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Sample records for laser ablation studies

  1. LASER ABLATION STUDIES OF CONCRETE

    EPA Science Inventory

    Laser ablation was studied as a means of removing radioactive contaminants from the surface and near-surface regions of concrete. We present the results of ablation tests on cement and concrete samples using a 1.6 kW pulsed Nd:YAG laser with fiber optic beam delivery. The laser-s...

  2. Laser ablation studies of concrete

    SciTech Connect

    Savina, M.; Xu, Z.; Wang, Y.; Reed, C.; Pellin, M.

    1999-10-20

    Laser ablation was studied as a means of removing radioactive contaminants from the surface and near-surface regions of concrete. The authors present the results of ablation tests on cement and concrete samples using a 1.6 kW pulsed Nd:YAG laser with fiber optic beam delivery. The laser-surface interaction was studied using cement and high density concrete as targets. Ablation efficiency and material removal rates were determined as functions of irradiance and pulse overlap. Doped samples were also ablated to determine the efficiency with which surface contaminants were removed and captured in the effluent. The results show that the cement phase of the material melts and vaporizes, but the aggregate portion (sand and rock) fragments. The effluent consists of both micron-size aerosol particles and chunks of fragmented aggregate material. Laser-induced optical emission spectroscopy was used to analyze the surface during ablation. Analysis of the effluent showed that contaminants such as cesium and strontium were strongly segregated into different regions of the particle size distribution of the aerosol.

  3. Laser Ablation Propulsion A Study

    NASA Astrophysics Data System (ADS)

    Irfan, Sayed A.; Ugalatad, Akshata C.

    Laser Ablation Propulsion (LAP) will serve as an alternative propulsion system for development of microthrusters. The principle of LAP is that when a laser (pulsed or continuous wave) with sufficient energy (more than the vaporization threshold energy of material) is incident on material, ablation or vaporization takes place which leads to the generation of plasma. The generated plasma has the property to move away from the material hence pressure is generated which leads to the generation of thrust. Nowadays nano satellites are very common in different space and defence applications. It is important to build micro thruster which are useful for orienting and re-positioning small aircraft (like nano satellites) above the atmosphere. modelling of LAP using MATLAB and Mathematica. Schematic is made for the suitable optical configuration of LAP. Practical experiments with shadowgraphy and self emission techniques and the results obtained are analysed taking poly (vinyl-chloride) (PVC) as propellant to study the

  4. Status of the Ablative Laser Propulsion Studies

    NASA Technical Reports Server (NTRS)

    Herren, Kenneth A.; Lin, Jun; Cohen, Tinothy; Pakhomov, Andrew V.; Thompson, M. Shane

    2004-01-01

    We present a short review of our laser-propulsion research as well as some of the current results of the Ablative Laser Propulsion (ALP) studies currently underway at the University of Alabama in Huntsville. It has been shown that direct surface ablation of a solid material produces high specific impulse (Isp) at relatively high energy conversion efficiency (20 - 40%). We detail measurements of specific impulse, thrust and coupling coefficients for elemental target materials both with single and with double pulse laser shots. We also present measurements taken using three independent methods for determination of Isp. The three methods produce consistent values from ion time-of-flight technique, impulse measurements and imaging of the expansion front of plasma plume. We present a demonstration of our ALP lightcraft, a small free-flying micro-vehicle that is propelled by ablation. For ALP lightcraft we use a subscale thin shell of nickel replicated over a diamond turned mandrel that produces a highly polished self-focusing, truncated at the focus parabolic mirror. The mass of the lightcraft is 54 mg and it is driven by 100-ps wide, 35-mJ laser pulses at 532 nm wavelength. This is an ongoing research. We also present the latest work on laserdriven micro-thrusters and detail some the near term goals of our program.

  5. Mechanism study of skin tissue ablation by nanosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Fang, Qiyin

    Understanding the fundamental mechanisms in laser tissue ablation is essential to improve clinical laser applications by reducing collateral damage and laser pulse energy requirement. The motive of this dissertation is to study skin tissue ablation by nanosecond laser pulses in a wide spectral region from near-infrared to ultraviolet for a clear understanding of the mechanism that can be used to improve future design of the pulsed lasers for dermatology and plastic surgery. Multiple laser and optical configurations have been constructed to generate 9 to 12ns laser pulses with similar profiles at 1064. 532, 266 and 213nm for this study of skin tissue ablation. Through measurements of ablation depth as a function cf laser pulse energy, the 589nm spectral line in the secondary radiation from ablated skin tissue samples was identified as the signature of the occurrence of ablation. Subsequently, this spectral signature has been used to investigate the probabilistic process of the ablation near the threshold at the four wavelengths. Measurements of the ablation probability were conducted as a function of the electrical field strength of the laser pulse and the ablation thresholds in a wide spectral range from 1064nm to 213nm were determined. Histology analysis and an optical transmission method were applied in assessing of the ablation depth per pulse to study the ablation process at irradiance levels higher than threshold. Because more than 70% of the wet weight of the skin tissue is water, optical breakdown and backscattering in water was also investigated along with a nonlinear refraction index measurement using a z-scan technique. Preliminary studies on ablation of a gelatin based tissue phantom are also reported. The current theoretical models describing ablation of soft tissue ablation by short laser pulses were critically reviewed. Since none of the existing models was found capable of explaining the experimental results, a new plasma-mediated model was developed

