confocal laser microscopy, and DermaScan studies. In vitro permeation experiment was performed on Franz diffusion cells to determine drug delivery into and across the skin. Both physical treatments resulted in a considerable decrease in skin resistance and an increase in transepidermal water loss value. The laser-created microchannels were significantly larger than those formed by microneedles (p < 0.05). An effective force of 41.04 ± 18.33 N was required to achieve 100% penetration efficiency of the microneedles. For both porcine ear and human skin, laser ablation provided a significantly higher methotrexate permeability into the receptor chamber and skin layers compared to microneedle poration and untreated skin (p < 0.05). Both fractional ablative laser and polymeric microneedles markedly enhanced in vitro transdermal delivery of methotrexate into and across skin. Graphical Abstract ᅟ.

The ablation threshold of Er;Cr:YSGG laser radiation in bone tissue

NASA Astrophysics Data System (ADS)

Benetti, Carolina; Zezell, Denise Maria

2015-06-01

In laser cut clinical applications, the use of energy densities lower than the ablation threshold causes increase of temperature of the irradiated tissue, which might result in an irreversible thermal damage. Hence, knowing the ablation threshold is crucial for insuring the safety of these procedures. The aim of this study was to determine the ablation threshold of the Er,Cr:YSGG laser in bone tissue. Bone pieces from jaws of New Zealand rabbits were cut as blocks of 5 mm × 8 mm and polished with sandpaper. The Er,Cr:YSGG laser used in this study had wavelength of 2780 nm, 20 Hz of frequency, and the irradiation condition was chosen so as to simulate the irradiation during a surgical procedure. The laser irradiation was performed with 12 different values of laser energy densities, between 3 J/cm2 and 42 J/cm2, during 3 seconds, resulting in the overlap of 60 pulses. This process was repeated in each sample, for all laser energy densities. After irradiation, the samples were analyzed by scanning electron microscope (SEM), and it was measured the crater diameter for each energy density. By fitting a curve that related the ablation threshold with the energy density and the corresponding diameter of ablation crater, it was possible to determine the ablation threshold. The results showed that the ablation threshold of the Er,Cr:YSGG in bone tissue was 1.95+/-0.42 J/cm2.

High efficient bone ablation with diode pumped Erbium and Thulium lasers including different delivery fibers: a comparative in vitro study

NASA Astrophysics Data System (ADS)

Stock, Karl; Hausladen, Florian; Stegmayer, Thomas; Wurm, Holger

2018-02-01

Er:YAG lasers (3μm) allow efficient bone ablation caused by the strong absorption in water. Unfortunately, there are only a few and comparable expensive fiber materials for this wavelength available which are suitable for high laser power. The bone ablation efficiency of the Tm:YAG laser is minor (2μm) but inexpensive silica fibers can be used. The aim of this study was to investigate the bone ablation, using novel diode pumped high power Er:YAG (laser power 40W) and Tm:YAG laser system (60W) and adaptive fiber delivery systems. Expected advantage of these lasers is the longer lifetime of the fibers because of the high repetition rate and low pulse energy compared to the flash lamp pumped laser systems. The bare fiber output ends of a sapphire fiber (Er:YAG laser) and of a silica fiber (Tm:YAG laser) were attached under water and a water filled container including the fixed sample (bovine bone slices) was moved by a computer controlled translation stage. In a second set-up we provided a focusing unit and appropriate water spray unit. The generated cut kerfs were analyzed by light microcopy and laser scanning microscopy. The results show that with the diode pumped Er:YAG laser and sapphire fiber a particular high efficient bone ablation (> 0.16mm2/J) is possible both with bare fiber under water and focusing unit with water spray. The higher power of the Tm:YAG laser also results in high ablation rates but causes enlarged thermal damages. In conclusion, this study demonstrates that efficient bone ablation is possible with both diode pumped laser systems. In terms of efficiency the Er:YAG laser is outstanding. The Tm:YAG laser also allows fast bone ablation, provided that the thermal impact is limited by effective cooling and high movement velocity of the laser spot, for example by using an automatic scanner.

Precise ablation of dental hard tissues with ultra-short pulsed lasers. Preliminary exploratory investigation on adequate laser parameters.

PubMed

Bello-Silva, Marina Stella; Wehner, Martin; Eduardo, Carlos de Paula; Lampert, Friedrich; Poprawe, Reinhart; Hermans, Martin; Esteves-Oliveira, Marcella

2013-01-01

This study aimed to evaluate the possibility of introducing ultra-short pulsed lasers (USPL) in restorative dentistry by maintaining the well-known benefits of lasers for caries removal, but also overcoming disadvantages, such as thermal damage of irradiated substrate. USPL ablation of dental hard tissues was investigated in two phases. Phase 1--different wavelengths (355, 532, 1,045, and 1,064 nm), pulse durations (picoseconds and femtoseconds) and irradiation parameters (scanning speed, output power, and pulse repetition rate) were assessed for enamel and dentin. Ablation rate was determined, and the temperature increase measured in real time. Phase 2--the most favorable laser parameters were evaluated to correlate temperature increase to ablation rate and ablation efficiency. The influence of cooling methods (air, air-water spray) on ablation process was further analyzed. All parameters tested provided precise and selective tissue ablation. For all lasers, faster scanning speeds resulted in better interaction and reduced temperature increase. The most adequate results were observed for the 1064-nm ps-laser and the 1045-nm fs-laser. Forced cooling caused moderate changes in temperature increase, but reduced ablation, being considered unnecessary during irradiation with USPL. For dentin, the correlation between temperature increase and ablation efficiency was satisfactory for both pulse durations, while for enamel, the best correlation was observed for fs-laser, independently of the power used. USPL may be suitable for cavity preparation in dentin and enamel, since effective ablation and low temperature increase were observed. If adequate laser parameters are selected, this technique seems to be promising for promoting the laser-assisted, minimally invasive approach.

Optimal management of common acquired melanocytic nevi (moles): current perspectives

PubMed Central

Sardana, Kabir; Chakravarty, Payal; Goel, Khushbu

2014-01-01

Although common acquired melanocytic nevi are largely benign, they are probably one of the most common indications for cosmetic surgery encountered by dermatologists. With recent advances, noninvasive tools can largely determine the potential for malignancy, although they cannot supplant histology. Although surgical shave excision with its myriad modifications has been in vogue for decades, the lack of an adequate histological sample, the largely blind nature of the procedure, and the possibility of recurrence are persisting issues. Pigment-specific lasers were initially used in the Q-switched mode, which was based on the thermal relaxation time of the melanocyte (size 7 μm; 1 μsec), which is not the primary target in melanocytic nevus. The cluster of nevus cells (100 μm) probably lends itself to treatment with a millisecond laser rather than a nanosecond laser. Thus, normal mode pigment-specific lasers and pulsed ablative lasers (CO2/erbium [Er]:yttrium aluminum garnet [YAG]) are more suited to treat acquired melanocytic nevi. The complexities of treating this disorder can be overcome by following a structured approach by using lasers that achieve the appropriate depth to treat the three subtypes of nevi: junctional, compound, and dermal. Thus, junctional nevi respond to Q-switched/normal mode pigment lasers, where for the compound and dermal nevi, pulsed ablative laser (CO2/Er:YAG) may be needed. If surgical excision is employed, a wide margin and proper depth must be ensured, which is skill dependent. A lifelong follow-up for recurrence and melanoma is warranted in predisposed individuals, although melanoma is decidedly uncommon in most acquired melanocytic nevi, even though histological markers may be seen on evaluation. PMID:24672253

Spatiotemporal closure of fractional laser-ablated channels imaged by optical coherence tomography and reflectance confocal microscopy.

PubMed

Banzhaf, Christina A; Wind, Bas S; Mogensen, Mette; Meesters, Arne A; Paasch, Uwe; Wolkerstorfer, Albert; Haedersdal, Merete

2016-02-01

Optical coherence tomography (OCT) and reflectance confocal microscopy (RCM) offer high-resolution optical imaging of the skin, which may provide benefit in the context of laser-assisted drug delivery. We aimed to characterize postoperative healing of ablative fractional laser (AFXL)-induced channels and dynamics in their spatiotemporal closure using in vivo OCT and RCM techniques. The inner forearm of healthy subjects (n = 6) was exposed to 10,600 nm fractional CO2 laser using 5 and 25% densities, 120 μm beam diameter, 5, 15, and 25 mJ/microbeam. Treatment sites were scanned with OCT to evaluate closure of AFXL-channels and RCM to evaluate subsequent re-epithelialization. OCT and RCM identified laser channels in epidermis and upper dermis as black, ablated tissue defects surrounded by characteristic hyper-and hyporeflective zones. OCT imaged individual laser channels of the entire laser grid, and RCM imaged epidermal cellular and structural changes around a single laser channel to the depth of the dermoepidermal junction (DEJ) and upper papillary dermis. OCT images visualized a heterogeneous material in the lower part of open laser channels, indicating tissue fluid. By OCT the median percentage of open channels was evaluated at several time points within the first 24 hours and laser channels were found to gradually close, depending on the used energy level. Thus, at 5 mJ/microbeam, 87% (range 73-100%) of channels were open one hour after laser exposure, which declined to 27% (range 20-100%) and 20% (range 7-93%) at 12 and 24 hours after laser exposure, respectively. At 25 mJ/microbeam, 100% (range 100-100%) of channels were open 1 hour after laser exposure while 53% (range 33-100%) and 40% (range 0-100%) remained open at 12 and 24 hours after exposure. Median depth and width of open channels decreased over time depending of applied energy. RCM verified initial re-epithelialization from day 2 for all energy levels used. Morphology of ablation defects by OCT and RCM corresponded to histological assessments. OCT and RCM enabled imaging of AFXL-channels and their spatiotemporal closure. Laser channels remained open up to 24 hours post laser, which may be important for the time perspective to deliver topical substances through AFXL channels. © 2015 Wiley Periodicals, Inc.

Laser ablation with applied magnetic field for electric propulsion

NASA Astrophysics Data System (ADS)

Batishcheva, Alla; Batishchev, Oleg; Cambier, Jean-Luc

2012-10-01

Using ultrafast lasers with tera-watt-level power allows efficient ablation and ionization of solid-density materials [1], creating dense and hot (˜100eV) plasma. We propose ablating small droplets in the magnetic nozzle configurations similar to mini-helicon plasma source [2]. Such approach may improve the momentum coupling compared to ablation of solid surfaces and facilitate plasma detachment. Results of 2D modeling of solid wire ablation in the applied magnetic field are presented and discussed. [4pt] [1] O. Batishchev et al, Ultrafast Laser Ablation for Space Propulsion, AIAA technical paper 2008-5294, -16p, 44th JPC, Hartford, 2008.[0pt] [2] O. Batishchev and J.L. Cambier, Experimental Study of the Mini-Helicon Thruster, Air Force Research Laboratory Report, AFRL-RZ-ED-TR-2009-0020, 2009.

Material removal effect of microchannel processing by femtosecond laser

NASA Astrophysics Data System (ADS)

Zhang, Pan; Chen, Lei; Chen, Jianxiong; Tu, Yiliu

2017-11-01

Material processing using ultra-short-pulse laser is widely used in the field of micromachining, especially for the precision processing of hard and brittle materials. This paper reports a theoretical and experimental study of the ablation characteristics of a silicon wafer under micromachining using a femtosecond laser. The ablation morphology of the silicon wafer surface is surveyed by a detection test with an optical microscope. First, according to the relationship between the diameter of the ablation holes and the incident laser power, the ablation threshold of the silicon wafer is found to be 0.227 J/cm2. Second, the influence of various laser parameters on the size of the ablation microstructure is studied and the ablation morphology is analyzed. Furthermore, a mathematical model is proposed that can calculate the ablation depth per time for a given laser fluence and scanning velocity. Finally, a microchannel milling test is carried out on the micromachining center. The effectiveness and accuracy of the proposed models are verified by comparing the estimated depth to the actual measured results.

Fractional resurfacing in the Asian patient: Current state of the art.

PubMed

Wat, Heidi; Wu, Douglas C; Chan, Henry Hin Lee

2017-01-01

Fractionated photothermolysis (FP) has revolutionized modern laser technology. By creating selective columns of microthermal damage, fractionated devices allows for greater treatment depths to be achieved without the prolonged downtime and risk of complications seen in traditional fully ablative laser resurfacing. Fractional resurfacing is a proven method to treat a variety of cutaneous conditions. In the Caucasian patient, a wide range of devices and treatment settings can be utilized safely and effectively. However, ethnic skin requires special consideration due to its unique pigmentary characteristics and clinical presentations. In this review article, we detail the current indications and strategies to optimize results and mitigate complications when utilizing fractional resurfacing for the Asian patient. A review of the MEDLINE English literature was conducted on fractionated laser devices studied in the Asian population. Articles included describe non-ablative devices including fractionated erbium glass, thulium fiber, diode, and radiofrequency devices; and ablative devices including fractionated carbon dioxide (CO 2 ) laser, erbium yttrium aluminum garnet and yttrium scandium gallium garnet (YSGG) laser. These data were integrated with the expert opinion of the authors. Taking into account the unique characteristics and cosmetic concerns of the Asian population, fractional resurfacing can be considered a safe and effective option for the treatment of atrophic and hypertrophic scarring, and photorejuvenation in ethnic skin types. Select cases of melasma may be treated with fractionated non-ablative devices, but utilized with caution. The predominant complication associated with fractional resurfacing for these conditions is post-inflammatory hyperpigmentation (PIH) and rebound worsening of melasma. A greater number of treatments at lower density settings and wider treatment intervals typically produce the lowest risks of PIH without compromising treatment efficacy. Lasers Surg. Med. 49:45-59, 2017. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Mid-IR enhanced laser ablation molecular isotopic spectrometry

NASA Astrophysics Data System (ADS)

Brown, Staci; Ford, Alan; Akpovo, Codjo A.; Johnson, Lewis

2016-08-01

A double-pulsed laser-induced breakdown spectroscopy (DP-LIBS) technique utilizing wavelengths in the mid-infrared (MIR) for the second pulse, referred to as double-pulse LAMIS (DP-LAMIS), was examined for its effect on detection limits compared to single-pulse laser ablation molecular isotopic spectrometry (LAMIS). A MIR carbon dioxide (CO2) laser pulse at 10.6 μm was employed to enhance spectral emissions from nanosecond-laser-induced plasma via mid-IR reheating and in turn, improve the determination of the relative abundance of isotopes in a sample. This technique was demonstrated on a collection of 10BO and 11BO molecular spectra created from enriched boric acid (H3BO3) isotopologues in varying concentrations. Effects on the overall ability of both LAMIS and DP-LAMIS to detect the relative abundance of boron isotopes in a starting sample were considered. Least-squares fitting to theoretical models was used to deduce plasma parameters and understand reproducibility of results. Furthermore, some optimization for conditions of the enhanced emission was achieved, along with a comparison of the overall emission intensity, plasma density, and plasma temperature generated by the two techniques.

Monitoring of KrF excimer laser ablation for burn scars: a comparative study of transient reflection measurement and time-resolved photography of ablation plume

NASA Astrophysics Data System (ADS)

Nakajima, Akio; Arai, Tsunenori; Kikuchi, Makoto; Iwaya, Akimi; Arai, Katsuyuki; Inazaki, Satoshi; Takaoka, Takatsugu; Kato, Masayoshi

1995-05-01

A simple laser ablation monitoring during burn scar removal by KrF laser irradiation was studied to control laser fluence in real-time. Because, to obtain suitable surface for auto skin-graft, the laser fluence should be precisely controlled at each laser shot. We employed simple probe transmission method which could detect ejected material/phenomena from irradiated surface. The time-course of measured probe intensity contained a couple of attenuated peaks, which might corresponded to a shock wave front and debris plume. The delay time from laser irradiation to the debris plume peak appearance varied with the ablation fluence. The delay time of 1 J/cm2 (near ablation threshold) case prolonged 25% from 8 J/cm2 (far above threshold) case. Therefore, we think the delay time measurement by means of the simple probe transmission method may be available to attain the laser fluence control for nonuniform burn scar removal. The time-resolved photography and probe reflection method were also studied to understand the measured time-course of the transmitted probe intensity.

Selective removal of cholesterol ester in atherosclerotic plaque using nanosecond pulsed laser at 5.75 μm

NASA Astrophysics Data System (ADS)

Ishii, K.; Tsukimoto, H.; Hazama, H.; Awazu, K.

2008-02-01

Laser angioplasty, for example XeCl excimer laser angioplasty, has gained more attention in addition to conventional methods of surgical and interventional treatment of atherosclerotic diseases such as bypass operation and balloon dilatation. Low degrees of thermal damage after ablation of atherosclerotic lesions have been achieved by XeCl excimer laser at 308 nm. However, in most cases, laser ablation is not selective and normal arterial wall is also damaged. To avoid complications such as severe dissections or perforation of the arterial wall in an angioplasty, a laser light source with high ablation efficiency but low arterial wall injury is desirable. At atherosclerotic lesions, cholesterol accumulates on the tunica intima by establishing an ester bond with fatty acids such as oleic acid, and thus cholesterol ester is the main component of atherosclerotic plaques. Mid-infrared pulsed laser at 5.75 μm is selectively well absorbed in C=O stretching vibration mode of ester bonds. The purpose of this study is to determine the effectiveness of nanosecond pulsed laser at 5.75 μm irradiation of cholesterol ester in atherosclerotic plaques. In this study, we used a mid-infrared tunable solid-state laser which is operated by difference frequency generation method, with a wavelength of 5.75 μm, a pulse width of 5 nsec and a pulse duration of 10 Hz. It was confirmed that non-invasive interaction to normal thoracic aortas could be induce by the parameters, the wavelength of 5.75 μm, the average power densities of 35 W/cm2 and the irradiation time under 10 sec. This study shows that nanosecond pulsed laser irradiations at 5.75 μm provide an alternative laser light source as an effectively cutting, less traumatic tool for removal of atherosclerotic plaque.

Magnetic-particles-composed wire structures produced by pulsed laser deposition in a magnetic field

NASA Astrophysics Data System (ADS)

Nikov, Ru; Dikovska, A.; Nedyalkov, N.; Atanasov, P.

2018-03-01

We demonstrate the possibility to fabricate wire structures composed by arranged magnetic particles using pulsed laser deposition (PLD) in the presence of a magnetic field. Ablation of Ni and Co targets was performed in air by nanosecond laser pulses delivered by a Nd:YAG laser system oscillating at 355 nm. Due to the high density of the ambient, particles and clusters were formed by condensation in the plasma plume close to the target. The strong deceleration of the ablated material under these conditions further benefited the efficiency of applying a magnetic field to the plume. We also studied the effect of the target-to-substrate distance and the ambient pressure on the morphology of the deposited structures.

Laser microprobe and resonant laser ablation for depth profile measurements of hydrogen isotope atoms contained in graphite.

PubMed

Yorozu, M; Yanagida, T; Nakajyo, T; Okada, Y; Endo, A

2001-04-20

We measured the depth profile of hydrogen atoms in graphite by laser microprobing combined with resonant laser ablation. Deuterium-implanted graphite was employed for the measurements. The sample was ablated by a tunable laser with a wavelength corresponding to the resonant wavelength of 1S-2S of deuterium with two-photon excitation. The ablated deuterium was ionized by a 2 + 1 resonant ionization process. The ions were analyzed by a time-of-flight mass spectrometer. The deuterium ions were detected clearly with the resonant ablation. The detection limit was estimated to be less than 10(16) atoms/cm(3) in our experiments. We determined the depth profile by considering the etching profile and the etching rate. The depth profile agreed well with Monte Carlo simulations to within a precision of 23 mum for the center position and 4-mum precision for distributions for three different implantation depths.

Pulsed laser ablation of dental calculus in the near ultraviolet.

PubMed

Schoenly, Joshua E; Seka, Wolf; Rechmann, Peter

2014-02-01

Pulsed lasers emitting wavelengths near 400 nm can selectively ablate dental calculus without damaging underlying and surrounding sound dental hard tissue. Our results indicate that calculus ablation at this wavelength relies on the absorption of porphyrins endogenous to oral bacteria commonly found in calculus. Sub- and supragingival calculus on extracted human teeth, irradiated with 400-nm, 60-ns laser pulses at ≤8  J/cm2, exhibits a photobleached surface layer. Blue-light microscopy indicates this layer highly scatters 400-nm photons, whereas fluorescence spectroscopy indicates that bacterial porphyrins are permanently photobleached. A modified blow-off model for ablation is proposed that is based upon these observations and also reproduces our calculus ablation rates measured from laser profilometry. Tissue scattering and a stratified layering of absorbers within the calculus medium explain the gradual decrease in ablation rate from successive pulses. Depending on the calculus thickness, ablation stalling may occur at <5  J/cm2 but has not been observed above this fluence.

Physical mechanisms of SiN{sub x} layer structuring with ultrafast lasers by direct and confined laser ablation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rapp, S., E-mail: rapp@hm.edu; Erlangen Graduate School in Advanced Optical Technologies; Heinrich, G.

2015-03-14

In the production process of silicon microelectronic devices and high efficiency silicon solar cells, local contact openings in thin dielectric layers are required. Instead of photolithography, these openings can be selectively structured with ultra-short laser pulses by confined laser ablation in a fast and efficient lift off production step. Thereby, the ultrafast laser pulse is transmitted by the dielectric layer and absorbed at the substrate surface leading to a selective layer removal in the nanosecond time domain. Thermal damage in the substrate due to absorption is an unwanted side effect. The aim of this work is to obtain a deepermore » understanding of the physical laser-material interaction with the goal of finding a damage-free ablation mechanism. For this, thin silicon nitride (SiN{sub x}) layers on planar silicon (Si) wafers are processed with infrared fs-laser pulses. Two ablation types can be distinguished: The known confined ablation at fluences below 300 mJ/cm{sup 2} and a combined partial confined and partial direct ablation at higher fluences. The partial direct ablation process is caused by nonlinear absorption in the SiN{sub x} layer in the center of the applied Gaussian shaped laser pulses. Pump-probe investigations of the central area show ultra-fast reflectivity changes typical for direct laser ablation. Transmission electron microscopy results demonstrate that the Si surface under the remaining SiN{sub x} island is not damaged by the laser ablation process. At optimized process parameters, the method of direct laser ablation could be a good candidate for damage-free selective structuring of dielectric layers on absorbing substrates.« less

The influence of the focus position on laser machining and laser micro-structuring monocrystalline diamond surface

NASA Astrophysics Data System (ADS)

Wu, Mingtao; Guo, Bing; Zhao, Qingliang; Fan, Rongwei; Dong, Zhiwei; Yu, Xin

2018-06-01

Micro-structured surface on diamond is widely used in microelectronics, optical elements, MEMS and NEMS components, ultra-precision machining tools, etc. The efficient micro-structuring of diamond material is still a challenging task. In this article, the influence of the focus position on laser machining and laser micro-structuring monocrystalline diamond surface were researched. At the beginning, the ablation threshold and its incubation effect of monocrystalline diamond were determined and discussed. As the accumulated laser pulses ranged from 40 to 5000, the laser ablation threshold decreased from 1.48 J/cm2 to 0.97 J/cm2. Subsequently, the variation of the ablation width and ablation depth in laser machining were studied. With enough pulse energy, the ablation width mainly depended on the laser propagation attributes while the ablation depth was a complex function of the focus position. Raman analysis was used to detect the variation of the laser machined diamond surface after the laser machining experiments. Graphite formation was discovered on the machined diamond surface and graphitization was enhanced after the defocusing quantity exceeded 45 μm. At last, several micro-structured surfaces were successfully fabricated on diamond surface with the defined micro-structure patterns and structuring ratios just by adjusting the defocusing quantity. The experimental structuring ratio was consistent with the theoretical analysis.

Localized Synthesis of Silicon Nanocrystals in Silicon-rich SiO2 by CO2 Laser Annealing

DTIC Science & Technology

2007-05-01

damage problem since the peak Plaser of 4.4 MW/cm2 on the sample surface is far beyond the ablation threshold. Gallas et al. [16] then observed that...577-580, 2004. [9] A. F. Maciente, V. R. Mastelaro, A. L. Martinez , A. C. Hernandes, and C. A. C. Carneiro, “Surface crystallization of β-BaB2O4...J. Appl. Phys., vol. 95, pp. 4060-4068, 2004. [16] B. Gallas , C.-C. Kao, S. Fisson, G. Vuye, J. Rivory, Y. Bernard, and C. Belouet, “Laser

Short incubation fractional CO2 laser-assisted photodynamic therapy vs. conventional photodynamic therapy in field-cancerized skin: 12-month follow-up results of a randomized intraindividual comparison study.

PubMed

Vrani, F; Sotiriou, E; Lazaridou, E; Vakirlis, E; Sideris, N; Kirmanidou, E; Apalla, Z; Lallas, A; Ioannides, D

2018-06-04

Topical methyl aminolevulinate photodynamic therapy (MAL-PDT) with 3 h incubation is recommended as a field directed treatment. Skin pretreatment with ablative CO 2 fractional laser (AFXL) prior to MAL-PDT enhances drug penetration and could minimize incubation time. To evaluate and compare the safety and the preventive effect in the development of new non-melanocytic skin cancers (NMSCs) of AFXL-assisted MAL-PDT with 1-h incubation with that of conventional MAL-PDT in patients with clinical and histological signs of field cancerization. Forty-two patients with two mirror cancerized areas of face or scalp were randomized to field treatment with 1-h incubation AFXL-assisted PDT or conventional PDT (CPDT). All patients underwent two treatment sessions 1 week apart. Irradiation was performed using a red light-emitting diode lamp at 37 J/cm 2 . Patients were followed up at 3, 6, 9 and 12 months for the evaluation of development of new NMSCs lesions. All patients completed the study. There was no statistically significant difference with respect to the total number of new actinic keratoses at any point of follow-up as well as to the mean time of occurrence of new lesions between treatment fields. Both treatment regimens were safe and well tolerated. Ablative CO 2 fractional laser pretreatment may be considered as an option for reducing photosensitizer occlusion time while providing the same preventative efficacy as CPDT in patients with field-cancerized skin. © 2018 European Academy of Dermatology and Venereology.

Analysis of atmospheric pollutant metals by laser ablation inductively coupled plasma mass spectrometry with a radial line-scan dried-droplet approach

NASA Astrophysics Data System (ADS)

Tang, Xiaoxing; Qian, Yuan; Guo, Yanchuan; Wei, Nannan; Li, Yulan; Yao, Jian; Wang, Guanghua; Ma, Jifei; Liu, Wei

2017-12-01

A novel method has been improved for analyzing atmospheric pollutant metals (Be, Mn, Fe, Co, Ni, Cu, Zn, Se, Sr, Cd, and Pb) by laser ablation inductively coupled plasma mass spectrometry. In this method, solid standards are prepared by depositing droplets of aqueous standard solutions on the surface of a membrane filter, which is the same type as used for collecting atmospheric pollutant metals. Laser parameters were optimized, and ablation behaviors of the filter discs were studied. The mode of radial line scans across the filter disc was a representative ablation strategy and can avoid error from the inhomogeneous filter standards and marginal effect of the filter disc. Pt, as the internal standard, greatly improved the correlation coefficient of the calibration curve. The developed method provides low detection limits, from 0.01 ng m- 3 for Be and Co to 1.92 ng m- 3 for Fe. It was successfully applied for the determination of atmospheric pollutant metals collected in Lhasa, China. The analytical results showed good agreement with those obtained by conventional liquid analysis. In contrast to the conventional acid digestion procedure, the novel method not only greatly reduces sample preparation and shortens the analysis time but also provides a possible means for studying the spatial distribution of atmospheric filter samples.

Preliminary clinical results of pulsed-dye laser therapy for recurrent respiratory papillomatosis

NASA Astrophysics Data System (ADS)

McMillan, Kathleen; Shapshay, Stanley M.; McGilligan, J. A.; Wang, Zhi; Rebeiz, Elie E.

1998-07-01

Recurrent respiratory papillomatosis (RRP) is a viral disease characterized by the growth of benign tumors on the vocal cords. Standard management of RRP currently consists of CO2 laser microsurgical ablation of the papillomas. Because of the recurrent nature of this disease, patients are often faced with significant cumulative risk of soft tissue complications such as vocal cord scarring. As a minimally traumatic alternative to management of RRP, we have investigated the use of the 585 nm pulsed dye laser (PDL) to cause regression of the papillomas by selective eradication of the tumor microvasculature. Three patients have been treated with the PDL at fluences of 6 J/cm2 (double pulses per irradiated site), 8 J/cm2 (single pulses), and 10 J/cm2 (single pulses), at noncritical areas within the larynx, using a specially designed micromanipulator. Lesions on the true cords were treated with the CO2 laser. Clinical examination showed that PDL treatment appeared to produce complete regression of papillomas. Unlike the sites of lesions treated by the CO2 laser, the epithelial surface at the PDL treatment sites was preserved intact. The presumed mechanism for papilloma regression following PDL treatment involves acute or chronic localized hypoxia caused by loss of tumor microvasculature.

Rapid and Selective Removal of Composite From Tooth Surfaces With a 9.3 μm CO2 Laser Using Spectral Feedback

PubMed Central

Chan, Kenneth H.; Hirasuna, Krista; Fried, Daniel

2015-01-01

Objective Dental composite restorative materials are color matched to the tooth and are difficult to remove by mechanical means without excessive removal or damage to peripheral enamel and dentin. Lasers are ideally suited for selective ablation to minimize healthy tissue loss when replacing existing restorations, sealants, or removing composite adhesives such as residual composite left after debonding orthodontic brackets. Methods In this study, a carbon dioxide laser operating at 9.3-μm with a pulse duration of 10–20-microsecond and a pulse repetition rate of ~200 Hz was integrated with a galvanometer based scanner and used to selectively remove composite from tooth surfaces. Spectra of the plume emission were acquired after each laser pulse and used to differentiate between the ablation of dental enamel or composite. Microthermocouples were used to monitor the temperature rise in the pulp chamber during composite removal. The composite was placed on tooth buccal and occlusal surfaces and the carbon dioxide laser beam was scanned across the surface to selectively remove the composite without excessive damage to the underlying sound enamel. The residual composite and the damage to the underlying enamel was evaluated using optical microscopy. Results The laser was able to rapidly remove composite from tooth buccal and occlusal surfaces with minimal damage to the underlying sound enamel and without excessive heat accumulation in the tooth. Conclusion This study demonstrated that composite can be selectively removed from tooth surfaces at clinically relevant rates using a CO2 laser operating at 9.3-μm with high pulse repetition rates with minimal heat deposition and damage to the underlying enamel. PMID:21956630

Rapid and selective removal of composite from tooth surfaces with a 9.3 µm CO2 laser using spectral feedback.

PubMed

Chan, Kenneth H; Hirasuna, Krista; Fried, Daniel

2011-09-01

Dental composite restorative materials are color matched to the tooth and are difficult to remove by mechanical means without excessive removal or damage to peripheral enamel and dentin. Lasers are ideally suited for selective ablation to minimize healthy tissue loss when replacing existing restorations, sealants, or removing composite adhesives such as residual composite left after debonding orthodontic brackets. In this study, a carbon dioxide laser operating at 9.3-µm with a pulse duration of 10-20-microsecond and a pulse repetition rate of ∼200 Hz was integrated with a galvanometer based scanner and used to selectively remove composite from tooth surfaces. Spectra of the plume emission were acquired after each laser pulse and used to differentiate between the ablation of dental enamel or composite. Microthermocouples were used to monitor the temperature rise in the pulp chamber during composite removal. The composite was placed on tooth buccal and occlusal surfaces and the carbon dioxide laser beam was scanned across the surface to selectively remove the composite without excessive damage to the underlying sound enamel. The residual composite and the damage to the underlying enamel was evaluated using optical microscopy. The laser was able to rapidly remove composite from tooth buccal and occlusal surfaces with minimal damage to the underlying sound enamel and without excessive heat accumulation in the tooth. This study demonstrated that composite can be selectively removed from tooth surfaces at clinically relevant rates using a CO(2) laser operating at 9.3-µm with high pulse repetition rates with minimal heat deposition and damage to the underlying enamel. Copyright © 2011 Wiley-Liss, Inc.

Preclinical investigations of articular cartilage ablation with femtosecond and pulsed infrared lasers as an alternative to microfracture surgery

NASA Astrophysics Data System (ADS)

Su, Erica; Sun, Hui; Juhasz, Tibor; Wong, Brian J. F.

2014-09-01

Microfracture surgery is a bone marrow stimulation technique for treating cartilage defects and injuries in the knee. Current methods rely on surgical skill and instrumentation. This study investigates the potential use of laser technology as an alternate means to create the microfracture holes. Lasers investigated in this study include an erbium:YAG laser (λ=2.94 μm), titanium:sapphire femtosecond laser system (λ=1700 nm), and Nd:glass femtosecond laser (λ=1053 nm). Bovine samples were ablated at fluences of 8 to 18 J/cm2 with the erbium:YAG laser, at a power of 300±15 mW with the titanium:sapphire femtosecond system, and at an energy of 3 μJ/pulse with the Nd:glass laser. Samples were digitally photographed and histological sections were taken for analysis. The erbium:YAG laser is capable of fast and efficient ablation; specimen treated with fluences of 12 and 18 J/cm2 experienced significant amounts of bone removal and minimal carbonization with saline hydration. The femtosecond laser systems successfully removed cartilage but not clinically significant amounts of bone. Precise tissue removal was possible but not to substantial depths due to limitations of the systems. With additional studies and development, the use of femtosecond laser systems to ablate bone may be achieved at clinically valuable ablation rates.

Preclinical investigations of articular cartilage ablation with femtosecond and pulsed infrared lasers as an alternative to microfracture surgery.

PubMed

Su, Erica; Sun, Hui; Juhasz, Tibor; Wong, Brian J F

2014-09-01

Microfracture surgery is a bone marrow stimulation technique for treating cartilage defects and injuriesin the knee. Current methods rely on surgical skill and instrumentation. This study investigates the potential useof laser technology as an alternate means to create the microfracture holes. Lasers investigated in this study include an erbium:YAG laser (λ = 2.94 μm), titanium:sapphire femtosecond laser system (λ = 1700 nm), and Nd:glass femtosecond laser (λ = 1053 nm). Bovine samples were ablated at fluences of 8 to 18 J∕cm2 with the erbium:YAG laser, at a power of 300 ± 15 mW with the titanium:sapphire femtosecond system, and at an energy of 3 μJ∕pulse with the Nd:glass laser. Samples were digitally photographed and histological sections were taken for analysis. The erbium:YAG laser is capable of fast and efficient ablation; specimen treated with fluences of 12 and 18 J∕cm2 experienced significant amounts of bone removal and minimal carbonization with saline hydration. The femtosecond laser systems successfully removed cartilage but not clinically significant amounts of bone. Precise tissue removal was possible but not to substantial depths due to limitations of the systems. With additional studies and development, the use of femtosecond laser systems to ablate bone may be achieved at clinically valuable ablation rates.

Effects of pulsed mid-IR lasers on bovine knee joint tissues

NASA Astrophysics Data System (ADS)

Vari, Sandor G.; Shi, Wei-Qiang; Pergadia, Vani R.; Duffy, J. T.; Miller, J. M.; van der Veen, Maurits J.; Weiss, Andrew B.; Fishbein, Michael C.; Grundfest, Warren S.

1993-07-01

We investigated the effect of varying Tm:YAG (2.014 micrometers ) and Ho:YAG (2.130 micrometers ) laser parameters on ablation rate and consequent thermal damage. Mid-infrared wavelengths are strongly absorbed by most biological tissues due to the tissue's high water content. The ablation rate of fresh bovine knee joint tissues (fibrous cartilage, hyaline cartilage, and bone) in saline was assessed as a function of radiant exposure (160 - 950 J/cm2), at pulse widths of 200 microsecond(s) ec for Tm:YAG and 250 microsecond(s) ec for Ho:YAG and a repetition rate of 2 Hz. All tissues used in this study could be efficiently ablated using two micron lasers. The mechanism of action is likely related to the formation and collapse of cavitation bubbles, associated with mid-infrared lasers. We concluded that the Tm:YAG and Ho:YAG lasers are capable of effective knee joint tissue ablation.

Demonstration of periodic nanostructure formation with less ablation by double-pulse laser irradiation on titanium

NASA Astrophysics Data System (ADS)

Furukawa, Yuki; Sakata, Ryoichi; Konishi, Kazuki; Ono, Koki; Matsuoka, Shusaku; Watanabe, Kota; Inoue, Shunsuke; Hashida, Masaki; Sakabe, Shuji

2016-06-01

By pairing femtosecond laser pulses (duration ˜40 fs and central wavelength ˜810 nm) at an appropriate time interval, a laser-induced periodic surface structure (LIPSS) is formed with much less ablation than one formed with a single pulse. On a titanium plate, a pair of laser pulses with fluences of 70 and 140 mJ/cm2 and a rather large time interval (>10 ps) creates a LIPSS with an interspace of 600 nm, the same as that formed by a single pulse of 210 mJ/cm2, while the double pulse ablates only 4 nm, a quarter of the ablation depth of a single pulse.

Evaluation of corneal ablation by an optical parametric oscillator (OPO) at 2.94 μm and an Er:YAG laser and comparison to ablation by a 193-nm excimer laser

NASA Astrophysics Data System (ADS)

Telfair, William B.; Hoffman, Hanna J.; Nordquist, Robert E.; Eiferman, Richard A.

1998-06-01

Purpose: This study first evaluated the corneal ablation characteristics of (1) an Nd:YAG pumped OPO (Optical Parametric Oscillator) at 2.94 microns and (2) a short pulse Er:YAG laser. Secondly, it compared the histopathology and surface quality of these ablations with (3) a 193 nm excimer laser. Finally, the healing characteristics over 4 months of cat eyes treated with the OPO were evaluated. Methods: Custom designed Nd:YAG/OPO and Er:YAG lasers were integrated with a new scanning delivery system to perform PRK myopic correction procedures. After initial ablation studies to determine ablation thresholds and rates, human cadaver eyes and in-vivo cat eyes were treated with (1) a 6.0 mm Dia, 30 micron deep PTK ablation and (2) a 6.0 mm Dia, -5.0 Diopter PRK ablation. Cadaver eyes were also treated with a 5.0 mm Dia, -5.0 Diopter LASIK ablation. Finally, cats were treated with the OPO in a 4 month healing study. Results: Ablation thresholds below 100 mJ/cm2 and ablation rates comparable to the excimer were demonstrated for both infrared systems. Light Microscopy (LM) showed no thermal damage for low fluence treatments, but noticeable thermal damage at higher fluences. SEM and TEM revealed morphologically similar surfaces for low fluence OPO and excimer samples with a smooth base and no evidence of collagen shrinkage. The Er:YAG and higher fluence OPO treated samples revealed more damage along with visible collagen coagulation and shrinkage in some cases. Healing was remarkably unremarkable. All eyes had a mild healing response with no stromal haze and showed topographic flattening. LM demonstrated nothing except a moderate increase in keratocyte activity in the upper third of the stroma. TEM confirmed this along with irregular basement membranes. Conclusions: A non- thermal ablation process called photospallation is demonstrated for the first time using short pulse infrared lasers yielding damage zones comparable to the excimer and healing which is also comparable to the excimer. Such Infrared sources are, therefore, potentially attractive competitors to the excimer to perform PRK and LASIK.

Laser tumor treatment in oral and maxillofacial surgery

NASA Astrophysics Data System (ADS)

Neukam, F. W.; Stelzle, F.

Cancer treatment is an integral part of oral and maxillofacial surgery. Oral cancer in particular is a highly prevalent neoplasm. Standard treatment for most of the tumors is radical surgery combined with stage-based neo-/adjuvant therapy. Laser surgery has become a reliable treatment option for oral cancer as well as for precancerous lesions. Widely used lasers in oral and maxillofacial tumor surgery are the CO2 laser, the Er:YAG laser, the Nd:YAG laser and the KTM laser. The use of lasers in tumor surgery has several advantages: remote application, precise cutting, hemostasis, low cicatrization, reduced postoperative pain and swelling, can be combined with endoscopic, microscopic and robotic surgery. However, laser surgery has some major drawbacks: In contrast to conventional incisions with scalpels, the surgeon gets no feedback during laser ablation. There is no depth sensation and no tissue specificity with a laser incision, increasing the risk of iatrogenic damage to nerves and major blood vessels. Future prospects may solve these problems by means of an optical feedback mechanism that provides a tissue-specific laser ablation. First attempts have been made to perform remote optical tissue differentiation. Additionally, real time optical tumor detection during laser surgery would allow for a very precise and straight forward cancer resection, enhancing organ preservation and hence the quality of life for patients with cancer in the head and neck region.

Comparison of 1470nm diode laser vs. C02-laserlaser for tonsillotomy and a clinical feasability trial on the use of 1940nm in ENT

NASA Astrophysics Data System (ADS)

Sroka, Ronald; Pongratz, Thomas; Havel, Miriam; Englert, Elsa; Kremser, Thomas; Betz, Christain S.; Leunig, Andreas

2013-03-01

Introduction: The need for reduction of post-tonsillectomy hemorrhage has led to promotion of tonsillotomy techniques for tonsil tissue reduction in obstructive tonsillar hypertrophy. A first study compares ablative tissue effects using 1470nm diode laser and CO2-laser for tonsillotomy in an intraindividual design. A number of different laser systems have been used for volume reduction of hyperplastic nasal turbinates. The aim of a 2nd clinical feasibility study was to show the coagulative and tissue reducing effects using a novel Tm: fiber laser system emitting at λ = 1940 nm Patients and methods: First 21 children aged 3 -13 years (mean age 6.3 years) underwent laser tonsillotomy for obstructive tonsillar hypertrophy in this double blind, prospective, randomized, clinical feasibility trial. In each case, tonsillotomy was performed using fibre guided 1470nm diode laser (contact mode, 15 W power) on the one side and CO2-laser (12 W power) on the other side. An independent physician documented clinical presentation and patients' symptoms preoperatively and on day 1, 3, 7, 14 and 21 postoperatively using standardized questionnaire including VAS (was ist das) for each side separately. The 2nd clinical feasibility trial included 11 patients suffering from hyperplastic inferior nasal turbinates, who were therapy-refractory to conservative medical treatment. The obstructive nasal cavity was treated using the 1940 nm Tm: fiber laser at < 5 W output power. The treatment was performed in non-contact mode under endoscopic control. Patients ' symptoms were documented both preoperatively and on days 1 - 3 and 28 postoperatively using a non-validated questionnaire. Additionally, an endoscopic examination was performed. Results: Mean duration of single tonsillotomy operative treatment was 2.7 min using 1470nm laser and 4.9 min using CO2 laser respectively. Intraoperative bleeding and the frequency of bipolar forceps use for intraoperative bleeding control was significantly less pronounced using the 1470nm diode laser system. There was no difference in postoperative pain scores between the CO2-laser treated and the 1470nm fibre guided diode laser treated side. No infections, hemorrhages or other complications occurred in the course of the three weeks postoperative period. In the turbinate study, none of the patients showed infections, and no hemorrhages or other complications occurred intraor postoperatively.The mean laser activation time was extremely short being 28.0 +/- 8.5 s. In conjunction with a low power setting (median, 3 W; mean +/- standard deviation, 3.3 +/- 1.1 W), a low energy of 90.2 +/- 37.8 J was applied. A significant reduction in nasal obstruction could be documented in all patients on day 28 postoperatively. Evaluation, as assessed preoperatively and 4 weeks postoperatively, showed significant subjective improvements. Conclusion: A fiber-guided 1470nm diode laser system offers an efficient and safe method for tonsillotomy as treatment of obstructive tonsillar hypertrophy. Compared to our standard practice with CO2- laser, 1470nm laser application provides comparable tissue ablation effects with less intraoperative bleeding and shorter operation time. The treatment of hyperplastic inferior turbinates using a 1940 nm Tm: fiber laser provides sufficient tissue reduction in a short operation time using low total energy. Patients described a significant improvement in nasal breathing postoperatively.

Formation of Gas-Phase Formate in Thermal Reactions of Carbon Dioxide with Diatomic Iron Hydride Anions.

PubMed

Jiang, Li-Xue; Zhao, Chongyang; Li, Xiao-Na; Chen, Hui; He, Sheng-Gui

2017-04-03

The hydrogenation of carbon dioxide involves the activation of the thermodynamically very stable molecule CO 2 and formation of a C-H bond. Herein, we report that HCO 2 - and CO can be formed in the thermal reaction of CO 2 with a diatomic metal hydride species, FeH - . The FeH - anions were produced by laser ablation, and the reaction with CO 2 was analyzed by mass spectrometry and quantum-chemical calculations. Gas-phase HCO 2 - was observed directly as a product, and its formation was predicted to proceed by facile hydride transfer. The mechanism of CO 2 hydrogenation in this gas-phase study parallels similar behavior of a condensed-phase iron catalyst. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

State of the art of CO laser angioplasty system

NASA Astrophysics Data System (ADS)

Arai, Tsunenori; Mizuno, Kyoichi; Miyamoto, Akira; Sakurada, Masami; Kikuchi, Makoto; Kurita, Akira; Nakamura, Haruo; Takaoka, Hidetsugu; Utsumi, Atsushi; Takeuchi, Kiyoshi

1994-07-01

A unique percutaneous transluminal coronary angioplasty system new IR therapy laser with IR glass fiber delivery under novel angioscope guidance was described. Carbon monoxide (CO) laser emission of 5 mm in wavelength was employed as therapy laser to achieve precise ablation of atheromatous plaque with a flexible As-S IR glass fiber for laser delivery. We developed the first medical CO laser as well as As-S IR glass fiber cable. We also developed 5.5 Fr. thin angioscope catheter with complete directional manipulatability at its tip. The system control unit could manage to prevent failure irradiations and fiber damages. This novel angioplasty system was evaluated by a stenosis model of mongrel dogs. We demonstrated the usefulness of our system to overcome current issues on laser angioplasty using multifiber catheter with over-the-guidewire system.

Deposition of functional nanoparticle thin films by resonant infrared laser ablation.

NASA Astrophysics Data System (ADS)

Haglund, Richard; Johnson, Stephen; Park, Hee K.; Appavoo, Kannatessen

2008-03-01

We have deposited thin films containing functional nanoparticles, using tunable infrared light from a picosecond free-electron laser (FEL). Thin films of the green light-emitting molecule Alq3 were first deposited by resonant infrared laser ablation at 6.68 μm, targeting the C=C ring mode of the Alq3. TiO2 nanoparticles 50-100 nm diameter were then suspended in a water matrix, frozen, and transferred by resonant infrared laser ablation at 2.94 μm through a shadow mask onto the Alq3 film. Photoluminescence was substantially enhanced in the regions of the film covered by the TiO2 nanoparticles. In a second experiment, gold nanoparticles with diameters in the range of 50-100 nm were suspended in the conducting polymer and anti-static coating material PEDOT:PSS, which was diluted by mixing with N-methyl pyrrolidinone (NMP). The gold nanoparticle concentration was 8-10% by weight. The mixture was frozen and then ablated by tuning the FEL to 3.47 μm, the C-H stretch mode of NMP. Optical spectroscopy of the thin film deposited by resonant infrared laser ablation exhibited the surface-plasmon resonance characteristic of the Au nanoparticles. These experiments illustrate the versatility of matrix-assisted resonant infrared laser ablation as a technique for depositing thin films containing functionalized nanoparticles.

Tungsten carbide precursors as an example for influence of a binder on the particle formation in the nanosecond laser ablation of powdered materials.

PubMed

Holá, Markéta; Mikuska, Pavel; Hanzlíková, Renáta; Kaiser, Jozef; Kanický, Viktor

2010-03-15

A study of LA-ICP-MS analysis of pressed powdered tungsten carbide precursors was performed to show the advantages and problems of nanosecond laser ablation of matrix-unified samples. Five samples with different compositions were pressed into pellets both with silver powder as a binder serving to keep the matrix unified, and without any binder. The laser ablation was performed by nanosecond Nd:YAG laser working at 213 nm. The particle formation during ablation of both sets of pellets was studied using an optical aerosol spectrometer allowing the measurement of particle concentration in two size ranges (10-250 nm and 0.25-17 microm) and particle size distribution in the range of 0.25-17 microm. Additionally, the structure of the laser-generated particles was studied after their collection on a filter using a scanning electron microscope (SEM) and the particle chemical composition was determined by an energy dispersive X-ray spectroscope (EDS). The matrix effect was proved to be reduced using the same silver powdered binder for pellet preparation in the case of the laser ablation of powdered materials. The LA-ICP-MS signal dependence on the element content present in the material showed an improved correlation for Co, Ti, Ta and Nb of the matrix-unified samples compared to the non-matrix-unified pellets. In the case of W, the ICP-MS signal of matrix-unified pellets was influenced by the changes in the particle formation. Copyright (c) 2009 Elsevier B.V. All rights reserved.

Laser ablation of dental calculus at 400 nm using a Ti:sapphire laser

NASA Astrophysics Data System (ADS)

Schoenly, Joshua E.; Seka, Wolf; Rechmann, Peter

2009-02-01

A Nd:YAG laser-pumped, frequency-doubled Ti:sapphire laser is used for selective ablation of calculus. The laser provides <=25 mJ at 400 nm (60-ns pulse width, 10-Hz repetition rate). The laser is coupled into an optical multimode fiber coiled around a 4-in.-diam drum to generate a top-hat output intensity profile. With coaxial water cooling, this is ideal for efficient, selective calculus removal. This is in stark contrast with tightly focused Gaussian beams that are energetically inefficient and lead to irreproducible results. Calculus is well ablated at high fluences >=2J/cm2 stalling occurs below this fluence because of photobleaching. Healthy hard tissue is not removed at fluences <=3 J/cm2.

Nonablative fractional laser resurfacing in Asian skin--a review.

PubMed

Sachdeva, Silonie

2010-12-01

Skin resurfacing has been a part of cosmetic dermatology for more than two decades now, and most of it has been ablative with traditional aggressive lasers including the CO(2) and erbium. The last few years have seen a revolutionary change with the invention of nonablative lasers for skin tightening. Fractional resurfacing is a new concept of cutaneous remodeling whereby laser-induced zones of microthermal injury are surrounded by normal untreated tissue that helps in quicker healing. The various wavelengths used are 1320, 1440, and 2940 nm with depth of penetration ranging from 25 μ to 1.2 mm. This article reviews the history of nonablative fractional laser resurfacing, its indications, contraindications, and a review of use in Asian skin with Fitzpatrick type III-VI. © 2010 Wiley Periodicals, Inc.

Thermal stress in dentin and enamel under CO2 laser irradiation

NASA Astrophysics Data System (ADS)

Meyer, Dirk H.; Foth, Hans-Jochen

1996-01-01

Ablation of dentin and tartar was studied under carbon dioxide-laser irradiation in cw and pulse mode with pulse length down to 150 microseconds. The specimens had been cut by a diamant blade to slices of thicknesses between 0.8 and 2.8 mm. The laser induced temperature rise was measured by an infrared camera monitoring the backside of the samples. The specimens shape and structure at the laser spot was analyzed by electron microscopy. Of special interest was the testing of the SwiftLaseTM to reducing the heat. The experimental results show the necessity of a water cooling in all application modes. The origin of the cracks which had been observed in many of the samples, is currently under investigation.

A randomized prospective long-term (>1 year) clinical trial comparing the efficacy and safety of radiofrequency ablation to 980 nm laser ablation of the great saphenous vein.

PubMed

Sydnor, Malcolm; Mavropoulos, John; Slobodnik, Natalia; Wolfe, Luke; Strife, Brian; Komorowski, Daniel

2017-07-01

Purpose To compare the short- and long-term (>1 year) efficacy and safety of radiofrequency ablation (ClosureFAST™) versus endovenous laser ablation (980 nm diode laser) for the treatment of superficial venous insufficiency of the great saphenous vein. Materials and methods Two hundred patients with superficial venous insufficiency of the great saphenous vein were randomized to receive either radiofrequency ablation or endovenous laser ablation (and simultaneous adjunctive therapies for surface varicosities when appropriate). Post-treatment sonographic and clinical assessment was conducted at one week, six weeks, and six months for closure, complications, and patient satisfaction. Clinical assessment of each patient was conducted at one year and then at yearly intervals for patient satisfaction. Results Post-procedure pain ( p < 0.0001) and objective post-procedure bruising ( p = 0.0114) were significantly lower in the radiofrequency ablation group. Improvements in venous clinical severity score were noted through six months in both groups (endovenous laser ablation 6.6 to 1; radiofrequency ablation 6.2 to 1) with no significant difference in venous clinical severity score ( p = 0.4066) or measured adverse effects; 89 endovenous laser ablation and 87 radiofrequency patients were interviewed at least 12 months out with a mean long-term follow-up of 44 and 42 months ( p = 0.1096), respectively. There were four treatment failures in each group, and every case was correctable with further treatment. Overall, there were no significant differences with regard to patient satisfaction between radiofrequency ablation and endovenous laser ablation ( p = 0.3009). There were no cases of deep venous thrombosis in either group at any time during this study. Conclusions Radiofrequency ablation and endovenous laser ablation are highly effective and safe from both anatomic and clinical standpoints over a multi-year period and neither modality achieved superiority over the other.

An Investigation on the Use of a Laser Ablation Treatment on Metallic Surfaces and the Influence of Temperature on Fracture Toughness of Hybrid Co-Cured Metal-PMC Interfaces

NASA Technical Reports Server (NTRS)

Connell, John; Palmieri, Frank; Truong, Hieu; Ochoa, Ozden; Lagoudas, Dimitris

2015-01-01

Hybrid composite laminates that contain alternating layers of titanium alloys and carbon fabric reinforced polyimide matrix composites (PMC) are excellent candidates for light-weight, high-temperature structural materials for high-speed aerospace vehicles. The delamination resistance of the hybrid titanium-PMC interface is of crucial consideration for structural integrity during service. Here, we report the first investigations on the use of laser ablation in combination with sol-gel treatment technique on Ti/NiTi foil surfaces in co-cured hybrid polyimide matrix composite laminates. Mode-I and mode-II fracture toughness of the hybrid Ti/NiTi-PMC interface as a function of temperature were determined via experimental testing and finite element analysis.

Study on laser-assisted drug delivery with optical coherence tomography

NASA Astrophysics Data System (ADS)

Tsai, Wen-Guei; Tsai, Ting-Yen; Yang, Chih-Hsun; Tsai, Meng-Tsan

2017-04-01

The nail provides a functional protection to the fingertips and surrounding tissue from external injuries. Nail plate divided into three layers including dorsal, intermediate, and ventral layers. The dorsal layer consists of compact, hard keratins, limiting topical drug delivery through the nail. In this study, we investigate the application of fractional CO2 laser that produces arrays of microthermal ablation zones (MAZs) to facilitate drug delivery in the nails. Moreover, optical coherence tomography (OCT) is implemented for real-time monitoring of the laser-skin tissue interaction, sparing the patient from invasive surgical sampling procedure. Observations of drug diffusion through the induced MAZ array are achieved by evaluating the time-dependent OCT intensity variance. Subsequently, nails are treated with cream and liquid topical drugs to investigate the feasibility and diffusion efficacy of laser-assisted drug delivery. Our results show that fractional CO2 laser improves the efficacy of topical drug delivery in the nail plate, and that OCT could potentially be used for in vivo monitoring of the depth of laser penetration as well as real-time observations of drug delivery.

Femtosecond laser ablation and nanoparticle formation in intermetallic NiAl

NASA Astrophysics Data System (ADS)

Jorgensen, David J.; Titus, Michael S.; Pollock, Tresa M.

2015-10-01

The ablation behavior of a stoichiometric intermetallic compound β-NiAl subjected to femtosecond laser pulsing in air has been investigated. The single-pulse ablation threshold for NiAl was determined to be 83 ± 4 mJ/cm2 and the transition to the high-fluence ablation regime occurred at 2.8 ± 0.3 J/cm2. Two sizes of nanoparticles consisting of Al, NiAl, Ni3Al and NiO were formed and ejected from the target during high-fluence ablation. Chemical analysis revealed that smaller nanoparticles (1-30 nm) tended to be rich in Al while larger nanoparticles (>100 nm) were lean in Al. Ablation in the low-fluence regime maintained this trend. Redeposited material and nanoparticles remaining on the surface after a single 3.7 J/cm2 pulse, one hundred 1.7 J/cm2 pulses, or one thousand 250 mJ/cm2 pulses were enriched in Al relative to the bulk target composition. Further, the surface of the irradiated high-fluence region was depleted in Al indicating that the fs laser ablation removal rate of the intermetallic constituents in this regime does not scale with the individual pure element ablation thresholds.

Millisecond laser ablation of molybdenum target in reactive gas toward MoS2 fullerene-like nanoparticles with thermally stable photoresponse.

PubMed

Song, Shu-Tao; Cui, Lan; Yang, Jing; Du, Xi-Wen

2015-01-28

As a promising material for photoelectrical application, MoS2 has attracted extensive attention on its facile synthesis and unique properties. Herein, we explored a novel strategy of laser ablation to synthesize MoS2 fullerene-like nanoparticles (FL-NPs) with stable photoresponse under high temperature. Specifically, we employed a millisecond pulsed laser to ablate the molybdenum target in dimethyl trisulfide gas, and as a result, the molybdenum nanodroplets were ejected from the target and interacted with the highly reactive ambient gas to produce MoS2 FL-NPs. In contrast, the laser ablation in liquid could only produce core-shell nanoparticles. The crucial factors for controlling final nanostructures were found to be laser intensity, cooling rate, and gas reactivity. Finally, the MoS2 FL-NPs were assembled into a simple photoresponse device which exhibited excellent thermal stability, indicating their great potentialities for high-temperature photoelectrical applications.

Lower energy and pulse stacking. A safer alternative for skin tightening using fractional CO2 laser.

PubMed

Motta, Marcos Matias; Stelini, Rafael Fantelli; Calderoni, Davi Reis; Gilioli, Rovilson; Kharmandayan, Paulo

2016-01-01

To evaluate the effect of different energies and stacking in skin shrinkage. Three decreasing settings of a fractional CO2 laser were applied to the abdomen of Twenty five Wistar rats divided into three groups. Group I (n=5) was histologically evaluated for microthermal zones dimensions. Groups II and III (n=10 each) were macroscopic evaluated with freeware ImageJ for area contraction immediately and after 30 and 60 days. No statistical significance was found within microthermal zone histological dimensions (Group I) in all settings studied. (Ablation depth: 76.90 to 97.18µm; Coagulation depth: 186.01 to 219.84 µm). In Group II, macroscopic evaluation showed that all settings cause significant immediate skin contraction. The highest setting cause significant more intense tightening effect initially, contracting skin area from 258.65 to 179.09 mm2. The same pattern was observed in Group III. At 30 and 60 days, the lowest setting significantly sustained contraction. Lower fractional CO2 laser energies associated to pulse stacking could cause consistent and long lasting tissue contraction in rats.

Effect of CO2 laser micromachining on physicochemical properties of poly(L-lactide)

NASA Astrophysics Data System (ADS)

Antończak, Arkadiusz J.; Stepak, Bogusz; Szustakiewicz, Konrad; Wójcik, Michał; Kozioł, Paweł E.; Łazarek, Łukasz; Abramski, Krzysztof M.

2014-08-01

In this paper, we present some examples of micromachining of poly(L-lactide) with a CO2 laser and an analysis of changes in material properties in the heat affected HAZ induced by the fluence well above the ablation threshold. The complexity of the processes of decomposition implies the need for simultaneous use of many selective analytical techniques which complement each other to give a full image of the changes. Introduced changes were characterized using Differential Scanning Calorimetry (DSC), Gel Permeation Chromatography (GPC), X-ray Photoelectron Spectroscopy (XPS) and Attenuated Total Reflectance Fourier Transform Infrared spectroscopy (ATR-FTIR). It turns out that CO2 laser processing of poly(L-lactide) mainly induces surface changes. However, oxidation of the surface was not observed. We recorded a bimodal distribution and some reduction in the molecular weight. Infrared spectroscopy in turn revealed the existence of absorption bands, characteristic for the vinyl groups (RCH=CH2). The appearance of these bands indicates that the decomposition of the polymer occurred, among others, by means of the cis-elimination reaction.

Fractionated Er:YAG laser versus fully ablative Er:YAG laser for scar revision: Results of a split scar, double blinded, prospective trial.

PubMed

Tidwell, W James; Owen, Cindy E; Kulp-Shorten, Carol; Maity, Abhishek; McCall, Michael; Brown, Timothy S

2016-11-01

Ablative laser resurfacing is a common treatment for post-surgical scars. Fractional ablative laser resurfacing has been an emerging treatment option that is replacing fully ablative lasers in many applications. Data comparing fractionated and fully ablative lasers in treating post-operative scars are lacking. Twenty patients were enrolled in a split scar study following excisions from dermatologic surgery. Wounds had to be older than 8 weeks but less than 1 year. The scars were randomly divided into two halves. One half of the scar was treated with fully ablative erbium-doped yttrium aluminum garnet (Er:YAG) and the other was treated with fractionated Er:YAG. The scars were treated at monthly intervals for 3 months, then followed up at months 1 and 2 after the last treatment. POSAS was used to evaluate the scars by a panel of dermatologists blinded to the lasers in conjunction with the patients, who were also blinded. Physicians and patients both observed a superior outcome of 32.5% (P = 0.019) and 58.1% (P = 0.001), respectively, using the POSAS. There was no trend in difference in pain reported by the patient between the two lasers. Patients overwhelmingly preferred the fractionated Er:YAG laser (94%) to the fully ablative laser when asked at the end of the study. Although this study is limited by a short follow-up period, it shows a statistically significant superior outcome in fractionated Er:YAG over fully ablative Er:YAG for scar revision. It also adds quantitative values to the assessment of scar appearance when treated with fractionated lasers compared to fully ablative lasers. It was also found that the fractionated Er:YAG had increased patient satisfaction, but there was no difference in reported pain scores. These data are useful when counseling patients undergoing laser surgery. Lasers Surg. Med. 48:837-843, 2016. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Thermal protection during percutaneous thermal ablation procedures: interest of carbon dioxide dissection and temperature monitoring.

PubMed

Buy, Xavier; Tok, Chung-Hong; Szwarc, Daniel; Bierry, Guillaume; Gangi, Afshin

2009-05-01

Percutaneous image-guided thermal ablation of tumor is widely used, and thermal injury to collateral structures is a known complication of this technique. To avoid thermal damage to surrounding structures, several protection techniques have been reported. We report the use of a simple and effective protective technique combining carbon dioxide dissection and thermocouple: CO(2) displaces the nontarget structures, and its low thermal conductivity provides excellent insulation; insertion of a thermocouple in contact with vulnerable structures achieves continuous thermal monitoring. We performed percutaneous thermal ablation of 37 tumors in 35 patients (4 laser, 10 radiofrequency, and 23 cryoablations) with protection of adjacent vulnerable structures by using CO(2) dissection combined with continuous thermal monitoring with thermocouple. Tumor locations were various (19 intra-abdominal tumors including 4 livers and 9 kidneys, 18 musculoskeletal tumors including 11 spinal tumors). CO(2) volume ranged from 10 ml (epidural space) to 1500 ml (abdominal). Repeated insufflations were performed if necessary, depending on the information given by the thermocouple and imaging control. Dissection with optimal thermal protection was achieved in all cases except two patients where adherences (one postoperative, one arachnoiditis) blocked proper gaseous distribution. No complication referred to this technique was noted. This safe, cost-effective, and simple method increases the safety and the success rate of percutaneous thermal ablation procedures. It also offers the potential to increase the number of tumors that can be treated via a percutaneous approach.

Preclinical investigations of articular cartilage ablation with femtosecond and pulsed infrared lasers as an alternative to microfracture surgery

PubMed Central

Su, Erica; Sun, Hui; Juhasz, Tibor; Wong, Brian J. F.

2014-01-01

Abstract. Microfracture surgery is a bone marrow stimulation technique for treating cartilage defects and injuries in the knee. Current methods rely on surgical skill and instrumentation. This study investigates the potential use of laser technology as an alternate means to create the microfracture holes. Lasers investigated in this study include an erbium:YAG laser (λ=2.94  μm), titanium:sapphire femtosecond laser system (λ=1700  nm), and Nd:glass femtosecond laser (λ=1053  nm). Bovine samples were ablated at fluences of 8 to 18  J/cm2 with the erbium:YAG laser, at a power of 300±15  mW with the titanium:sapphire femtosecond system, and at an energy of 3  μJ/pulse with the Nd:glass laser. Samples were digitally photographed and histological sections were taken for analysis. The erbium:YAG laser is capable of fast and efficient ablation; specimen treated with fluences of 12 and 18  J/cm2 experienced significant amounts of bone removal and minimal carbonization with saline hydration. The femtosecond laser systems successfully removed cartilage but not clinically significant amounts of bone. Precise tissue removal was possible but not to substantial depths due to limitations of the systems. With additional studies and development, the use of femtosecond laser systems to ablate bone may be achieved at clinically valuable ablation rates. PMID:25200394

Guiding flying-spot laser transepithelial phototherapeutic keratectomy with optical coherence tomography

PubMed Central

Li, Yan; Yokogawa, Hideaki; Tang, Maolong; Chamberlain, Winston; Zhang, Xinbo; Huang, David

2017-01-01

PURPOSE To analyze transepithelial phototherapeutic keratectomy (PTK) results using optical coherence tomography (OCT) and develop a model to guide the laser dioptric and depth settings. SETTING Casey Eye Institute, Portland, Oregon, USA. DESIGN Prospective nonrandomized case series. METHODS Patients with superficial corneal opacities and irregularities had transepithelial PTK with a flying-spot excimer laser by combining wide-zone myopic and hyperopic astigmatic ablations. Optical coherence tomography was used to calculate corneal epithelial lenticular masking effects, guide refractive laser settings, and measure opacity removal. The laser ablation efficiency and the refractive outcome were investigated using multivariate linear regression models. RESULTS Twenty-six eyes of 20 patients received PTK to remove opacities and irregular astigmatism due to scar, dystrophy, radial keratotomy, or previous corneal surgeries. The uncorrected distance visual acuity (UDVA) and corrected distance visual acuity (CDVA) were significantly improved (P < .01) by 3.7 Snellen lines and 2.0 Snellen lines, respectively, to a mean of 20/41.2 and 20/22.0, respectively. Achieved laser ablation depths were 31.3% (myopic ablation) and 63.0% (hyperopic ablation) deeper than the manufacturer’s nomogram. The spherical equivalent of the corneal epithelial lenticular masking effect was 0.73 diopter ± 0.61 (SD). The refractive outcome highly correlated to the laser settings and epithelial lenticular masking effect (Pearson R = 0.96, P < .01). The ablation rate of granular dystrophy opacities appeared to be slower. Smoothing ablation under masking fluid was needed to prevent focal steep islands in these cases. CONCLUSIONS The OCT-measured ablation depth efficiency could guide opacity removal. The corneal epithelial lenticular masking effect could refine the spherical refractive nomogram to achieve a better refractive outcome after transepithelial ablation. PMID:28532939

Guiding flying-spot laser transepithelial phototherapeutic keratectomy with optical coherence tomography.

PubMed

Li, Yan; Yokogawa, Hideaki; Tang, Maolong; Chamberlain, Winston; Zhang, Xinbo; Huang, David

2017-04-01

To analyze transepithelial phototherapeutic keratectomy (PTK) results using optical coherence tomography (OCT) and develop a model to guide the laser dioptric and depth settings. Casey Eye Institute, Portland, Oregon, USA. Prospective nonrandomized case series. Patients with superficial corneal opacities and irregularities had transepithelial PTK with a flying-spot excimer laser by combining wide-zone myopic and hyperopic astigmatic ablations. Optical coherence tomography was used to calculate corneal epithelial lenticular masking effects, guide refractive laser settings, and measure opacity removal. The laser ablation efficiency and the refractive outcome were investigated using multivariate linear regression models. Twenty-six eyes of 20 patients received PTK to remove opacities and irregular astigmatism due to scar, dystrophy, radial keratotomy, or previous corneal surgeries. The uncorrected distance visual acuity and corrected distance visual acuity were significantly improved (P < .01) by 3.7 Snellen lines and 2.0 Snellen lines, respectively, to a mean of 20/41.2 and 20/22.0, respectively. Achieved laser ablation depths were 31.3% (myopic ablation) and 63.0% (hyperopic ablation) deeper than the manufacturer's nomogram. The spherical equivalent of the corneal epithelial lenticular masking effect was 0.73 diopter ± 0.61 (SD). The refractive outcome highly correlated to the laser settings and epithelial lenticular masking effect (Pearson R = 0.96, P < .01). The ablation rate of granular dystrophy opacities appeared to be slower. Smoothing ablation under masking fluid was needed to prevent focal steep islands in these cases. The OCT-measured ablation depth efficiency could guide opacity removal. The corneal epithelial lenticular masking effect could refine the spherical refractive nomogram to achieve a better refractive outcome after transepithelial ablation. Copyright © 2017 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

Demonstration of periodic nanostructure formation with less ablation by double-pulse laser irradiation on titanium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Furukawa, Yuki; Graduate School of Science, Kyoto University, Kitashirakawa, Sakyo, Kyoto 606-8502; Advanced Research Center for Beam Science, Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011

By pairing femtosecond laser pulses (duration ∼40 fs and central wavelength ∼810 nm) at an appropriate time interval, a laser-induced periodic surface structure (LIPSS) is formed with much less ablation than one formed with a single pulse. On a titanium plate, a pair of laser pulses with fluences of 70 and 140 mJ/cm{sup 2} and a rather large time interval (>10 ps) creates a LIPSS with an interspace of 600 nm, the same as that formed by a single pulse of 210 mJ/cm{sup 2}, while the double pulse ablates only 4 nm, a quarter of the ablation depth of a single pulse.

Enhanced laser proton acceleration by target ablation on a femtosecond laser system

NASA Astrophysics Data System (ADS)

Liao, Q.; Wu, M. J.; Gong, Z.; Geng, Y. X.; Xu, X. H.; Li, D. Y.; Shou, Y. R.; Zhu, J. G.; Li, C. C.; Yang, M.; Li, T. S.; Lu, H. Y.; Ma, W. J.; Zhao, Y. Y.; Lin, C.; Yan, X. Q.

2018-06-01

Proton acceleration during the interaction of an ultraintense (6 × 1019 W/cm2) femtosecond (fs) laser pulse with a thin (2.5 μm) foil target pre-ablated by a picosecond (ps) pulse is experimentally and numerically investigated. Enhancements in both proton cut-off energy and charge are observed with the target ablation due to a large number of energetic electrons generated from the preformed preplasma in front of the target. The enhanced proton beams are successfully collected at 4-9 MeV with ±4% energy spread and then transported to the irradiating platform. The results show that for the interaction between fs laser pulse and μm-thickness target, proton energy and charge can be enhanced by target ablation using a ps laser pulse, which is valuable for application like cancer radiotherapy.

Unsteady motion of laser ablation plume by vortex induced by the expansion of curved shock wave

NASA Astrophysics Data System (ADS)

Tran, D. T.; Mori, K.

2017-02-01

There are a number of industrial applications of laser ablation in a gas atmosphere. When an intense pulsed laser beam is irradiated on a solid surface in the gas atmosphere, the surface material is ablated and expands into the atmosphere. At the same time, a spherical shock wave is launched by the ablation jet to induce the unsteady flow around the target surface. The ablated materials, luminously working as tracer, exhibit strange unsteady motions depending on the experimental conditions. By using a high-speed video camera (HPV-X2), unsteady motion ablated materials are visualized at the frame rate more than 106 fps, and qualitatively characterized.

Ultra-fast Movies Resolve Ultra-short Pulse Laser Ablation and Bump Formation on Thin Molybdenum Films

NASA Astrophysics Data System (ADS)

Domke, Matthias; Rapp, Stephan; Huber, Heinz

For the monolithic serial interconnection of CIS thin film solar cells, 470 nm molybdenum films on glass substrates must be separated galvanically. The single pulse ablation with a 660 fs laser at a wavelength of 1053 nm is investigated in a fluence regime from 0.5 to 5.0 J/cm2. At fluences above 2.0 J/cm2 bump and jet formation can be observed that could be used for creating microstructures. For the investigation of the underlying mechanisms of the laser ablation process itself as well as of the bump or jet formation, pump probe microscopy is utilized to resolve the transient ablation behavior.

Synthesis of oxocarbon-encapsulated gold nanoparticles with blue-shifted localized surface plasmon resonance by pulsed laser ablation in water with CO2 absorbers

NASA Astrophysics Data System (ADS)

Del Rosso, T.; Rey, N. A.; Rosado, T.; Landi, S.; Larrude, D. G.; Romani, E. C.; Freire Junior, F. L.; Quinteiro, S. M.; Cremona, M.; Aucelio, R. Q.; Margheri, G.; Pandoli, O.

2016-06-01

Colloidal suspensions of oxocarbon-encapsulated gold nanoparticles have been synthesized in a one-step procedure by pulsed-laser ablation (PLA) at 532 nm of a solid gold target placed in aqueous solution containing CO2 absorbers, but without any stabilizing agent. Multi-wavelength surface enhanced Raman spectroscopy allows the identification of adsorbed amorphous carbon and graphite, Au-carbonyl, Au coordinated CO2-derived bicarbonates/carbonates and hydroxyl groups around the AuNPs core. Scanning electron microscopy, energy dispersive x-ray analysis and high resolution transmission electron microscopy highlight the organic shell structure around the crystalline metal core. The stability of the colloidal solution of nanocomposites (NCs) seems to be driven by solvation forces and is achieved only in neutral or basic pH using monovalent hydroxide counter-ions (NaOH, KOH). The NCs are characterized by a blue shift of the localized surface plasmon resonance (LSPR) band typical of metal-ligand stabilization by terminal π-back bonding, attributed to a core charging effect caused by Au-carbonyls. Total organic carbon measurements detect the final content of organic carbon in the colloidal solution of NCs that is about six times higher than the value of the water solution used to perform PLA. The colloidal dispersions of NCs are stable for months and are applied as analytical probes in amino glycoside antibiotic LSPR based sensing.

Synthesis of oxocarbon-encapsulated gold nanoparticles with blue-shifted localized surface plasmon resonance by pulsed laser ablation in water with CO2 absorbers.

PubMed

Del Rosso, T; Rey, N A; Rosado, T; Landi, S; Larrude, D G; Romani, E C; Junior, F L Freire; Quinteiro, S M; Cremona, M; Aucelio, R Q; Margheri, G; Pandoli, O

2016-06-24

Colloidal suspensions of oxocarbon-encapsulated gold nanoparticles have been synthesized in a one-step procedure by pulsed-laser ablation (PLA) at 532 nm of a solid gold target placed in aqueous solution containing CO2 absorbers, but without any stabilizing agent. Multi-wavelength surface enhanced Raman spectroscopy allows the identification of adsorbed amorphous carbon and graphite, Au-carbonyl, Au coordinated CO2-derived bicarbonates/carbonates and hydroxyl groups around the AuNPs core. Scanning electron microscopy, energy dispersive x-ray analysis and high resolution transmission electron microscopy highlight the organic shell structure around the crystalline metal core. The stability of the colloidal solution of nanocomposites (NCs) seems to be driven by solvation forces and is achieved only in neutral or basic pH using monovalent hydroxide counter-ions (NaOH, KOH). The NCs are characterized by a blue shift of the localized surface plasmon resonance (LSPR) band typical of metal-ligand stabilization by terminal π-back bonding, attributed to a core charging effect caused by Au-carbonyls. Total organic carbon measurements detect the final content of organic carbon in the colloidal solution of NCs that is about six times higher than the value of the water solution used to perform PLA. The colloidal dispersions of NCs are stable for months and are applied as analytical probes in amino glycoside antibiotic LSPR based sensing.

l- and n-changing collisions during interaction of a pulsed beam of Li Rydberg atoms with CO2

NASA Astrophysics Data System (ADS)

Dubreuil, B.; Harnafi, M.

1989-07-01

The pulsed Li atomic beam produced in our experiment is based on controlled transversely-excited-atmospheric CO2 laser-induced ablation of a Li metal target. The atomic beam is propagated in vacuum or in CO2 gas at low pressure. Atoms in the beam are probed by laser-induced fluorescence spectroscopy. This allows the determination of time-of-flight and velocity distributions. Li Rydberg states (n=5-13) are populated in the beam by two-step pulsed-laser excitation. The excited atoms interact with CO2 molecules. l- and n-changing cross sections are deduced from the time evolution of the resonant or collision-induced fluorescence following this selective excitation. l-changing cross sections of the order of 104 AṦ are measured; they increase with n as opposed to the plateau observed for Li* colliding with a diatomic molecule. This behavior is qualitatively well explained in the framework of the free-electron model. n-->n' changing processes with large cross sections (10-100 AṦ) are also observed even in the case of large electronic energy change (ΔEnn'>103 cm-1). These results can be interpreted in terms of resonant-electronic to vibrational energy transfers between Li Rydberg states and CO2 vibrational modes.

Femtosecond laser for cavity preparation in enamel and dentin: ablation efficiency related factors.

PubMed

Chen, H; Li, H; Sun, Yc; Wang, Y; Lü, Pj

2016-02-11

To study the effects of laser fluence (laser energy density), scanning line spacing and ablation depth on the efficiency of a femtosecond laser for three-dimensional ablation of enamel and dentin. A diode-pumped, thin-disk femtosecond laser (wavelength 1025 nm, pulse width 400 fs) was used for the ablation of enamel and dentin. The laser spot was guided in a series of overlapping parallel lines on enamel and dentin surfaces to form a three-dimensional cavity. The depth and volume of the ablated cavity was then measured under a 3D measurement microscope to determine the ablation efficiency. Different values of fluence, scanning line spacing and ablation depth were used to assess the effects of each variable on ablation efficiency. Ablation efficiencies for enamel and dentin were maximized at different laser fluences and number of scanning lines and decreased with increases in laser fluence or with increases in scanning line spacing beyond spot diameter or with increases in ablation depth. Laser fluence, scanning line spacing and ablation depth all significantly affected femtosecond laser ablation efficiency. Use of a reasonable control for each of these parameters will improve future clinical application.

Laser Ablation of Dental Calculus Around 400 nm Using a Ti:Sapphire Laser

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schoenly, J.; Seka, W.; Rechmann, P.

2009-10-19

A Nd:YAG laser-pumped, frequency-doubled Ti:sapphire laser is used for selective ablation of calculus. The laser provides ≤25 mJ at 400 nm (60-ns pulse width, 10-Hz repetition rate). The laser is coupled into an optical multimode fiber coiled around a 4-in.-diam drum to generate a top-hat output intensity profile. With coaxial water cooling, this is ideal for efficient, selective calculus removal. This is in stark contrast with tightly focused Gaussian beams that are energetically inefficient and lead to irreproducible results. Calculus is well ablated at high fluences ≥2 J/cm^2; stalling occurs below this fluence because of photobleaching. Healthy hard tissue ismore » not removed at fluences ≤3 J/cm^2.« less

Image-guided removal of occlusal caries lesions with a λ= 9.3-µm CO2 laser using near-IR transillumination

PubMed Central

Chung, Leon C.; Tom, Henry; Chan, Kenneth H.; Simon, Jacob C.; Fried, Daniel; Darling, Cynthia L.

2015-01-01

Previous studies have shown that near-IR transillumination is well suited for imaging deep occlusal lesions. The purpose of this study was to determine if near-IR images can be used to guide a CO2 laser for the selective removal of natural occlusal lesions on extracted teeth. Near-IR occlusal transillumination images of extracted human teeth with natural occlusal caries lesions were acquired using an InGaAs camera and near-IR light at wavelengths from 1290 to 1470-nm from a filtered tungsten halogen source. A CO2 laser operating at 9.3-µm with a pulse duration of 10–15-µs and a pulse repetition rate of 100–300-Hz was used for caries removal. Optical Coherence tomography was used to confirm lesion presence and serial scans were used to assess selective removal. Teeth were also sectioned for histological examination using polarized light microscopy. This study suggests that near-infrared transillumination is a promising method for the image guided laser ablation of occlusal caries lesions but the use of serial near-IR transillumination imaging for monitoring lesion removal was limited. PMID:25914498

Image-guided removal of occlusal caries lesions with a λ= 9.3-μm CO2 laser using near-IR transillumination

NASA Astrophysics Data System (ADS)

Chung, Leon C.; Tom, Henry; Chan, Kenneth H.; Simon, Jacob C.; Fried, Daniel; Darling, Cynthia L.

2015-02-01

Previous studies have shown that near-IR transillumination is well suited for imaging deep occlusal lesions. The purpose of this study was to determine if near-IR images can be used to guide a CO2 laser for the selective removal of natural occlusal lesions on extracted teeth. Near-IR occlusal transillumination images of extracted human teeth with natural occlusal caries lesions were acquired using an InGaAs camera and near-IR light at wavelengths from 1290 to 1470-nm from a filtered tungsten halogen source. A CO2 laser operating at 9.3-μm with a pulse duration of 10-15-μs and a pulse repetition rate of 100-300-Hz was used for caries removal. Optical Coherence tomography was used to confirm lesion presence and serial scans were used to assess selective removal. Teeth were also sectioned for histological examination using polarized light microscopy. This study suggests that near-infrared transillumination is a promising method for the image guided laser ablation of occlusal caries lesions but the use of serial near-IR transillumination imaging for monitoring lesion removal was limited.

Effect analysis of material properties of picosecond laser ablation for ABS/PVC

NASA Astrophysics Data System (ADS)

Tsai, Y. H.; Ho, C. Y.; Chiou, Y. J.

2017-06-01

This paper analytically investigates the picosecond laser ablation of ABS/PVC. Laser-pulsed ablation is a wellestablished tool for polymer. However the ablation mechanism of laser processing for polymer has not been thoroughly understood yet. This study utilized a thermal transport model to analyze the relationship between the ablation rate and laser fluences. This model considered the energy balance at the decomposition interface and Arrhenius law as the ablation mechanisms. The calculated variation of the ablation rate with the logarithm of the laser fluence agrees with the measured data. It is also validated in this work that the variation of the ablation rate with the logarithm of the laser fluence obeys Beer's law for low laser fluences. The effects of material properties and processing parameters on the ablation depth per pulse are also discussed for picosecond laser processing of ABS/PVC.

Functional and Physical Outcomes following Use of a Flexible CO2 Laser Fiber and Bipolar Electrocautery in Close Proximity to the Rat Sciatic Nerve with Correlation to an In Vitro Thermal Profile Model

PubMed Central

Robinson, A. M.; Fishman, A. J.; Bendok, B. R.; Richter, C.-P.

2015-01-01

This study compared functional and physical collateral damage to a nerve when operating a Codman MALIS Bipolar Electrosurgical System CMC-III or a CO2 laser coupled to a laser, with correlation to an in vitro model of heating profiles created by the devices in thermochromic ink agarose. Functional damage of the rat sciatic nerve after operating the MALIS or CO2 laser at various power settings and proximities to the nerve was measured by electrically evoked nerve action potentials, and histology of the nerve was used to assess physical damage. Thermochromic ink dissolved in agarose was used to model the spatial and temporal profile of the collateral heating zone of the electrosurgical system and the laser ablation cone. We found that this laser can be operated at 2 W directly above the nerve with minimal damage, while power settings of 5 W and 10 W resulted in acute functional and physical nerve damage, correlating with the maximal heating cone in the thermochromic ink model. MALIS settings up to 40 (11 W) did not result in major functional or physical nerve damage until the nerve was between the forceps tips, correlating with the hottest zone, localized discretely between the tips. PMID:25699266

Shielding effects in the laser-generated copper plasma under reduced pressures of He atmosphere

NASA Astrophysics Data System (ADS)

Burger, M.; Pantić, D.; Nikolić, Z.; Djeniže, S.