  6. Endometrial laser ablation in rabbits: A comparative study of three laser types

    SciTech Connect

    Rosenberg, C.; Tadir, Y.; Braslavsky, D.; Fisch, B.; Karni, Z.; Ovadia, J. )

    1990-01-01

    Endometrial laser ablation is one of the alternatives to hysterectomy in cases of intractable uterine bleeding. It is currently performed using the Nd:YAG laser at 1.06 microns. The aim of this study was to compare the tissue effect of three types of laser irradiation (Nd:YAG laser at 1.06 and 1.32 microns and holmium laser at 2.12 microns) on the rabbit endometrium. Crater formation, coagulation necrosis, and muscle necrosis were evaluated at the time of ablation, as well as at 1 week and 4 weeks postablation. The results were assessed by determining the depth and width of the affected portion in the uterine wall (lumen to serosa). It was shown that Nd:YAG laser at 1.32 microns caused more generalized and extended effects as compared with the other laser types examined. Endometrial regeneration was faster after ablation by the Nd:YAG laser at 1.06 microns and the holmium laser than by the Nd:YAG laser at 1.32 microns. The widest range of ablation energy (defined as that causing ablation without muscle damage) was achieved by applying the holmium laser. Further evaluation of the holmium laser for this indication is recommended.

  7. Spectroscopic studies of laser ablation plumes of artwork materials

    NASA Astrophysics Data System (ADS)

    Oujja, M.; Rebollar, E.; Castillejo, M.

    2003-04-01

    Studies on the plasma plume created during KrF laser (248 nm) ablation of dosimeter tempera samples in vacuum have been carried out to investigate the basic interactions of the laser with paint materials. Time resolved optical emission spectroscopy (OES) was used to measure the translational velocity of electronically excited transients in the plasma plume. Laser-induced fluorescence (LIF) studies using a probe dye laser, allowed to determine the velocities of non-emitting species. The propagation velocities of C 2 in the a 3π u and d 3π g electronic states and of excited atomic species are indicative of a high translational temperature. Differences between the velocities of organic and inorganic species and between emissions from the tempera systems and from the pigments as pellets allow to discuss the participation of photochemical mechanisms in the laser irradiation of the paint systems.

  8. Study of Laser Ablation Efficiency for an Acrylic-Based Photopolymerizing Composition

    NASA Astrophysics Data System (ADS)

    Loktionov, E. Yu.

    2014-05-01

    Results are presented from study of the effi ciency (ablated mass per unit energy, mechanical recoil momentum per unit energy) of laser ablation for a light-curable polymer. A substantial difference is seen between the thresholds and indicated criteria for laser ablation effi ciency in the liquid and cured phases. The highest energy effi ciency for laser ablation (~22.6 %) is achieved when the initially liquid polymer is exposed to radiation with the wavelength optimal for photopolymerization (365 ± 15 nm).

  9. Infrared laser bone ablation

    SciTech Connect

    Nuss, R.C.; Fabian, R.L.; Sarkar, R.; Puliafito, C.A.

    1988-01-01

    The bone ablation characteristics of five infrared lasers, including three pulsed lasers (Nd:YAG, lambda = 1064 micron; Hol:YSGG, lambda = 2.10 micron; and Erb:YAG, lambda = 2.94 micron) and two continuous-wave lasers (Nd:YAG, lambda = 1.064 micron; and CO/sub 2/, lambda = 10.6 micron), were studied. All laser ablations were performed in vitro, using moist, freshly dissected calvarium of guinea pig skulls. Quantitative etch rates of the three pulsed lasers were calculated. Light microscopy of histologic sections of ablated bone revealed a zone of tissue damage of 10 to 15 micron adjacent to the lesion edge in the case of the pulsed Nd:YAG and the Erb:YAG lasers, from 20 to 90 micron zone of tissue damage for bone ablated by the Hol:YSGG laser, and 60 to 135 micron zone of tissue damage in the case of the two continuous-wave lasers. Possible mechanisms of bone ablation and tissue damage are discussed.

  10. Laser ablation of concrete.

    SciTech Connect

    Savina, M.