2016-02-01

Irradiation of samples was performed with 6 ns, 1064 nm Nd:YAG laser. For an applied irradiance range (108-1010 W/cm2), the ablation process exhibits non-linear dependance. Ablated mass of the sample was directly determined using 100 ng resolution mass comparator after ablation under various pressures of helium. The ablation rates were dictated by plasma formation mechanisms as well as ambient conditions. However, the surrounding atmosphere did not significantly affect the value of threshold irradiance of about 2 ×109 W /cm2 for the onset of ablation mechanism change. This value is additionally verified via spectroscopic information from Cu I lines in the range from 0.4 to 1 μs after the laser pulse. Behaviour of spectral lines was monitored with respect to the laser pulse energy. Plasma diagnostics of axial electron density and excitation temperature distributions was performed under He pressure of 200 Torr. An influence of the possible shielding mechanisms responsible for the plasma absorption is discussed.

Laser-Driven Mini-Thrusters

NASA Astrophysics Data System (ADS)

Sterling, Enrique; Lin, Jun; Sinko, John; Kodgis, Lisa; Porter, Simon; Pakhomov, Andrew V.; Larson, C. William; Mead, Franklin B.

2006-05-01

Laser-driven mini-thrusters were studied using Delrin® and PVC (Delrin® is a registered trademark of DuPont) as propellants. TEA CO2 laser (λ = 10.6 μm) was used as a driving laser. Coupling coefficients were deduced from two independent techniques: force-time curves measured with a piezoelectric sensor and ballistic pendulum. Time-resolved ICCD images of the expanding plasma and combustion products were analyzed in order to determine the main process that generates the thrust. The measurements were also performed in a nitrogen atmosphere in order to test the combustion effects on thrust. A pinhole transmission experiment was performed for the study of the cut-off time when the ablation/air breakdown plasma becomes opaque to the incoming laser pulse.

Morphological studies of laser-induced photoacoustic damage

NASA Astrophysics Data System (ADS)

Flotte, Thomas J.; Yashima, Yutaka; Watanabe, Shinichi; McAuliffe, Daniel J., Sr.; Jacques, Steven L.

1990-06-01

Argon-fluoride excimer laser ablation of stratum comeum causes deeper tissue damage than expected for thermal or photochemical mechanisms, suggesting thatphotoacoustic waves have arole in tissue damage. Laserirradiation (193 nm, 14 ns pulses, 1-2 Hz) attworadiantexposures, 60 and 160 mJ/cm2perpulse was usedto ablate the stratumcomeumofskin. Light and electron microscopy ofimmediate biopsies demonstrated damage to fibroblasts as deep as 88 and 220 jun, respectively, below the ablation site. Ablation throughwaterwas usedtoinertially confine the ablation zone. Partial ablationofs.c. through airproducedno damage, whereas partial ablation through water damaged skin to amean depth of 1 14.5 8.8( Full thickness ablation of s.c. through air and water produced damage zones measuring 192.2 16.2 and 293.0 71.6 rim, respectively (p <0.05). The increased depth ofdamage in the presence ofinertial confinementprovided by the layer of water strongly supports a photoacoustic mechanism ofdamage. The depths ofdamage for thelarge spot, line, and small spots were 43 1 164 urn, 269 96xni, andno damage. The spot size dependence ofthedepthofdamage is consistentwiththe geometric attenuation one would expect to be present from a pressure wave related phenomena. Sequential biopsies were taken over a 7 day period for light and transmission electron microscopy. At 24 hours, there was necrosis of the epidermis and papillary dermis subjacent to the ablation site, with neutrophils surrounding and demarcating the affected area. The necrotic zone sloughedby48 hours. Thereepithelializationwas completeby7 days. The sequenceofrepairis similartoknife wound healing which we have previously studied, and is analogous to other wound healing processes. We have used an experimental model of ArF excimer laser ablation of stratum corneum to investigate laser-induced photoacoustic damage. The evidence for the injury being due to pressure transients is indirectbutcompelling. Whether these pressuretransients are acoustic transients orshockwaves has notbeendetermined, although itis ourprejudicethatshockwaves are the predominant force under these conditions. It is important to consider the possible effects of pressure transients in evaluating laser-tissue interactions, particularly when using short pulse, high peak power lasers.

Photoactive dye-enhanced tissue ablation for endoscopic laser prostatectomy.

PubMed

Ahn, Minwoo; Hau, Nguyen Trung; Van Phuc, Nguyen; Oh, Junghwan; Kang, Hyun Wook

2014-11-01

Laser light has been widely used as a surgical tool to treat benign prostate hyperplasia (BPH) over 20 years. Recently, application of high laser power up to 200 W was often reported to swiftly remove a large amount of prostatic tissue. The purpose of this study was to validate the feasibility of photoactive dye injection to enhance light absorption and eventually to facilitate tissue vaporization with low laser power. Chicken breast tissue was selected as a target tissue due to minimal optical absorption at the visible wavelength. Four biocompatible photoactive dyes, including amaranth (AR), black dye (BD), hemoglobin powder (HP), and endoscopic marker (EM), were selected and tested in vitro with a customized 532 nm laser system with radiant exposure ranging from 0.9 to 3.9 J/cm(2) . Light absorbance and ablation threshold were measured with UV-Vis spectrometer and Probit analysis, respectively, and compared to feature the function of the injected dyes. Ablation performance with dye-injection was evaluated in light of radiant exposure, dye concentration, and number of injection. Higher light absorption by injected dyes led to lower ablation threshold as well as more efficient tissue removal in the order of AR, BD, HP, and EM. Regardless of the injected dyes, ablation efficiency principally increased with radiant exposure, dye concentration, and number of injection. Among the dyes, AR created the highest ablation rate of 44.2 ± 0.2 µm/pulse due to higher absorbance and lower ablation threshold. High aspect ratios up to 7.1 ± 0.4 entailed saturation behavior in the tissue ablation injected with AR and BD, possibly resulting from plume shielding and increased scattering due to coagulation. Preliminary tests on canine prostate with a hydraulic injection system demonstrated that 80 W with dye injection yielded comparable ablation efficiency to 120 W with no injection, indicating 33% reduced laser power with almost equivalent performance. Due to efficient coupling of optical energy, pre-injection of photoactive dyes promoted the degree of tissue removal during laser irradiation. Further studies will investigate spatial distribution of dyes and optimal injecting pressure to govern the extent of dye-assisted ablation in a predictable manner. In-depth comprehension on photoactive dye-enhanced tissue ablation can help accomplish efficient and safe laser vaporization for BPH with low power application. © 2014 Wiley Periodicals, Inc.

Pulsed laser ablation of IC packages for device failure analyses

NASA Astrophysics Data System (ADS)

Hong, Ming Hui; Mai, ZhiHong; Chen, G. X.; Thiam, Thomas; Song, Wen D.; Lu, Yongfeng; Soh, Chye E.; Chong, Tow Chong

2002-06-01

Pulsed laser ablation of mold compounds for IC packaging in air and with steam assistance is investigated. It is applied to decap IC packages and expose computer CPU dies for the device failure analyses. Compared with chemical decapping, the laser ablation has advantages of being fast speed, non- contact and dry processing. Laser ablation with the steam assistance results in higher ablation rate and wider ablated crater with much smoother surface morphology. It implies that the steam assisted laser ablation can achieve a faster and better quality laser processing. Audible acoustic wave and plasma optical signal diagnostics are also carried out to have a better understanding of the mechanisms behind. Light wavelength and laser fluence applied in the decapping are two important parameters. The 532 nm Nd:YAG laser decapping at a low laser fluence can achieve a large decapping area with a fine ablation profile. IC packages decapped by the laser ablation show good quality for the device failure analyses.

Laser-Induced Focused Ultrasound for Cavitation Treatment: Toward High-Precision Invisible Sonic Scalpel.

PubMed

Lee, Taehwa; Luo, Wei; Li, Qiaochu; Demirci, Hakan; Guo, L Jay

2017-10-01

Beyond the implementation of the photoacoustic effect to photoacoustic imaging and laser ultrasonics, this study demonstrates a novel application of the photoacoustic effect for high-precision cavitation treatment of tissue using laser-induced focused ultrasound. The focused ultrasound is generated by pulsed optical excitation of an efficient photoacoustic film coated on a concave surface, and its amplitude is high enough to produce controllable microcavitation within the focal region (lateral focus <100 µm). Such microcavitation is used to cut or ablate soft tissue in a highly precise manner. This work demonstrates precise cutting of tissue-mimicking gels as well as accurate ablation of gels and animal eye tissues. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Mass Spectrometric Imaging Using Laser Ablation and Solvent Capture by Aspiration (LASCA)

NASA Astrophysics Data System (ADS)

Brauer, Jonathan I.; Beech, Iwona B.; Sunner, Jan

2015-09-01

A novel interface for ambient, laser ablation-based mass spectrometric imaging (MSI) referred to as laser ablation and solvent capture by aspiration (LASCA) is presented and its performance demonstrated using selected, unaltered biological materials. LASCA employs a pulsed 2.94 μm laser beam for specimen ablation. Ablated materials in the laser plumes are collected on a hanging solvent droplet with electric field-enhanced trapping, followed by aspiration of droplets and remaining plume material in the form of a coarse aerosol into a collection capillary. The gas and liquid phases are subsequently separated in a 10 μL-volume separatory funnel, and the solution is analyzed with electrospray ionization in a high mass resolution Q-ToF mass spectrometer. The LASCA system separates the sampling and ionization steps in MSI and combines high efficiencies of laser plume sampling and of electrospray ionization (ESI) with high mass resolution MS. Up to 2000 different compounds are detected from a single ablation spot (pixel). Using the LASCA platform, rapid (6 s per pixel), high sensitivity, high mass-resolution ambient imaging of "as-received" biological material is achieved routinely and reproducibly.

Low cost, patterning of human hNT brain cells on parylene-C with UV & IR laser machining.

PubMed

Raos, Brad J; Unsworth, C P; Costa, J L; Rohde, C A; Doyle, C S; Delivopoulos, E; Murray, A F; Dickinson, M E; Simpson, M C; Graham, E S; Bunting, A S

2013-01-01

This paper describes the use of 800nm femtosecond infrared (IR) and 248nm nanosecond ultraviolet (UV) laser radiation in performing ablative micromachining of parylene-C on SiO2 substrates for the patterning of human hNT astrocytes. Results are presented that support the validity of using IR laser ablative micromachining for patterning human hNT astrocytes cells while UV laser radiation produces photo-oxidation of the parylene-C and destroys cell patterning. The findings demonstrate how IR laser ablative micromachining of parylene-C on SiO2 substrates can offer a low cost, accessible alternative for rapid prototyping, high yield cell patterning.

Morphology and structure of TixOy nanoparticles generated by femtosecond laser ablation in water

NASA Astrophysics Data System (ADS)

Donėlienė, Jolanta; Rudzikas, Matas; Rades, Steffi; Dörfel, Ilona; Peplinski, Burkhard; Sahre, Mario; Pellegrino, Francesco; Maurino, Valter; Ulbikas, Juras; Galdikas, Algirdas; Hodoroaba, Vasile-Dan

2018-04-01

In this work femto-second pulsed laser ablation in liquid (PLAL) procedure for the generation of titanium oxide nanoparticles (NP) is reported with the purpose of understanding morphology and structure of the newly generated NPs. Ablation duration was varied for optimization of NP generation processes between 10 and 90 min. Surface morphology of NPs as well as their size and shape (distribution) were analysed by various complementary electron microscopy techniques, i.e. SEM, TSEM and TEM. The crystalline structure of titanium oxide particles was investigated by XRD (two instruments operated in different geometries) and HR-TEM. Concentration of generated titanium oxide NPs in liquid was analysed by ICP-MS. A mix of crystalline (mainly anatase), partly crystalline and amorphous spherical titanium oxide NPs can be reported having a mean size between 10 and 20 nm, which is rather independent of the laser ablation (LA) duration. A second component consisting of irregularly shaped, but crystalline titanium oxide nanostructures is co-generated in the LA water, with more pronounced occurrence at longer LA times. The provenance of this component is assigned to those spherical particles generated in suspension and passing through the converging laser beam, being hence subject to secondary irradiation effects, e. g. fragmentation.

Application of erbium: YAG laser in ocular ablation.

PubMed

Tsubota, K

1990-01-01

Recent developments in lasers have provided us the possibility of laser ocular surgery. The xenon, argon, neodymium:YAG and dye lasers have been successfully used in out-patient clinics. The excimer laser has been attracting researchers' interest in the new application of laser to cornea and lens. The erbium:YAG laser emits a 2.94-microns beam that can ablate the transparent ocular tissues such as lenses and corneas. The author has applied this laser to the cornea, lens, vitreous and other ocular tissues. The erbium:YAG laser beam was directed through a 1.5-meter-long, 200-microns-diameter fiberoptic guide. The radiant energy measured about 50 mJ at the end of the probe. The laser was emitted as a 400-microsecond pulse. Freshly enucleated rabbit eyes were used in this study. Laser burns were applied to the tissue surface at various energy settings. At minimal power, the tissues were coagulated by the erbium:YAG laser application. At a power of more than 636-954 mJ/mm2, tissue began to evaporate; the tissue loss was observed under a surgical light microscope. Corneal photoablation, lens ablation, iridotomy, trabeculotomy, cutting of the vitreous and retinal ablation were easily performed. Like the excimer laser, the erbium:YAG laser is a potential tool for ocular surgery.

Benign thyroid nodule unresponsive to radiofrequency ablation treated with laser ablation: a case report.

PubMed

Oddo, Silvia; Balestra, Margherita; Vera, Lara; Giusti, Massimo

2018-05-11

Radiofrequency ablation and laser ablation are safe and effective techniques for reducing thyroid nodule volume, neck symptoms, and cosmetic complaints. Therapeutic success is defined as a nodule reduction > 50% between 6 and 12 months after the procedure, but a percentage of nodules inexplicably do not respond to thermal ablation. We describe the case of a young Caucasian woman with a solid benign thyroid nodule who refused surgery and who had undergone radiofrequency ablation in 2013. The nodule did not respond in terms of either volume reduction or improvement in neck symptoms. After 2 years, given the patient's continued refusal of thyroidectomy, we proposed laser ablation. The nodule displayed a significant volume reduction (- 50% from radiofrequency ablation baseline volume, - 57% from laser ablation baseline), and the patient reported a significant improvement in neck symptoms (from 6/10 to 1/10 on a visual analogue scale). We conjecture that some benign thyroid nodules may be intrinsically resistant to necrosis when one specific ablation technique is used, but may respond to another technique. To the best of our knowledge, this is the first description of the effect of performing a different percutaneous ablation technique in a nodule that does not respond to radiofrequency ablation.

Design Considerations For A Clinical XeC1 Excimer Laser Angioplasty System

NASA Astrophysics Data System (ADS)

Laudenslager, James B.; Goldenberg, Tsvi; Naghieh, Harry R.; Pham, Andrew A.; Narciso, Hugh L.; Tranis, Art; Pacala, Thomas J.

1989-09-01

Laser ablation and removal of intravascular plaque has long been a goal of physicians and physicists as an alternative treatment for coronary and peripheral artery disease. Early application of cw free light beam visible and infrared lasers such as argon ion or Nd:YAG lasers for this application were plagued by thermal side effects of the ablation process. Specifically, imprecise control of the boundary tissue injury produced by the deep penetration depth of the laser beam gave rise to early reclosure of the vessel due to the thermal nature of the ablation process. Pulsed ultraviolet laser free beam ablation of atherosclerotic plaque, however, does not produce thermal effects, cuts tissue precisely leaving a smooth wall and can ablate hard calcific lesions. We have chosen to develop a XeC1 excimer laser-fiberoptic delivery system for the clinical application of laser angioplasty based on achieving the desired therapeutic results for a laser revascularization procedure. Four major engineering design issues must be considered in order to produce a successful clinical laser angioplasty product. These engineering issues are: 1) Functional clinical engineering, 2) Regulatory design issues, 3) Hospital facility and user requirements, and 4) Economic issues for the manufacturer, the hospital and the patient.

Pulsed laser ablation of complex oxides: The role of congruent ablation and preferential scattering for the film stoichiometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wicklein, S.; Koehl, A.; Dittmann, R.

2012-09-24

By combining structural and chemical thin film analysis with detailed plume diagnostics and modeling of the laser plume dynamics, we are able to elucidate the different physical mechanisms determining the stoichiometry of the complex oxides model material SrTiO{sub 3} during pulsed laser deposition. Deviations between thin film and target stoichiometry are basically a result of two effects, namely, incongruent ablation and preferential scattering of lighter ablated species during their motion towards the substrate in the O{sub 2} background gas. On the one hand, a progressive preferential ablation of the Ti species with increasing laser fluence leads to a regime ofmore » Ti-rich thin film growth at larger fluences. On the other hand, in the low laser fluence regime, a more effective scattering of the lighter Ti plume species results in Sr rich films.« less

Dermal Remodeling of Burn Scar by Fractional CO2 Laser.

PubMed

Lee, Sang-Jun; Suh, Dong-Hye; Lee, Ji Min; Song, Kye-Yong; Ryu, Hwa Jung

2016-10-01

Ablative CO2 fractional lasers have recently been introduced for burn scar treatment because of pronounced clinical outcomes with fewer treatment sessions than nonablative fractional laser. This study was conducted to observe clinical as well as histologic changes of burn scars after treatment with CO2 fractional laser. Eleven patients (one female and 10 males, aged 31-59 years) with skin phototypes III to V with burn scars received 10 sessions of fractional CO2 laser treatments (UltraPulse(®) Encore; Lumenis, Santa Clara, CA, USA) over an average 5-week interval. Two passes were performed using the following parameters: deep FX mode, 12.5-30 mJ, with a density setting of 5-10 %. Clinical evaluations by three blinded dermatologists were obtained at baseline and at 6 months after the final treatment via photographs using the Vancouver scar scale (VSS). Skin biopsies were done on four patients before and after treatment. All patients showed clinical improvement in their scars with significant decrease in VSS. Histologic findings showed the changes in the upper dermis with newly formed dermal papilla. This characteristic upper dermis change was presented as improvement in surface smoothness and skin tension clinically. Postinflammatory hyperpigmentation and itching sensation were the most common adverse effects. Burn scar treatment by fractional CO2 laser is effective by forming new collagen fibers mainly in the upper dermis. This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Randomized, Controlled Trial of Fractional Carbon Dioxide Laser Resurfacing Followed by Ultrashort Incubation Aminolevulinic Acid Blue Light Photodynamic Therapy for Actinic Keratosis.

PubMed

Alexiades, Macrene

2017-08-01

Aminolevulinic acid (ALA) photodynamic therapy (PDT) is an established treatment option for actinic keratosis (AK), and recently fractional carbon dioxide (CO2) laser was shown to improve outcomes; but studies of short incubation photosensitizer are lacking. Assess the efficacy of short incubation ALA followed by blue light PDT with and without previous fractional CO2 treatment for the treatment of AK. Randomized, paired split-design, controlled trial of fractional CO2 followed by ultrashort 15-minute versus 30-minute incubation ALA and blue light PDT for the treatment of AK on the face. The complete clearance rates (CRs) at 8 weeks after ALA PDT with and without FxCO2 at 30- and 15-minute ALA incubation times were 89.78% (+FxCO2) versus 71.20% CR (-FxCO2) at 30', and 86.38% (+FxCO2) versus 69.23% (-FxCO2) at 15' ALA incubation. All lesion improvements were statistically significant. This randomized, comparative paired group controlled clinical study demonstrates that ultrashort 15- and 30-minute incubation ALA PDTs are of limited efficacy for the treatment of AK. Pretreatment with fractional ablative resurfacing yields statistically significant greater AK clearance with ALA-PDT at ultrashort ALA incubations followed by blue light.

Ablative and transport fractionation of trace elements during laser sampling of glass and copper

NASA Astrophysics Data System (ADS)

Outridge, P. M.; Doherty, W.; Gregoire, D. C.

1997-12-01

The fractionation of trace elements due to ablation and transport processes was quantified during Q-switched infrared laser sampling of glass and copper reference materials. Filter-trapping of the ablated product at different points in the sample introduction system showed ablation and transport sometimes caused opposing fractionation effects, leading to a confounded measure of overall (ablative + transport) fractionation. An unexpected result was the greater ablative fractionation of some elements (Au, Ag, Bi, Te in glass and Au, Be, Bi, Ni, Te in copper) at a higher laser fluence of 1.35 × 10 4W cm -2 than at 0.62 × 10 4W cm -2, which contradicted predictions from modelling studies of ablation processes. With glass, there was an inverse logarithmic relationship between the extent of ablative and overall fractionation and element oxide melting point (OMPs), with elements with OMPs < 1000° C exhibiting overall concentration increases of 20-1340%. Fractionation during transport was quantitatively important for most certified elements in copper, and for the most volatile elements (Au, Ag, Bi, Te) in glass. Elements common to both matrices showed 50-100% higher ablative fractionation in copper, possibly because of greater heat conductance away from the ablation site causing increased element volatilisation or zone refinement. These differences between matrices indicate that non-matrix-matched standardisation is likely to provide inaccurate calibration of laser ablation inductively coupled plasma-mass spectrometry analyses of at least some elements.

308-nm excimer laser ablation of human cartilage

NASA Astrophysics Data System (ADS)

Prodoehl, John A.; Rhodes, Anthony L.; Meller, Menachem M.; Sherk, Henry H.

1993-07-01

The XeCl excimer laser was investigated as an ablating tool for human fibrocartilage and hyaline cartilage. Quantitative measurements were made of tissue ablation rates as a function of fluence in meniscal fibrocartilage and articular hyaline cartilage. A force of 1.47 Newtons was applied to an 800 micrometers fiber with the laser delivering a range of fluences (40 to 190 mj/mm2) firing at a frequency of 5 Hz. To assess the effect of repetition rate on ablation rate, a set of measurements was made at a constant fluence of 60 mj/mm2, with the repetition rate varying from 10 to 40 Hz. Histologic and morphometric analysis was performed using light microscopy. The results of these studies revealed that the ablation rate was directly proportional to fluence over the range tested. Fibrocartilage was ablated at a rate 2.56 times faster than hyaline cartilage at the maximum fluence tested. Repetition rate had no effect on the penetration per pulse. Adjacent tissue damage was noted to be minimal (10 - 70 micrometers ).

Dual beam optical system for pulsed laser ablation film deposition

DOEpatents

Mashburn, D.N.

1996-09-24

A laser ablation apparatus having a laser source outputting a laser ablation beam includes an ablation chamber having a sidewall, a beam divider for dividing the laser ablation beam into two substantially equal halves, and a pair of mirrors for converging the two halves on a surface of the target from complementary angles relative to the target surface normal, thereby generating a plume of ablated material emanating from the target. 3 figs.

Dual beam optical system for pulsed laser ablation film deposition

DOEpatents

Mashburn, Douglas N.

1996-01-01

A laser ablation apparatus having a laser source outputting a laser ablation beam includes an ablation chamber having a sidewall, a beam divider for dividing the laser ablation beam into two substantially equal halves, and a pair of mirrors for converging the two halves on a surface of the target from complementary angles relative to the target surface normal, thereby generating a plume of ablated material emanating from the target.

Dental hard tissue ablation using mid-infrared tunable nanosecond pulsed Cr:CdSe laser.

PubMed

Lin, Taichen; Aoki, Akira; Saito, Norihito; Yumoto, Masaki; Nakajima, Sadahiro; Nagasaka, Keigo; Ichinose, Shizuko; Mizutani, Koji; Wada, Satoshi; Izumi, Yuichi

2016-12-01

Mid-infrared erbium: yttrium-aluminum-garnet (Er:YAG) and erbium, chromium: yttrium-scandium-gallium-garnet (Er,Cr:YSGG) lasers (2.94- and 2.78-μm, respectively) are utilized for effective dental hard tissue treatment because of their high absorption in water, hydroxide ion, or both. Recently, a mid-infrared tunable, nanosecond pulsed, all-solid-state chromium-doped: cadmium-selenide (Cr:CdSe) laser system was developed, which enables laser oscillation in the broad spectral range around 2.9 μm. The purpose of this study was to evaluate the ablation of dental hard tissue by the nanosecond pulsed Cr:CdSe laser at a wavelength range of 2.76-3.00 μm. Enamel, dentin, and cementum tissue were irradiated at a spot or line at a fluence of 0-11.20 J/cm 2 /pulse (energy output: 0-2.00 mJ/pulse) with a repetition rate of 10 Hz and beam diameter of ∼150 μm on the target (pulse width ∼250 ns). After irradiation, morphological changes, ablation threshold, depth, and efficiency, and thickness of the structurally and thermally affected layer of irradiated surfaces were analyzed using stereomicroscopy, scanning electron microscopy (SEM), and light microscopy of non-decalcified histological sections. The nanosecond pulsed irradiation without water spray effectively ablated dental hard tissue with no visible thermal damage such as carbonization. The SEM analysis revealed characteristic micro-irregularities without major melting and cracks in the lased tissue. The ablation threshold of dentin was the lowest at 2.76 μm and the highest at 3.00 μm. The histological analysis revealed minimal thermal and structural changes ∼20 μm wide on the irradiated dentin surfaces with no significant differences between wavelengths. The efficiency of dentin ablation gradually increased from 3.00 to 2.76 μm, at which point the highest ablation efficiency was observed. The nanosecond pulsed Cr:CdSe laser demonstrated an effective ablation ability of hard dental tissues, which was remarkably wavelength-dependent on dentin at the spectral range of 2.76-3.00 μm. These results demonstrate the potential feasibility of the use of pulsed Cr:CdSe laser as a novel laser system for dental treatment. Lasers Surg. Med. 48:965-977, 2016. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

OCDR guided laser ablation device

DOEpatents

Dasilva, Luiz B.; Colston, Jr., Bill W.; James, Dale L.

2002-01-01

A guided laser ablation device. The device includes a mulitmode laser ablation fiber that is surrounded by one or more single mode optical fibers that are used to image in the vicinity of the laser ablation area to prevent tissue damage. The laser ablation device is combined with an optical coherence domain reflectometry (OCDR) unit and with a control unit which initializes the OCDR unit and a high power laser of the ablation device. Data from the OCDR unit is analyzed by the control unit and used to control the high power laser. The OCDR images up to about 3 mm ahead of the ablation surface to enable a user to see sensitive tissue such as a nerve or artery before damaging it by the laser.

Laser ablation for the synthesis of carbon nanotubes

DOEpatents

Holloway, Brian C; Eklund, Peter C; Smith, Michael W; Jordan, Kevin C; Shinn, Michelle

2012-11-27

Single walled carbon nanotubes are produced in a novel apparatus by the laser-induced ablation of moving carbon target. The laser used is of high average power and ultra-fast pulsing. According to various preferred embodiments, the laser produces and output above about 50 watts/cm.sup.2 at a repetition rate above about 15 MHz and exhibits a pulse duration below about 10 picoseconds. The carbon, carbon/catalyst target and the laser beam are moved relative to one another and a focused flow of "side pumped", preheated inert gas is introduced near the point of ablation to minimize or eliminate interference by the ablated plume by removal of the plume and introduction of new target area for incidence with the laser beam. When the target is moved relative to the laser beam, rotational or translational movement may be imparted thereto, but rotation of the target is preferred.

Laser ablation for the synthesis of carbon nanotubes

DOEpatents

Holloway, Brian C.; Eklund, Peter C.; Smith, Michael W.; Jordan, Kevin C.; Shinn, Michelle

2010-04-06

Single walled carbon nanotubes are produced in a novel apparatus by the laser-induced ablation of moving carbon target. The laser used is of high average power and ultra-fast pulsing. According to various preferred embodiments, the laser produces an output above about 50 watts/cm.sup.2 at a repetition rate above about 15 MHz and exhibits a pulse duration below about 10 picoseconds. The carbon, carbon/catalyst target and the laser beam are moved relative to one another and a focused flow of "side pumped", preheated inert gas is introduced near the point of ablation to minimize or eliminate interference by the ablated plume by removal of the plume and introduction of new target area for incidence with the laser beam. When the target is moved relative to the laser beam, rotational or translational movement may be imparted thereto, but rotation of the target is preferred.

Laser ablation for the synthesis of carbon nanotubes

NASA Technical Reports Server (NTRS)

Holloway, Brian C. (Inventor); Eklund, Peter C. (Inventor); Smith, Michael W. (Inventor); Jordan, Kevin C. (Inventor); Shinn, Michelle (Inventor)

2010-01-01

Single walled carbon nanotubes are produced in a novel apparatus by the laser-induced ablation of moving carbon target. The laser used is of high average power and ultra-fast pulsing. According to various preferred embodiments, the laser produces an output above about 50 watts/cm.sup.2 at a repetition rate above about 15 MHz and exhibits a pulse duration below about 10 picoseconds. The carbon, carbon/catalyst target and the laser beam are moved relative to one another and a focused flow of side pumped, preheated inert gas is introduced near the point of ablation to minimize or eliminate interference by the ablated plume by removal of the plume and introduction of new target area for incidence with the laser beam. When the target is moved relative to the laser beam, rotational or translational movement may be imparted thereto, but rotation of the target is preferred.

Laser ablation for the synthesis of carbon nanotubes

NASA Technical Reports Server (NTRS)

Holloway, Brian C. (Inventor); Eklund, Peter C. (Inventor); Smith, Michael W. (Inventor); Jordan, Kevin C. (Inventor); Shinn, Michelle (Inventor)

2012-01-01

Single walled carbon nanotubes are produced in a novel apparatus by the laser-induced ablation of moving carbon target. The laser used is of high average power and ultra-fast pulsing. According to various preferred embodiments, the laser produces and output above about 50 watts/cm.sup.2 at a repetition rate above about 15 MHz and exhibits a pulse duration below about 10 picoseconds. The carbon, carbon/catalyst target and the laser beam are moved relative to one another and a focused flow of "side pumped", preheated inert gas is introduced near the point of ablation to minimize or eliminate interference by the ablated plume by removal of the plume and introduction of new target area for incidence with the laser beam. When the target is moved relative to the laser beam, rotational or translational movement may be imparted thereto, but rotation of the target is preferred.

Two-dimensional fluorescence spectroscopy of uranium isotopes in femtosecond laser ablation plumes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Phillips, Mark C.; Brumfield, Brian E.; LaHaye, Nicole

Here, we demonstrate measurement of uranium isotopes in femtosecond laser ablation plumes using two-dimensional fluorescence spectroscopy (2DFS). The high-resolution, tunable CW-laser spectroscopy technique clearly distinguishes atomic absorption from 235U and 238U in natural and highly enriched uranium metal samples. We present analysis of spectral resolution and analytical performance of 2DFS as a function of ambient pressure. Simultaneous measurement using time-resolved absorption spectroscopy provides information on temporal dynamics of the laser ablation plume and saturation behavior of fluorescence signals. The rapid, non-contact measurement is promising for in-field, standoff measurements of uranium enrichment for nuclear safety and security.

Two-dimensional fluorescence spectroscopy of uranium isotopes in femtosecond laser ablation plumes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Phillips, Mark C.; Brumfield, Brian E.; LaHaye, Nicole L.

We demonstrate measurement of uranium isotopes in femtosecond laser ablation plumes using two-dimensional fluorescence spectroscopy (2DFS). The high-resolution, tunable CW-laser spectroscopy technique clearly distinguishes atomic absorption from 235U and 238U in natural and highly enriched uranium metal samples. We present analysis of spectral resolution and analytical performance of 2DFS as a function of ambient pressure. Simultaneous measurement using time-resolved absorption spectroscopy provides information on temporal dynamics of the laser ablation plume and saturation behavior of fluorescence signals. The rapid, non-contact measurement is promising for in-field, standoff measurements of uranium enrichment for nuclear safety and security applications.

Two-dimensional fluorescence spectroscopy of uranium isotopes in femtosecond laser ablation plumes

DOE PAGES

Phillips, Mark C.; Brumfield, Brian E.; LaHaye, Nicole; ...

2017-06-19

Here, we demonstrate measurement of uranium isotopes in femtosecond laser ablation plumes using two-dimensional fluorescence spectroscopy (2DFS). The high-resolution, tunable CW-laser spectroscopy technique clearly distinguishes atomic absorption from 235U and 238U in natural and highly enriched uranium metal samples. We present analysis of spectral resolution and analytical performance of 2DFS as a function of ambient pressure. Simultaneous measurement using time-resolved absorption spectroscopy provides information on temporal dynamics of the laser ablation plume and saturation behavior of fluorescence signals. The rapid, non-contact measurement is promising for in-field, standoff measurements of uranium enrichment for nuclear safety and security.

Laser selective cutting of biological tissues by impulsive heat deposition through ultrafast vibrational excitations.

PubMed

Franjic, Kresimir; Cowan, Michael L; Kraemer, Darren; Miller, R J Dwayne

2009-12-07

Mechanical and thermodynamic responses of biomaterials after impulsive heat deposition through vibrational excitations (IHDVE) are investigated and discussed. Specifically, we demonstrate highly efficient ablation of healthy tooth enamel using 55 ps infrared laser pulses tuned to the vibrational transition of interstitial water and hydroxyapatite around 2.95 microm. The peak intensity at 13 GW/cm(2) was well below the plasma generation threshold and the applied fluence 0.75 J/cm(2) was significantly smaller than the typical ablation thresholds observed with nanosecond and microsecond pulses from Er:YAG lasers operating at the same wavelength. The ablation was performed without adding any superficial water layer at the enamel surface. The total energy deposited per ablated volume was several times smaller than previously reported for non-resonant ultrafast plasma driven ablation with similar pulse durations. No micro-cracking of the ablated surface was observed with a scanning electron microscope. The highly efficient ablation is attributed to an enhanced photomechanical effect due to ultrafast vibrational relaxation into heat and the scattering of powerful ultrafast acoustic transients with random phases off the mesoscopic heterogeneous tissue structures.

Conductive Channel for Energy Transmission

NASA Astrophysics Data System (ADS)

Apollonov, Victor V.

2011-11-01

For many years the attempts to create conductive channels of big length were taken in order to study the upper atmosphere and to settle special tasks, related to energy transmission. There upon the program of creation of "Impulsar" represents a great interest, as this program in a combination with high-voltage high repetition rate electrical source can be useful to solve the above mentioned problems (N. Tesla ideas for the days of high power lasers). The principle of conductive channel production can be shortly described as follows. The "Impulsar"—laser jet engine vehicle—propulsion take place under the influence of powerful high repetition rate pulse-periodic laser radiation. In the experiments the CO2—laser and solid state Nd:YAG laser systems had been used. Active impulse appears thanks to air breakdown (<30 km) or to the breakdown of ablated material on the board (>30 km), placed in the vicinity of the focusing mirror-acceptor of the breakdown waves. With each pulse of powerful laser the device rises up, leaving a bright and dense trace of products with high degree of ionization and metallization by conductive nano-particles due to ablation. Conductive dust plasma properties investigation in our experiments was produced by two very effective approaches: high power laser controlled ablation and by explosion of wire. Experimental and theoretical results of conductive canal modeling will be presented. The estimations show that with already experimentally demonstrated figures of specific thrust impulse the lower layers of the Ionosphere can be reached in several ten seconds that is enough to keep the high level of channel conductivity and stability with the help of high repetition rate high voltage generator. Some possible applications for new technology are highlighted.

Laser ablation mechanism of transparent layers on semiconductors with ultrashort laser pulses

NASA Astrophysics Data System (ADS)

Rublack, Tino; Hartnauer, Stefan; Mergner, Michael; Muchow, Markus; Seifert, Gerhard

2011-12-01

Transparent dielectric layers on semiconductors are used as anti-reflection coatings both for photovoltaic applications and for mid-infrared optical elements. We have shown recently that selective ablation of such layers is possible using ultrashort laser pulses at wavelengths being absorbed by the semiconductor. To get a deeper understanding of the ablation mechanism, we have done ablation experiments for different transparent materials, in particular SiO2 and SixNy on silicon, using a broad range of wavelengths ranging from UV to IR, and pulse durations between 50 and 2000 fs. The characterization of the ablated regions was done by light microscopy and atomic force microscopy (AFM). Utilizing laser wavelengths above the silicon band gap, selective ablation of the dielectric layer without noticeable damage of the opened silicon surface is possible. In contrast, ultrashort pulses (1-2 ps) at mid-infrared wavelengths already cause damage in the silicon at lower intensities than in the dielectric layer, even when a vibrational resonance (e.g. at λ = 9.26 μm for SiO2) is addressed. The physical processes behind this, on the first glance counterintuitive, observation will be discussed.

In situ x-ray surface diffraction chamber for pulsed laser ablation film growth studies

NASA Astrophysics Data System (ADS)

Tischler, J. Z.; Eres, G.; Lowndes, D. H.; Larson, B. C.; Yoon, M.; Chiang, T.-C.; Zschack, Paul

2000-06-01

Pulsed laser deposition is highly successful for growing complex films such as oxides for substrate buffer layers and HiTc oxide superconductors. A surface diffraction chamber has been constructed to study fundamental aspects of non-equilibrium film growth using pulsed laser deposition. Due to the pulsed nature of the ablating laser, the deposited atoms arrive on the substrate in short sub-millisecond pulses. Thus monitoring the surface x-ray diffraction following individual laser pulses (with resolution down to ˜1 ms) provides direct information on surface kinetics and the aggregation process during film growth. The chamber design, based upon a 2+2 surface diffraction geometry with the modifications necessary for laser ablation, is discussed, and initial measurements on homo-epitaxial growth of SrTiO3 are presented.

Fast production of microfluidic devices by CO2 laser engraving of wax-coated glass slides.

PubMed

da Costa, Eric T; Santos, Mauro S F; Jiao, Hong; do Lago, Claudimir L; Gutz, Ivano G R; Garcia, Carlos D

2016-07-01

Glass is one of the most convenient materials for the development of microfluidic devices. However, most fabrication protocols require long processing times and expensive facilities. As a convenient alternative, polymeric materials have been extensively used due their lower cost and versatility. Although CO2 laser ablation has been used for fast prototyping on polymeric materials, it cannot be applied to glass devices because the local heating causes thermal stress and results in extensive cracking. A few papers have shown the ablation of channels or thin holes (used as reservoirs) on glass but the process is still far away from yielding functional glass microfluidic devices. To address these shortcomings, this communication describes a simple method to engrave glass-based capillary electrophoresis devices using standard (1 mm-thick) microscope glass slides. The process uses a sacrificial layer of wax as heat sink and enables the development of both channels (with semicircular shape) and pass-through reservoirs. Although microscope images showed some small cracks around the channels (that became irrelevant after sealing the engraved glass layer to PDMS) the proposed strategy is a leap forward in the application of the technology to glass. In order to demonstrate the capabilities of the approach, the separation of dopamine, catechol and uric acid was accomplished in less than 100 s. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thompson, Scott M., E-mail: Thompson.scott@mayo.edu; Callstrom, Matthew R., E-mail: callstrom.matthew@mayo.edu; McKusick, Michael A., E-mail: mckusick.michael@mayo.edu

PurposeThe purpose of this study was to determine the feasibility, safety, and early effectiveness of percutaneous image-guided ablation as second-line treatment for symptomatic soft-tissue vascular anomalies (VA).Materials and MethodsAn IRB-approved retrospective review was undertaken of all patients who underwent percutaneous image-guided ablation as second-line therapy for treatment of symptomatic soft-tissue VA during the period from 1/1/2008 to 5/20/2014. US/CT- or MRI-guided and monitored cryoablation or MRI-guided and monitored laser ablation was performed. Clinical follow-up began at one-month post-ablation.ResultsEight patients with nine torso or lower extremity VA were treated with US/CT (N = 4) or MRI-guided (N = 2) cryoablation or MRI-guided laser ablation (N = 5)more » for moderate to severe pain (N = 7) or diffuse bleeding secondary to hemangioma–thrombocytopenia syndrome (N = 1). The median maximal diameter was 9.0 cm (6.5–11.1 cm) and 2.5 cm (2.3–5.3 cm) for VA undergoing cryoablation and laser ablation, respectively. Seven VA were ablated in one session, one VA initially treated with MRI-guided cryoablation for severe pain was re-treated with MRI-guided laser ablation due to persistent moderate pain, and one VA was treated in a planned two-stage session due to large VA size. At an average follow-up of 19.8 months (range 2–62 months), 7 of 7 patients with painful VA reported symptomatic pain relief. There was no recurrence of bleeding at five-year post-ablation in the patient with hemangioma–thrombocytopenia syndrome. There were two minor complications and no major complications.ConclusionImage-guided percutaneous ablation is a feasible, safe, and effective second-line treatment option for symptomatic VA.« less

Laser Microperforated Biodegradable Microbial Polyhydroxyalkanoate Substrates for Tissue Repair Strategies: An Infrared Microspectroscopy Studey

DOE Office of Scientific and Technical Information (OSTI.GOV)

G Ellis; P Cano; M Jadraque

Flexible and biodegradable film substrates prepared by solvent casting from poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBHV) solutions in chloroform were microperforated by ultraviolet laser ablation and subsequently characterized using infrared (IR) microspectroscopy and imaging techniques and scanning electron microscopy (SEM). Both transmission synchrotron IR microspectroscopy and attenuated total reflectance microspectroscopy measurements demonstrate variations in the polymer at the ablated pore rims, including evidence for changes in chemical structure and crystallinity. SEM results on microperforated PHBHV substrates after cell culture demonstrated that the physical and chemical changes observed in the biomaterial did not hinder cell migration through the pores.

Deviation from threshold model in ultrafast laser ablation of graphene at sub-micron scale

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gil-Villalba, A.; Xie, C.; Salut, R.

We investigate a method to measure ultrafast laser ablation threshold with respect to spot size. We use structured complex beams to generate a pattern of craters in CVD graphene with a single laser pulse. A direct comparison between beam profile and SEM characterization allows us to determine the dependence of ablation probability on spot-size, for crater diameters ranging between 700 nm and 2.5 μm. We report a drastic decrease of ablation probability when the crater diameter is below 1 μm which we interpret in terms of free-carrier diffusion.

Laser Microdissection and Atmospheric Pressure Chemical Ionization Mass Spectrometry Coupled for Multimodal Imaging

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lorenz, Matthias; Ovchinnikova, Olga S; Kertesz, Vilmos

2013-01-01

This paper describes the coupling of ambient laser ablation surface sampling, accomplished using a laser capture microdissection system, with atmospheric pressure chemical ionization mass spectrometry for high spatial resolution multimodal imaging. A commercial laser capture microdissection system was placed in close proximity to a modified ion source of a mass spectrometer designed to allow for sampling of laser ablated material via a transfer tube directly into the ionization region. Rhodamine 6G dye of red sharpie ink in a laser etched pattern as well as cholesterol and phosphatidylcholine in a cerebellum mouse brain thin tissue section were identified and imaged frommore » full scan mass spectra. A minimal spot diameter of 8 m was achieved using the 10X microscope cutting objective with a lateral oversampling pixel resolution of about 3.7 m. Distinguishing between features approximately 13 m apart in a cerebellum mouse brain thin tissue section was demonstrated in a multimodal fashion including co-registered optical and mass spectral chemical images.« less

Comparison of acoustic shock waves generated by micro and nanosecond lasers for a smart laser surgery system

NASA Astrophysics Data System (ADS)

Nguendon Kenhagho, Hervé K.; Rauter, Georg; Guzman, Raphael; C. Cattin, Philippe; Zam, Azhar

2018-02-01

Characterization of acoustic shock wave will guarantee efficient tissue differentiation as feedback to reduce the probability of undesirable damaging (i.e. cutting) of tissues in laser surgery applications. We ablated hard (bone) and soft (muscle) tissues using a nanosecond pulsed Nd:YAG laser at 532 nm and a microsecond pulsed Er:YAG laser at 2.94 μm. When the intense short ns-pulsed laser is applied to material, the energy gain causes locally a plasma at the ablated spot that expands and propagates as an acoustic shock wave with a rarefaction wave behind the shock front. However, when using a μs-pulsed Er:YAG laser for material ablation, the acoustic shock wave is generated during the explosion of the ablated material. We measured and compared the emitted acoustic shock wave generated by a ns-pulsed Nd:YAG laser and a μs-pulsed Er:YAG laser measured by a calibrated microphone. As the acoustic shock wave attenuates as it propagates through air, the distance between ablation spots and a calibrated microphone was at 5 cm. We present the measurements on the propagation characteristics of the laser generated acoustic shock wave by measuring the arrival time-of-flight with a calibrated microphone and the energy-dependent evolution of acoustic parameters such as peak-topeak pressure, the ratio of the peak-to-peak pressures for the laser induced breakdown in air, the ablated muscle and the bone, and the spectral energy.

Constructing a Low-budget Laser Axotomy System to Study Axon Regeneration in C. elegans

PubMed Central

Williams, Wes; Nix, Paola; Bastiani, Michael

2011-01-01

Laser axotomy followed by time-lapse microscopy is a sensitive assay for axon regeneration phenotypes in C. elegans1. The main difficulty of this assay is the perceived cost ($25-100K) and technical expertise required for implementing a laser ablation system2,3. However, solid-state pulse lasers of modest costs (<$10K) can provide robust performance for laser ablation in transparent preparations where target axons are "close" to the tissue surface. Construction and alignment of a system can be accomplished in a day. The optical path provided by light from the focused condenser to the ablation laser provides a convenient alignment guide. An intermediate module with all optics removed can be dedicated to the ablation laser and assures that no optical elements need be moved during a laser ablation session. A dichroic in the intermediate module allows simultaneous imaging and laser ablation. Centering the laser beam to the outgoing beam from the focused microscope condenser lens guides the initial alignment of the system. A variety of lenses are used to condition and expand the laser beam to fill the back aperture of the chosen objective lens. Final alignment and testing is performed with a front surface mirrored glass slide target. Laser power is adjusted to give a minimum size ablation spot (<1um). The ablation spot is centered with fine adjustments of the last kinematically mounted mirror to cross hairs fixed in the imaging window. Laser power for axotomy will be approximately 10X higher than needed for the minimum ablation spot on the target slide (this may vary with the target you use). Worms can be immobilized for laser axotomy and time-lapse imaging by mounting on agarose pads (or in microfluidic chambers4). Agarose pads are easily made with 10% agarose in balanced saline melted in a microwave. A drop of molten agarose is placed on a glass slide and flattened with another glass slide into a pad approximately 200 um thick (a single layer of time tape on adjacent slides is used as a spacer). A "Sharpie" cap is used to cut out a uniformed diameter circular pad of 13mm. Anesthetic (1ul Muscimol 20mM) and Microspheres (Chris Fang-Yen personal communication) (1ul 2.65% Polystyrene 0.1 um in water) are added to the center of the pad followed by 3-5 worms oriented so they are lying on their left sides. A glass coverslip is applied and then Vaseline is used to seal the coverslip and prevent evaporation of the sample. PMID:22126922

Image-guided removal of interproximal lesions with a CO2 laser

NASA Astrophysics Data System (ADS)

Ngo, Albert; Chan, Kenneth H.; Le, Oanh; Simon, Jacob C.; Fried, Daniel

2018-02-01

Recent studies have shown that near-IR (NIR) imaging methods such as NIR reflectance can be used to image lesions on proximal surfaces, and optical coherence tomography (OCT) can be used to measure the depth of those lesions below the tooth surface. These imaging modalities can be used to acquire high contrast images of demineralized tooth surfaces, and 2-D and 3-D images can be extracted from this data. At NIR wavelengths longer than 1200-nm, there is no interference from stains and the contrast is only due to the increased light scattering of the demineralization. Previous studies have shown that image-guided laser ablation can be used to remove occlusal lesions, but its use for the removal of subsurface lesions on proximal surfaces has not been investigated. The objective of this study is to demonstrate that simultaneously scanned NIR and CO2 lasers can be used to selectively remove natural and artificial interproximal caries lesions with minimal damage to sound tooth structure. In this study, images of simulated and natural interproximal lesions on extracted teeth were imaged using a digital microscope, a scanned 1460-nm superluminescent laser diode with an InGaAs detector and a cross polarization OCT system operating at 1300-nm. The lesions were subsequently removed with a CO2 laser operating at 9.3-μm and the dental handpiece and the volume of sound tissue removed was compared.

Transmission Geometry Laser Ablation into a Non-Contact Liquid Vortex Capture Probe for Mass Spectrometry Imaging

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ovchinnikova, Olga S; Bhandari, Deepak; Lorenz, Matthias

2014-01-01

RATIONALE: Capture of material from a laser ablation plume into a continuous flow stream of solvent provides the means for uninterrupted sampling, transport and ionization of collected material for coupling with mass spectral analysis. Reported here is the use of vertically aligned transmission geometry laser ablation in combination with a new non-contact liquid vortex capture probe coupled with electrospray ionization for spot sampling and chemical imaging with mass spectrometry. Methods: A vertically aligned continuous flow liquid vortex capture probe was positioned directly underneath a sample surface in a transmission geometry laser ablation (355 nm, 10 Hz, 7 ns pulse width)more » setup to capture into solution the ablated material. The outlet of the vortex probe was coupled to the Turbo V ion source of an AB SCIEX TripleTOF 5600+ mass spectrometer. System operation and performance metrics were tested using inked patterns and thin tissue sections. Glass slides and slides designed especially for laser capture microdissection, viz., DIRECTOR slides and PEN 1.0 (polyethylene naphthalate) membrane slides, were used as sample substrates. Results: The estimated capture efficiency of laser ablated material was 24%, which was enabled by the use of a probe with large liquid surface area (~ 2.8 mm2) and with gravity to help direct ablated material vertically down towards the probe. The swirling vortex action of the liquid surface potentially enhanced capture and dissolution of not only particulates, but also gaseous products of the laser ablation. The use of DIRECTOR slides and PEN 1.0 (polyethylene naphthalate) membrane slides as sample substrates enabled effective ablation of a wide range of sample types (basic blue 7, polypropylene glycol, insulin and cyctochrome c) without photodamage using a UV laser. Imaging resolution of about 6 m was demonstrated for stamped ink on DIRECTOR slides based on the ability to distinguish features present both in the optical and in the chemical image. This imaging resolution was 20 times better than the previous best reported results with laser ablation/liquid sample capture mass spectrometry imaging. Using thin sections of brain tissue the chemical image of a selected lipid was obtained with an estimated imaging resolution of about 50 um. Conclusions: A vertically aligned, transmission geometry laser ablation liquid vortex capture probe, electrospray ionization mass spectrometry system provides an effective means for spatially resolved spot sampling and imaging with mass spectrometry.« less

Transmission geometry laser ablation into a non-contact liquid vortex capture probe for mass spectrometry imaging.

PubMed

Ovchinnikova, Olga S; Bhandari, Deepak; Lorenz, Matthias; Van Berkel, Gary J

2014-08-15

Capture of material from a laser ablation plume into a continuous flow stream of solvent provides the means for uninterrupted sampling, transport and ionization of collected material for coupling with mass spectral analysis. Reported here is the use of vertically aligned transmission geometry laser ablation in combination with a new non-contact liquid vortex capture probe coupled with electrospray ionization for spot sampling and chemical imaging with mass spectrometry. A vertically aligned continuous flow liquid vortex capture probe was positioned directly underneath a sample surface in a transmission geometry laser ablation (355 nm, 10 Hz, 7 ns pulse width) set up to capture into solution the ablated material. The outlet of the vortex probe was coupled to the Turbo V™ ion source of an AB SCIEX TripleTOF 5600+ mass spectrometer. System operation and performance metrics were tested using inked patterns and thin tissue sections. Glass slides and slides designed especially for laser capture microdissection, viz., DIRECTOR(®) slides and PEN 1.0 (polyethylene naphthalate) membrane slides, were used as sample substrates. The estimated capture efficiency of laser-ablated material was 24%, which was enabled by the use of a probe with large liquid surface area (~2.8 mm(2) ) and with gravity to help direct ablated material vertically down towards the probe. The swirling vortex action of the liquid surface potentially enhanced capture and dissolution not only of particulates, but also of gaseous products of the laser ablation. The use of DIRECTOR(®) slides and PEN 1.0 (polyethylene naphthalate) membrane slides as sample substrates enabled effective ablation of a wide range of sample types (basic blue 7, polypropylene glycol, insulin and cyctochrome c) without photodamage using a UV laser. Imaging resolution of about 6 µm was demonstrated for stamped ink on DIRECTOR(®) slides based on the ability to distinguish features present both in the optical and in the chemical image. This imaging resolution was 20 times better than the previous best reported results with laser ablation/liquid sample capture mass spectrometry imaging. Using thin sections of brain tissue the chemical image of a selected lipid was obtained with an estimated imaging resolution of about 50 µm. A vertically aligned, transmission geometry laser ablation liquid vortex capture probe, electrospray ionization mass spectrometry system provides an effective means for spatially resolved spot sampling and imaging with mass spectrometry. Published in 2014. This article is a U.S. Government work and is in the public domain in the USA.

Minor element partitioning and mineralogy in limpets from the Ischia CO2 vent site

NASA Astrophysics Data System (ADS)

Langer, Gerald; Sadekov, Aleksey; Nehrke, Gernot; Baggini, Cecilia; Rodolfo-Metalpa, Riccardo; Hall-Spencer, Jason; Bijma, Jelle; Elderfield, Henry

2015-04-01

Specimens of the patellogastropod limpet Patella caerulea were collected within and outside a CO2 vent site at Ischia, Italy. The shells were sectioned transversally and scanned for polymorph distribution by means of confocal Raman microscopy. Minor element to calcium ratios were measured using laser-ablation-inductively-coupled-plasma-mass-spectroscopy (LA-ICPMS). Mg/Ca, Sr/Ca, and Li/Ca ratios were determined in calcitic as well as aragonitic parts of the shells. This approach allows for investigating the effects of the polymorph and the seawater carbonate chemistry on minor element partitioning separately.

Infrared glass fiber cables for CO laser medical applications

NASA Astrophysics Data System (ADS)

Arai, Tsunenori; Mizuno, Kyoichi; Sensaki, Koji; Kikuchi, Makoto; Watanabe, Tamishige; Utsumi, Atsushi; Takeuchi, Kiyoshi; Akai, Yoshiro

1993-05-01

We developed the medical fiber cables which were designed for CO laser therapy, i.e., angioplasty and endoscopic therapy. As-S chalcogenide glass fibers were used for CO laser delivery. A 230 micrometers core-diameter fiber was used for the angioplasty laser cable. The outer diameter of this cable was 600 micrometers . The total length and insertion length of the angioplasty laser cable were 2.5 m and 1.0 m, respectively. Typically, 2.0 W of fiber output was used in the animal experiment in vivo for the ablation of the model plaque which consisted of human atheromatous aorta wall. The transmission of the angioplasty laser cable was approximately 35%, because the reflection loss occurred at both ends of the fiber and window. Meanwhile, the core diameter of the energy delivery fiber for the endoscopic therapy was 450 micrometers . The outer diameter of this cable was 1.7 mm. Approximately 4.5 W of fiber output was used for clinical treatment of pneumothorax through a pneumoscope. Both types of the cables had the ultra-thin thermocouples for temperature monitoring at the tip of the cables. This temperature monitoring was extremely useful to prevent the thermal destruction of the fiber tip. Moreover, the As-S glass fibers were completely sealed by the CaF2 windows and outer tubes. Therefore, these cables were considered to have sufficient safety properties for medical applications. These laser cables were successfully used for the in vivo animal experiments and/or actual clinical therapies.

[Stapedotomie with the use of CO2 laser--"one shot" technique].

PubMed

Szyfter, Witold; Mielcarek-Kuchta, Daniela; Młodkowska, Anna; Miętkiewska-Leszniewska, Dorota; Obrębowska, Zofia; Łączkowska-Przybylska, Joanna

2013-01-01

CO2 laser is used in stapes surgery due to good water absorption and quite optimal ablation of a bony structure without the influence of inner ear parameters. the assessment of the influence of CO2 - "one shot" laser on hearing results in the patients group with otosclerosis. The study was carried out on a patients group after surgical treatment. The follow up time was at least 6 months. The hearing results were described according to the guidelines of the American Committee on Hearing and Equilibrium. The obtained results were statistically analysed with the use of the Wilcoxon sequence pair test. The CO2 - "one shot" laser has been used in Department of Otolaryngology in Poznań since July 2009. Using this system 101 operations were carried out to the end of December 2011. 54 patients were in the analysed group, there were 40 women and 14 men, the age range from 22 to 59. In the Wilcoxon sequence pair test there was a statistically significant correlation between the value of the hearing threshold in pre- and post-operative examinations at 0.5, 1, 2 and 3kHz for bone and air conduction. We found also a statistically significant correlation between the mean value of the air-bone gap before and after treatment. In the group after the surgery the cochlear reserved became closed or decreased (p<0.001). based of the hearing results we found great usefulness of CO2 - "one shot" laser in stapes surgery. Copyright © 2012 Polish Otorhinolaryngology - Head and Neck Surgery Society. Published by Elsevier Urban & Partner Sp. z.o.o. All rights reserved.

Analysis of the change in peak corneal temperature during excimer laser ablation in porcine eyes

NASA Astrophysics Data System (ADS)

Mosquera, Samuel Arba; Verma, Shwetabh

2015-07-01

The objective is to characterize the impact of different ablation parameters on the thermal load during corneal refractive surgery by means of excimer laser ablation on porcine eyes. One hundred eleven ablations were performed in 105 porcine eyes. Each ablation was recorded using infrared thermography and analyzed mainly based on the two tested local frequencies (40 Hz, clinical local frequency; 1000 Hz, no local frequency). The change in peak corneal temperature was analyzed with respect to varying ablation parameters [local frequency, system repetition rate, pulse energy, optical zone (OZ) size, and refractive correction]. Transepithelial ablations were also compared to intrastromal ablations. The average of the baseline temperature across all eyes was 20.5°C±1.1 (17.7°C to 22.2°C). Average of the change in peak corneal temperature for all clinical local frequency ablations was 5.8°C±0.8 (p=3.3E-53 to baseline), whereas the average was 9.0°C±1.5 for all no local frequency ablations (p=1.8E-35 to baseline, 1.6E-16 to clinical local frequency ablations). A logarithmic relationship was observed between the changes in peak corneal temperature with increasing local frequency. For clinical local frequency, change in peak corneal temperature was comparatively flat (r2=0.68 with a range of 1.5°C) with increasing system repetition rate and increased linearly with increasing OZ size (r2=0.95 with a range of 2.4°C). Local frequency controls help maintain safe corneal temperature increase during excimer laser ablations. Transepithelial ablations induce higher thermal load compared to intrastromal ablations, indicating a need for stronger thermal controls in transepithelial refractive procedures.

The Femtosecond Laser Ablation on Ultrafine-Grained Copper

NASA Astrophysics Data System (ADS)

Lu, Jianxun; Wu, Xiaoyu; Ruan, Shuangchen; Guo, Dengji; Du, Chenlin; Liang, Xiong; Wu, Zhaozhi

2018-07-01

To investigate the effects of femtosecond laser ablation on the surface morphology and microstructure of ultrafine-grained copper, point, single-line scanning, and area scanning ablation of ultrafine-grained and coarse-grained copper were performed at room temperature. The ablation threshold gradually increased and materials processing became more difficult with decreasing grain size. In addition, the ablation depth and width of the channels formed by single-line scanning ablation gradually increased with increasing grain size for the same laser pulse energy. The microhardness of the ablated specimens was also evaluated as a function of laser pulse energy using area scanning ablation. The microhardness difference before and after ablation increased with decreasing grain size for the same laser pulse energy. In addition, the microhardness after ablation gradually decreased with increasing laser pulse energy for the ultrafine-grained specimens. However, for the coarse-grained copper specimens, no clear changes of the microhardness were observed after ablation with varying laser pulse energies. The grain sizes of the ultrafine-grained specimens were also surveyed as a function of laser pulse energy using electron backscattered diffraction (EBSD). The heat generated by laser ablation caused recrystallization and grain growth of the ultrafine-grained copper; moreover, the grain size gradually increased with increasing pulse energy. In contrast, no obvious changes in grain size were observed for the coarse-grained copper specimens with increasing pulse energy.

The Femtosecond Laser Ablation on Ultrafine-Grained Copper

NASA Astrophysics Data System (ADS)

Lu, Jianxun; Wu, Xiaoyu; Ruan, Shuangchen; Guo, Dengji; Du, Chenlin; Liang, Xiong; Wu, Zhaozhi

2018-05-01

To investigate the effects of femtosecond laser ablation on the surface morphology and microstructure of ultrafine-grained copper, point, single-line scanning, and area scanning ablation of ultrafine-grained and coarse-grained copper were performed at room temperature. The ablation threshold gradually increased and materials processing became more difficult with decreasing grain size. In addition, the ablation depth and width of the channels formed by single-line scanning ablation gradually increased with increasing grain size for the same laser pulse energy. The microhardness of the ablated specimens was also evaluated as a function of laser pulse energy using area scanning ablation. The microhardness difference before and after ablation increased with decreasing grain size for the same laser pulse energy. In addition, the microhardness after ablation gradually decreased with increasing laser pulse energy for the ultrafine-grained specimens. However, for the coarse-grained copper specimens, no clear changes of the microhardness were observed after ablation with varying laser pulse energies. The grain sizes of the ultrafine-grained specimens were also surveyed as a function of laser pulse energy using electron backscattered diffraction (EBSD). The heat generated by laser ablation caused recrystallization and grain growth of the ultrafine-grained copper; moreover, the grain size gradually increased with increasing pulse energy. In contrast, no obvious changes in grain size were observed for the coarse-grained copper specimens with increasing pulse energy.

Synthesis of Mg(OH) 2, MgO, and Mg nanoparticles using laser ablation of magnesium in water and solvents

NASA Astrophysics Data System (ADS)

Phuoc, Tran X.; Howard, Bret. H.; Martello, Donald V.; Soong, Yee; Chyu, Minking K.

2008-11-01

Laser ablation of magnesium in deionized water (DW), solutions of DW and sodium dodecyl sulfate (SDS) with different concentrations, acetone and 2-propanol has been conducted. The results showed that ablation in acetone and 2-propanol yielded MgO and Mg nanocrystallites as isolated particles and agglomerated chains probably intermixed with organic residues resulting from the alteration/decomposition of the solvents under the high-energy conditions. Brucite-like Mg(OH) 2 particles were mainly produced by laser ablation of Mg in either DW or DW-SDS solutions. Ablation in DW yielded particles of fiber-like shapes having a diameter of about 5-10 nm and length as long as 150 nm. Materials produced in DW-SDS solutions were composed of various size and shape particles. Some had rough surfaces with irregular shapes. Small particles were about 20-30 nm and larger particles were about 120 nm. Particles with rod-like, triangular, and plate-like shapes were also observed.

Ablation behaviors of carbon reinforced polymer composites by laser of different operation modes

NASA Astrophysics Data System (ADS)

Wu, Chen-Wu; Wu, Xian-Qian; Huang, Chen-Guang

2015-10-01

Laser ablation mechanism of Carbon Fiber Reinforced Polymer (CFRP) composite is of critical meaning for the laser machining process. The ablation behaviors are investigated on the CFRP laminates subject to continuous wave, long duration pulsed wave and short duration pulsed wave lasers. Distinctive ablation phenomena have been observed and the effects of laser operation modes are discussed. The typical temperature patterns resulted from laser irradiation are computed by finite element analysis and thereby the different ablation mechanisms are interpreted.

Optical emission spectroscopic study of plasma plumes generated by IR CO2 pulsed laser on carbon targets

NASA Astrophysics Data System (ADS)

Camacho, J. J.; Díaz, L.; Santos, M.; Reyman, D.; Poyato, J. M. L.

2008-05-01

Optical emission spectroscopy studies, in the spectral range ultraviolet-visible-near infrared (UV-Vis-NIR), were performed to investigate thermal and dynamical properties of a plume produced by laser ablation of a graphite target. Ablation is carried out using a high-power IR CO2 pulsed laser at λ = 9.621 µm, power density ranging from 0.22 to 5.36 GW cm-2 and air pressures around 4 Pa. The strong emission observed in the plasma region is mainly due to electronic relaxation of excited C, ionic fragments C+, C2+ and C3+ and molecular features of C2(d 3Πg-a 3Πu Swan band system). The medium-weak emission is mainly due to excited atomic N, H, O, ionic fragment C4+ and molecular features of C2( E\\,^1\\Sigma _g^+\\--A\\,^{1}\\Pi _u ; Freymark system), C2( D\\,^1\\Sigma _u^+\\--X\\,^1\\Sigma _g^+ ; Mulliken system), CN(D 2Π-A 2Π), C2(e 3Πg-a 3Πu Fox-Herzberg system), C2(C 1Πg-A 1Πu Deslandres-d'Azambuja system), OH(A 2Σ+-X 2Π), CH(C 2Σ+-X 2Π), NH(A 3Π-X 3Σ-), CN(B 2Σ+-X 2Σ+ violet system), CH(B 2Σ+-X 2Π), CH(A 2Δ-X 2Π), C2( A\\,^{1}\\Pi_u\\--X\\,^{1}\\Sigma ^{+}_g ; Phillips system) and CN(A 2Π-X 2Σ+ red system). An excitation temperature Texc = 23 000 ± 1900 K and electron densities in the range (0.6-5.6) × 1016 cm-3 were estimated by means of C+ ionic lines. The characteristics of the spectral emission intensities from different species have been investigated as functions of the ambient pressure and laser irradiance. Estimates of vibrational temperatures of C2 and CN electronically excited species under various laser irradiance conditions are made.

Characterization of Tin/Ethylene Glycol Solar Nanofluids Synthesized by Femtosecond Laser Radiation.

PubMed

Torres-Mendieta, Rafael; Mondragón, Rosa; Puerto-Belda, Verónica; Mendoza-Yero, Omel; Lancis, Jesús; Juliá, J Enrique; Mínguez-Vega, Gladys

2017-05-05

Solar energy is available over wide geographical areas and its harnessing is becoming an essential tool to satisfy the ever-increasing demand for energy with minimal environmental impact. Solar nanofluids are a novel solar receiver concept for efficient harvesting of solar radiation based on volumetric absorption of directly irradiated nanoparticles in a heat transfer fluid. Herein, the fabrication of a solar nanofluid by pulsed laser ablation in liquids was explored. This study was conducted with the ablation of bulk tin immersed in ethylene glycol with a femtosecond laser. Laser irradiation promotes the formation of tin nanoparticles that are collected in the ethylene glycol as colloids, creating the solar nanofluid. The ability to trap incoming electromagnetic radiation, thermal conductivity, and the stability of the solar nanofluid in comparison with conventional synthesis methods is enhanced. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

In-vivo optical imaging of hsp70 expression to assess collateral tissue damage associated with infrared laser ablation of skin

PubMed Central

Wilmink, Gerald J.; Opalenik, Susan R.; Beckham, Joshua T.; Mackanos, Mark A.; Nanney, Lillian B.; Contag, Christopher H.; Davidson, Jeffrey M.; Jansen, E. Duco

2013-01-01

Laser surgical ablation is achieved by selecting laser parameters that remove confined volumes of target tissue and cause minimal collateral damage. Previous studies have measured the effects of wavelength on ablation, but neglected to measure the cellular impact of ablation on cells outside the lethal zone. In this study, we use optical imaging in addition to conventional assessment techniques to evaluate lethal and sublethal collateral damage after ablative surgery with a free-electron laser (FEL). Heat shock protein (HSP) expression is used as a sensitive quantitative marker of sublethal damage in a transgenic mouse strain, with the hsp70 promoter driving luciferase and green fluorescent protein (GFP) expression (hsp70A1-L2G). To examine the wavelength dependence in the mid-IR, laser surgery is conducted on the hsp70A1-L2G mouse using wavelengths targeting water (OH stretch mode, 2.94 μm), protein (amide-II band, 6.45 μm), and both water and protein (amide-I band, 6.10 μm). For all wavelengths tested, the magnitude of hsp70 expression is dose-dependent and maximal 5 to 12 h after surgery. Tissues treated at 6.45 μm have approximately 4× higher hsp70 expression than 6.10 μm. Histology shows that under comparable fluences, tissue injury at the 2.94-μm wavelength was 2× and 3× deeper than 6.45 and 6.10 μm, respectively. The 6.10-μm wavelength generates the least amount of epidermal hyperplasia. Taken together, this data suggests that the 6.10-μm wavelength is a superior wavelength for laser ablation of skin. PMID:19021444

The use of lasers for periodontal debridement: marketing tool or proven therapy?

PubMed

Chanthaboury, Rachel; Irinakis, Tassos

2005-10-01

The use of lasers in dentistry has recently received much attention, in both clinical practice and research; their unique properties produce favourable clinical results in some cases and encourage patient acceptance. Various types of lasers have been investigated as an adjunct to periodontal therapy; these include carbon dioxide (CO₂), diode, neodymium:yttrium-aluminium-garnet (Nd:YAG) and erbium:yttrium-aluminium-garnet (Er:YAG) lasers.However, adverse results have been associated with each type, including thermal damage to root surfaces, increases in pulpal temperature and the production of toxic by-products. The Er:YAG laser has produced the most promising results, as it can ablate effectively with minimal adverse effects. More research is needed to determine the ideal settings and methods for using the laser safely and effectively in clinical practice.

Nd:YAG 1.44 laser ablation of human cartilage

NASA Astrophysics Data System (ADS)

Cummings, Robert S.; Prodoehl, John A.; Rhodes, Anthony L.; Black, Johnathan D.; Sherk, Henry H.

1993-07-01

This study determined the effectiveness of a Neodymium:YAG 1.44 micrometers wavelength laser on human cartilage. This wavelength is strongly absorbed by water. Cadaveric meniscal fibrocartilage and articular hyaline cartilage were harvested and placed in normal saline during the study. A 600 micrometers quartz fiber was applied perpendicularly to the tissues with a force of 0.098 N. Quantitative measurements were then made of the ablation rate as a function of fluence. The laser energy was delivered at a constant repetition rate of 5 Hz., 650 microsecond(s) pulsewidth, and energy levels ranging from 0.5 joules to 2.0 joules. Following the ablation of the tissue, the specimens were fixed in formalin for histologic evaluation. The results of the study indicate that the ablation rate is 0.03 mm/mj/mm2 for hyaline cartilage and fibrocartilage. Fibrocartilage was cut at approximately the same rate as hyaline cartilage. There was a threshold fluence projected to be 987 mj/mm2 for hyaline cartilage and fibrocartilage. Our results indicate that the pulsed Nd:YAG laser operating at 1.44 micrometers has a threshold fluence above which it will ablate human cartilage, and that its ablation rate is directly proportional to fluence over the range of parameters tested. Fibrocartilage and hyaline cartilage demonstrated similar threshold fluence and ablation rates which is related to the high water content of these tissues.

Higher Order Chemistry Models in the CFD Simulation of Laser-Ablated Carbon Plumes

NASA Technical Reports Server (NTRS)

Greendyke, R. B.; Creel, J. R.; Payne, B. T.; Scott, C. D.

2005-01-01

Production of single-walled carbon nanotubes (SWNT) has taken place for a number of years and by a variety of methods such as laser ablation, chemical vapor deposition, and arc-jet ablation. Yet, little is actually understood about the exact chemical kinetics and processes that occur in SWNT formation. In recent time, NASA Johnson Space Center has devoted a considerable effort to the experimental evaluation of the laser ablation production process for SWNT originally developed at Rice University. To fully understand the nature of the laser ablation process it is necessary to understand the development of the carbon plume dynamics within the laser ablation oven. The present work is a continuation of previous studies into the efforts to model plume dynamics using computational fluid dynamics (CFD). The ultimate goal of the work is to improve understanding of the laser ablation process, and through that improved understanding, refine the laser ablation production of SWNT.

Effects of 1,540-nm Fractional Nonablative Erbium and 2,940-nm Fractional Ablative Erbium on p53 Epidermal Expression After 3 months: A Split-Face Interventional Study.

PubMed

Borges, Juliano; Araújo, Luciana; de Oliveira, Rodrigo P B; Manela-Azulay, Monica

2018-04-16

Expression of p53 by keratinocytes may be important in the pathogenesis of skin cancer induced by ultraviolet light. We used side-by-side nonablative and ablative erbium fractional laser resurfacing to assess the effects on expression of p53 by facial keratinocytes. Ten female patients (age range, 50-63 years) with Fitzpatrick skin Types I-IV and clinical signs of photoaging underwent erbium fractional laser resurfacing (nonablative, 1,540-nm; ablative, 2,940-nm) on opposite sides of the face. Skin biopsies were obtained before treatment and 3 months after treatment for comparison with control biopsies of face and inner arm, quantifying p53 in immunostained tissue sections. Only ablative (2,940-nm) treatments produced a statistically significant reduction in p53 scoring after 3 months. The histologic appearance of skin after ablative resurfacing more closely resembled inner arm skin (rather than facial skin) of control subjects. Epidermal repopulation with p53-negative keratinocytes through ablative erbium fractional laser resurfacing may diminish the risk of eventual malignancy in photoaged skin.

Risk assessment of excess drug and sunscreen absorption via skin with ablative fractional laser resurfacing : optimization of the applied dose for postoperative care.

PubMed

Chen, Wei-Yu; Fang, Chia-Lang; Al-Suwayeh, Saleh A; Yang, Hung-Hsu; Li, Yi-Ching; Fang, Jia-You

2013-09-01

The ablative fractional laser is a new modality used for surgical resurfacing. It is expected that laser treatment can generally deliver drugs into and across the skin, which is toxicologically relevant. The aim of this study was to establish skin absorption characteristics of antibiotics, sunscreens, and macromolecules via laser-treated skin and during postoperative periods. Nude mice were employed as the animal model. The skin received a single irradiation of a fractional CO2 laser, using fluences of 4-10 mJ with spot densities of 100-400 spots/cm(2). In vitro skin permeation using Franz cells was performed. Levels of skin water loss and erythema were evaluated, and histological examinations with staining by hematoxylin and eosin, cyclooxygenase-2, and claudin-1 were carried out. Significant signs of erythema, edema, and scaling of the skin treated with the fractional laser were evident. Inflammatory infiltration and a reduction in tight junctions were also observed. Laser treatment at 6 mJ increased tetracycline and tretinoin fluxes by 70- and 9-fold, respectively. A higher fluence resulted in a greater tetracycline flux, but lower skin deposition. On the other hand, tretinoin skin deposition increased following an increase in the laser fluence. The fractional laser exhibited a negligible effect on modulating oxybenzone absorption. Dextrans with molecular weights of 4 and 10 kDa showed increased fluxes from 0.05 to 11.05 and 38.54 μg/cm(2)/h, respectively. The optimized drug dose for skin treated with the fractional laser was 1/70-1/60 of the regular dose. The skin histology and drug absorption had recovered to a normal status within 2-3 days. Our findings provide the first report on risk assessment of excessive skin absorption after fractional laser resurfacing.

Femtosecond laser ablation of bovine cortical bone

NASA Astrophysics Data System (ADS)

Cangueiro, Liliana T.; Vilar, Rui; Botelho do Rego, Ana M.; Muralha, Vania S. F.

2012-12-01

We study the surface topographical, structural, and compositional modifications induced in bovine cortical bone by femtosecond laser ablation. The tests are performed in air, with a Yb:KYW chirped-pulse-regenerative amplification laser system (500 fs, 1030 nm) at fluences ranging from 0.55 to 2.24 J/cm2. The ablation process is monitored by acoustic emission measurements. The topography of the laser-treated surfaces is studied by scanning electron microscopy, and their constitution is characterized by glancing incidence x-ray diffraction, x-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and micro-Raman spectroscopy. The results show that femtosecond laser ablation allows removing bone without melting, carbonization, or cracking. The structure and composition of the remaining tissue are essentially preserved, the only constitutional changes observed being a reduction of the organic material content and a partial recrystallization of hydroxyapatite in the most superficial region of samples. The results suggest that, within this fluence range, ablation occurs by a combination of thermal and electrostatic mechanisms, with the first type of mechanism predominating at lower fluences. The associated thermal effects explain the constitutional changes observed. We show that femtosecond lasers are a promising tool for delicate orthopaedic surgeries, where small amounts of bone must be cut with negligible damage, thus minimizing surgical trauma.

Fractional carbon dioxide laser resurfacing of rhytides and photoaged skin--a prospective clinical study on patient expectation and satisfaction.

PubMed

Kohl, Elisabeth; Meierhöfer, Julia; Koller, Michael; Zeman, Florian; Groesser, Leopold; Karrer, Sigrid; Hohenleutner, Ulrich; Landthaler, Michael; Hohenleutner, Silvia

2015-02-01

Fractional CO2 -laser resurfacing is increasingly used for treating rhytides and photoaged skin because of its favorable benefit-risk ratio. A key outcome measure and treatment goal in aesthetic laser therapy is patient satisfaction. However, few data are available on patient-reported outcomes after fractional ablative skin-resurfacing. To compare patient expectations before and patient satisfaction after three fractional CO2 -laser treatments and to correlate objectively measured wrinkle reduction with patient satisfaction after treatment. We investigated patient expectation and satisfaction using a 14-item questionnaire in 24 female patients. We assessed the skin-related quality of life and patient satisfaction with skin appearance. We profilometrically measured wrinkle size in four facial areas before and three months after treatment and investigated correlations between wrinkle reduction and patient satisfaction. The high patient expectations before treatment (ceiling effect) were actually slightly exceeded. The average score of 14 items delineating patient satisfaction with laser treatment was higher (4.64 ± 0.82; n = 24) than the respective expectations before treatment (4.43 ± 0.88; n = 24). Skin-related quality of life and patient satisfaction with skin appearance had significantly improved after the last treatment. Patients dissatisfied with their skin appearance before treatment (mean 2.1 ± 1.5; evaluated on a scale ranging from 0-6) were satisfied (mean 5.1 ± 1.2) (P < 0.001) with skin appearance at the follow-up. Patient satisfaction with skin appearance was not correlated to the profilometrically measured reduction of wrinkle size of any facial area. Our results show high patient satisfaction with ablative fractional skin resurfacing, also regarding improved self-esteem and self-satisfaction despite high pre-treatment expectations. Skin-specific quality of life had significantly improved. Thus, this treatment modality can be recommended for patients with photoaged skin wishing to improve skin appearance. © 2015 Wiley Periodicals, Inc.

Cluster formation in laser-induced ablation and evaporation of solids observed by laser ionization time-of-flight mass spectrometry and scanning tunneling microscopy

NASA Astrophysics Data System (ADS)

Tench, R. J.; Balooch, M.; Bernardez, L.; Allen, Mike J.; Siekhaus, W. J.; Olander, D. R.; Wang, W.

1990-04-01

Laser ionization time-of-flight mass analysis (LIMA) used pulses (5ns) of a frequency-quadrupled Nd-YAG laser (266 nm) focused onto spots of 4 to 100 microns diameter to ablate material, and a reflectron time of flight tube to mass-analyze the plume. The observed mass spectra for Si, Pt, SiC, and UO 2 varied in the distribution of ablation products among atoms, molecules and clusters, depending on laser power density and target material. Cleaved surfaces of highly oriented pyrolytic graphite (HOPG) positioned at room temperature either 10 cm away from materials ablated at 10(exp -5) Torr by 1 to 3 excimer laser (308 nm) pulses of 20 ns duration or 1 m away from materials vaporized at 10(exp -8) Torr by 10 Nd-Glass laser pulses of 1 ms duration were analyzed by Scanning Tunneling Microscopy (STM) in air with angstrom resolution. Clusters up to 30 A in diameter were observed.

Femtosecond laser ablation of gold interdigitated electrodes for electronic tongues

NASA Astrophysics Data System (ADS)

Manzoli, Alexandra; de Almeida, Gustavo F. B.; Filho, José A.; Mattoso, Luiz H. C.; Riul, Antonio; Mendonca, Cleber R.; Correa, Daniel S.

2015-06-01

Electronic tongue (e-tongue) sensors based on impedance spectroscopy have emerged as a potential technology to evaluate the quality and chemical composition of food, beverages, and pharmaceuticals. E-tongues usually employ transducers based on metal interdigitated electrodes (IDEs) coated with a thin layer of an active material, which is capable of interacting chemically with several types of analytes. IDEs are usually produced by photolithographic methods, which are time-consuming and costly, therefore, new fabrication technologies are required to make it more affordable. Here, we employed femtosecond laser ablation with pulse duration of 50 fs to microfabricate gold IDEs having finger width from 2.3 μm up to 3.2 μm. The parameters used in the laser ablation technique, such as light intensity, scan speed and beam spot size have been optimized to achieve uniform IDEs, which were characterized by optical and scanning electron microscopy. The electrical properties of gold IDEs fabricated by laser ablation were evaluated by impedance spectroscopy, and compared to those produced by conventional photolithography. The results show that femtosecond laser ablation is a promising alternative to conventional photolithography for fabricating metal IDEs for e-tongue systems.

Healing of chronic wounds with adjunctive ablative fractional laser resurfacing in two pediatric patients.

PubMed

Krakowski, Andrew C; Diaz, Lucia; Admani, Shehla; Uebelhoer, Nathan S; Shumaker, Peter R

2016-02-01

The development of chronic non-healing wounds is multifactorial and can lead to increased patient morbidity. When traditional wound care methods fail, alternative treatments are needed to prevent chronic ulcer complications. Ablative fractional laser resurfacing (AFR) is an emerging therapy for chronic wounds. We report the successful use of AFR to facilitate the healing of chronic wounds in two pediatric patients. This is a case series including two patients with chronic wounds within scars that were treated with a micro-fractionated carbon dioxide (CO2 ) laser in a single pass at a pulse energy of 50 mJ and a treatment density of 5%. One patient had one treatment and the other had two treatments 1 month apart. AFR led to rapid healing of chronic wounds in both pediatric patients. The wounds remained epithelialized after 9 months in one patient and 4 months in the other. There were no complications. The combination of tolerability and efficacy observed in these cases introduces AFR as a potential promising adjunct to existing treatments for chronic, non-healing wounds in the pediatric population. © 2015 Wiley Periodicals, Inc.