    1998-10-05

    Laser ablation is effective both as an analytical tool and as a means of removing surface coatings. The elemental composition of surfaces can be determined by either mass spectrometry or atomic emission spectroscopy of the atomized effluent. Paint can be removed from aircraft without damage to the underlying aluminum substrate, and environmentally damaged buildings and sculptures can be restored by ablating away deposited grime. A recent application of laser ablation is the removal of radioactive contaminants from the surface and near-surface regions of concrete. We present the results of ablation tests on concrete samples using a high power pulsed Nd:YAG laser with fiber optic beam delivery. The laser-surface interaction was studied on various model systems consisting of Type I Portland cement with varying amounts of either fine silica or sand in an effort to understand the effect of substrate composition on ablation rates and mechanisms. A sample of non-contaminated concrete from a nuclear power plant was also studied. In addition, cement and concrete samples were doped with non-radioactive isotopes of elements representative of cooling waterspills, such as cesium and strontium, and analyzed by laser-resorption mass spectrometry to determine the contamination pathways. These samples were also ablated at high power to determine the efficiency with which surface contaminants are removed and captured. The results show that the neat cement matrix melts and vaporizes when little or no sand or aggregate is present. Surface flows of liquid material are readily apparent on the ablated surface and the captured aerosol takes the form of glassy beads up to a few tens of microns in diameter. The presence of sand and aggregate particles causes the material to disaggregate on ablation, with intact particles on the millimeter size scale leaving the surface. Laser resorption mass spectrometric analysis showed that cesium and potassium have similar chemical environments in the

  11. A study of particle generation during laser ablation withapplications

    SciTech Connect

    Liu, Chunyi

    2005-08-12

    A study has been made of the generation of particles during laser ablation and has included size distribution measurements and observation of the formation processes. The particle size distribution with respect to different laser parameters was obtained in-line using a differential mobility analyzer (DMA) and a particle counter. The experimental results show that the particle size varies with laser energy, laser pulsewidth, ambient gas flow rate and sample properties. The results serve as a basis for controlling the size of nanoparticles generated by laser ablation. Laser shadowgraph imaging was used to study mass ejection processes and mechanisms. At higher laser irradiance, some particles were ejected in the liquid and even in the solid phase. Time-resolved images show the propagation of the shockwaves: external shockwaves propagate outward and decelerate, and internal shockwaves reflect back and forth between the gas contact surface and the sample surface. The internal shockwave is proposed to cause the ejection of liquid particles when the internal shockwave strikes the liquid molten layer. A simulation based on vapor plume expansion was carried out and provides satisfactory agreement with experimental results. Different material properties result in different particle ejection behavior:particle ejection for most materials including metals result in a conically shaped envelope for the ejected material while ejection for silicon resembles a liquid jet. The difference in density change when the materials melt was proposed to be an important factor in the different ejection behavior. The characteristics of particles generated by laser ablation have a strong influence on the chemical analysis of the irradiated sample. Large particles are more difficult to completely vaporize and ionize, and induced preferential vaporization causes fractionation (i.e. a detected chemical composition that differs from the sample material). Large particles also result in spikes in

  12. Laser ablation of blepharopigmentation

    SciTech Connect

    Tanenbaum, M.; Karas, S.; McCord, C.D. Jr. )

    1988-01-01

    This article discusses laser ablation of blepharopigmentation in four stages: first, experimentally, where pigment vaporization is readily achieved with the argon blue-green laser; second, in the rabbit animal model, where eyelid blepharopigmentation markings are ablated with the laser; third, in human subjects, where the argon blue-green laser is effective in the ablation of implanted eyelid pigment; and fourth, in a case report, where, in a patient with improper pigment placement in the eyelid, the laser is used to safely and effectively ablate the undesired pigment markings. This article describes in detail the new technique of laser ablation of blepharopigmentation. Potential complications associated with the technique are discussed.

  13. Spectroscopic and morphological study of laser ablated Titanium

    NASA Astrophysics Data System (ADS)

    Hayat, Asma; Bashir, Shazia; Rafique, Muahmamd Shahid; Akram, Mahreen; Mahmood, Khaliq; Iqbal, Saman; Dawood, Asadullah; Arooj