The Laser Ablation of Aluminum at 193, 248 and 351 nm

DTIC Science & Technology

1991-05-01

36, 462 (1965); c. R.K Singh, D. Bhattacharya, and J. Narayan,AppL Phys. Lett. 57, 2022 (1990). 16. R.Welle and H . Helvajian , AIP Conference...function of delay time with the probe laser at a fixed distance from h ,:.,1 disk. Delay times are typically varied from 50ns to 51Ls. Typical velocity...SUj~j GIID10 H ~4~ 2o V V- rn AI!SUGIUaI GAID 00 co to CDo 0O 0O CJ! 0GIU19A 9 References 1. R.K. Singh, AXK Singh, C.B.Lee and J. Narayan, J. Appi

Dynamic features of bubble induced by a nanosecond pulse laser in still and flowing water

NASA Astrophysics Data System (ADS)

Charee, Wisan; Tangwarodomnukun, Viboon

2018-03-01

Underwater laser ablation techniques have been developed and employed to synthesis nanoparticles, to texture workpiece surface and to assist the material removal in laser machining process. However, the understanding of laser-material-water interactions, bubble formation and effects of water flow on ablation performance has still been very limited. This paper thus aims at exploring the formation and collapse of bubbles during the laser ablation of silicon in water. The effects of water flow rate on bubble formation and its consequences to the laser disturbance and cut features obtained in silicon were observed by using a high speed camera. A nanosecond pulse laser emitting the laser pulse energy of 0.2-0.5 mJ was employed in the experiment. The results showed that the bubble size was found to increase with the laser pulse energy. The use of high water flow rate can importantly facilitate the ejection of ablated particles from the workpiece surface, hence resulting in less deposition to the work surface and minimizing any disturbance to the laser beam during the ablation in water. Furthermore, a clean micro-groove in silicon wafer can successfully be produced when the process was performed in the high water flow rate condition. The findings of this study could provide an essential guideline for process selection, control and improvement in the laser micro-/submicro-fabrication using the underwater technique.

Tissue effects of Ho:YAG laser with varying fluences and pulse widths

NASA Astrophysics Data System (ADS)

Vari, Sandor G.; van der Veen, Maurits J.; Pergadia, Vani R.; Shi, Wei-Qiang; Duffy, J. T.; Weiss, Andrew B.; Fishbein, Michael C.; Grundfest, Warren S.

1994-02-01

We investigated the effect of varying fluence and pulse width on the ablation rate and consequent thermal damage of the Ho:YAG (2.130 micrometers ) laser. The rate of ablation on fresh bovine knee joint tissues, fibrous cartilage, hyaline cartilage, and bone in saline was determined after varying the fluence (160 - 640 J/cm2) and pulse width (150, 250, 450 microsecond(s) ec, FWHM) at a repetition rate of 2 Hz. A 400/440 micrometers fiber was used. The ablation rate increased linearly with the fluence. In fibrocartilage, different pulse durations generated significant changes in the ablation rates, but showed minor effects on hyaline cartilage and bone. The heat of ablation for all three tissue types decreased after lengthening the pulse.

Effect of limbal marking prior to laser ablation on the magnitude of cyclotorsional error.

PubMed

Chen, Xiangjun; Stojanovic, Aleksandar; Stojanovic, Filip; Eidet, Jon Roger; Raeder, Sten; Øritsland, Haakon; Utheim, Tor Paaske

2012-05-01

To evaluate the residual registration error after limbal-marking-based manual adjustment in cyclotorsional tracker-controlled laser refractive surgery. Two hundred eyes undergoing custom surface ablation with the iVIS Suite (iVIS Technologies) were divided into limbal marked (marked) and non-limbal marked (unmarked) groups. Iris registration information was acquired preoperatively from all eyes. Preoperatively, the horizontal axis was recorded in the marked group for use in manual cyclotorsional alignment prior to surgical iris registration. During iris registration, the preoperative iris information was compared to the eye-tracker captured image. The magnitudes of the registration error angle and cyclotorsional movement during the subsequent laser ablation were recorded and analyzed. Mean magnitude of registration error angle (absolute value) was 1.82°±1.31° (range: 0.00° to 5.50°) and 2.90°±2.40° (range: 0.00° to 13.50°) for the marked and unmarked groups, respectively (P<.001). Mean magnitude of cyclotorsional movement during the laser ablation (absolute value) was 1.15°±1.34° (range: 0.00° to 7.00°) and 0.68°±0.97° (range: 0.00° to 6.00°) for the marked and unmarked groups, respectively (P=.005). Forty-six percent and 60% of eyes had registration error >2°, whereas 22% and 20% of eyes had cyclotorsional movement during ablation >2° in the marked and unmarked groups, respectively. Limbal-marking-based manual alignment prior to laser ablation significantly reduced cyclotorsional registration error. However, residual registration misalignment and cyclotorsional movements remained during ablation. Copyright 2012, SLACK Incorporated.

A method for rapid measurement of laser ablation rate of hard dental tissue

NASA Astrophysics Data System (ADS)

Perhavec, T.; Gorkič, A.; Bračun, D.; Diaci, J.

2009-06-01

The aim of the study reported here is the development of a new method which allows rapid and accurate in-vitro measurements of three-dimensional (3D) shape of laser ablated craters in hard dental tissues and the determination of crater volume, ablation rate and speed. The method is based on the optical triangulation principle. A laser sheet projector illuminates the surface of a tooth, mounted on a linear translation stage. As the tooth is moved by the translation stage a fast digital video camera captures series of images of the illuminated surface. The images are analyzed to determine a 3D model of the surface. Custom software is employed to analyze the 3D model and to determine the volume of the ablated craters. Key characteristics of the method are discussed as well as some practical aspects pertinent to its use. The method has been employed in an in-vitro study to examine the ablation rates and speeds of the two main laser types currently employed in dentistry, Er:YAG and Er,Cr:YSGG. Ten samples of extracted human molar teeth were irradiated with laser pulse energies from 80 mJ to the maximum available energy (970 mJ with the Er:YAG, and 260 mJ with the Er,Cr:YSGG). About 2000 images of each ablated tooth surface have been acquired along a translation range of 10 mm, taking about 10 s and providing close to 1 million surface measurement points. Volumes of 170 ablated craters (half of them in dentine and the other half in enamel) were determined from this data and used to examine the ablated volume per pulse energy and ablation speed. The results show that, under the same conditions, the ablated volume per pulse energy achieved by the Er:YAG laser exceeds that of the Er,Cr:YSGG laser in almost all regimes for dentine and enamel. The maximum Er:YAG laser ablation speeds (1.2 mm 3/s in dentine and 0.7 mm 3/s in enamel) exceed those obtained by the Er,Cr:YSGG laser (0.39 mm 3/s in dentine and 0.12 mm 3/s in enamel). Since the presented method proves to be easy to use and allows quite rapid measurements it may become a valuable tool to study the influence of various laser parameters on the outcome of laser ablation of dental tissues.

Evaluation of the cavity margins after Er:YAG laser ablation of the enamel and dentin

NASA Astrophysics Data System (ADS)

Dostalova, Tatjana; Krejsa, Otakar; Jelinkova, Helena; Hamal, Karel

1994-12-01

This study investigates the checks of cavity margin after enamel and dentin ablation. The Er:YAG laser enamel and dentin ablation can be directly connected with the danger of cracks originating in the enamel near the cavity. This study evaluates the quality of the enamel edges after Er:YAG laser preparation. The enamel and dentin of buccal surfaces were ablated by the Er:YAG laser radiation. An Erbium:YAG laser system with the energy of 200 mJ was used to generate 200 microsecond(s) long pulses of mid-infrared 2.94 micrometers light in multimode configuration. The laser was operating in a free running mode, the repetition rate being 0.5 Hz with average laser power of 100 mW. Laser radiation was focused on the tooth tissue. Water cooling was used during the procedure in order to prevent tooth tissue destruction. The time of laser preparation was 5 minutes. A cavity of class V was prepared. The teeth were immersed into 0.5% basic fuchsin and then centrifuged at 6000 rev/min for 20 minutes. The microphotographs of the margins stained with 0.5% basic fuchsin were made and then the longitudinal section of the teeth were evaluated. The micrographs of the longitudinal section were checked and measured afterwards. The effect of the investigated laser irradiation on the origin of cracks was analyzed in the scanning electron microscope. Micrographs of each tooth before and after the laser ablation were compared. Micrographs of the intact teeth after extraction present the cracks of the enamel. They depend on the pressure exerted during extraction. The influence of the laser ablation proper is it bears no signs of new cracks. The conclusions of this study demonstrate the non-invasive nature of the Er:YAG laser ablation of the hard dental tissues.

The characterization of neural tissue ablation rate and corresponding heat affected zone of a 2 micron Tm3+ doped fiber laser(Conference Presentation)

NASA Astrophysics Data System (ADS)

Marques, Andrew J.; Jivraj, Jamil; Reyes, Robnier; Ramjist, Joel; Gu, Xijia J.; Yang, Victor X. D.

2017-02-01

Tissue removal using electrocautery is standard practice in neurosurgery since tissue can be cut and cauterized simultaneously. Thermally mediated tissue ablation using lasers can potentially possess the same benefits but with increased precision. However, given the critical nature of the spine, brain, and nerves, the effects of direct photo-thermal interaction on neural tissue needs to be known, yielding not only high precision of tissue removal but also increased control of peripheral heat damage. The proposed use of lasers as a neurosurgical tool requires that a common ground is found between ablation rates and resulting peripheral heat damage. Most surgical laser systems rely on the conversion of light energy into heat resulting in both desirable and undesirable thermal damage to the targeted tissue. Classifying the distribution of thermal energy in neural tissue, and thus characterizing the extent of undesirable thermal damage, can prove to be exceptionally challenging considering its highly inhomogenous composition when compared to other tissues such as muscle and bone. Here we present the characterization of neural tissue ablation rate and heat affected zone of a 1.94 micron thulium doped fiber laser for neural tissue ablation. In-Vivo ablation of porcine cerebral cortex is performed. Ablation volumes are studied in association with laser parameters. Histological samples are taken and examined to characterize the extent of peripheral heat damage.

Physical and optical limitations using ArF-excimer and Er:YAG lasers for PRK

NASA Astrophysics Data System (ADS)

Semchishen, Vladimir A.; Mrochen, Michael; Seiler, Theo

1998-06-01

The Erbium:YAG laser emitting at a wavelength of 2,94 micrometer have been promised as an alternative laser for the ArF-excimer laser (193 nm) in photorefractive keratectomy (PRK). This report discusses the limitations of laser parameters such as wavelength, energy density and pulse duration for the ablation of the cornea. In addition, the melting process during ablation on the corneal surface roughness may play a role.

Selective ablation of sub- and supragingival calculus with a frequency-doubled Alexandrite laser

NASA Astrophysics Data System (ADS)

Rechmann, Peter; Hennig, Thomas

1995-05-01

In a preceding trial the absorption characteristics of subgingival calculus were calculated using fluorescence emission spectroscopy (excitation laser: N2-laser, wavelength 337 nm, pulse duration 4 ns). Subgingival calculus seems to contain chromophores absorbing in the ultraviolet spectral region up to 420 nm. The aim of the actual study was the ablation of sub- and supragingival calculus using a frequency doubled Alexandrite-laser (wavelength 377 nm, pulse duration 100 ns, repetition rate 110 Hz). Extracted human teeth presenting sub- and supragingival calculus were irradiated perpendicular to their axis with a laser fluence of 1 Jcm-2. Using a standard application protocol calculus was irradiated at the enamel surface, at the junction between enamel and root, and at the root surface (located on dentin or on cementum). During the irradiation procedure an effective water cooling-system was engaged. For light microscopical investigations undecalcified histological sections were prepared after treatment. The histological sections revealed that a selective and total removal of calculus is possible at all locations without ablation of healthy enamel, dentin or cementum. Even low fluences provide us with a high effectiveness for the ablation of calculus. Thus, based on different absorption characteristics and ablation thresholds, engaging a frequency doubled Alexandrite-laser a fast and, even more, a selective ablation of sub- and supragingival calculus is possible without adverse side effects to the surrounding tissues. Even more, microbial dental plaque can be perfectly removed.

Application of CO II laser for removal of oral mucocele

NASA Astrophysics Data System (ADS)

Kato, J.; Moriya, K.; Hirai, Y.

2006-02-01

Mucocele is an oral soft tissue cyst caused by the disturbance of saliva flow. Mucocele is widely observed in child patients and recurrence is high. The objective of this study was to clarify the effect of CO II laser irradiation in the case of mucocele. A CO II laser was used on 45 subjects, aged between 0 to 15 years, having mucocele on lip, lingual, or buccal mucosa. Our procedure in using CO II laser was not to vaporize the mucocele but to remove the whole mucocele mass. The border of mucocele was firstly incised by laser following defocusly ablating the root or body of mucocele separating from sorrounding tissue. As a result, mucocele was easily and completely removed without breaking the wall of mucocele. None of the cases required suturing. The results were as follows. 1. The mucocele of lip or lingual mucosa with a rich blood supply, was efficiently removed, without bleeding, giving a clear operative field during the operation. 2. The surgery itself was simple and less time-consuming. 3. After two or three weeks the wound was completely healed without almost any discomfort in all patients 4. Wound contraction and scarring were decreased or eliminated. 5. The reoccurrence of mucocele was not seen, except only in one case of lingual mucocele. In conclusion the use of CO II laser proved to be a very safe and effective mode for the removal of mucocele, especially in small children.

Ultrafast Passive Shields for Laser and Ballistic Protection

DTIC Science & Technology

1991-07-15

chemically polymerized P(DPA)) as a binder, and these were tested for ablation (i.e. laser damage threshold ) limits. Table IV below summarizes these results...50, 100, 250 and 500 AJ/pulse o 1.G, 2.5, 5.0 mJ/pulse. The following energies were used for the preliminary laser damage threshold tests: o 2.5, 5.0...these were tested for ablation (i.e. laser damage threshold ) limits. Table VI summarizes these results which are all for tests in the absence of an iris

Numerical study of double-pulse laser ablation of Al

NASA Astrophysics Data System (ADS)

Förster, G. D.; Lewis, Laurent J.

2018-06-01

The effect of double laser pulses (DPs) on the ablation process in solids is studied using a hybrid two-temperature model combining a continuum description of the conduction band electrons with a classical molecular dynamics (MD) approach for the ions. The study is concerned with double pulses with delays in the range of 0-50 ps and absorbed laser fluences of 0.5, 1.0, and 1.5 J/m 2 [i.e., 1-3 times the ablation threshold for single-pulse ablation (SP)], taking Al as a generic example of simple metals. A detailed analysis, including the assessment of thermodynamic pathways and cavitation rates, leads to a comprehensive picture of the mechanisms active during the different stages of the ablation process initiated by DPs. This study provides an explanation for several phenomena observed in DP ablation experiments. In particular, with respect to SP ablation, crater depths are reduced, which can be explained by the compensation of the rarefaction wave from the first laser pulse with the compression wave from the second pulse, or, at higher fluences and larger delays, by the fact that the target surface is shielded with matter ablated by the first laser pulse. Also, we discuss how smoother surface structures obtained using DPs may be related to features found in the simulations—viz., reduced mechanical strain and peak lattice temperatures. Finally, vaporization appears to be enhanced in DP ablation, which may improve the resolution of emission spectra.

Determination of Cross-Sectional Area of Focused Picosecond Gaussian Laser Beam

NASA Technical Reports Server (NTRS)

Ledesma, Rodolfo; Fitz-Gerald, James; Palmieri, Frank; Connell, John

2018-01-01

Measurement of the waist diameter of a focused Gaussian-beam at the 1/e(sup 2) intensity, also referred to as spot size, is key to determining the fluence in laser processing experiments. Spot size measurements are also helpful to calculate the threshold energy and threshold fluence of a given material. This work reports an application of a conventional method, by analyzing single laser ablated spots for different laser pulse energies, to determine the cross-sectional area of a focused Gaussian-beam, which has a nominal pulse width of approx. 10 ps. Polished tungsten was used as the target material, due to its low surface roughness and low ablation threshold, to measure the beam waist diameter. From the ablative spot measurements, the ablation threshold fluence of the tungsten substrate was also calculated.

Femtosecond Laser Ablation Multicollector ICPMS Analysis of Uranium Isotopes in NIST Glass

DOE Office of Scientific and Technical Information (OSTI.GOV)

Duffin, Andrew M.; Springer, Kellen WE; Ward, Jesse D.

We have utilized femtosecond laser ablation coupled to multi-collector inductively couple plasma mass spectrometry to measure the uranium isotopic content of NIST 61x (x=0,2,4,6) glasses. The uranium content of these glasses is a linear two-component mixing between isotopically natural uranium and the isotopically depleted spike used in preparing the glasses. Laser ablation results match extremely well, generally within a few ppm, with solution analysis following sample dissolution and chemical separation. In addition to isotopic data, sample utilization efficiency measurements indicate that over 1% of ablated uranium atoms reach a mass spectrometer detector, making this technique extremely efficient. Laser sampling alsomore » allows for spatial analysis and our data indicate that rare uranium concentration inhomogeneities exist in NIST 616 glass.« less

Retinotomy using an erbium:YAG laser on human autopsy eyes

NASA Astrophysics Data System (ADS)

Ellsworth, Lansing G.; Kramer, Theresa R.; Noecker, Robert J.; Snyder, Robert W.; Yarborough, J. Michael

1994-06-01

Mid-IR lasers that operate near the absorption peak of water have a short penetration depth in ocular tissues. Ablation of tissue can be accomplished with minimal coagulative damage to underlying structures. We used an erbium:YAG laser equipped with a contact probe to create retinotomy sites in the human retina of eye bank eyes. An erbium:YAG laser (2.94 micrometers ) equipped with an infrared transmitting glass fiber and a sapphire tip (400 micrometers ) was used to directly ablate the surface of the retina. We administered both single and multiple pulses to the macula and peripheral retina using energy levels from 4 to 16 mJ per pulse. The retinas were then examined histopathologically to evaluate the extent of ablation and coagulative damage. Single pulses at low energy levels were noted to cause ablative damage to the nerve fiber layer and ganglion cell layer without a notable coagulative effect. The mean ablation depth at lower energy levels was less than the mean ablation depth at higher energy levels. Extensive laser application produced disruption of the retinal pigment epithelium, choroid and sclera. the erbium:YAG laser equipped with a contact probe is an effective means of creating retinotomies in human autopsy eyes. When used in the single pulse mode at lower energy levels, the erbium:YAG laser appears capable of removing superficial retinal layers without damaging deeper structures.

Comparison of Internal Energy Distributions of Ions Created by Electrospray Ionization and Laser Ablation-Liquid Vortex Capture-Electrospray Ionization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cahill, John F.; Kertesz, Vilmos; Ovchinnikova, Olga S.

2015-06-27

Recently a number of techniques have combined laser ablation with liquid capture for mass spectrometry spot sampling and imaging applications. The newly developed non-contact liquid-vortex capture probe has been used to efficiently collect 355 nm UV laser ablated material in a continuous flow solvent stream in which the captured material dissolves and then undergoes electrospray ionization. This sampling and ionization approach has produced what appear to be classic electrospray ionization spectra; however, the softness of this sampling/ionization process versus simple electrospray ionization has not been definitely determined. A series of benzlypyridinium salts, known as thermometer ions, were used to comparemore » internal energy distributions between electrospray ionization and the UV laser ablation liquid-vortex capture probe electrospray combination. Measured internal energy distributions were identical between the two techniques, even with differences in laser fluence (0.7-3.1 J cm-2) and when using UV-absorbing or non-UV-absorbing sample substrates. This data indicates ions formed directly by UV laser ablation, if any, are likely an extremely small constituent of the total ion signal observed. Instead, neutral molecules, clusters or particulates ejected from the surface during laser ablation, subsequently captured and dissolved in the flowing solvent stream then electrosprayed are the predominant source of ion signal observed. The electrospray ionization process used controls the softness of the technique.« less

Picosecond laser ablation of poly-L-lactide: Effect of crystallinity on the material response

NASA Astrophysics Data System (ADS)

Ortiz, Rocío; Quintana, Iban; Etxarri, Jon; Lejardi, Ainhoa; Sarasua, Jose-Ramon

2011-11-01

The picosecond laser ablation of poly-L-lactide (PLLA) as a function of laser fluence and degree of crystallinity was examined. The ablation parameters and the surface modifications were analyzed under various irradiation conditions using laser wavelengths ranging from the ultraviolet through the visible. When processing the amorphous PLLA, both energy threshold and topography varied considerably depending on laser wavelength. Laser irradiation showed a reduction in the energy ablation threshold as the degree of crystallinity increased, probably related to photomechanical effects involved in laser ablation with ultra-short pulses and the lower stress accommodation behavior of semicrystalline polymers. In particular, cooperative chain motions are impeded by the higher degree of crystallinity, showing fragile mechanical behavior and lower energy dissipation. The experimental results on ablation rate versus laser energy showed that UV laser ablation on semicrystalline PLLA was more efficient than the visible ablation, i.e., it exhibits higher etch rates over a wide range of pulse energy conditions. These results were interpreted in terms of photo-thermal and photo-chemical response of polymers as a function of material micro-structure and incident laser wavelength. High quality micro-grooves were produced in amorphous PLLA, reveling the potential of ultra-fast laser processing technique in the field of micro-structuring biocompatible and biodegradable polymers for biomedical applications.

Setup for functional cell ablation with lasers: coupling of a laser to a microscope.

PubMed

Sweeney, Sean T; Hidalgo, Alicia; de Belle, J Steven; Keshishian, Haig

2012-06-01

The selective removal of cells by ablation is a powerful tool in the study of eukaryotic developmental biology, providing much information about their origin, fate, or function in the developing organism. In Drosophila, three main methods have been used to ablate cells: chemical, genetic, and laser ablation. Each method has its own applicability with regard to developmental stage and the cells to be ablated, and its own limitations. The primary advantage of laser-based ablation is the flexibility provided by the method: The operations can be performed in any cell pattern and at any time in development. Laser-based techniques permit manipulation of structures within cells, even to the molecular level. They can also be used for gene activation. However, laser ablation can be expensive, labor-intensive, and time-consuming. Although live cells can be difficult to image in Drosophila embryos, the use of vital fluorescent imaging methods has made laser-mediated cell manipulation methods more appealing; the methods are relatively straightforward. This article provides the information necessary for setting up and using a laser microscope for lasesr ablation studies.

Signal enhancement in laser-induced breakdown spectroscopy using fast square-pulse discharges

NASA Astrophysics Data System (ADS)

Sobral, H.; Robledo-Martinez, A.

2016-10-01

A fast, high voltage square-shaped electrical pulse initiated by laser ablation was investigated as a means to enhance the analytical capabilities of laser Induced breakdown spectroscopy (LIBS). The electrical pulse is generated by the discharge of a charged coaxial cable into a matching impedance. The pulse duration and the stored charge are determined by the length of the cable. The ablation plasma was produced by hitting an aluminum target with a nanosecond 532-nm Nd:YAG laser beam under variable fluence 1.8-900 J cm- 2. An enhancement of up to one order of magnitude on the emission signal-to-noise ratio can be achieved with the spark discharge assisted laser ablation. Besides, this increment is larger for ionized species than for neutrals. LIBS signal is also increased with the discharge voltage with a tendency to saturate for high laser fluences. Electron density and temperature evolutions were determined from time delays of 100 ns after laser ablation plasma onset. Results suggest that the spark discharge mainly re-excites the laser produced plume.

Flexible CO2 laser waveguide: a comparison of tracheal resection dosimetry and histology with the rigid waveguide

NASA Astrophysics Data System (ADS)

Slack, Christopher L.; Pankratov, Michail M.; Perrault, Donald F., Jr.; Shapshay, Stanley M.; Aretz, H. Thomas

1993-07-01

The CO2 laser has been limited in its application within the tracheobronchial tree by its lack of a fiber delivery system. Recently a new product has been marketed, Luxar's flexible CO2 laser waveguide or FlexiguideTM, a spin-off of the presently used rigid waveguide or MicroguideTM. The study was undertaken so as to delineate the properties and thus the usefulness of this new product which promised an increased ease of delivery of the CO2 laser wavelength. We compared the flexiguide with its rigid counterpart along two parameters. Specifically, we determined the total energy necessary to endoscopically resect bovine tracheal rings with each guide and then examined the histologic crater characteristics of each guide at a given energy setting. In so doing we endeavored to see if the experience of the surgeon with the microguide could be translated to the use of the flexiguide. We found the flexiguide to require a greater total energy than the microguide in the continuous wave (cw) and chopped pulse (cp) operational modes p < 0.01. There was, however, no demonstrated difference in required energy in the superpulse (sp) operational mode. Preliminary histologic evidence when measuring such indices as crater depth, crater width, and shoulder width thermal damage seem to suggest that the flexiguide is less efficient at tissue ablation than its rigid counterpart at the same given energy. It also appears to cause a greater degree of associated thermal injury.

Perioral Rejuvenation With Ablative Erbium Resurfacing.

PubMed

Cohen, Joel L

2015-11-01

Since the introduction of the scanning full-field erbium laser, misconceptions regarding ablative erbium resurfacing have resulted in its being largely overshadowed by ablative fractional resurfacing. This case report illustrates the appropriateness of full-field erbium ablation for perioral resurfacing. A patient with profoundly severe perioral photodamage etched-in lines underwent full-field ablative perioral resurfacing with an erbium laser (Contour TRL, Sciton Inc., Palo Alto, CA) that allows separate control of ablation and coagulation. The pre-procedure consultations included evaluation of the severity of etched-in lines, and discussion of patient goals, expectations, and appropriate treatment options, as well as a review of patient photos and post-treatment care required. The author generally avoids full-field erbium ablation in patients with Fitzpatrick type IV and above. For each of 2 treatment sessions (separated by approximately 4 months), the patient received (12 cc plain 2% lidodaine) sulcus blocks before undergoing 4 passes with the erbium laser at 150 μ ablation, no coagulation, and then some very focal 30 μ ablation to areas of residual lines still visualized through the pinpoint bleeding. Similarly, full-field ablative resurfacing can be very reliable for significant wrinkles and creping in the lower eyelid skin--where often a single treatment of 80 μ ablation, 50 μ coagulation can lead to a nice improvement. Standardized digital imaging revealed significant improvement in deeply etched rhytides without significant adverse events. For appropriately selected patients requiring perioral (or periorbital) rejuvenation, full-field ablative erbium resurfacing is safe, efficacious and merits consideration.

Comparison of the ablation ability of nucleus pulposus after 1,064 nm Nd:YAG laser and 980 nm diode laser radiation.

PubMed

Yin, Jian; Han, Zhengfeng; Guo, Baofeng; Guo, Han; Zhang, Tongtong; Zeng, Yanjun; Ren, Longxi

2015-07-01

To compare the ablation ability of nucleus pulposus after 1,064 nm Nd:YAG laser and 980 nm diode laser radiation. Goat spine specimen (GSS) was radiated using Nd:YAG laser and 980 nm diode laser and then divided into five groups based on the final energy--200, 400, 600, 800 and 1,000 J groups. The ablation quality of nucleus pulposus after radiation was recorded. The ablation quality of GSS was greater at higher radiation energies in both lasers. When compared at the same energy level, the ablation quality of GSS was greater in 980 nm diode laser than in 1,064 nm Nd:YAG laser. Statistical significance was observed in 200 and 400 J groups (P < 0.05) and in 600, 800 and 1,000 J groups (P < 0.01). Radiation with 980 nm diode laser showed better ablation ability than 1,064 nm Nd:YAG laser.

Pulsed Laser Ablation Synthesis of Diamond Molecules in Supercritical Fluids

NASA Astrophysics Data System (ADS)

Nakahara, Sho; Stauss, Sven; Miyazoe, Hiroyuki; Shizuno, Tomoki; Suzuki, Minoru; Kataoka, Hiroshi; Sasaki, Takehiko; Terashima, Kazuo

2010-09-01

Nanocarbon materials have been synthesized by pulsed laser ablation (532 nm; 52 J/cm2; 7 ns; 10 Hz) of highly oriented pyrolytic graphite in adamantane-dissolved supercritical xenon at a temperature T = 290.2 K and pressure p = 5.86 MPa. Micro-Raman spectroscopy of the products revealed the presence of hydrocarbons possessing sp3 hybridized bonds also found in diamond structures. The synthesis of diamantane was confirmed by gas chromatography-mass spectrometry. The same measurements also indicate the possible synthesis of other diamondoids up to octamantane. Thus, laser ablation in supercritical fluids is proposed as one practical method of synthesizing diamondoids.

Facile and fast synthesis of SnS2 nanoparticles by pulsed laser ablation in liquid

NASA Astrophysics Data System (ADS)

Johny, J.; Sepulveda-Guzman, S.; Krishnan, B.; Avellaneda, D.; Shaji, S.

2018-03-01

Nanoparticles (NPs) of tin disulfide (SnS2) were synthesized using pulsed laser ablation in liquid (PLAL) technique. Effects of different liquid media and ablation wavelengths on the morphology and optical properties of the nanoparticles were studied. Nd: YAG laser wavelengths of 532 nm and 1064 nm (frequency 10 Hz and pulse width 10 ns) were used to irradiate SnS2 target immersed in liquid for the synthesis of SnS2 nanoparticles. Here PLAL was a fast synthesis technique, the ablation was only for 30 s. Transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, UV-vis absorption spectroscopy and photoluminescence spectroscopy were used to characterize the SnS2 NPs. TEM images showed that the liquid medium and laser wavelength influence the morphology of the NPs. SAED patterns and high resolution TEM (HRTEM) images confirmed the crystallinity of the particles. XRD and XPS analyses confirmed that SnS2 NPs were having exact crystalline structure and chemical states as that of the target. Raman analysis also supported the results obtained by XRD and XPS. Optical band gaps of the nanocolloids evaluated from their UV-vis absorption spectra were 2.4-3.05 eV. SnS2 NPs were having luminescence spectra in the blue-green region irrespective of the liquid media and ablation wavelength.

Feedback-controlled laser fabrication of micromirror substrates.

PubMed

Petrak, Benjamin; Konthasinghe, Kumarasiri; Perez, Sonia; Muller, Andreas

2011-12-01

Short (40-200 μs) single focused CO(2) laser pulses of energy ≳100 μJ were used to fabricate high quality concave micromirror templates on silica and fluoride glass. The ablated features have diameters of ≈20-100 μm and average root-mean-square (RMS) surface microroughness near their center of less than 0.2 nm. Temporally monitoring the fabrication process revealed that it proceeds on a time scale shorter than the laser pulse duration. We implement a fast feedback control loop (≈20 kHz bandwidth) based on the light emitted by the sample that ensures an RMS size dispersion of less than 5% in arrays on chips or in individually fabricated features on an optical fiber tip, a significant improvement over previous approaches using longer pulses and open loop operation.

Ho:YAG laser arthroscopy of the knee

NASA Astrophysics Data System (ADS)

Sisto, Domenick J.; Blazina, Martin E.; Hirsh, Linda C.

1994-09-01

The HO:YAG laser is a near-contact laser with a capacity to ablate or cut tissues. The ablation function allows the surgeon to remove meniscal tissue, lyse and resect adhesions, melt loose bodies, and dissolve inflamed synovium. The cutting function of the laser is utilized to perform a lateral release or resect torn menisci. The laser can also be utilized to drill holes in Grade IV chondromalacic lesions to initiate a healing response. The laser has been embraced by orthopaedic surgeons because of its shape and versatility. The tip is only 2 mm wide and can be delivered into the tight posterior compartments of the knee with no damaging contact with the articular surfaces. The laser coagulates as it works and bleeding is minimized. The laser can function both as a cutting and ablating tool. The laser can also drill holes into subchondral bone to, hopefully, initiate a healing response.

Fractional laser skin resurfacing.

PubMed

Alexiades-Armenakas, Macrene R; Dover, Jeffrey S; Arndt, Kenneth A

2012-11-01

Laser skin resurfacing (LSR) has evolved over the past 2 decades from traditional ablative to fractional nonablative and fractional ablative resurfacing. Traditional ablative LSR was highly effective in reducing rhytides, photoaging, and acne scarring but was associated with significant side effects and complications. In contrast, nonablative LSR was very safe but failed to deliver consistent clinical improvement. Fractional LSR has achieved the middle ground; it combined the efficacy of traditional LSR with the safety of nonablative modalities. The first fractional laser was a nonablative erbium-doped yttrium aluminum garnet (Er:YAG) laser that produced microscopic columns of thermal injury in the epidermis and upper dermis. Heralding an entirely new concept of laser energy delivery, it delivered the laser beam in microarrays. It resulted in microscopic columns of treated tissue and intervening areas of untreated skin, which yielded rapid reepithelialization. Fractional delivery was quickly applied to ablative wavelengths such as carbon dioxide, Er:YAG, and yttrium scandium gallium garnet (2,790 nm), providing more significant clinical outcomes. Adjustable laser parameters, including power, pitch, dwell time, and spot density, allowed for precise determination of percent surface area, affected penetration depth, and clinical recovery time and efficacy. Fractional LSR has been a significant advance to the laser field, striking the balance between safety and efficacy.

Ablative fractional CO2 laser for burn scar reconstruction: An extensive subjective and objective short-term outcome analysis of a prospective treatment cohort.

PubMed

Issler-Fisher, Andrea C; Fisher, Oliver M; Smialkowski, Ania O; Li, Frank; van Schalkwyk, Constant P; Haertsch, Peter; Maitz, Peter K M

2017-05-01

The introduction of ablative fractional CO 2 lasers (CO 2 -AFL) for burn scar management shows promising results. Whilst recent studies have focused on objective scar outcomes following CO 2 -AFL treatment, to date no data on patient subjective factors such as quality of life are available. A prospective study was initiated to analyze the safety and efficacy of the CO 2 -AFL. Various objective and subjective outcome parameters were prospectively collected from the date of first consultation and follow-up following treatment. Objective factors include the Vancouver Scar Scale (VSS), the Patient and Observer Scar Assessment Scale (POSAS), and ultrasound measurements of the thickness of the scar. Subjective parameters included the assessment of neuropathic pain and pruritus, as well as the evaluation of improvement of quality of life following CO 2 -AFL with the Burns Specific Health Scale (BSHS-B). For treatment effect analysis, patients were stratified according to scar maturation status (> or <2 years after injury). 47 patients with 118 burn scars completed at least one treatment cycle. At a median of 55 days (IQR 32-74) after CO 2 -AFL treatment all analyzed objective parameters decreased significantly: intra-patient normalized scar thickness decreased from a median of 2.4mm to 1.9mm (p<0.001) with a concomitant VSS-drop from a median of 7 to 6 (p<0.001). The overall POSAS patient scale decreased from a median of 9 to 5 (p<0.001) with similar effects documented in POSAS observer scales. Both pain and pruritus showed significant reduction. Quality of life increased significantly by 15 points (median 120 to 135; p<0.001). All of the identified changes following CO 2 -AFL were equally significant irrespective of scar maturation status. Our preliminary results confirm significant improvement in thickness, texture, colour, and symptoms following treatment with CO 2 -AFL. Foremost, quality of life of patients with both immature and mature scars (up to 23 years after injury) improved significantly after just one treatment session. To our knowledge, this is the first study to document such holistic treatment effects in burn patients treated by CO 2 -AFL. Copyright © 2016 Elsevier Ltd and ISBI. All rights reserved.

Femtosecond laser fluence based nanostructuring of W and Mo in ethanol

NASA Astrophysics Data System (ADS)

Bashir, Shazia; Rafique, Muhammad Shahid; Nathala, Chandra Sekher; Ajami, Ali Asghar; Husinsky, Wolfgang

2017-05-01

The effect of femtosecond laser fluence on nanostructuring of Tungsten (W) and Molybdenum (Mo) has been investigated after ablation in ethanol environment. A Ti: Sapphire laser (800 nm, 30 fs) at fluences ranging from 0.6 to 5.7 J cm-2 was employed to ablate targets. The growth of structures on the surface of irradiated targets is investigated by Field Emission Scanning Electron Microscope (FESEM) analysis. The SEM was performed for both central as well as the peripheral ablated regions. It is observed that both the development and shape of nanoscale features is dependent upon deposited energies to the target surface as well as nature of material. Nanostructures grown on Mo are more distinct and well defined as compared to W. At central ablated areas of W, unorganized Laser Induced Periodic Surface Structures (LIPSS) are grown at low fluences, whereas, nonuniform melting along with cracking is observed at higher fluences. In case of Mo, well-defined and organized LIPSS are observed for low fluences. With increasing fluence, LIPSS become unorganized and broken with an appearance of cracks and are completely vanished with the formation of nanoscale cavities and conical structures. In case of peripheral ablated areas broken and bifurcated LIPSS are grown for all fluences for both materials. The, ablated diameter, ablation depth, ablation rate and the dependence of periodicity of LIPSS on the laser fluence are also estimated for both W and Mo. Parametric instabilities of laser-induced plasma along with generation and scattering of surface plasmons is considered as a possible cause for the formation of LIPSS. For ethanol assisted ablation, the role of bubble cavitation, precipitation, confinement and the convective flow is considered to be responsible for inducing increased hydrodynamic instabilities at the liquid-solid interface.

Laser dissection sampling modes for direct mass spectral analysis [using a hybrid optical microscopy/laser ablation liquid vortex capture/electrospray ionization system

DOE PAGES

Cahill, John F.; Kertesz, Vilmos; Van Berkel, Gary J.

2016-02-01

Here, laser microdissection coupled directly with mass spectrometry provides the capability of on-line analysis of substrates with high spatial resolution, high collection efficiency, and freedom on shape and size of the sampling area. Establishing the merits and capabilities of the different sampling modes that the system provides is necessary in order to select the best sampling mode for characterizing analytically challenging samples. The capabilities of laser ablation spot sampling, laser ablation raster sampling, and laser 'cut and drop' sampling modes of a hybrid optical microscopy/laser ablation liquid vortex capture electrospray ionization mass spectrometry system were compared for the analysis ofmore » single cells and tissue. Single Chlamydomonas reinhardtii cells were monitored for their monogalactosyldiacylglycerol (MGDG) and diacylglyceryltrimethylhomo-Ser (DGTS) lipid content using the laser spot sampling mode, which was capable of ablating individual cells (4-15 m) even when agglomerated together. Turbid Allium Cepa cells (150 m) having unique shapes difficult to precisely measure using the other sampling modes could be ablated in their entirety using laser raster sampling. Intact microdissections of specific regions of a cocaine-dosed mouse brain tissue were compared using laser 'cut and drop' sampling. Since in laser 'cut and drop' sampling whole and otherwise unmodified sections are captured into the probe, 100% collection efficiencies were achieved. Laser ablation spot sampling has the highest spatial resolution of any sampling mode, while laser ablation raster sampling has the highest sampling area adaptability of the sampling modes. In conclusion, laser ablation spot sampling has the highest spatial resolution of any sampling mode, useful in this case for the analysis of single cells. Laser ablation raster sampling was best for sampling regions with unique shapes that are difficult to measure using other sampling modes. Laser 'cut and drop' sampling can be used for cases where the highest sensitivity is needed, for example, monitoring drugs present in trace amounts in tissue.« less

Laser dissection sampling modes for direct mass spectral analysis [using a hybrid optical microscopy/laser ablation liquid vortex capture/electrospray ionization system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cahill, John F.; Kertesz, Vilmos; Van Berkel, Gary J.

Here, laser microdissection coupled directly with mass spectrometry provides the capability of on-line analysis of substrates with high spatial resolution, high collection efficiency, and freedom on shape and size of the sampling area. Establishing the merits and capabilities of the different sampling modes that the system provides is necessary in order to select the best sampling mode for characterizing analytically challenging samples. The capabilities of laser ablation spot sampling, laser ablation raster sampling, and laser 'cut and drop' sampling modes of a hybrid optical microscopy/laser ablation liquid vortex capture electrospray ionization mass spectrometry system were compared for the analysis ofmore » single cells and tissue. Single Chlamydomonas reinhardtii cells were monitored for their monogalactosyldiacylglycerol (MGDG) and diacylglyceryltrimethylhomo-Ser (DGTS) lipid content using the laser spot sampling mode, which was capable of ablating individual cells (4-15 m) even when agglomerated together. Turbid Allium Cepa cells (150 m) having unique shapes difficult to precisely measure using the other sampling modes could be ablated in their entirety using laser raster sampling. Intact microdissections of specific regions of a cocaine-dosed mouse brain tissue were compared using laser 'cut and drop' sampling. Since in laser 'cut and drop' sampling whole and otherwise unmodified sections are captured into the probe, 100% collection efficiencies were achieved. Laser ablation spot sampling has the highest spatial resolution of any sampling mode, while laser ablation raster sampling has the highest sampling area adaptability of the sampling modes. In conclusion, laser ablation spot sampling has the highest spatial resolution of any sampling mode, useful in this case for the analysis of single cells. Laser ablation raster sampling was best for sampling regions with unique shapes that are difficult to measure using other sampling modes. Laser 'cut and drop' sampling can be used for cases where the highest sensitivity is needed, for example, monitoring drugs present in trace amounts in tissue.« less

Surface ablation of aluminum and silicon by ultrashort laser pulses of variable width

NASA Astrophysics Data System (ADS)

Zayarny, D. A.; Ionin, A. A.; Kudryashov, S. I.; Makarov, S. V.; Kuchmizhak, A. A.; Vitrik, O. B.; Kulchin, Yu. N.

2016-06-01

Single-shot thresholds of surface ablation of aluminum and silicon via spallative ablation by infrared (IR) and visible ultrashort laser pulses of variable width τlas (0.2-12 ps) have been measured by optical microscopy. For increasing laser pulse width τlas < 3 ps, a drastic (threefold) drop of the ablation threshold of aluminum has been observed for visible pulses compared to an almost negligible threshold variation for IR pulses. In contrast, the ablation threshold in silicon increases threefold with increasing τlas for IR pulses, while the corresponding thresholds for visible pulses remained almost constant. In aluminum, such a width-dependent decrease in ablation thresholds has been related to strongly diminished temperature gradients for pulse widths exceeding the characteristic electron-phonon thermalization time. In silicon, the observed increase in ablation thresholds has been ascribed to two-photon IR excitation, while in the visible range linear absorption of the material results in almost constant thresholds.

Laser-ablated poly(methyl methacrylate) microdevices for sub-microliter DNA amplification suitable for micro-total analysis systems

NASA Astrophysics Data System (ADS)

Lounsbury, Jenny A.; Poe, Brian L.; Do, Michael; Landers, James P.

2012-08-01

Biochemical techniques, such as the polymerase chain reaction (PCR), can take up to 3.5 h for completion using a commercial bench-top instrument, creating a bottleneck in sample preparation processes. PCR has been successfully adapted to microfluidic devices, reducing the time needed to as little as 7-10 min. Recently, a trend in the field is to use alternative substrates, such as poly(methyl methacyrlate) (PMMA), for the fabrication of microfluidic devices. PMMA has several advantages over more expensive substrates including rigidity without fragility, disposability, and it is easy to fabricate, using techniques such as hot embossing or CO2 laser ablation. Here, we report the fabrication of PMMA microdevices to explore their effectiveness for PCR amplification. Several types of PMMA microdevices were fabricated using a CO2 laser ablation system, with two or three PMMA layers of different thicknesses. Bonding of the microdevices was significantly improved through the use of a grid system etched into the device, allowing for trapped air to escape, eliminating leakage. Using infrared thermal cycling, the ramping rates were determined to be dependent on the thickness of the PMMA used in fabrication, allowing for customization of cycling conditions. Further reduction of the thermal mass by isolation of the chambers provided a significant increase in the heating and cooling rates (up to 6.19 (±0.32 °C s-1) and -7.99 (±0.06 °C s-1), respectively). Bubble formation, a chronic problem in microfluidic systems in general and problematic during the heating phase of PCR, was minimized through the use of a biocompatible adhesive/manifold combination to seal the reservoirs. Finally, successful PCR amplification was demonstrated with both a fragment from the β-globin gene and 15 tetra-nucleotide repeat regions with a sex-typing marker in a conventional STR kit with the latter facilitated by the dynamic coating of the fluidic architecture with poly(ethylene glycol) (PEG).

Pure colloidal metal and ceramic nanoparticles from high-power picosecond laser ablation in water and acetone.

PubMed

Bärsch, Niko; Jakobi, Jurij; Weiler, Sascha; Barcikowski, Stephan

2009-11-04

The generation of colloids by laser ablation of solids in a liquid offers a nearly unlimited material variety and a high purity as no chemical precursors are required. The use of novel high-power ultra-short-pulsed laser systems significantly increases the production rates even in inflammable organic solvents. By applying an average laser power of 50 W and pulse durations below 10 ps, up to 5 mg min(-1) of nanoparticles have been generated directly in acetone, marking a breakthrough in productivity of ultra-short-pulsed laser ablation in liquids. The produced colloids remain stable for more than six months. In the case of yttria-stabilized zirconia ceramic, the nanoparticles retain the tetragonal crystal structure of the ablated target. Laser beam self-focusing plays an important role, as a beam radius change of 2% on the liquid surface can lead to a decrease of nanoparticle production rates of 90% if the target position is not re-adjusted.

Confocal microscopy to guide laser ablation of basal cell carinoma: a preliminary feasibility study

NASA Astrophysics Data System (ADS)

Larson, Bjorg A.; Sierra, Heidy; Chen, Jason; Rajadhyaksha, Milind

2013-03-01

Laser ablation may be a promising method for removal of skin lesions, with the potential for better cosmetic outcomes and reduced scarring and infection. An obstacle to implementing laser ablation is that the treatment leaves no tissue for histopathological analysis. Pre-operative and intra-operative mapping of BCCs using confocal microscopy may guide the ablation of the tumor until all tumor is removed. We demonstrate preliminary feasibility of confocal microscopy to guide laser ablation of BCCs in freshly excised tissue from Mohs surgery. A 2940 nm Er:YAG laser provides efficient ablation of tumor with reduced thermal damage to the surrounding tissue.

Morphological effects of nanosecond- and femtosecond-pulsed laser ablation on human middle ear ossicles

NASA Astrophysics Data System (ADS)

Ilgner, Justus F.; Wehner, Martin; Lorenzen, Johann; Bovi, Manfred; Westhofen, Martin

2004-07-01

Introduction: Since the early 1980's, a considerable number of different laser systems have been introduced into reconstructive middle ear surgery. Depending on the ablation mode, however, pressure transients or thermal load to inner ear structures continue to be subject to discussion. Material and methods: We examined single spot ablations by a nanosecond-pulsed, frequency-tripled Nd:YAG-Laser (355 nm, beam diameter 10 μm, pulse rate 2 kHz, power 250 mW) on isolated human mallei. In a second set-up, a similar system (355 nm, beam diameter 20 μm, pulse rate 10 kHz, power 160-1500 mW) was coupled to a scanner to examine the morphology of bone surface ablation over an area of 1mm2. A third set-up employed a femtosecond-pulsed CrLiSAF-Oscillator (850 nm, pulse duration 100 fs, pulse energy 40μJ, beam diameter 36 μm, pulse rate 1 kHz) to compare these results with the former and with those obtained from a commercially available Er:YAG laser for ear surgery (Zeiss ORL E, 2940 nm, single pulse, energy 10-25 mJ). Results: In set-up 1 and 2, thermal effects in terms of marginal carbonization were visible in all single spot ablations of 1 s and longer. With ablations of 0.5 seconds, precise cutting margins with preservation of surrounding tissue could be observed. Cooling with saline solution resulted in no carbonization at 1500 mW and a scan speed of 500 mm/s. Set-up 3 equally showed no carbonization, although scanning times were longer and ablation less pronounced. Conclusion: Ultrashort pulsed laser systems could potentially aid further refinement of reconstructive microsurgery of the middle ear.

Experimental study on ablative stabilization of Rayleigh-Taylor instability of laser-irradiated targets

NASA Astrophysics Data System (ADS)

Shigemori, Keisuke; Sakaiya, Tatsuhiko; Otani, Kazuto; Fujioka, Shinsuke; Nakai, Mitsuo; Azechi, Hiroshi; Shiraga, Hiroyuki; Tamari, Yohei; Okuno, Kazuki; Sunahara, Atsushi; Nagatomo, Hideo; Murakami, Masakatsu; Nishihara, Katsunobu; Izawa, Yasukazu

2004-09-01

Hydrodynamic instabilities are key issues of the physics of inertial confinement fusion (ICF) targets. Among the instabilities, Rayleigh-Taylor (RT) instability is the most important because it gives the largest growth factor in the ICF targets. Perturbations on the laser irradiated surface grow exponentially, but the growth rate is reduced by ablation flow. The growth rate γ is written as Takabe-Betti formula: γ = [kg/(1+kL)]1/2-βkm/pa, where k is wave number of the perturbation, g is acceleration, L is density scale-length, β is a coefficient, m is mass ablation rate per unit surface, and ρa is density at the ablation front. We experimentally measured all the parameters in the formula for polystyrene (CH) targets. Experiments were done on the HIPER laser facility at Institute of Laser Engineering, Osaka University. We found that the β value in the formula is ~ 1.7, which is in good agreements with the theoretical prediction, whereas the β for certain perturbation wavelengths are larger than the prediction. This disagreement between the experiment and the theory is mainly due to the deformation of the cutoff surface, which is created by non-uniform ablation flow from the ablation surface. We also found that high-Z doped plastic targets have multiablation structure, which can reduce the RT growth rate. When a low-Z target with high-Z dopant is irradiated by laser, radiation due to the high-Z dopant creates secondary ablation front deep inside the target. Since, the secondary ablation front is ablated by x-rays, the mass ablation rate is larger than the laser-irradiated ablation surface, that is, further reduction of the RT growth is expected. We measured the RT growth rate of Br-doped polystyrene targets. The experimental results indicate that of the CHBr targets show significantly small growth rate, which is very good news for the design of the ICF targets.

Investigation into the optimum beam shape and fluence for selective ablation of dental calculus at lambda = 400 nm.

PubMed

Schoenly, Joshua E; Seka, Wolf; Rechmann, Peter

2010-01-01

A frequency-doubled Ti:sapphire laser is shown to selectively ablate dental calculus. The optimal transverse shape of the laser beam, including its variability under water-cooling, is determined for selective ablation of dental calculus. Intensity profiles under various water-cooling conditions were optically observed. The 400-nm laser was coupled into a multimode optical fiber using an f = 2.5-cm lens and light-shaping diffuser. Water-cooling was supplied coaxially around the fiber. Five human tooth samples (four with calculus and one pristine) were irradiated perpendicular to the tooth surface while the tooth was moved back and forth at 0.3 mm/second, varying between 20 and 180 iterations. The teeth were imaged before and after irradiation using light microscopy with a flashing blue light-emitting diode (LED). An environmental scanning electron microscope imaged each tooth after irradiation. High-order super-Gaussian intensity profiles are observed at the output of a fiber coiled around a 4-in. diameter drum. Super-Gaussian beams have a more-homogenous fluence distribution than Gaussian beams and have a higher energy efficiency for selective ablation. Coaxial water-cooling does not noticeably distort the intensity distribution within 1 mm from the optical fiber. In contrast, lasers focused to a Gaussian cross section (< or =50-microm diameter) without fiber propagation and cooled by a water spray are heavily distorted and may lead to variable ablation. Calculus is preferentially ablated at high fluences (> or =2 J/cm(2)); below this fluence, stalling occurs because of photo-bleaching of the calculus. Healthy dental hard tissue is not removed at fluences < or =3 J/cm(2). Supplying laser light to a tooth using an optical fiber with coaxial water-cooling is determined to be the most appropriate method when selectively removing calculus with a frequency-doubled Ti:sapphire laser. Fluences over 2 J/cm(2) are required to remove calculus efficiently since photo-bleaching stalls calculus removal below that value.

Investigation Into the Optimum Beam Shape and Fluence for Selective Ablation of Dental Calculus at lambda = 400 nm

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schoenly, J.E.; Seka. W.; Rechmann, P.

A frequency-doubled Ti:sapphire laser is shown to selectively ablate dental calculus. The optimal transverse shape of the laser beam, including its variability under water-cooling, is determined for selective ablation of dental calculus. Intensity profiles under various water-cooling conditions were optically observed. The 400-nm laser was coupled into a multimode optical fiber using an f = 2.5-cm lens and light-shaping diffuser. Water-cooling was supplied coaxially around the fiber. Five human tooth samples (four with calculus and one pristine) were irradiated perpendicular to the tooth surface while the tooth was moved back and forth at 0.3 mm/second, varying between 20 and 180more » iterations. The teeth were imaged before and after irradiation using light microscopy with a flashing blue light-emitting diode (LED). An environmental scanning electron microscope imaged each tooth after irradiation. High-order super-Gaussian intensity profiles are observed at the output of a fiber coiled around a 4-in. diameter drum. Super-Gaussian beams have a morehomogenous fluence distribution than Gaussian beams and have a higher energy efficiency for selective ablation. Coaxial water-cooling does not noticeably distort the intensity distribution within 1 mm from the optical fiber. In contrast, lasers focused to a Gaussian cross section (<=50-mm diameter) without fiber propagation and cooled by a water spray are heavily distorted and may lead to variable ablation. Calculus is preferentially ablated at high fluences (>= 2 J/cm^2); below this fluence, stalling occurs because of photo-bleaching of the calculus. Healthy dental hard tissue is not removed at fluences <=3 J/cm^2. Supplying laser light to a tooth using an optical fiber with coaxial water-cooling is determined to be the most appropriate method when selectively removing calculus with a frequency-doubled Ti:sapphire laser. Fluences over 2 J/cm^2 are required to remove calculus efficiently since photo-bleaching stalls calculus removal below that value.« less

CO2 laser laparoscopic surgery. Adhesiolysis, salpingostomy, laser uterine nerve ablation and tubal pregnancy.

PubMed

Donnez, J; Nisolle, M

1989-09-01

Used endoscopically, the CO2 laser offers some advantages over other operative techniques for endometriosis and adhesions but, in spite of the continuing development of new instrumentation there are still problems with the system. The technique needs specialized equipment requiring ongoing biomedical maintenance and specialized technical care in the operating room. Some problems such as the intraperitoneal accumulation of smoke, gas leakage, and difficulty with maintenance of proper beam alignment still occur. In spite of these problems the advantages are numerous: the system allows precise bloodless destruction of diseased tissue and eliminates the risks of cautery. In the hands of an experienced laparoscopist, it appears safe and effective in vaporization of endometriotic lesions, utero-sacral neurectomy, adhesiolysis and salpingostomy. The judicious use of these techniques, combined with carefully planned further investigations by well-trained and experienced laparoscopists and continuing improvements in the delivery systems, will soon reveal the true efficacy of the CO2 laser laparoscope. If studies continue to show pregnancy rates and pain relief to be equivalent to those patients treated by laparotomy, CO2 laser laparoscopy will become the preferred procedure for the management of pelvic endometriosis and its associated adhesions, distal tubal occlusion, pelvic pain and tubal pregnancy. With the exception of using the argon laser to treat endometriosis, the selective absorption characteristic of lasers has not been greatly utilized. While the CO2 laser is heavily absorbed by water and hence vaporizes most cells in a rather indiscriminate fashion, this is not true for other wavelengths, such as argon, Nd-YAG, KTP, krypton, xenon, copper and gold vapour lasers. The energy form of each of these lasers has different properties of penetration, absorption, reflection and heat dissipation. Many of these lasers have not yet been evaluated in human subjects. An exciting, although not new, area of possible laser application involves the use of photosensitizers and fluorescing agents (Dougherty et al, 1978). Some recent experimental studies (Schellhas and Schneider, 1986; Schneider et al, 1988) may lead to new therapeutic possibilities. The surgical laser is not, however, a panacea. Only controlled trials carried out carefully over the next few years will clearly define its potential. In the meantime it is incumbent upon all of us to investigate the clinical, gynaecological and surgical applications in a careful, methodical and scientific manner.

Formation of 238U16O and 238U18O observed by time-resolved emission spectroscopy subsequent to laser ablation

NASA Astrophysics Data System (ADS)

Weisz, David G.; Crowhurst, Jonathan C.; Siekhaus, Wigbert J.; Rose, Timothy P.; Koroglu, Batikan; Radousky, Harry B.; Zaug, Joseph M.; Armstrong, Michael R.; Isselhardt, Brett H.; Savina, Michael R.; Azer, Magdi; Finko, Mikhail S.; Curreli, Davide

2017-07-01

We have measured vibronic emission spectra of an oxide of uranium formed after laser ablation of the metal in gaseous oxygen. Specifically, we have measured the time-dependent relative intensity of a band located at approximately 593.6 nm in 16O2. This band grew in intensity relative to neighboring atomic features as a function time in an oxygen environment but was relatively invariant with time in argon. In addition, we have measured the spectral shift of this band in an 18O2 atmosphere. Based on this shift, and by comparison with earlier results obtained from free-jet expansion and laser excitation, we can confirm that the oxide in question is UO, consistent with recent reports based on laser ablation in 16O2 only.

A Capillary Absorption Spectrometer for Stable Carbon Isotope Ratio (13C/12C) Analysis in Very Small Samples

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kelly, James F.; Sams, Robert L.; Blake, Thomas A.

2012-02-06

A capillary absorption spectrometer (CAS) suitable for IR laser isotope analysis of small CO{sub 2} samples is presented. The system employs a continuous-wave (cw) quantum cascade laser to study nearly adjacent rovibrational transitions of different isotopologues of CO{sub 2} near 2307 cm{sup -1} (4.34 {mu}m). This initial CAS system can achieve relative isotopic precision of about 10 ppm {sup 13}C, or {approx}1{per_thousand} (per mil in delta notation relative to Vienna Pee Dee Belemnite) with 20-100 picomoles of entrained sample within the hollow waveguide for CO{sub 2} concentrations {approx}400 to 750 ppm. Isotopic analyses of such gas fills in a 1-mmmore » ID hollow waveguide of 0.8 m overall physical path length can be carried out down to {approx}2 Torr. Overall {sup 13}C/{sup 12}C ratios can be calibrated to {approx}2{per_thousand} accuracy with diluted CO{sub 2} standards. A novel, low-cost method to reduce cw-fringing noise resulting from multipath distortions in the hollow waveguide is presented, which allows weak absorbance features to be studied at the few ppm level (peak-to-rms) after 1,000 scans are co-added in {approx}10 sec. The CAS is meant to work directly with converted CO{sub 2} samples from a Laser Ablation-Catalytic-Combustion (LA CC) micro-sampler to provide {sup 13}C/{sup 12}C ratios of small biological isolates with spatial resolutions {approx}50 {mu}m.« less

Effect of parameters on picosecond laser ablation of Cr12MoV cold work mold steel

NASA Astrophysics Data System (ADS)

Wu, Baoye; Liu, Peng; Zhang, Fei; Duan, Jun; Wang, Xizhao; Zeng, Xiaoyan

2018-01-01

Cr12MoV cold work mold steel, which is a difficult-to-machining material, is widely used in the mold and dye industry. A picosecond pulse Nd:YVO4 laser at 1064 nm was used to conduct the study. Effects of operation parameters (i.e., laser fluence, scanning speed, hatched space and number of scans) were studied on ablation depth and quality of Cr12MoV at the repetition rate of 20 MHz. The experimental results reveal that all the four parameters affect the ablation depth significantly. While the surface roughness depends mainly on laser fluence or scanning speed and secondarily on hatched space or number of scans. For laser fluence and scanning speed, three distinct surface morphologies were observed experiencing transition from flat (Ra < 1.40 μm) to bumpy (Ra = 1.40 - 2.40 μm) eventually to rough (Ra > 2.40 μm). However, for hatched space and number of scan, there is a small bumpy and rough zone or even no rough zone. Mechanisms including heat accumulation, plasma shielding and combustion reaction effects are proposed based on the ablation depth and processing morphology. By appropriate management of the laser fluence and scanning speed, high ablation depth with low surface roughness can be obtained at small hatched space and high number of scans.

A high-throughput comparative characterization of laser-induced soft tissue damage using 3D digital microscopy.

PubMed

Das, Debobrato; Reed, Stephanie; Klokkevold, Perry R; Wu, Benjamin M

2013-02-01

3D digital microscopy was used to develop a rapid alternative approach to quantify the effects of specific laser parameters on soft tissue ablation and charring in vitro without the use of conventional tissue processing techniques. Two diode lasers operating at 810 and 980 nm wavelengths were used to ablate three tissue types (bovine liver, turkey breast, and bovine muscle) at varying laser power (0.3, 1.0, and 2.0 W) and velocities (1-50 mm/s). Spectrophotometric analyses were performed on each tissue to determine tissue-specific absorption coefficients and were considered in creating wavelength-dependent energy attenuation models to evaluate minimum heat of tissue ablations. 3D surface contour profiles characterizing tissue damage revealed that ablation depth and tissue charring increased with laser power and decreased with lateral velocity independent of wavelength and tissue type. While bovine liver ablation and charring were statistically higher at 810 than 980 nm (p < 0.05), turkey breast and bovine muscle ablated and charred more at 980 than 810 nm (p < 0.05). Spectrophotometric analysis revealed that bovine liver tissue had a greater tissue-specific absorption coefficient at 810 than 980 nm, while turkey breast and bovine muscle had a larger absorption coefficient at 980 nm (p < 0.05). This rapid 3D microscopic analysis of robot-driven laser ablation yielded highly reproducible data that supported well-defined trends related to laser-tissue interactions and enabled high throughput characterization of many laser-tissue permutations. Since 3D microscopy quantifies entire lesions without altering the tissue specimens, conventional and immunohistologic techniques can be used, if desired, to further interrogate specific sections of the digitized lesions.

The effect of ultrafast laser wavelength on ablation properties and implications on sample introduction in inductively coupled plasma mass spectrometry

PubMed Central

LaHaye, N. L.; Harilal, S. S.; Diwakar, P. K.; Hassanein, A.; Kulkarni, P.

2015-01-01

We investigated the role of femtosecond (fs) laser wavelength on laser ablation (LA) and its relation to laser generated aerosol counts and particle distribution, inductively coupled plasma-mass spectrometry (ICP-MS) signal intensity, detection limits, and elemental fractionation. Four different NIST standard reference materials (610, 613, 615, and 616) were ablated using 400 nm and 800 nm fs laser pulses to study the effect of wavelength on laser ablation rate, accuracy, precision, and fractionation. Our results show that the detection limits are lower for 400 nm laser excitation than 800 nm laser excitation at lower laser energies but approximately equal at higher energies. Ablation threshold was also found to be lower for 400 nm than 800 nm laser excitation. Particle size distributions are very similar for 400 nm and 800 nm wavelengths; however, they differ significantly in counts at similar laser fluence levels. This study concludes that 400 nm LA is more beneficial for sample introduction in ICP-MS, particularly when lower laser energies are to be used for ablation. PMID:26640294

Cartilage ablation studies using mid-IR free electron laser

NASA Astrophysics Data System (ADS)

Youn, Jong-In; Peavy, George M.; Venugopalan, Vasan

2005-04-01

The ablation rate of articular cartilage and fibrocartilage (meniscus), were quantified to examine wavelength and tissue-composition dependence of ablation efficiency for selected mid-infrared wavelengths. The wavelengths tested were 2.9 um (water dominant absorption), 6.1 (protein and water absorption) and 6.45 um (protein dominant absorption) generated by the Free Electron Laser (FEL) at Vanderbilt University. The measurement of tissue mass removal using a microbalance during laser ablation was conducted to determine the ablation rates of cartilage. The technique can be accurate over methods such as profilometer and histology sectioning where tissue surface and the crater morphology may be affected by tissue processing. The ablation efficiency was found to be dependent upon the wavelength. Both articular cartilage and meniscus (fibrocartilage) ablations at 6.1 um were more efficient than those at the other wavelengths evaluated. We observed the lowest ablation efficiency of both types of cartilage with the 6.45 um wavelength, possibly due to the reduction in water absorption at this wavelength in comparison to the other wavelengths that were evaluated.

Soft tissue molding technique in cleft lip and palate patient using laser surgery in combination with orthodontic appliance: A case report.

PubMed

Theerasopon, Pornpat; Wangsrimongkol, Tasanee; Sattayut, Sajee

2017-03-31

Although surgical treatment protocols for cleft lip and palate patients have been established, many patients still have some soft tissue defects after complete healing from surgical interventions. These are excess soft tissue, high attached fraena and firmed tethering scares. These soft tissue defects resulted shallowing of vestibule, restricted tooth movement, compromised periodontal health and trended to limit the maxillary growth. The aim of this case report was to present a method of correcting soft tissue defects after conventional surgery in cleft lip and palate patient by using combined laser surgery and orthodontic appliance. A bilateral cleft lip and palate patient with a clinical problem of shallow upper anterior vestibule after alveolar bone graft received a vestibular extension by using CO 2 laser with ablation and vaporization techniques at 4 W and continuous wave. A customized orthodontic appliance, called a buccal shield, was placed immediately after surgery and retained for 1 month to 3 months until complete soft tissue healing. The procedures were performed 2 episodes. Both interventions used the same CO 2 laser procedure. The first treatment resulted in partial re-attachment of soft tissue at surgical area. The second laser operation with the proper design of buccal shield providing passive contact with more extended flange resulting in a favorable outcome from 1 year follow up. Then the corrective orthodontic treatment could be continued effectively. The CO 2 laser surgery was a proper treatment for correcting soft tissue defects and the design of buccal shield was a key for success in molding surgical soft tissue.

Ablation of film stacks in solar cell fabrication processes

DOEpatents

Harley, Gabriel; Kim, Taeseok; Cousins, Peter John

2013-04-02

A dielectric film stack of a solar cell is ablated using a laser. The dielectric film stack includes a layer that is absorptive in a wavelength of operation of the laser source. The laser source, which fires laser pulses at a pulse repetition rate, is configured to ablate the film stack to expose an underlying layer of material. The laser source may be configured to fire a burst of two laser pulses or a single temporally asymmetric laser pulse within a single pulse repetition to achieve complete ablation in a single step.

Permanent fine tuning of silicon microring devices by femtosecond laser surface amorphization and ablation.

PubMed

Bachman, Daniel; Chen, Zhijiang; Fedosejevs, Robert; Tsui, Ying Y; Van, Vien

2013-05-06

We demonstrate the fine tuning capability of femtosecond laser surface modification as a permanent trimming mechanism for silicon photonic components. Silicon microring resonators with a 15 µm radius were irradiated with single 400 nm wavelength laser pulses at varying fluences. Below the laser ablation threshold, surface amorphization of the crystalline silicon waveguides yielded a tuning rate of 20 ± 2 nm/J · cm(-2)with a minimum resonance wavelength shift of 0.10nm. Above that threshold, ablation yielded a minimum resonance shift of -1.7 nm. There was some increase in waveguide loss for both trimming mechanisms. We also demonstrated the application of the method by using it to permanently correct the resonance mismatch of a second-order microring filter.

Fast and automatic depth control of iterative bone ablation based on optical coherence tomography data

NASA Astrophysics Data System (ADS)

Fuchs, Alexander; Pengel, Steffen; Bergmeier, Jan; Kahrs, Lüder A.; Ortmaier, Tobias

2015-07-01

Laser surgery is an established clinical procedure in dental applications, soft tissue ablation, and ophthalmology. The presented experimental set-up for closed-loop control of laser bone ablation addresses a feedback system and enables safe ablation towards anatomical structures that usually would have high risk of damage. This study is based on combined working volumes of optical coherence tomography (OCT) and Er:YAG cutting laser. High level of automation in fast image data processing and tissue treatment enables reproducible results and shortens the time in the operating room. For registration of the two coordinate systems a cross-like incision is ablated with the Er:YAG laser and segmented with OCT in three distances. The resulting Er:YAG coordinate system is reconstructed. A parameter list defines multiple sets of laser parameters including discrete and specific ablation rates as ablation model. The control algorithm uses this model to plan corrective laser paths for each set of laser parameters and dynamically adapts the distance of the laser focus. With this iterative control cycle consisting of image processing, path planning, ablation, and moistening of tissue the target geometry and desired depth are approximated until no further corrective laser paths can be set. The achieved depth stays within the tolerances of the parameter set with the smallest ablation rate. Specimen trials with fresh porcine bone have been conducted to prove the functionality of the developed concept. Flat bottom surfaces and sharp edges of the outline without visual signs of thermal damage verify the feasibility of automated, OCT controlled laser bone ablation with minimal process time.

Non-Ablative Fractional Laser to Facilitate Transdermal Delivery.

PubMed

Ganti, Sindhu S; Banga, Ajay K

2016-11-01

The advances in laser technology have led to its rapidly expanding applications in dermatology. This study aims at the novel use of a non-ablative fractional laser to enhance transdermal permeation of diclofenac sodium and sumatriptan succinate. The effects of the laser on skin were characterized visually with dye binding, scanning electron microscopy, pore permeability index, and histology. In vitro transdermal permeation of drugs through laser treated and untreated human dermatomed skin was analyzed over 24 h and quantified by HPLC. Drug transport through untreated skin resulted in transdermal delivery of 72.61 μg/cm 2 ± 50.35 and 22.80 ± 0.64 μg/cm 2 of diclofenac sodium and sumatriptan succinate, respectively. Laser treatment of skin significantly increased (p < 0.005) delivery of diclofenac sodium to 575.66 ± 207.18 μg/cm 2 and sumatriptan succinate to 498.32 ± 97.54 μg/cm 2 . This is a first of its kind study that demonstrates the use of 1410 nm non-ablative fractional laser to enhance transdermal permeation of 2 small molecular weight drugs. Copyright © 2016 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

Laser inscription of pseudorandom structures for microphotonic diffuser applications.

PubMed

Alqurashi, Tawfiq; Alhosani, Abdulla; Dauleh, Mahmoud; Yetisen, Ali K; Butt, Haider

2018-04-19

Optical diffusers provide a solution for a variety of applications requiring a Gaussian intensity distribution including imaging systems, biomedical optics, and aerospace. Advances in laser ablation processes have allowed the rapid production of efficient optical diffusers. Here, we demonstrate a novel technique to fabricate high-quality glass optical diffusers with cost-efficiency using a continuous CO2 laser. Surface relief pseudorandom microstructures were patterned on both sides of the glass substrates. A numerical simulation of the temperature distribution showed that the CO2 laser drills a 137 μm hole in the glass for every 2 ms of processing time. FFT simulation was utilized to design predictable optical diffusers. The pseudorandom microstructures were characterized by optical microscopy, Raman spectroscopy, and angle-resolved spectroscopy to assess their chemical properties, optical scattering, transmittance, and polarization response. Increasing laser exposure and the number of diffusing surfaces enhanced the diffusion and homogenized the incident light. The recorded speckle pattern showed high contrast with sharp bright spot free diffusion in the far field view range (250 mm). A model of glass surface peeling was also developed to prevent its occurrence during the fabrication process. The demonstrated method provides an economical approach in fabricating optical glass diffusers in a controlled and predictable manner. The produced optical diffusers have application in fibre optics, LED systems, and spotlights.

In-situ tomographic observation of tissue surface during laser ablation

NASA Astrophysics Data System (ADS)

Haruna, Masamitsu; Konoshita, Ryuh; Ohmi, Masato; Kunizawa, Naomi; Miyachi, Mayumi

2001-07-01

In laser ablation of tissues, tomography of the tissue surface is necessary for measurement of the crater depth and observation of damage of the surrounding tissue. We demonstrate here OCT images of craters made by UV laser ablation of different tissues. The maximum depth of a crater is found among several OCT images, and then the ablation rate is determined. The conventional OCT of the spatial resolution of 15 μm was used in our experiment, but OCT of the resolution of the order of 1 μm is required because the ablation rate is usually a few microns per pulse. Such a high-resolution OCT is also demonstrated in this paper, where the light source is a halogen lamp. Combination of laser ablation and OCT will lead to in situ tomographic observation of tissue surface during laser ablation, which should allow us to develop new laser surgeries.

Excimer laser calibration system.

PubMed

Gottsch, J D; Rencs, E V; Cambier, J L; Hall, D; Azar, D T; Stark, W J

1996-01-01

Excimer laser photoablation for refractive and therapeutic keratectomies has been demonstrated to be feasible and practicable. However, corneal laser ablations are not without problems, including the delivery and maintenance of a homogeneous beam. We have developed an excimer laser calibration system capable of characterizing a laser ablation profile. Beam homogeneity is determined by the analysis of a polymethylmethacrylate (PMMA)-based thin-film using video capture and image processing. The ablation profile is presented as a color-coded map. Interpolation of excimer calibration system analysis provides a three-dimensional representation of elevation profiles that correlates with two-dimensional scanning profilometry. Excimer calibration analysis was performed before treating a monkey undergoing phototherapeutic keratectomy and two human subjects undergoing myopic spherocylindrical photorefractive keratectomy. Excimer calibration analysis was performed before and after laser refurbishing. Laser ablation profiles in PMMA are resolved by the excimer calibration system to .006 microns/pulse. Correlations with ablative patterns in a monkey cornea were demonstrated with preoperative and postoperative keratometry using corneal topography, and two human subjects using video-keratography. Excimer calibration analysis predicted a central-steep-island ablative pattern with the VISX Twenty/Twenty laser, which was confirmed by corneal topography immediately postoperatively and at 1 week after reepithelialization in the monkey. Predicted central steep islands in the two human subjects were confirmed by video-keratography at 1 week and at 1 month. Subsequent technical refurbishing of the laser resulted in a beam with an overall increased ablation rate measured as microns/pulse with a donut ablation profile. A patient treated after repair of the laser electrodes demonstrated no central island. This excimer laser calibration system can precisely detect laser-beam ablation profiles. The calibration system correctly predicted central islands after excimer photoablation in a treated monkey cornea and in two treated human subjects. Detection of excimer-laser-beam ablation profiles may be useful for precise calibration of excimer lasers before human photorefractive and therapeutic surgery.

Simulation of the impact of refractive surgery ablative laser pulses with a flying-spot laser beam on intrasurgery corneal temperature.

PubMed

Shraiki, Mario; Arba-Mosquera, Samuel

2011-06-01

To evaluate ablation algorithms and temperature changes in laser refractive surgery. The model (virtual laser system [VLS]) simulates different physical effects of an entire surgical process, simulating the shot-by-shot ablation process based on a modeled beam profile. The model is comprehensive and directly considers applied correction; corneal geometry, including astigmatism; laser beam characteristics; and ablative spot properties. Pulse lists collected from actual treatments were used to simulate the temperature increase during the ablation process. Ablation efficiency reduction in the periphery resulted in a lower peripheral temperature increase. Steep corneas had lesser temperature increases than flat ones. The maximum rise in temperature depends on the spatial density of the ablation pulses. For the same number of ablative pulses, myopic corrections showed the highest temperature increase, followed by myopic astigmatism, mixed astigmatism, phototherapeutic keratectomy (PTK), hyperopic astigmatism, and hyperopic treatments. The proposed model can be used, at relatively low cost, for calibration, verification, and validation of the laser systems used for ablation processes and would directly improve the quality of the results.

Safe and effective one-session fractional skin resurfacing using a carbon dioxide laser device in super-pulse mode: a clinical and histologic study.

PubMed

Trelles, Mario A; Shohat, Michael; Urdiales, Fernando

2011-02-01

Carbon dioxide (CO(2)) laser ablative fractional resurfacing produces skin damage, with removal of the epidermis and variable portions of the dermis as well as associated residual heating, resulting in new collagen formation and skin tightening. The nonresurfaced epidermis helps tissue to heal rapidly, with short-term postoperative erythema. The results for 40 patients (8 men and 32 women) after a single session of a fractional CO(2) resurfacing mode were studied. The treatments included resurfacing of the full face, periocular upper lip, and residual acne scars. The patients had skin prototypes 2 to 4 and wrinkle degrees 1 to 3. The histologic effects, efficacy, and treatment safety in various clinical conditions and for different phototypes are discussed. The CO(2) laser for fractional treatment is used in super-pulse mode. The beam is split by a lens into several microbeams, and super-pulse repetition is limited by the pulse width. The laser needs a power adaptation to meet the set fluence per microbeam. Laser pulsing can operate repeatedly on the same spot or be moved randomly over the skin, using several passes to achieve a desired residual thermal effect. Low, medium, and high settings are preprogrammed in the device, and they indicate the strength of resurfacing. A single treatment was given with the patient under topical anesthesia. However, the anesthesia was injected on areas of scar tissue. Medium settings (2 Hz, 30 W, 60 mJ) were used, and two passes were made for dark skins and degree 1 wrinkles. High settings (2 Hz, 60 W, 120 mJ) were used, and three passes were made for degree 3 wrinkles and scar tissue. Postoperatively, resurfaced areas were treated with an ointment of gentamycin, Retinol Palmitate, and DL-methionine (Novartis; Farmaceutics, S.A., Barcelona, Spain). Once epithelialization was achieved, antipigment and sun protection agents were recommended. Evaluations were performed 15 days and 2 months after treatment by both patients and clinicians. Treatment improved wrinkle aspect and scar condition, and no patient reported adverse effects or complications, irrespective of skin type, except for plaques of erythema in areas that received extra laser passes, which were not seen at the 2-month assessment. The results evaluated by clinicians were very much in correlation with those of patients. Immediately after treatment, vaporization was produced by stacked pulses, with clear ablation and collateral heat coagulation. An increased number of random pulses removed more epidermis, and with denser pulses per area, a thermal deposit was noted histologically. At 2 months, a thicker, multicelluar epidermis and an evident increase in collagen were observed. Fractional CO(2) laser permits a variety of resurfacing settings that obtain safe, effective skin rejuvenation and correct scar tissue in a single treatment.

Fractional versus ablative erbium:yttrium-aluminum-garnet laser resurfacing for facial rejuvenation: an objective evaluation.

PubMed

El-Domyati, Moetaz; Abd-El-Raheem, Talal; Abdel-Wahab, Hossam; Medhat, Walid; Hosam, Wael; El-Fakahany, Hasan; Al Anwer, Mustafa

2013-01-01

Laser is one of the main tools for skin resurfacing. Erbium:yttrium-aluminum-garnet (Er:YAG) was the second ablative laser, after carbon dioxide, emitting wavelength of 2940 nm. Fractional laser resurfacing has been developed to overcome the drawbacks of ablative lasers. We aimed to objectively evaluate the histopathological and immunohistochemical effects of Er:YAG 2940-nm laser for facial rejuvenation (multiple sessions of fractional vs single session of ablative Er:YAG laser). Facial resurfacing with single-session ablative Er:YAG laser was performed on 6 volunteers. Another 6 were resurfaced using fractional Er:YAG laser (4 sessions). Histopathological (hematoxylin-eosin, orcein, Masson trichrome, and picrosirius red stains) and immunohistochemical assessment for skin biopsy specimens were done before laser resurfacing and after 1 and 6 months. Histometry for epidermal thickness and quantitative assessment for neocollagen formation; collagen I, III, and VII; elastin; and tropoelastin were done for all skin biopsy specimens. Both lasers resulted in increased epidermal thickness. Dermal collagen showed increased neocollagen formation with increased concentration of collagen types I, III, and VII. Dermal elastic tissue studies revealed decreased elastin whereas tropoelastin concentration increased after laser resurfacing. Neither laser showed significant difference between their effects clinically and on dermal collagen. Changes in epidermal thickness, elastin, and tropoelastin were significantly more marked after ablative laser. The small number of patients is a limitation, yet the results show significant improvement. Multiple sessions of fractional laser have comparable effects to a single session of ablative Er:YAG laser on dermal collagen but ablative laser has more effect on elastic tissue and epidermis. Copyright © 2012 American Academy of Dermatology, Inc. Published by Mosby, Inc. All rights reserved.

Time-of-flight mass spectrometry of laser exploding foil initiated PETN samples

NASA Astrophysics Data System (ADS)

Fajardo, Mario E.; Molek, Christopher D.; Fossum, Emily C.

2017-01-01

We report the results of time-of-flight mass spectrometry (TOFMS) measurements of the gaseous products of thin-film pentaerythritol tetranitrate [PETN, C(CH2NO3)4] samples reacting in vacuo. The PETN sample spots are produced by masked physical vapor deposition [A.S. Tappan, et al., AIP Conf. Proc. 1426, 677 (2012)] onto a first-surface aluminum mirror. A pulsed laser beam imaged through the soda lime glass mirror substrate converts the aluminum layer into a high-temperature high-pressure plasma which initiates chemical reactions in the overlying PETN sample. We had previously proposed [E.C. Fossum, et al., AIP Conf. Proc. 1426, 235 (2012)] to exploit differences in gaseous product chemical identities and molecular velocities to provide a chemically-based diagnostic for distinguishing between "detonation-like" and deflagration responses. Briefly: we expect in-vacuum detonations to produce hyperthermal (v˜10 km/s) thermodynamically-stable products such as N2, CO2, and H2O, and for deflagrations to produce mostly reaction intermediates, such as NO and NO2, with much slower molecular velocities - consistent with the expansion-quenched thermal decomposition of PETN. We observe primarily slow reaction intermediates (NO2, CH2NO3) at low laser pulse energies, the appearance of NO at intermediate laser pulse energies, and the appearance of hyperthemal CO/N2 at mass 28 amu at the highest laser pulse energies. However, these results are somewhat ambiguous, as the NO, NO2, and CH2NO3 intermediates persist and all species become hyperthermal at the higher laser pulse energies. Also, the purported CO/N2 signal at 28 amu may be contaminated by silicon ablated from the glass mirror substrate. We plan to mitigate these problems in future experiments by adopting the "Buelow" sample configuration which employs an intermediate foil barrier to shield the energetic material from the laser and the laser driven plasma [S.J. Buelow, et al., AIP Conf. Proc. 706, 1377 (2003)].

Controlling dental enamel-cavity ablation depth with optimized stepping parameters along the focal plane normal using a three axis, numerically controlled picosecond laser.

PubMed

Yuan, Fusong; Lv, Peijun; Wang, Dangxiao; Wang, Lei; Sun, Yuchun; Wang, Yong

2015-02-01

The purpose of this study was to establish a depth-control method in enamel-cavity ablation by optimizing the timing of the focal-plane-normal stepping and the single-step size of a three axis, numerically controlled picosecond laser. Although it has been proposed that picosecond lasers may be used to ablate dental hard tissue, the viability of such a depth-control method in enamel-cavity ablation remains uncertain. Forty-two enamel slices with approximately level surfaces were prepared and subjected to two-dimensional ablation by a picosecond laser. The additive-pulse layer, n, was set to 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70. A three-dimensional microscope was then used to measure the ablation depth, d, to obtain a quantitative function relating n and d. Six enamel slices were then subjected to three dimensional ablation to produce 10 cavities, respectively, with additive-pulse layer and single-step size set to corresponding values. The difference between the theoretical and measured values was calculated for both the cavity depth and the ablation depth of a single step. These were used to determine minimum-difference values for both the additive-pulse layer (n) and single-step size (d). When the additive-pulse layer and the single-step size were set 5 and 45, respectively, the depth error had a minimum of 2.25 μm, and 450 μm deep enamel cavities were produced. When performing three-dimensional ablating of enamel with a picosecond laser, adjusting the timing of the focal-plane-normal stepping and the single-step size allows for the control of ablation-depth error to the order of micrometers.

Capabilities of laser ablation mass spectrometry in the differentiation of natural and artificial opal gemstones.

PubMed

Erel, Eric; Aubriet, Frédéric; Finqueneisel, Gisèle; Muller, Jean-François

2003-12-01

The potentialities of laser ablation coupled to ion cyclotron resonance Fourier transform mass spectrometry are evaluated to distinguish natural and artificial opals. The detection of specific species in both ion detection modes leads us to obtain relevant criteria of differentiation. In positive ions, species including hafnium and large amounts of zirconium atoms are found to be specific for artificial opal. In contrast, aluminum, titanium, iron, and rubidium are systematically detected in the study of natural opals. Moreover, some ions allow us to distinguish between natural opal from Australia and from Mexico. Australian gemstone includes specifically strontium, cesium, and barium. Moreover, it is also found that the yield of (H2O)0-1(SiO2)nX- (X- = O-, OH-, KO-, NaO-, SiO2-, AlO1-2-, FeO2-, ZrO2-, and ZrO3-) and (Al2O3)(SiO2)nAlO2- ions depends on the composition of the sample when opals are laser ablated. Ions, which include zirconium oxide species, are characteristics of artificial gem. In contrast, natural opals lead us, after laser ablation, to the production of ions including H2O, Al2O3 motifs and AlO-, KO-, NaO-, and FeO2- species.

In vivo monitoring laser tissue interaction using high resolution Fourier-domain optical coherence tomography

NASA Astrophysics Data System (ADS)

Jo, Hang Chan; Shin, Dong Jun; Ahn, Jin-Chul; Chung, Phil-Sang; Kim, DaeYu

2017-02-01

Laser-induced therapies include laser ablation to remove or cut target tissue by irradiating high-power focused laser beam. These laser treatments are widely used tools for minimally invasive surgery and retinal surgical procedures in clinical settings. In this study, we demonstrate laser tissue interaction images of various sample tissues using high resolution Fourier-domain optical coherence tomography (Fd-OCT). We use a Q-switch diode-pumped Nd:YVO4 nanosecond laser (532nm central wavelength) with a 4W maximum output power at a 20 kHz repetition rate to ablate in vitro and in vivo samples including chicken breast and mouse ear tissues. The Fd-OCT system acquires time-series Bscan images at the same location during the tissue ablation experiments with 532nm laser irradiation. The real-time series of OCT cross-sectional (B-scan) images compare structural changes of 532nm laser ablation using same and different laser output powers. Laser tissue ablation is demonstrated by the width and the depth of the tissue ablation from the B-scan images.

Comparison of Er:YAG and Er:YSGG laser ablation of dental hard tissues

NASA Astrophysics Data System (ADS)

Stock, Karl; Hibst, Raimund; Keller, Ulrich

1997-12-01

To compare ablation quality of Er:YAG and Er:YSGG laser the surface quality, crater shape, mass loss, and temperature development were determined using the same fiber transmission system and handpiece. Similar crater depths for both lasers but greater diameters for the Er:YAG laser were measured. Also mass loss per pulse of the Er:YAG laser exceeds that of the Er:YSGG laser. Temperature development while ablation of dentin is more pronounced for the Er:YSGG laser. The observed minor ablation quality of the Er:YSGG laser can be explained by the lower absorption coefficient of dental hard substances compared to the Er:YAG laser.

Loading of mass spectrometry ion trap with Th ions by laser ablation for nuclear frequency standard application.

PubMed

Borisyuk, Petr V; Derevyashkin, Sergey P; Khabarova, Ksenia Y; Kolachevsky, Nikolay N; Lebedinsky, Yury Y; Poteshin, Sergey S; Sysoev, Alexey A; Tkalya, Evgeny V; Tregubov, Dmitry O; Troyan, Viktor I; Vasiliev, Oleg S; Yakovlev, Valery P; Yudin, Valery I

2017-08-01

We describe an original multisectional quadrupole ion trap aimed to realize nuclear frequency standard based on the unique isomer transition in thorium nucleus. It is shown that the system effectively operates on Th + , Th 2+ and Th 3+ ions produced by laser ablation of metallic thorium-232 target. Laser intensity used for ablation is about 6 GW/cm 2 . Via applying a bias potential to every control voltage including the RF one, we are able not only to manipulate ions within the energy range as wide as 1-500 eV but to specially adjust trap potentials in order to work mainly with ions that belong to energy distribution maximum and therefore to effectively enhance the number of trapped ions. Measurement of energy distributions of 232 Th + , 232 Th 2+ , 232 Th 3+ ions obtained by laser ablation allows us to define optimal potential values for trapping process. Observed number of ions inside trap in dependence on trapping time is found to obey an unusually slow - logarithmic decay law that needs more careful study.

Comparison of holmium:YAG and thulium fiber laser lithotripsy: ablation thresholds, ablation rates, and retropulsion effects.

PubMed

Blackmon, Richard L; Irby, Pierce B; Fried, Nathaniel M

2011-07-01

The holmium:YAG (Ho:YAG) laser lithotriptor is capable of operating at high pulse energies, but efficient operation is limited to low pulse rates (∼10 Hz) during lithotripsy. On the contrary, the thulium fiber laser (TFL) is limited to low pulse energies, but can operate efficiently at high pulse rates (up to 1000 Hz). This study compares stone ablation threshold, ablation rate, and retropulsion for the two different Ho:YAG and TFL operation modes. The TFL (λ = 1908 nm) was operated with pulse energies of 5 to 35 mJ, 500-μs pulse duration, and pulse rates of 10 to 400 Hz. The Ho:YAG laser (λ = 2120 nm) was operated with pulse energies of 30 to 550 mJ, 350-μs pulse duration, and a pulse rate of 10 Hz. Laser energy was delivered through 200- and 270-μm-core optical fibers in contact mode with human calcium oxalate monohydrate (COM) stones for ablation studies and plaster-of-Paris stone phantoms for retropulsion studies. The COM stone ablation threshold for Ho:YAG and TFL measured 82.6 and 20.8 J∕cm(2), respectively. Stone retropulsion with the Ho:YAG laser linearly increased with pulse energy. Retropulsion with TFL was minimal at pulse rates less than 150 Hz, then rapidly increased at higher pulse rates. For minimal stone retropulsion, Ho:YAG operation at pulse energies less than 175 mJ at 10 Hz and TFL operation at 35 mJ at 100 Hz is recommended, with both lasers producing comparable ablation rates. Further development of a TFL operating with both high pulse energies of 100 to 200 mJ and high pulse rates of 100 to 150 Hz may also provide an alternative to the Ho:YAG laser for higher ablation rates, when retropulsion is not a primary concern.

Towards endoscopic ultrafast laser microsurgery of vocal folds

NASA Astrophysics Data System (ADS)

Hoy, Christopher L.; Everett, W. Neil; Yildirim, Murat; Kobler, James; Zeitels, Steven M.; Ben-Yakar, Adela

2012-03-01

Vocal fold scarring is a predominant cause of voice disorders yet lacks a reliable treatment method. The injection of soft biomaterials to improve mechanical compliance of the vocal folds has emerged as a promising treatment. Here, we study the use of precise femtosecond laser microsurgery to ablate subsurface voids, with a goal of eventually creating a plane in dense subepithelial scar tissue into which biomaterials can be injected for their improved localization. Specifically, we demonstrate the ablation of small subepithelial voids in porcine vocal fold tissue up to 120 µm below the surface such that larger voids in the active area of vocal fold mucosa (~3×10 mm2) can eventually be ablated in about 3 min. We use sub-µJ, 776-nm pulses from a compact femtosecond fiber laser system operating at a 500-kHz repetition rate. The use of relatively high repetition rates, with a small number of overlapping pulses, is critical to achieving ablation in a very short time while still avoiding significant heat deposition. Additionally, we use the same laser for nonlinear optical imaging to provide visual feedback of tissue structure and to confirm successful ablation. The ablation parameters, including pulse duration, pulse energy, spot size, and scanning speed, are comparable to the specifications in our recently developed miniaturized femtosecond laser surgery probes, illustrating the feasibility of developing an ultrafast laser surgical instrument.

Numerical Response Surfaces of Volume of Ablation and Retropulsion Amplitude by Settings of Ho:YAG Laser Lithotripter

PubMed Central

Rutherford, Jonathan; Solomon, Metasebya; Cheng, Brian; Xuan, Jason R.; Gong, Jason; Yu, Honggang; Xia, Michael L. D.; Yang, Xirong; Hasenberg, Thomas; Curran, Sean

2018-01-01

Objectives Although laser lithotripsy is now the preferred treatment option for urolithiasis due to shorter operation time and a better stone-free rate, the optimal laser settings for URS (ureteroscopic lithotripsy) for less operation time remain unclear. The aim of this study was to look for quantitative responses of calculus ablation and retropulsion by performing operator-independent experiments to determine the best fit versus the pulse energy, pulse width, and the number of pulses. Methods A lab-built Ho:YAG laser was used as the laser pulse source, with a pulse energy from 0.2 J up to 3.0 J and a pulse width of 150 μs up to 1000 μs. The retropulsion was monitored using a high-speed camera, and the laser-induced craters were evaluated with a 3-D digital microscope. The best fit to the experimental data is done by a design of experiment software. Results The numerical formulas for the response surfaces of ablation speed and retropulsion amplitude are generated. Conclusions The longer the pulse, the less the ablation or retropulsion, while the longer pulse makes the ablation decrease faster than the retropulsion. The best quadratic fit of the response surface for the volume of ablation varied nonlinearly with pulse duration and pulse number. PMID:29707187

A Systematic Study on the Generation of Multimetallic Lanthanide Fullerene ions by Laser Ablation Mass Spectrometry.

PubMed

Wang, Yiyun; Ma, LiFu; Mu, Lei; Ren, Juan; Kong, Xianglei

2018-06-01

Laser ablation masss spectromety has been previously proved to be a powerful tool for studying endohedro metallofullerene (EMF) ions. Our previous study showed the possiblity of forming multi-metallofullerene ions containg more than six metal atoms for La, Y and Lu. Thus, it is important to conduct a systematic study on the generation of multi-metallofullerenes and their distribuitons for all lanthanide elements. Experiments were performed on a 7.0 T Fourier transform ion cyclotron resonance (FT ICR) mass spectrometer. Laser ablation mass spectra were obtained by laser irradiation on mixtures of graphene and MCl 3 on a stainless steel plate, applying a 355 nm Nd: YAG laser with a typical energy of 2.5 mJ/pulse. Reaction test experiments were performed by introducing O 2 into the FT ICR cell with a pulse valve. Multi-metallofullerene ions Ce2-4C2m+, Pr2-4C2m+, Gd2-4C2m+, Nd3C2m+, Dy2-3C2m+, Tb2-7C2m+, Ho2-6C2m+ were observed in the mass spectra. For metal Sm and Eu, no multi-metallofullerene ion was observed. No reaction with O 2 was observed in the reaction experiments, verifying that these species had endohedral structures. For the observed series of multi-metallofullerene ions, tri-metallofullerene ions dominated their mass spectra. The results were further compared with previously generated EMF ions for La, Er, Tm, Yb and Lu. Endohedral lanthanide metallofullerene ions were generated by laser ablation of graphene and the corresponding metal salts MCl 3 (M = Ce, Pr, Nd, Gd, Tb, Dy and Ho) and studied with a FT ICR mass spectrometer. Typically, multi-metallofullerene ions of TbnC2m+2≤n≤780≤2m≤176, Ho6C2m+2≤n≤674≤2m≤162 were observed. The results show that the formation of multi-EMF ions containing lanthanides that have +3 and +4 oxidation states is easier than those containing +2 oxidation states in the process of laser ablation. This article is protected by copyright. All rights reserved.

Laser Ablation Experiments on the Tamdakht H5 Chondrite

NASA Technical Reports Server (NTRS)

White, Susan M.; Stern, Eric

2017-01-01

High-powered lasers were used to induce ablation and to form fusion crusts in the lab on Tamdakht H5 chondrites and basalt. These ground tests were undertaken to improve our understanding, and ultimately improve our abilty to model and predict, meteoroid ablation during atmospheric entry. The infrared fiber laser at the LHMEL facilty, operated in the continuous wave (i.e. non-pulsed) mode, provided radiation surface heat flux at levels similar to meteor entry for these tests. Results are presented from the first round of testing on samples of Tamdakht H5 ordinary chondrite which were ex-posed to entry-relevant heating rates between 2 and 10 kWcm2.

Estimation of Al2O3 critical temperature using a Langmuir probe in laser ablation

NASA Astrophysics Data System (ADS)

Yahiaoui, K.; Abdelli-Messaci, S.; Messaoud Aberkane, S.; Kellou, A.

2016-11-01

Pulsed laser deposition (PLD) has demonstrated its capacity in thin films growing under the moderate laser intensity. But when the laser intensity increases, the presence of droplets on the thin film limits the PLD efficiency such that the process needs an optimization study. In this way, an experimental study has been conducted in order to correlate between the appearance of those droplets and the laser fluence. The comprehension of the physical mechanism during ablation and the control of the deposition parameters allowed to get a safe process. Our experiment consists in measuring the amount of ejected matter from polycrystalline alumina target as a function of the laser fluence when irradiated by a KrF laser. According to laser fluence, several kinds of ablation regimes have been identified. Below a threshold value found as 12 J/cm2, the mechanism of ablation was assigned to normal evaporation, desorption and nonthermal processes. While above this threshold value, the mechanism of ablation was assigned to phase explosion phenomenon which is responsible of droplets formation when the surface temperature approaches the critical temperature T tc. A negative charge collector was used to collect the positive ions in the plume. Their times of flight (TOF) signal were used to estimate the appropriate T tc for alumina target. Ions yield, current as well as kinetic energy were deduced from the TOF signal. Their evolutions show the occurrence of an optical breakdown in the vapor plume which is well correlated with the onset of the phase explosion phenomenon. At 10 J/cm2, the ions velocities collected by the probe have been compared to those obtained from optical emission spectroscopy diagnostic and were discussed. To prove the occurrence of phase explosion by the appearance of droplets, several thin films were elaborated on Si (100) substrate at different laser fluence into vacuum. They have been characterized by scanning electron microscope. The results were well correlated with those obtained with mass measurements as function of laser fluence.

Effects of Plume Hydrodynamics and Oxidation on the Composition of a Condensing Laser-Induced Plasma

DOE PAGES

Weisz, David G.; Crowhurst, Jonathan C.; Finko, Mikhail S.; ...

2018-02-01

High-temperature chemistry in laser ablation plumes leads to vapor-phase speciation, which can induce chemical fractionation during condensation. In this work, using emission spectroscopy acquired after ablation of a SrZrO 3 target, we have experimentally observed the formation of multiple molecular species (ZrO and SrO) as a function of time as the laser ablation plume evolves. Although the stable oxides SrO and ZrO 2 are both refractory, we observed emission from the ZrO intermediate at earlier times than SrO. We deduced the time-scale of oxygen entrainment into the laser ablation plume using an 18O 2 environment by observing the in-growth ofmore » Zr 18O in the emission spectra relative to Zr 16O, which was formed by reaction of Zr with 16O from the target itself. Using temporally resolved plume-imaging, we determined that ZrO formed more readily at early times, volumetrically in the plume, while SrO formed later in time, around the periphery. Lastly, using a simple temperature-dependent reaction model, we have illustrated that the formation sequence of these oxides subsequent to ablation is predictable to first order.« less

Laser ablation efficiency during the production of Ag nanoparticles in ethanol at a low pulse repetition rate (1-10 Hz)

NASA Astrophysics Data System (ADS)

Valverde-Alva, M. A.; García-Fernández, T.; Esparza-Alegría, E.; Villagrán-Muniz, M.; Sánchez-Aké, C.; Castañeda-Guzmán, R.; de la Mora, M. B.; Márquez-Herrera, C. E.; Sánchez Llamazares, J. L.

2016-10-01

We studied the effect of the repetition rate of laser pulses (RRLP) in the range from 1-10 Hz in the production of silver nanoparticles (Ag-NPs) by laser ablation in ethanol. Laser pulses with a duration of 7 ns, a wavelength of 1064 nm and an energy of 60 mJ were used to ablate a 99.99% pure silver target immersed in 10 ml of ethanol. Transmittance analysis and atomic absorption spectroscopy were used to study the silver concentration in the colloidal solutions. The ablation process was studied by measuring the transmission of the laser pulses through the colloid. It is shown that for a fixed number of laser pulses (NLP) the ablation efficiency, in terms of the ablated silver mass per laser pulse, increases with the RRLP. This result contradicts what had previously been established in the literature.

First-principles simulation of the optical response of bulk and thin-film α-quartz irradiated with an ultrashort intense laser pulse

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Kyung-Min; Min Kim, Chul; Moon Jeong, Tae, E-mail: jeongtm@gist.ac.kr

A computational method based on a first-principles multiscale simulation has been used for calculating the optical response and the ablation threshold of an optical material irradiated with an ultrashort intense laser pulse. The method employs Maxwell's equations to describe laser pulse propagation and time-dependent density functional theory to describe the generation of conduction band electrons in an optical medium. Optical properties, such as reflectance and absorption, were investigated for laser intensities in the range 10{sup 10} W/cm{sup 2} to 2 × 10{sup 15} W/cm{sup 2} based on the theory of generation and spatial distribution of the conduction band electrons. The method was applied tomore » investigate the changes in the optical reflectance of α-quartz bulk, half-wavelength thin-film, and quarter-wavelength thin-film and to estimate their ablation thresholds. Despite the adiabatic local density approximation used in calculating the exchange–correlation potential, the reflectance and the ablation threshold obtained from our method agree well with the previous theoretical and experimental results. The method can be applied to estimate the ablation thresholds for optical materials, in general. The ablation threshold data can be used to design ultra-broadband high-damage-threshold coating structures.« less

Phosphorus, Barium and Bioactive Metals (Zn, Cu, Co) in Coral Aragonite: Relationships to Upper Ocean Productivity

NASA Astrophysics Data System (ADS)

Sherrell, R. M.; Lavigne, M. G.; Linsley, B. K.

2006-12-01

Coral records of surface ocean properties related to primary productivity could reveal much about the history of upper ocean biogeochemistry over decades to centuries, but are currently relatively undeveloped. This presentation will explore the utility of high-resolution records of P/Ca, Ba/Ca, and the micronutrient metals Zn/Ca, Cu/Ca, and Co/Ca. Using high sensitivity laser ablation ICP-MS, we have obtained multi-year records of these variables with ~ bi-weekly resolution and seasonal dating for Porites corals from Rarotonga (21S, 159W) and Clipperton Atoll (10N, 109W) Results are compared to data for Porites and Acropora spp. grown in culture at Rutgers University, to explore the applicability of cultured corals for quantifying the effects of seawater chemistry on trace elements in coralline aragonite. The P/Ca results suggest lattice-bound incorporation and encourage the development of a surface ocean PO4 proxy details will be presented by LaVigne et al. elsewhere in this session. At Rarotonga, Ba/Ca shows regular, ~ annual, 2-5 week duration spikes a factor of 2-3 higher than the ~ constant background signal, appearing in austral spring- summer. These are not associated with runoff or authigenic mineral incorporation, and are similar to Ba spikes observed at least twice in the literature. We explore the hypothesis that these signals are related to biogenic organically-bound or barite Ba in the ambient surface water, and might therefore serve as a proxy of phytoplankton bloom intensity during the most productive part of the year. Potential mechanisms of incorporation must include the possibility of suspended particulate elements finding a route to permanent sequestration in the skeleton. Laser ablation values for Zn, and Cu are similar at Rarotonga and Clipperton, and higher by factors of 500 and 15 than literature values for cleaned aragonite analyzed in solution, while our Co/Ca values are the lowest ever determined. Seasonal and shorter scale variations at Rarotonga are muted for Zn, but substantial for Cu and Co, possibly reflecting biologically-driven changes in ambient dissolved metal concentration or speciation. Corals grown in non-metal clean artificial seawater are higher for Zn, but surprisingly lower for Cu and Co. We suggest that the distribution coefficient model of metal incorporation may need to be revised to include aspects of dissolved metal speciation and particulate metal sources. In sum, these results will be used to evaluate the utility of laser ablation data for revealing aspects of open ocean biogeochemistry in the past.

Effect of Various Laser Surface Treatments on Repair Shear Bond Strength of Aged Silorane-Based Composite

PubMed Central

Alizadeh Oskoee, Parnian; Savadi Oskoee, Siavash; Rikhtegaran, Sahand; Pournaghi-Azar, Fatemeh; Gholizadeh, Sarah; Aleyasin, Yasaman; Kasrae, Shahin

2017-01-01

Introduction: Successful repair of composite restorations depends on a strong bond between the old composite and the repair composite. This study sought to assess the repair shear bond strength of aged silorane-based composite following surface treatment with Nd:YAG, Er,Cr:YSGG and CO2 lasers. Methods: Seventy-six Filtek silorane composite cylinders were fabricated and aged by 2 months of water storage at 37°C. The samples were randomly divided into 4 groups (n=19) of no surface treatment (group 1) and surface treatment with Er,Cr:YSGG (group 2), Nd:YAG (group 3) and CO2 (group 4) lasers. The repair composite was applied and the shear bond strength was measured. The data were analyzed using one-way analysis of variance (ANOVA) and Tukey posthoc test. Prior to the application of the repair composite, 2 samples were randomly selected from each group and topographic changes on their surfaces following laser irradiation were studied using a scanning electron microscope (SEM). Seventeen other samples were also fabricated for assessment of cohesive strength of composite. Results: The highest and the lowest mean bond strength values were 8.99 MPa and 6.69 MPa for Er,Cr:YSGG and control groups, respectively. The difference in the repair bond strength was statistically significant between the Er,Cr:YSGG and other groups. Bond strength of the control, Nd:YAG and CO2 groups was not significantly different. The SEM micrographs revealed variable degrees of ablation and surface roughness in laser-treated groups. Conclusion: Surface treatment with Er,Cr:YSGG laser significantly increase the repair bond strength of aged silorane-based composite resin. PMID:29071025

Fractional ablative laser skin resurfacing: a review.

PubMed

Tajirian, Ani L; Tarijian, Ani L; Goldberg, David J

2011-12-01

Ablative laser technology has been in use for many years now. The large side effect profile however has limited its use. Fractional ablative technology is a newer development which combines a lesser side effect profile along with similar efficacy. In this paper we review fractional ablative laser skin resurfacing.

Comparison between different thickness umbrella-shaped expandable radiofrequency electrodes (SuperSlim and CoAccess): Experimental and clinical study

PubMed Central

KODA, MASAHIKO; TOKUNAGA, SHIHO; MATONO, TOMOMITSU; SUGIHARA, TAKAAKI; NAGAHARA, TAKAKAZU; MURAWAKI, YOSHIKAZU

2011-01-01

The purpose of the present study was to compare the size and configuration of the ablation zones created by SuperSlim and CoAccess electrodes, using various ablation algorithms in ex vivo bovine liver and in clinical cases. In the experimental study, we ablated explanted bovine liver using 2 types of electrodes and 4 ablation algorithms (combinations of incremental power supply, stepwise expansion and additional low-power ablation) and evaluated the ablation area and time. In the clinical study, we compared the ablation volume and the shape of the ablation zone between both electrodes in 23 hepatocellular carcinoma (HCC) cases with the best algorithm (incremental power supply, stepwise expansion and additional low-power ablation) as derived from the experimental study. In the experimental study, the ablation area and time by the CoAccess electrode were significantly greater compared to those by the SuperSlim electrode for the single-step (algorithm 1, p=0.0209 and 0.0325, respectively) and stepwise expansion algorithms (algorithm 2, p=0.0002 and <0.0001, respectively; algorithm 3, p= 0.006 and 0.0407, respectively). However, differences were not significant for the additional low-power ablation algorithm. In the clinical study, the ablation volume and time in the CoAccess group were significantly larger and longer, respectively, compared to those in the SuperSlim group (p=0.0242 and 0.009, respectively). Round ablation zones were acquired in 91.7% of the CoAccess group, while irregular ablation zones were obtained in 45.5% of the SuperSlim group (p=0.0428). In conclusion, the CoAccess electrode achieves larger and more uniform ablation zones compared with the SuperSlim electrode, though it requires longer ablation times in experimental and clinical studies. PMID:22977647

Self-limiting and complete oxidation of silicon nanostructures produced by laser ablation in water

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vaccaro, L.; Messina, F.; Camarda, P.

2016-07-14

Oxidized Silicon nanomaterials produced by 1064 nm pulsed laser ablation in deionized water are investigated. High-resolution transmission electron microscopy coupled with energy dispersive X-ray spectroscopy allows to characterize the structural and chemical properties at a sub-nanometric scale. This analysis clarifies that laser ablation induces both self-limiting and complete oxidation processes which produce polycrystalline Si surrounded by a layer of SiO{sub 2} and amorphous fully oxidized SiO{sub 2}, respectively. These nanostructures exhibit a composite luminescence spectrum which is investigated by time-resolved spectroscopy with a tunable laser excitation. The origin of the observed luminescence bands agrees with the two structural typologies: Si nanocrystalsmore » emit a μs-decaying red band; defects of SiO{sub 2} give rise to a ns-decaying UV band and two overlapping blue bands with lifetime in the ns and ms timescale.« less

Formation of 238U 16O and 238U 18O observed by time-resolved emission spectroscopy subsequent to laser ablation

DOE PAGES

Weisz, David G.; Crowhurst, Jonathan C.; Siekhaus, Wigbert J.; ...

2017-07-17

Here, we have measured vibronic emission spectra of an oxide of uranium formed after laser ablation of the metal in gaseous oxygen. Specifically, we have measured the time-dependent relative intensity of a band located at approximately 593.6 nm in 16O 2. This band grew in intensity relative to neighboring atomic features as a function time in an oxygen environment but was relatively invariant with time in argon. In addition, we have measured the spectral shift of this band in an 18O 2 atmosphere. Based on this shift, and by comparison with earlier results obtained from free-jet expansion and laser excitation,more » we can confirm that the oxide in question is UO, consistent with recent reports based on laser ablation in 16O 2 only.« less

Formation of 238U 16O and 238U 18O observed by time-resolved emission spectroscopy subsequent to laser ablation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Weisz, David G.; Crowhurst, Jonathan C.; Siekhaus, Wigbert J.

Here, we have measured vibronic emission spectra of an oxide of uranium formed after laser ablation of the metal in gaseous oxygen. Specifically, we have measured the time-dependent relative intensity of a band located at approximately 593.6 nm in 16O 2. This band grew in intensity relative to neighboring atomic features as a function time in an oxygen environment but was relatively invariant with time in argon. In addition, we have measured the spectral shift of this band in an 18O 2 atmosphere. Based on this shift, and by comparison with earlier results obtained from free-jet expansion and laser excitation,more » we can confirm that the oxide in question is UO, consistent with recent reports based on laser ablation in 16O 2 only.« less

High peak power Q-switched Er:YAG laser with two polarizers and its ablation performance for hard dental tissues.

PubMed

Yang, Jingwei; Wang, Li; Wu, Xianyou; Cheng, Tingqing; Jiang, Haihe

2014-06-30

An electro-optically Q-switched high-energy Er:YAG laser with two polarizers is proposed. By using two Al(2)O(3) polarizing plates and a LiNbO(3) crystal with Brewster angle, the polarization efficiency is significantly improved. As a result, 226 mJ pulse energy with 62 ns pulse width is achieved at the repetition rate of 3 Hz, the corresponding peak power is 3.6 MW. To our knowledge, such a high peak power has not been reported in literature. With our designed laser, in-vitro teeth were irradiated under Q-switched and free-running modes. Results of a laser ablation experiment on hard dental tissue with the high-peak-power laser demonstrates that the Q-switched Er:YAG laser has higher ablation precision and less thermal damage than the free-running Er:YAG laser.

Precision drilling of fused silica with 157-nm excimer laser radiation

NASA Astrophysics Data System (ADS)

Temme, Thorsten; Ostendorf, Andreas; Kulik, Christian; Meyer, Klaus

2003-07-01

μFor drilling fused silica, mechanical techniques like with diamond drills, ultrasonic machining, sand blasting or water jet machining are used. Also chemical techniques like laser assisted wet etching or thermal drilling with CO2-lasers are established. As an extension of these technologies, the drilling of micro-holes in fused silica with VUV laser radiation is presented here. The high absorption of the 157 nm radiation emitted by the F2 excimer laser and the short pulse duration lead to a material ablation with minimised impact on the surrounding material. Contrary to CO2-laser drilling, a molten and solidified phase around the bore can thus be avoided. The high photon energy of 7.9 eV requires either high purity nitrogen flushing or operation in vacuum, which also effects the processing results. Depending on the required precision, the laser can be used for percussion drilling as well as for excimer laser trepanning, by applying rotating masks. Rotating masks are especially used for high aspect ratio drilling with well defined edges and minimised debris. The technology is suitable particularly for holes with a diameter below 200 μm down to some microns in substrates with less than 200 μm thickness, that can not be achieved with mechanical methods. Drilling times in 200 μm fused silica substrates are in the range of ten seconds, which is sufficient to compete with conventional methods while providing similar or even better accuracy.

Skin pre-ablation and laser assisted microjet injection for deep tissue penetration.

PubMed

Jang, Hun-Jae; Yeo, Seonggu; Yoh, Jack J

2017-04-01

For conventional needless injection, there still remain many unresolved issues such as the potential for cross-contamination, poor reliability of targeted delivery dose, and significantly painstaking procedures. As an alternative, the use of microjets generated with Er:YAG laser for delivering small doses with controlled penetration depths has been reported. In this study, a new system with two stages is evaluated for effective transdermal drug delivery. First, the skin is pre-ablated to eliminate the hard outer layer and second, laser-driven microjet penetrates the relatively weaker and freshly exposed epidermis. Each stage of operation shares a single Er:YAG laser that is suitable for skin ablation as well as for the generation of a microjet. In this study, pig skin is selected for quantification of the injection depth based on the two-stage procedure, namely pre-ablation and microjet injection. The three types of pre-ablation devised here consists of bulk ablation, fractional ablation, and fractional-rotational ablation. The number of laser pulses are 12, 18, and 24 for each ablation type. For fractional-rotational ablation, the fractional beams are rotated by 11.25° at each pulse. The drug permeation in the skin is evaluated using tissue marking dyes. The depth of penetration is quantified by a cross sectional view of the single spot injections. Multi-spot injections are also carried out to control the dose and spread of the drug. The benefits of a pre-ablation procedure prior to the actual microjet injection to the penetration is verified. The four possible combinations of injection are (a) microjet only; (b) bulk ablation and microjet injection; (c) fractional ablation and microjet injection; and (d) fractional-rotational ablation and microjet injection. Accordingly, the total depth increases with injection time for all cases. In particular, the total depth of penetration attained via fractional pre-ablation increased by 8 ∼ 11% and that of fractional-rotational pre-ablation increased by 13 ∼ 33%, when compared with the no pre-ablation or microjet only cases. A noticeable point is that the fraction-rotational pre-ablation and microjet result is comparable to the bulk ablation and microjet result of 11 ∼ 42%. The penetration depth underneath ablated stratum corneum (SC) is also measured in order to verify the pre-ablation effect. The penetration depths for each case are (a) 443 ± 104 µm; (b) 625 ± 98 µm; (c) 523 ± 95 µm; and (d) 595 ± 141 µm for microjet only, bulk ablation and microjet, fractional ablation and microjet, and fractional-rotational ablation and microjet, respectively. This is quite beneficial since any healing time associated with ablation is significantly reduced by avoiding hard-core bulk ablation. Thus the bulk pre-ablation and microjet may well be superseded by the less invasive fractiona-rotational ablation followed by the microjet injection. The density of micro-holes is 1.27 number/mm 2 for fractional ablation and 4.84 number/mm 2 for fractional-rotational ablation. The penetration depths measured underneath the ablated SC are 581 µm (fractional ablation and microjet) and 691 µm (fractional-rotational ablation and microjet). Fractional-rotational ablation increases number of micro-holes in a unit area, enabling fast reepithelialization and high drug delivery efficiency. Optimization of system parameters such as ablation time, number of ablations, and injection time will eventually ensure a macromolecule delivery technique with the potential to include vaccines, insulins, and growth hormones, all of which require deeper penetration into the skin. Lasers Surg. Med. 49:387-394, 2017. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

From Laser Desorption to Laser Ablation of Biopolymers

NASA Astrophysics Data System (ADS)

Franz, Hillenkamp

1998-03-01

For selected indications laser ablation and cutting of biological tissues is clinical practice. Preferentially lasers with emission wavelengths in the far UV and the mid IR are used, for which tissue absorption is very high. Morphologically the ablation sites look surprisingly similar for the two wavelength ranges, despite of the very different prim y putative interaction mechanisms. Ablation depth as a function of fluence follows a sigmoidal curve. Even factors below the nominal ablation threshold superficial layers of material get removed from the surface. This is the fluence range for Matrix-Assisted Laser Desorption/Ionization (MALDI). Evidence will be presented which suggest that strong similarities exist between the desorption and ablation processes both for UV- as well as for IR-wavelengths.

Induratio penis plastica (IPP) and laser: a review

NASA Astrophysics Data System (ADS)

Longo, Leonardo; Mancini, S.; Postiglione, M. G.

2002-10-01

The first employments of Laser therapy for I.P.P. came from back to more than twenty years ago. At the beginning it was employed only in the acute forms as analgesic laser laser was used also as anti-inflammatory following the doses of Low Level Laser Therapy. Than the science tried to use the laser effect remodelling phase of the scars, to make the fibrosis regrade in the chronic forms. Tunable laser in small optical fiber was used for ablation of calcified zones with very good results. For the slight forms were used diode laser 660 and 904 nm, alone ir coupling with CO2 laser with large spot. At first some Author used helium-Neon laser 632. Some of these lasers were combined wtih microiontophoresis and ultrasounds therapy in teh same treatment. Now we use 810 nm surgical diode laser in almost all induratio forms. The immediate results and follow up will be discussed. Thanks to these results we could conclude that IPP laser therapy can be effective in most of the clinic forms. Although the used procedure is subject to improvement.

Raman-shifted alexandrite laser for soft tissue ablation in the 6- to 7-µm wavelength range

PubMed Central

Kozub, John; Ivanov, Borislav; Jayasinghe, Aroshan; Prasad, Ratna; Shen, Jin; Klosner, Marc; Heller, Donald; Mendenhall, Marcus; Piston, David W.; Joos, Karen; Hutson, M. Shane

2011-01-01

Prior work with free-electron lasers (FELs) showed that wavelengths in the 6- to 7-µm range could ablate soft tissues efficiently with little collateral damage; however, FELs proved too costly and too complex for widespread surgical use. Several alternative 6- to 7-µm laser systems have demonstrated the ability to cut soft tissues cleanly, but at rates that were much too low for surgical applications. Here, we present initial results with a Raman-shifted, pulsed alexandrite laser that is tunable from 6 to 7 µm and cuts soft tissues cleanly—approximately 15 µm of thermal damage surrounding ablation craters in cornea—and does so with volumetric ablation rates of 2–5 × 10−3 mm3/s. These rates are comparable to those attained in prior successful surgical trials using the FEL for optic nerve sheath fenestration. PMID:21559139

Femtosecond laser induced tunable surface transformations on (111) Si aided by square grids diffraction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Han, Weina; Jiang, Lan; Li, Xiaowei, E-mail: lixiaowei@bit.edu.cn

We report an extra freedom to modulate the femtosecond laser energy distribution to control the surface ablated structures through a copper-grid mask. Due to the reduced deposited pulse energy by changing the scanning speed or the pulse fluence, a sequential evolution of three distinctly different surface patterns with periodic distributions is formed, namely, striped ripple lines, ripple microdots, and surface modification. By changing the scanning speed, the number of the multiple dots in a lattice can be modulated. Moreover, by exploring the ablation process through the copper grid mask, it shows an abnormal enhanced ablation effect with strong dependence ofmore » the diffraction-aided fs laser ablated surface structures on polarization direction. The sensitivity shows a quasi-cosinusoid-function with a periodicity of π/2. Particularly, the connection process of striped ripple lines manifests a preferential formation direction with the laser polarization.« less

Direct writing of tunable multi-wavelength polymer lasers on a flexible substrate.

PubMed

Zhai, Tianrui; Wang, Yonglu; Chen, Li; Zhang, Xinping

2015-08-07

Tunable multi-wavelength polymer lasers based on two-dimensional distributed feedback structures are fabricated on a transparent flexible substrate using interference ablation. A scalene triangular lattice structure was designed to support stable tri-wavelength lasing emission and was achieved through multiple exposure processes. Three wavelengths were controlled by three periods of the compound cavity. Mode competition among different cavity modes was observed by changing the pump fluence. Both a redshift and blueshift of the laser wavelength could be achieved by bending the soft substrate. These results not only provide insight into the physical mechanisms behind co-cavity polymer lasers but also introduce new laser sources and laser designs for white light lasers.

Percutaneous laser ablation of benign and malignant thyroid nodules.

PubMed

Papini, Enrico; Bizzarri, Giancarlo; Pacella, Claudio M

2008-10-01

Percutaneous image-guided procedures, largely based on thermal ablation, are at present under investigation for achieving a nonsurgical targeted cytoreduction in benign and malignant thyroid lesions. In several uncontrolled clinical trials and in two randomized clinical trials, laser ablation has demonstrated a good efficacy and safety for the shrinkage of benign cold thyroid nodules. In hyperfunctioning nodules, laser ablation induced a nearly 50% volume reduction with a variable frequency of normalization of thyroid-stimulating hormone levels. Laser ablation has been tested for the palliative treatment of poorly differentiated thyroid carcinomas, local recurrences or distant metastases. Laser ablation therapy is indicated for the shrinkage of benign cold nodules in patients with local pressure symptoms who are at high surgical risk. The treatment should be performed only by well trained operators and after a careful cytological evaluation. Laser ablation does not seem to be consistently effective in the long-term control of hyperfunctioning thyroid nodules and is not an alternative treatment to 131I therapy. Laser ablation may be considered for the cytoreduction of tumor tissue prior to external radiation therapy or chemotherapy of local or distant recurrences of thyroid malignancy that are not amenable to surgical or radioiodine treatment.

Femtosecond laser lithotripsy: feasibility and ablation mechanism.

PubMed

Qiu, Jinze; Teichman, Joel M H; Wang, Tianyi; Neev, Joseph; Glickman, Randolph D; Chan, Kin Foong; Milner, Thomas E

2010-01-01

Light emitted from a femtosecond laser is capable of plasma-induced ablation of various materials. We tested the feasibility of utilizing femtosecond-pulsed laser radiation (lambda=800 nm, 140 fs, 0.9 mJ/pulse) for ablation of urinary calculi. Ablation craters were observed in human calculi of greater than 90% calcium oxalate monohydrate (COM), cystine (CYST), or magnesium ammonium phosphate hexahydrate (MAPH). Largest crater volumes were achieved on CYST stones, among the most difficult stones to fragment using Holmium:YAG (Ho:YAG) lithotripsy. Diameter of debris was characterized using optical microscopy and found to be less than 20 microm, substantially smaller than that produced by long-pulsed Ho:YAG ablation. Stone retropulsion, monitored by a high-speed camera system with a spatial resolution of 15 microm, was negligible for stones with mass as small as 0.06 g. Peak shock wave pressures were less than 2 bars, measured by a polyvinylidene fluoride (PVDF) needle hydrophone. Ablation dynamics were visualized and characterized with pump-probe imaging and fast flash photography and correlated to shock wave pressures. Because femtosecond-pulsed laser ablates urinary calculi of soft and hard compositions, with micron-sized debris, negligible stone retropulsion, and small shock wave pressures, we conclude that the approach is a promising candidate technique for lithotripsy.

Role of near-field enhancement in plasmonic laser nanoablation using gold nanorods on a silicon substrate.

PubMed

Harrison, R K; Ben-Yakar, Adela

2010-10-11

We present experimental results for the plasmonic laser ablation of silicon with nanoscale features as small as 22 x 66 nm using single near-infrared, femtosecond laser pulses incident on gold nanorods. Near the ablation threshold, these features are photo-imprints of gold nanorod particles positioned on the surface of the silicon and have feature sizes similar to the nanorods. The single rod-shaped ablation pattern matches the enhancement patterns of the Poynting vector magnitude on the surface of silicon, implying that the ablation is a result of the plasmonic enhancement of the incident electromagnetic waves in the near-field of the particles. Interestingly, the ablation pattern is different from the two separated holes at the ends of the nanorod, as would be expected from the electric field--|E|(2) enhancement pattern. We measured the plasmonic ablation threshold fluence to be almost two orders of magnitude less than the femtosecond laser ablation threshold of silica, present in the thin native oxide layer on the surface of silicon. This value also agrees with the enhancement of the Poynting vector of a nanorod on silicon as calculated with electromagnetic simulations. We thus conclude that plasmonic ablation with plasmonic nanoparticles depends directly on the polarization and the value of the near-field enhancement of the Poynting vector and not the square of the electric field as previously suggested.

Ablation-cooled material removal with ultrafast bursts of pulses

NASA Astrophysics Data System (ADS)

Kerse, Can; Kalaycıoğlu, Hamit; Elahi, Parviz; Çetin, Barbaros; Kesim, Denizhan K.; Akçaalan, Önder; Yavaş, Seydi; Aşık, Mehmet D.; Öktem, Bülent; Hoogland, Heinar; Holzwarth, Ronald; Ilday, Fatih Ömer

2016-09-01

The use of femtosecond laser pulses allows precise and thermal-damage-free removal of material (ablation) with wide-ranging scientific, medical and industrial applications. However, its potential is limited by the low speeds at which material can be removed and the complexity of the associated laser technology. The complexity of the laser design arises from the need to overcome the high pulse energy threshold for efficient ablation. However, the use of more powerful lasers to increase the ablation rate results in unwanted effects such as shielding, saturation and collateral damage from heat accumulation at higher laser powers. Here we circumvent this limitation by exploiting ablation cooling, in analogy to a technique routinely used in aerospace engineering. We apply ultrafast successions (bursts) of laser pulses to ablate the target material before the residual heat deposited by previous pulses diffuses away from the processing region. Proof-of-principle experiments on various substrates demonstrate that extremely high repetition rates, which make ablation cooling possible, reduce the laser pulse energies needed for ablation and increase the efficiency of the removal process by an order of magnitude over previously used laser parameters. We also demonstrate the removal of brain tissue at two cubic millimetres per minute and dentine at three cubic millimetres per minute without any thermal damage to the bulk.

Ablation-cooled material removal with ultrafast bursts of pulses.

PubMed

Kerse, Can; Kalaycıoğlu, Hamit; Elahi, Parviz; Çetin, Barbaros; Kesim, Denizhan K; Akçaalan, Önder; Yavaş, Seydi; Aşık, Mehmet D; Öktem, Bülent; Hoogland, Heinar; Holzwarth, Ronald; Ilday, Fatih Ömer

2016-09-01

The use of femtosecond laser pulses allows precise and thermal-damage-free removal of material (ablation) with wide-ranging scientific, medical and industrial applications. However, its potential is limited by the low speeds at which material can be removed and the complexity of the associated laser technology. The complexity of the laser design arises from the need to overcome the high pulse energy threshold for efficient ablation. However, the use of more powerful lasers to increase the ablation rate results in unwanted effects such as shielding, saturation and collateral damage from heat accumulation at higher laser powers. Here we circumvent this limitation by exploiting ablation cooling, in analogy to a technique routinely used in aerospace engineering. We apply ultrafast successions (bursts) of laser pulses to ablate the target material before the residual heat deposited by previous pulses diffuses away from the processing region. Proof-of-principle experiments on various substrates demonstrate that extremely high repetition rates, which make ablation cooling possible, reduce the laser pulse energies needed for ablation and increase the efficiency of the removal process by an order of magnitude over previously used laser parameters. We also demonstrate the removal of brain tissue at two cubic millimetres per minute and dentine at three cubic millimetres per minute without any thermal damage to the bulk.

The effect of laser ablation parameters on optical limiting properties of silver nanoparticles

NASA Astrophysics Data System (ADS)

Gursoy, Irmak; Yaglioglu, Halime Gul

2017-09-01

This paper presents the effect of laser ablation parameters on optical limiting properties of silver nanoparticles. The current applications of lasers such as range finding, guidance, detection, illumination and designation have increased the potential of damaging optical imaging systems or eyes temporary or permanently. The applications of lasers introduce risks for sensors or eyes, when laser power is higher than damage threshold of the detection system. There are some ways to protect these systems such as neutral density (nd) filters, shutters, etc. However, these limiters reduce the total amount of light that gets into the system. Also, response time of these limiters may not be fast enough to prevent damage and cause precipitation in performance due to deprivation of transmission or contrast. Therefore, optical limiting filters are needed that is transparent for low laser intensities and limit or block the high laser intensities. Metal nanoparticles are good candidates for such optical limiting filters for ns pulsed lasers or CW lasers due to their high damage thresholds. In this study we investigated the optical limiting performances of silver nanoparticles produced by laser ablation technique. A high purity silver target immersed in pure water was ablated with a Nd:YAG nanosecond laser at 532 nm. The effect of altering laser power and ablation time on laser ablation efficiency of nanoparticles was investigated experimentally and optimum values were specified. Open aperture Zscan experiment was used to investigate the effect of laser ablation parameters on the optical limiting performances of silver nanoparticles in pure water. It was found that longer ablation time decreases the optical limiting threshold. These results are useful for silver nanoparticles solutions to obtain high performance optical limiters.

High speed pulsed laser cutting of LiCoO2 Li-ion battery electrodes

NASA Astrophysics Data System (ADS)

Lutey, Adrian H. A.; Fortunato, Alessandro; Carmignato, Simone; Fiorini, Maurizio

2017-09-01

Laser cutting of Li-ion battery electrodes represents an alternative to mechanical blanking that avoids complications associated with tool wear and allows assembly of different cell geometries with a single device. In this study, laser cutting of LiCoO2 Li-ion battery electrodes is performed at up to 5m /s with a 1064nm wavelength nanosecond pulsed fiber laser with a maximum average power of 500W and a repetition rate of up to 2MHz . Minimum average cutting power for cathode and anode multi-layer films is established for 12 parameter groups with velocities over the range 1 - 5m /s , varying laser pulse fluence and overlap. Within the tested parameter range, minimum energy per unit cut length is found to decrease with increasing repetition rate and velocity. SEM analysis of the resulting cut edges reveals visible clearance widths in the range 20 - 50 μm , with cut quality found to improve with velocity due to a reduction in lateral heat conduction losses. Raman line map spectra reveal changes in the cathode at 60 μm from the cut edge, where bands at 486cm-1 and 595cm-1 , corresponding to the Eg and A1g modes of LiCoO2 , are replaced with a single wide band centered at 544cm-1 , and evidence of carbon black is no longer present. No changes in Raman spectra are observed in the anode. The obtained results suggest that further improvements in cutting efficiency and quality could be achieved by increasing the repetition rate above 2MHz , thereby improving ablation efficiency of the metallic conductor layers. The laser source utilized in the present study nonetheless represents an immediately available solution for repeatability and throughput that are superior to mechanical blanking.

Flowing atmospheric pressure afterglow combined with laser ablation for direct analysis of compounds separated by thin-layer chromatography.

PubMed

Cegłowski, Michał; Smoluch, Marek; Reszke, Edward; Silberring, Jerzy; Schroeder, Grzegorz

2016-01-01

A thin-layer chromatography-mass spectrometry (TLC-MS) setup for characterization of low molecular weight compounds separated on standard TLC plates has been constructed. This new approach successfully combines TLC separation, laser ablation, and ionization using flowing atmospheric pressure afterglow (FAPA) source. For the laser ablation, a low-priced 445-nm continuous-wave diode laser pointer, with a power of 1 W, was used. The combination of the simple, low-budget laser pointer and the FAPA ion source has made this experimental arrangement broadly available, also for small laboratories. The approach was successfully applied for the characterization of low molecular weight compounds separated on TLC plates, such as a mixture of pyrazole derivatives, alkaloids (nicotine and sparteine), and an extract from a drug tablet consisting of paracetamol, propyphenazone, and caffeine. The laser pointer used was capable of ablating organic compounds without the need of application of any additional substances (matrices, staining, etc.) on the TLC spots. The detection limit of the proposed method was estimated to be 35 ng/cm(2) of a pyrazole derivative.

Femtosecond ablation applied to deep-drilling of hard metals

NASA Astrophysics Data System (ADS)

Bruneau, Sebastien; Hermann, Joerg; Dumitru, Gabriel; Sentis, Marc L.

2004-09-01

Mechanisms responsible for the limitation of the aspect ratio obtained by deep drilling of hard metals are investigated in the present work. Cemented carbide targets have been irradiated with laser pulses of 100 fs duration and 100 μJ maximum energy delivered by a Ti:sapphire laser system. The experiments are carried out in different gas environments (vacuum, air, helium up to atmospheric pressure) with incident laser fluences ranging from 1 to 20 Jcm-2. During deep drilling, the laser-induced ablation plume is characterized by means of in-situ plasma diagnostics. Fast imaging is used to observe the expansion behavior of the plasma plume whereas time- and space-resolved emission spectroscopy is employed to analyze the plasma composition. After irradiation, the laser-produced craters were examined by optical microscopy. A correlation between the ablation plume characteristics and the morphological changes of the mciro-holes is established. The results indicate that nanoclusters, that present a significant part of the ablated material, are responsbile for the alteration of the crater shape in the high laser fluence regime.

Atomistic simulation of laser-pulse surface modification: Predictions of models with various length and time scales

DOE Office of Scientific and Technical Information (OSTI.GOV)

Starikov, Sergey V., E-mail: starikov@ihed.ras.ru; Pisarev, Vasily V.; Joint Institute for High Temperatures, Russian Academy of Sciences, Moscow 125412

2015-04-07

In this work, the femtosecond laser pulse modification of surface is studied for aluminium (Al) and gold (Au) by use of two-temperature atomistic simulation. The results are obtained for various atomistic models with different scales: from pseudo-one-dimensional to full-scale three-dimensional simulation. The surface modification after laser irradiation can be caused by ablation and melting. For low energy laser pulses, the nanoscale ripples may be induced on a surface by melting without laser ablation. In this case, nanoscale changes of the surface are due to a splash of molten metal under temperature gradient. Laser ablation occurs at a higher pulse energymore » when a crater is formed on the surface. There are essential differences between Al ablation and Au ablation. In the first step of shock-wave induced ablation, swelling and void formation occur for both metals. However, the simulation of ablation in gold shows an additional athermal type of ablation that is associated with electron pressure relaxation. This type of ablation takes place at the surface layer, at a depth of several nanometers, and does not induce swelling.« less

Influence of a pulsed CO2 laser operating at 9.4 μm on the surface morphology, reflectivity, and acid resistance of dental enamel below the threshold for melting

NASA Astrophysics Data System (ADS)

Kim, Jin Wan; Lee, Raymond; Chan, Kenneth H.; Jew, Jamison M.; Fried, Daniel

2017-02-01

Below the threshold for laser ablation, the mineral phase of enamel is converted into a purer phase hydroxyapatite with increased acid resistance. Studies suggest the possibility of achieving the conversion without visible surface alteration. In this study, changes in the surface morphology, reflectivity, and acid resistance were monitored with varying irradiation intensity. Bovine enamel specimens were irradiated using a CO2 laser operating at 9.4 μm with a Gaussian spatial beam profile-1.6 to 3.1 mm in diameter. After laser treatment, samples were subjected to demineralization to simulate the acidic intraoral conditions of dental decay. The resulting demineralization and erosion were assessed using polarization-sensitive optical coherence tomography, three-dimensional digital microscopy, and polarized light microscopy. Distinct changes in the surface morphology and the degree of inhibition were found within the laser-treated area in accordance with the laser intensity profile. Subtle visual changes were noted below the melting point for enamel that appear to correspond to thresholds for denaturation of the organic phase and thermal decomposition of the mineral phase. There was significant protection from laser irradiation in areas in which the reflectivity was not increased significantly, suggesting that aesthetically sensitive areas of the tooth can be treated for caries prevention.

Formation of silicon carbide by laser ablation in graphene oxide-N-methyl-2-pyrrolidone suspension on silicon surface

NASA Astrophysics Data System (ADS)

Jaleh, Babak; Ghasemi, Samaneh; Torkamany, Mohammad Javad; Salehzadeh, Sadegh; Maleki, Farahnaz

2018-01-01

Laser ablation of a silicon wafer in graphene oxide-N-methyl-2-pyrrolidone (GO-NMP) suspension was carried out with a pulsed Nd:YAG laser (pulse duration = 250 ns, wavelength = 1064 nm). The surface of silicon wafer before and after laser ablation was studied using optical microscopy, scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX). The results showed that the ablation of silicon surface in liquid by pulsed laser was done by the process of melt expulsion under the influence of the confined plasma-induced pressure or shock wave trapped between the silicon wafer and the liquid. The X-ray diffraction‌ (XRD) pattern of Si wafer after laser ablation showed that 4H-SiC layer is formed on its surface. The formation of the above layer was also confirmed by Raman spectroscopy, and X-ray photoelectron spectroscopy‌ (XPS), as well as EDX was utilized. The reflectance of samples decreased with increasing pulse energy. Therefore, the morphological alteration and the formation of SiC layer at high energy increase absorption intensity in the UV‌-vis regions. Theoretical calculations confirm that the formation of silicon carbide from graphene oxide and silicon wafer is considerably endothermic. Development of new methods for increasing the reflectance without causing harmful effects is still an important issue for crystalline Si solar cells. By using the method described in this paper, the optical properties of solar cells can be improved.

Data Fitting to Study Ablated Hard Dental Tissues by Nanosecond Laser Irradiation.

PubMed

Al-Hadeethi, Y; Al-Jedani, S; Razvi, M A N; Saeed, A; Abdel-Daiem, A M; Ansari, M Shahnawaze; Babkair, Saeed S; Salah, Numan A; Al-Mujtaba, A

2016-01-01

Laser ablation of dental hard tissues is one of the most important laser applications in dentistry. Many works have reported the interaction of laser radiations with tooth material to optimize laser parameters such as wavelength, energy density, etc. This work has focused on determining the relationship between energy density and ablation thresholds using pulsed, 5 nanosecond, neodymium-doped yttrium aluminum garnet; Nd:Y3Al5O12 (Nd:YAG) laser at 1064 nanometer. For enamel and dentin tissues, the ablations have been performed using laser-induced breakdown spectroscopy (LIBS) technique. The ablation thresholds and relationship between energy densities and peak areas of calcium lines, which appeared in LIBS, were determined using data fitting. Furthermore, the morphological changes were studied using Scanning Electron Microscope (SEM). Moreover, the chemical stability of the tooth material after ablation has been studied using Energy-Dispersive X-Ray Spectroscopy (EDX). The differences between carbon atomic % of non-irradiated and irradiated samples were tested using statistical t-test. Results revealed that the best fitting between energy densities and peak areas of calcium lines were exponential and linear for enamel and dentin, respectively. In addition, the ablation threshold of Nd:YAG lasers in enamel was higher than that of dentin. The morphology of the surrounded ablated region of enamel showed thermal damages. For enamel, the EDX quantitative analysis showed that the atomic % of carbon increased significantly when laser energy density increased.

Optimum Laser Beam Characteristics for Achieving Smoother Ablations in Laser Vision Correction.

PubMed

Verma, Shwetabh; Hesser, Juergen; Arba-Mosquera, Samuel

2017-04-01

Controversial opinions exist regarding optimum laser beam characteristics for achieving smoother ablations in laser-based vision correction. The purpose of the study was to outline a rigorous simulation model for simulating shot-by-shot ablation process. The impact of laser beam characteristics like super Gaussian order, truncation radius, spot geometry, spot overlap, and lattice geometry were tested on ablation smoothness. Given the super Gaussian order, the theoretical beam profile was determined following Lambert-Beer model. The intensity beam profile originating from an excimer laser was measured with a beam profiler camera. For both, the measured and theoretical beam profiles, two spot geometries (round and square spots) were considered, and two types of lattices (reticular and triangular) were simulated with varying spot overlaps and ablated material (cornea or polymethylmethacrylate [PMMA]). The roughness in ablation was determined by the root-mean-square per square root of layer depth. Truncating the beam profile increases the roughness in ablation, Gaussian profiles theoretically result in smoother ablations, round spot geometries produce lower roughness in ablation compared to square geometry, triangular lattices theoretically produce lower roughness in ablation compared to the reticular lattice, theoretically modeled beam profiles show lower roughness in ablation compared to the measured beam profile, and the simulated roughness in ablation on PMMA tends to be lower than on human cornea. For given input parameters, proper optimum parameters for minimizing the roughness have been found. Theoretically, the proposed model can be used for achieving smoothness with laser systems used for ablation processes at relatively low cost. This model may improve the quality of results and could be directly applied for improving postoperative surface quality.

Corneal tissue ablation using 6.1 μm quantum cascade laser

NASA Astrophysics Data System (ADS)

Huang, Yong; Kang, Jin U.

2012-03-01

High absorption property of tissues in the IR range (λ> 2 μm) results in effective tissue ablation, especially near 3 μm. In the mid-infrared range, wavelengths of 6.1 μm and 6.45 μm fall into the absorption bands of the amide protein groups Amide-I and Amide-II, respectively. They also coincide with the deformation mode of water, which has an absorption peak at 6.1 μm. This coincidence makes 6.1 μm laser a better ablation tool that has promising effectiveness and minimum collateral damages than 3 μm lasers. In this work, we performed bovine corneal ablation test in-vitro using high-power 6.1μm quantum cascade laser (QCL) operated at pulse mode. Quantum cascade laser has the advantages of low cost, compact size and tunable wavelength, which makes it great alternative Mid-IR light source to conventional tunable free-electron lasers (FEL) for medical applications. Preliminary results show that effective corneal stroma craters were achieved with much less collateral damage in corneal tissue that contains less water. Future study will focus on optimizing the control parameters of QCL to attain neat and precise ablation of corneal tissue and development of high peak power QCL.

Meteoric ion layers in the Martian atmosphere.

PubMed

Whalley, Charlotte L; Plane, John M C

2010-01-01

Low-lying plasma layers have been observed sporadically in the Martian atmosphere by radio occultation measurements from spacecraft such as the Mars Express Orbiter and the Mars Global Surveyor. These layers are just a few km wide, and tend to occur around 90 km. It has been proposed that the layers consist of metallic ions, for two reasons: they occur in the aerobraking region of the planet where meteoroids ablate; and they resemble sporadic E layers in the terrestrial atmosphere which are known to be composed principally of Fe+ and Mg+ ions. This paper addresses the problem of how metallic ions can persist in a CO2-rich atmosphere, where the ions should be neutralized rapidly by formation of metal-CO2 cluster ions followed by dissociative electron recombination. Laboratory studies using the pulsed laser photolysis/laser induced fluorescence and flow tube/mass spectrometer techniques were used to measure the following rate coefficients: k (Mg+ + CO2 (+ CO2) --> Mg+ x CO2, 190-403 K) = (5.3 +/- 0.7) x 10(-29) (T/300 K)(-1.86 +/- 0.03) cm6 molecule --> 2 s(-1); k(Mg+ x CO2 + O2 --> MgO2(+) + CO2, 297 K) = (2.2 +/- 0.8) x 10(-11) cm3 molecule(-1) s(-1); k(MgO2(+) + O --> MgO(+) + O2, 297 K) = (6.5 +/- 1.8) x 10(-10) cm3 molecule(-1) s(-1); and k(MgO(+) + O --> Mg(+) + O2, 297 K) = (5.9 +/- 2.4) x 10(-10) cm3 molecule(-1) s(-1). A model of magnesium and iron chemistry in the Martian atmosphere was then constructed, which includes meteoric differential ablation rates calculated with the Leeds CABMOD model, photo-ionization, and gas-phase ion-molecule and neutral chemistry. The model shows that nearly all the metallic ions between 70 and 110 km should be Mg+, because the reactions of MgO2+ and MgO+ with atomic O are fast enough to prevent these molecular ions undergoing dissociative electron recombination (unlike the analogous Fe species). There are enough Mg+ ions to form sporadic layers of the observed plasma density, and the layers can have a lifetime against neutralization in excess of 20 h.

Novel Laser Ablation Technology for Surface Decontamination

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cheng, Chung H.

2004-06-01

Laser ablation for surface cleaning has been pursued for the removal of paint on airplanes. It has also been pursued for the cleaning of semiconductor surfaces. However, all these approaches have been pursued by laser ablation in air. For highly contaminated surface, laser ablation in air can easily cause secondary contamination. Thus it is not suitable to apply to achieve surface decontamination for DOE facilities since many of these facilities have radioactive contaminants on the surface. Any secondary contamination will be a grave concern. The objective of this project is to develop a novel technology for laser ablation in liquidmore » for surface decontamination. It aims to achieve more efficient surface decontamination without secondary contamination and to evaluate the economic feasibility for large scale surface decontamination with laser ablation in liquid. When laser ablation is pursued in the solution, all the desorbed contaminants will be confined in liquid. The contaminants can be precipitated and subsequently contained in a small volume for disposal. It can reduce the risk of the decontamination workers. It can also reduce the volume of contaminants dramatically.« less

Synthesis of Ultra-Small Palladium Nanoparticles Deposited on CdS Nanorods by Pulsed Laser Ablation in Liquid: Role of Metal Nanocrystal Size in the Photocatalytic Hydrogen Production.

PubMed

Park, Hanbit; Reddy, D Amaranatha; Kim, Yujin; Lee, Seunghee; Ma, Rory; Kim, Tae Kyu

2017-09-21

It is imperative to suppress the rate of recombination of photogenerated carriers to improve the semiconductor-catalyzed solar-driven production of hydrogen. To this end, photocatalysts comprising active sunlight-harvesting photo-absorbers and stable metal co-catalysts have attracted significant attention. However, the size, clean surface, and highly dispersed nature of the metal co-catalysts are crucial factors affecting catalyst performance and reaction rate. Nevertheless, most of the available metal nanocrystals have been synthesized by complex procedures using harmful organic templates and stabilizers, affording high-purity compounds with difficulty and high cost. To overcome these problems, in this study, the pulsed laser ablation in liquid approach was utilized to generate palladium and bimetallic palladium-platinum nanoparticles with an average size and distribution by adjusting the laser wavelength and fluence. A high rate of evolution of hydrogen of 130.33 mmol g -1  h -1 was obtained by using the optimized CdS-PdPt catalyst under simulated sunlight irradiation. This value is 51.31 times greater than that observed for bare CdS nanostructures. Furthermore, the amount of hydrogen evolved was significantly better than that obtained by using several other noble-metal co-catalysts deposited on CdS. This proposed strategy is thought to open new avenues for the design of advanced photocatalytic materials for efficient solar-driven production of hydrogen. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Development of double-pulse lasers ablation system and electron paramagnetic resonance spectroscopy for direct spectral analysis of manganese doped PVA polymer

NASA Astrophysics Data System (ADS)

Khalil, A. A. I.; Morsy, M. A.; El-Deen, H. Z.

2017-11-01

Series of manganese-co-precipitated poly (vinyl alcohol) (PVA) polymer were quantitatively and qualitatively analyzed using laser ablation system (LAS) based on double-pulse laser induced breakdown spectroscopy (DP-LIBS) and electron paramagnetic resonance (EPR) spectroscopy. The collinear nanosecond laser beams of 266 and 1064 nm were optimized to focus on the surface of the PVA polymer target. Both laser beams were employed to estimate the natural properties of the excited Mn-PVA plasma, such as electron number density (Ne), electron temperature (Te), and Mn concentration. Individual transition lines of manganese (Mn), carbon (C), lithium (Li), hydrogen (H) and oxygen (O) atoms are identified based on the NIST spectral database. The results show better responses with DP-LIBS than the single-pulse laser induced breakdown spectroscopy (SP-LIBS). On the other hand, the EPR investigation shows characteristic broad peak of Mn-nano-particles (Mn-NPs) in the range of quantum dots of superparamagnetic materials. The line width (peak-to-peak, ΔHpp) and g-value of the observed Mn-EPR peak are ∼20 mT and 2.0046, respectively. The intensities of Mn-emission line at a wavelength 403.07 nm and the Mn-EPR absorption peak were used to accurate quantify the Mn-content in the polymer matrix. The results produce linear trends within the studied concentration range with regression coefficient (R2) value of ∼0.99, and limit of detection (LOD) of 0.026 mol.% and 0.016 mol.%, respectively. The LOD values are at a fold change of about -0.2 of the studied lowest mol.%. The proposed protocols of trace element detection are of significant advantage and can be applied to the other metal analysis.

Ultrashort pulsed laser (USPL) application in dentistry: basic investigations of ablation rates and thresholds on oral hard tissue and restorative materials.

PubMed

Schelle, Florian; Polz, Sebastian; Haloui, Hatim; Braun, Andreas; Dehn, Claudia; Frentzen, Matthias; Meister, Jörg

2014-11-01

Modern ultrashort pulse lasers with scanning systems provide a huge set of parameters affecting the suitability for dental applications. The present study investigates thresholds and ablation rates of oral hard tissues and restorative materials with a view towards a clinical application system. The functional system consists of a 10 W Nd:YVO4 laser emitting pulses with a duration of 8 ps at 1,064 nm. Measurements were performed on dentin, enamel, ceramic, composite, and mammoth ivory at a repetition rate of 500 kHz. By employing a scanning system, square-shaped cavities with an edge length of 1 mm were created. Ablation threshold and rate measurements were assessed by variation of the applied fluence. Examinations were carried out employing a scanning electron microscope and optical profilometer. Irradiation time was recorded by the scanner software in order to calculate the overall ablated volume per time. First high power ablation rate measurements were performed employing a laser source with up to 50 W. Threshold values in the range of 0.45 J/cm(2) (composite) to 1.54 J/cm(2) (enamel) were observed. Differences between any two materials are statistically significant (p < 0.05). Preparation speeds up to 37.53 mm(3)/min (composite) were achieved with the 10 W laser source and differed statistically significant for any two materials (p < 0.05) with the exception of dentin and mammoth ivory (p > 0.05). By employing the 50 W laser source, increased rates up to ∼50 mm(3)/min for dentin were obtained. The results indicate that modern USPL systems provide sufficient ablation rates to be seen as a promising technology for dental applications.

Laser imprint reduction for the critical-density foam buffered target driven by a relatively strong foot pulse at early stage of laser implosions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, J. W., E-mail: li-jiwei@iapcm.ac.cn; He, X. T.; Institute of Applied Physics and Computational Mathematics, P. O. Box 8009, Beijing 100094

In order to reduce the effect of laser imprint in direct-drive ignition scheme a low-density foam buffered target has been proposed. This target is driven by a laser pulse with a low-intensity foot at the early stage of implosion, which heats the foam and elongates the thermal conduction zone between the laser absorption region and ablation front, increasing the thermal smoothing effect. In this paper, a relatively strong foot pulse is adopted to irradiate the critical-density foam buffered target. The stronger foot, near 1 × 10{sup 14 }W/cm{sup 2}, is able to drive a radiative shock in the low-density foam, which helps smoothmore » the shock and further reduce the effect of laser imprint. The radiative shock also forms a double ablation front structure between the two ablation fronts to further stabilize the hydrodynamics, achieving the similar results to a target with a high-Z dopant in the ablator. 2D analysis shows that for the critical-density foam buffered target irradiated by the strong foot pulse, the laser imprint can be reduced due to the radiative shock in the foam and an increased thermal smoothing effect. It seems viable for the critical-density foam buffered target to be driven by a relatively strong foot pulse with the goal of reducing the laser imprint and achieving better implosion symmetry in the direct-drive laser fusion.« less

Amalgam ablation with the Er:YAG laser

NASA Astrophysics Data System (ADS)

Wigdor, Harvey A.; Visuri, Steven R.; Walsh, Joseph T., Jr.

1995-04-01

Any laser that will be used by dentist to replace the dental drill (handpiece) must remove dental hard tissues safely. These lasers must also have the ability to ablate the restorative dental materials which are present in the teeth being treated. Prior to any laser being used to treat humans a thorough knowledge of the effects of the laser treatment on dental materials must be understood. Cores of dental amalgam were created and sliced into thin wafers for this experiment. Ablation efficiency and thermal changes were evaluated with and without water. It appears as if the Er:YAG laser can effectively ablate amalgam dental material with and without water. The water prevents the temperature from increasing much above baseline and does not reduce efficiency of ablation.

Stress assisted selective ablation of ITO thin film by picosecond laser

NASA Astrophysics Data System (ADS)

Farid, Nazar; Chan, Helios; Milne, David; Brunton, Adam; M. O'Connor, Gerard

2018-01-01

Fast selective pattering with high precession on 175 nm ITO thin film with IR ps lasers is investigated. Ablation parameters are optimized with detailed studies on the scribed depth, topography, and particle generation using AFM and SEM. A comparison of 10 and 150 ps laser revealed that the shorter pulse (10 ps) laser is more appropriate in selective and partial ablation; up to 20 nm resolution for controlled depth with multipulses having energy below the damage threshold is demonstrated. The experimental results are interpreted to involve stress assisted ablation mechanism for the 10 ps laser while thermal ablation along with intense melting occurs for 150 ps laser. The transition between these regimes is estimated to occur at approximately 30 ps.

Observing laser ablation dynamics with sub-picosecond temporal resolution

NASA Astrophysics Data System (ADS)

Tani, Shuntaro; Kobayashi, Yohei

2017-04-01

Laser ablation is one of the most fundamental processes in laser processing, and the understanding of its dynamics is of key importance for controlling and manipulating the outcome. In this study, we propose a novel way of observing the dynamics in the time domain using an electro-optic sampling technique. We found that an electromagnetic field was emitted during the laser ablation process and that the amplitude of the emission was closely correlated with the ablated volume. From the temporal profile of the electromagnetic field, we analyzed the motion of charged particles with subpicosecond temporal resolution. The proposed method can provide new access to observing laser ablation dynamics and thus open a new way to optimize the laser processing.

Selective ablation of rabbit atherosclerotic plaque with less thermal effect by the control of pulse structure of a quantum cascade laser in the 5.7 μm wavelength range

NASA Astrophysics Data System (ADS)

Hashimura, Keisuke; Ishii, Katsunori; Awazu, Kunio

2016-03-01

Cholesteryl esters are main components of atherosclerotic plaques and have an absorption peak at the wavelength of 5.75 μm originated from C=O stretching vibration mode of ester bond. Our group achieved the selective ablation of atherosclerotic lesions using a quantum cascade laser (QCL) in the 5.7 μm wavelength range. QCLs are relatively new types of semiconductor lasers that can emit mid-infrared range. They are sufficiently compact and considered to be useful for clinical application. However, large thermal effects were observed because the QCL worked as quasicontinuous wave (CW) lasers due to its short pulse interval. Then we tried macro pulse irradiation (irradiation of pulses at intervals) of the QCL and achieved effective ablation with less-thermal effects than conventional quasi-CW irradiation. However, lesion selectivity might be changed by changing pulse structure. Therefore, in this study, irradiation effects of the macro pulse irradiation to rabbit atherosclerotic plaque and normal vessel were compared. The macro pulse width and the macro pulse interval were set to 0.5 and 12 ms, respectively, because the thermal relaxation time of rabbit normal and atherosclerotic aortas in the oscillation wavelength of the QCL was 0.5-12 ms. As a result, cutting difference was achieved between rabbit atherosclerotic and normal aortas by the macro pulse irradiation. Therefore, macro pulse irradiation of a QCL in the 5.7 μm wavelength range is effective for reducing thermal effects and selective ablation of the atherosclerotic plaque. QCLs have the potential of realizing less-invasive laser angioplasty.

Study of Mn laser ablation in methane atmosphere

NASA Astrophysics Data System (ADS)

Krstulović, N.; Labazan, I.; Milošević, S.

2006-02-01

Laser ablation of Mn target in vacuum and in the presence of CH4 was studied under 308 nm laser irradiation. Time-resolved emission using gated detection and scanning monochromator and absorption using the cavity ring-down spectroscopy were used to study vaporized plume. In the CH4 atmosphere we observed transitions identified as C2 and MnH bands, while these spectral features were not detected in emission spectra. This is a clear evidence of importance in combining both spectroscopic techniques in laser vaporized plume study.

Estimation of ultrashort laser irradiation effect over thin transparent biopolymer films morphology

NASA Astrophysics Data System (ADS)

Daskalova, A.; Nathala, C.; Bliznakova, I.; Slavov, D.; Husinsky, W.

2015-01-01

The collagen - elastin biopolymer thin films treated by CPA Ti:Sapphire laser (Femtopower - Compact Pro) at 800nm central wavelength with 30fs and 1kHz repetition rate are investigated. A process of surface modifications and microporous scaffold creation after ultrashort laser irradiation has been observed. The single-shot (N=1) and multi-shot (N<1) ablation threshold values were estimated by studying the linear relationship between the square of the crater diameter D2 and the logarithm of the laser fluence F for determination of the threshold fluences for N=1, 2, 5, 10, 15 and 30 number of laser pulses. The incubation analysis by calculation of the incubation coefficient ξ for multi - shot fluence threshold for selected materials by power - law relationship form Fth(N)=Fth(1)Nξ-1 was also obtained. In this paper, we have also shown another consideration of the multi - shot ablation threshold calculation by logarithmic dependence of the ablation rate d on the laser fluence. The morphological surface changes of the modified regions were characterized by scanning electron microscopy to estimate the generated variations after the laser treatment.

CuInGaSe{sub 2} nanoparticles by pulsed laser ablation in liquid medium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mendivil, M.I.; García, L.V.; Krishnan, B.

2015-12-15

Highlights: • CIGS nanocolloids were synthesized using PLAL technique. • Characterized their morphology, structure, composition and optical properties. • Morphologies were dependent on ablation wavelength and liquid medium. • Optical absorption and bandgap of these nanocolloids were tunable. - Abstract: Pulsed laser ablation in liquid medium (PLALM) is a nanofabrication technique to produce complex nanostructures. CuInGaSe{sub 2} (CIGS) is an alloy with applications in photovoltaic industry. In this work, we studied the effects of laser ablation wavelength, energy fluence and liquid medium on the properties of the CIGS nanoparticles synthesized by PLALM. The nanoparticles obtained were analyzed by transmission electronmore » microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), selected area electron diffraction (SAED), X-ray photoelectron spectroscopy (XPS) and UV–vis absorption spectroscopy. XPS results confirmed the chemical states and composition of the ablated products. TEM analysis showed different morphologies for the nanomaterials obtained in different liquid media and ablation wavelengths. The optical properties for these CIGS nanocolloids were analyzed using UV–vis absorption spectroscopy. The results demonstrated the use of PLALM as a useful synthesis technique for nanoparticles of quaternary photovoltaic materials.« less

Preliminary characterisation of new glass reference materials (GSA-1G, GSC-1G, GSD-1G and GSE-1G) by laser ablation-inductively coupled plasma-mass spectrometry using 193 nm, 213 nm and 266 nm wavelengths

USGS Publications Warehouse

Guillong, M.; Hametner, K.; Reusser, E.; Wilson, S.A.; Gunther, D.

2005-01-01

New glass reference materials GSA-1G, GSC-1G, GSD-1G and GSE-1G have been characterised using a prototype solid state laser ablation system capable of producing wavelengths of 193 nm, 213 nm and 266 nm. This system allowed comparison of the effects of different laser wavelengths under nearly identical ablation and ICP operating conditions. The wavelengths 213 nm and 266 nm were also used at higher energy densities to evaluate the influence of energy density on quantitative analysis. In addition, the glass reference materials were analysed using commercially available 266 nm Nd:YAG and 193 nm ArF excimer lasers. Laser ablation analysis was carried out using both single spot and scanning mode ablation. Using laser ablation ICP-MS, concentrations of fifty-eight elements were determined with external calibration to the NIST SRM 610 glass reference material. Instead of applying the more common internal standardisation procedure, the total concentration of all element oxide concentrations was normalised to 100%. Major element concentrations were compared with those determined by electron microprobe. In addition to NIST SRM 610 for external calibration, USGS BCR-2G was used as a more closely matrix-matched reference material in order to compare the effect of matrix-matched and non matrix-matched calibration on quantitative analysis. The results show that the various laser wavelengths and energy densities applied produced similar results, with the exception of scanning mode ablation at 266 nm without matrix-matched calibration where deviations up to 60% from the average were found. However, results acquired using a scanning mode with a matrix-matched calibration agreed with results obtained by spot analysis. The increased abundance of large particles produced when using a scanning ablation mode with NIST SRM 610, is responsible for elemental fractionation effects caused by incomplete vaporisation of large particles in the ICP.

Varicose vein - noninvasive treatment

MedlinePlus

Sclerotherapy; Laser therapy - varicose veins; Radiofrequency vein ablation; Endovenous thermal ablation; Ambulatory phlebectomy; Transilluminated power phlebotomy; Endovenous laser ablation; Varicose vein therapy

Micro-fractional ablative skin resurfacing with two novel erbium laser systems.

PubMed

Dierickx, Christine C; Khatri, Khalil A; Tannous, Zeina S; Childs, James J; Cohen, Richard H; Erofeev, Andrei; Tabatadze, David; Yaroslavsky, Ilya V; Altshuler, Gregory B

2008-02-01

Fractional ablation offers the potential benefits of full-surface ablative skin resurfacing while minimizing adverse effects. The purpose of this study was to evaluate the safety, damage profile, and efficacy of erbium fractional lasers. Histology from animal and human skin as well as clinical evaluations were conducted with erbium YAG (2,940 nm) and erbium YSGG (2,790 nm) fractional lasers varying pulse width, microbeam (microb) energy, number of passes, and stacking of pulses. Single-pulse treatment parameters from 1 to 12 mJ per 50-70 microm diameter microbeam and 0.25-5 milliseconds pulse widths produced microcolumns of ablation with border coagulation of up to 100 microm width and 450 microm depth. Stacking of pulses generated deeper microcolumns. Clinical observations and in vivo histology demonstrate rapid re-epithelization and limited adverse side effects. Facial treatments were performed in the periorbital and perioral areas using 1-8 passes of single and stacked pulses. Treatments were well-tolerated and subjects could resume their normal routine in 4 days. A statistically significant reduction in wrinkle scores at 3 months was observed for both periorbital and perioral wrinkles using blinded grading. For periorbital treatments of four passes or more, over 90% had > or =1 score wrinkle reduction (0-9 scale) and 42% had > or =2. For perioral wrinkles, over 50% had substantial improvements (> or =2). The clinical observations and histology findings demonstrate that micro-fractional ablative treatment with 2,790 and 2,940 nm erbium lasers resulted in safe and effective wrinkle reduction with minimal patient downtime. The depth and width of the ablated microcolumns and varying extent of surrounding coagulation can be controlled and used to design new treatment procedures targeted for specific indications and areas such as moderate to severe rhytides and photodamaged skin.

Significant skin-tightening by closure of fractional ablative laser holes.

PubMed

Russe, Elisabeth; Purschke, Martin; Limpiangkanan, Wikunda; Farinelli, William A; Wang, Ying; Doukas, Apostolos G; Sakamoto, Fernanda H; Wechselberger, Gottfried; Anderson, Richard Rox

2018-01-01

Ablative fractional laser treatment uses thousands of very small laser beam wounds to damage a fraction of the skin, which stimulates tissue remodeling. Each open micro-wound heals without scarring, but the amount of skin tightening achieved is limited. This animal study was performed to test the hypothesis that immediate temporary closure of fractional laser wounds could increase skin tightening after fractional ablative laser treatment. Four adult swine were used for the study; 98 square test sites (3 × 3 cm) were tattooed on the abdomen and flanks of each pig. An ablative fractional Erbium:YAG laser (Sciton Profile, Sciton Inc, Palo Alto, CA) was used to treat the test areas. A laser micro-spot fluence of 375 J/cm 2 was delivered in 150-250 microseconds pulses, resulting in an array of ablation channels extending 1.5 mm deep into the skin, with a spot size of 250 µm, with 10% treatment density. Immediately following laser exposure the resulting holes were closed using a stretched elastic adhesive dressing, which, when applied, recoiled and compressed the diameter of the ablation holes. The compressive dressings were removed after 7 days. This procedure was compared to removing the same amount of skin (10%) mechanically by specially designed 19 gauge coring needles, as well as to the same laser and coring methods without compression closure. Area and shape of test sites were measured by digital photography before and 28 days after treatment. Data analysis included compensation for animal growth, as measured by increase in the area of the untreated control sites. All treated and control sites healed within a week, without scarring evident at 28 days. Laser treatment combined with compressive wound closure caused significant shrinkage at 28 days compared with untreated control sites. The treated skin area was reduced by 11.5% (P = 0.0001). Needle coring with wound closure produced similar, significant shrinkage (8%, P < 0.0021), whereas laser and needle coring treatment without closure did not result in significant area reduction (P = 0.1289) compared with untreated control sites. Significant skin tightening can be achieved by immediate temporary non-invasive wound closure after short pulse Er:YAG fractional ablative laser treatment, as well as after mechanically removing skin with a coring needle. This approach may improve skin tightening after ablative laser treatments. Further clinical studies are necessary to confirm successful application in humans. Lasers Surg. Med. 50:64-69, 2018. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

A novel integration of spectral-domain optical-coherence-tomography and laser-ablation system for precision treatment.

PubMed

Fan, Yingwei; Zhang, Boyu; Chang, Wei; Zhang, Xinran; Liao, Hongen

2018-03-01

Complete resection of diseased lesions reduces the recurrence of cancer, making it critical for surgical treatment. However, precisely resecting residual tumors is a challenge during operation. A novel integrated spectral-domain optical-coherence-tomography (SD-OCT) and laser-ablation therapy system for soft-biological-tissue resection is proposed. This is a prototype optical integrated diagnosis and therapeutic system as well as an optical theranostics system. We develop an optical theranostics system, which integrates SD-OCT, a laser-ablation unit, and an automatic scanning platform. The SD-OCT image of biological tissue provides an intuitive and clear view for intraoperative diagnosis and monitoring in real time. The effect of laser ablation is analyzed using a quantitative mathematical model. The automatic endoscopic scanning platform combines an endoscopic probe and an SD-OCT sample arm to provide optical theranostic scanning motion. An optical fiber and a charge-coupled device camera are integrated into the endoscopic probe, allowing detection and coupling of the OCT-aiming beam and laser spots. The integrated diagnostic and therapeutic system combines SD-OCT imaging and laser-ablation modules with an automatic scanning platform. OCT imaging, laser-ablation treatment, and the integration and control of diagnostic and therapeutic procedures were evaluated by performing phantom experiments. Furthermore, SD-OCT-guided laser ablation provided precision laser ablation and resection for the malignant lesions in soft-biological-tissue-lesion surgery. The results demonstrated that the appropriate laser-radiation power and duration time were 10 W and 10 s, respectively. In the laser-ablation evaluation experiment, the error reached approximately 0.1 mm. Another validation experiment was performed to obtain OCT images of the pre- and post-ablated craters of ex vivo porcine brainstem. We propose an optical integrated diagnosis and therapeutic system. The primary experimental results show the high efficiency and feasibility of our theranostics system, which is promising for realizing accurate resection of tumors in vivo and in situ in the future.

[Laser-assisted blepharoplasty].

PubMed

Thiesmann, R

2018-04-01

Blepharoplasty is one of the most frequently performed plastic cosmetic interventions. For this purpose the CO 2 laser is an instrument that can be used as a laser scalpel to cut as well as in its ablative function to remove skin irregularities, such as scars and tumors and also to treat changes of the skin due to aging. Fractionated laser irradiation reduces the duration of skin redness and the postoperative rehabilitation time after a resurfacing. The advantages of the CO 2 laser are a gentle intraoperative preparation and less postoperative swelling due to an additional cauterization of blood vessels. Disadvantages are an increased occurrence of wound dehiscence and the high cost of instrumentation. Before performing a blepharoplasty an exact analysis of changes of the eyelid and also the wishes of the patients are necessary to establish the most suitable surgical procedure and the correct dosage. In addition to skin and fat resection, depending on the original situation it is possible to tighten slack skin with a resurfacing, to shift the fat compartments, to change the position of the eyebrows, to correct a ptosis and also to modulate the tension of the lid. The frequency of complications can be reduced by good planning of the surgical intervention. In the case of occurrence of complications, suitable treatment strategies should be available.