    2016-07-01

    The laser-induced breakdown spectroscopy (LIBS) and surface morphology of Titanium (Ti) plasma as a function of laser irradiance have been investigated under ambient environment of argon at fixed pressure of 50 Torr. Ablation was performed by employing Q-switched Nd:YAG laser pulses (λ ≈ 1064 nm, τ ≈ 10 ns, repetition rate ≈ 10 Hz). Ti targets were exposed to various laser intensities ranging from 6 to 50 GW/cm2. LIBS analysis has been employed for the investigation of plasma parameters. Scanning Electron Microscope (SEM) analysis was employed for investigation of surface morphology. Ablation depth was measured by optical microscopy technique. It was observed that both plasma parameters, i.e., excitation temperature and electron density have been significantly influenced by laser irradiance. It is observed that with increasing laser irradiance up to 13 GW/cm2, the electron temperature decreases whereas number density significantly increases and attains its maxima. Afterwards by increasing irradiance electron temperature increases, attains its maxima and a decrease in electron number density is observed at irradiance of 19 GW/cm2. Further increase in irradiance causes saturation with insignificant changes in both electron temperature and electron number density. This saturation in both excitation temperature and electron number density is explainable on the basis of self-sustaining regime. SEM micrographs reveal the ripple and coneformation at the boundaries of ablated region of Ti. The height of cones as well as the ablation depth is maximum at irradiance of 13 GW/cm2 whereas electron number density is also maximum. The maximum electron number density is considered to be responsible for maximum ablation as well as mass removal. A strong correlation between plasma parameters and surface morphology is established.

  14. Laser-ablation processes

    SciTech Connect

    Dingus, R.S.

    1992-01-01

    The various mechanisms by which ablation of materials can be induced with lasers are discussed in this paper. The various ablation processes and potential applications are reviewed from the threshold for ablation up to fluxes of about 10{sup 13} W/cm{sup 2}, with emphasis on three particular processes; namely, front-surface spallation, two-dimensional blowoff, and contained vaporization.

  15. Data Fitting to Study Ablated Hard Dental Tissues by Nanosecond Laser Irradiation

    PubMed Central

    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. PMID:27228169

  16. 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. PMID:27228169

  17. Effects of Laser Irradiation on Artwork Pigments Studied by Laser Ablation and Time-of-Flight Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Torres, R.; Jadraque, M.; Castillejo, M.; Martín, M.

    Laser ablation and time-of-flight mass spectrometric analysis of the ablation plume is used to study the different response of several inorganic pigments to laser irradiation. Lead white and lead chromate in pellets and in a binding media are studied. Lead white is compared to azurite, of similar stoichiometry. For lead white the plume composition is rather independent on laser ablation wavelength and does not show important changes after repeated laser beam exposure opposite to that observed for azurite. Ablation of lead white pellets leads to ionized and neutral Pb and PbnOmHx clusters. Much less extent of aggregation in the plume is observed for lead chromate pellets and for the lead pigments in tempera. Similarities can be found between plume composition of ablated lead white and PbO, suggesting that laser/pigment interaction involves formation of PbO, therefore providing indications of the participation of a thermal decomposition mechanism.

  18. A study of structure formation on PET, PBT, and PS surfaces by excimer laser ablation

    NASA Astrophysics Data System (ADS)

    Kim, Jongdae

    Usually polymer surface treatment is performed to modify surface layers by inserting some functional group and/or by inducing roughness on surfaces to improve their wettability, printability, and adhesion to other polymers or metals. In this work, different polymer surfaces were treated using an excimer laser (LPX 240i, Lambda Physik). Polystyrene, polyethylene terephtalate, and polybutylene terephtalate were chosen as model materials for this study. Films were made by cast film processing and stretched with biaxial stretching machine. With excimer laser treatment on polymer surfaces, it was found that we could produce 1--2 micron size structures depending on material properties and film processing conditions. Materials with lower UV absorption coefficient produced double digit micron size structures, while those with higher UV absorption coefficients produced single digit micron size structures. In all these cases the structures formed only on stretched films. In addition to those microstructure developments, the determination of ablation threshold fluence was of interest mainly for understanding fundamentals of ablation behavior and technical applications. In this study, ablation thresholds were measured by various methods including ablation depth, ablation weight, and ablation sound level measurements. Among these methods, we confirmed that the measurement by ablation sound level gives the most reliable results, because this method is based on single pulse ablation. To understand the ablation phenomenon, and how microstructures can be developed during ablation, different material processing and excimer laser conditions were chosen for experimentation. During our experiments, we observed incubation phenomenon during laser ablation and showed that this incubation was significant for materials with low UV absorption coefficients. Based on UV absorption value change after excimer laser irradiation, we proposed a mechanism to explain the ablation of PS films. From

  19. Comparative study of the ablation of materials by femtosecond and pico- or nanosecond laser pulses

    SciTech Connect

    Kononenko, Taras V; Konov, Vitalii I; Garnov, Sergei V; Danielius, R; Piskarskas, A; Tamosauskas, G; Dausinger, F

    1999-08-31

    A series of studies was carried out on the ablation of steel, Si{sub 3}N{sub 4} ceramic, and diamond in air by femtosecond (200 and 900 fs) pulses of different wavelengths (532 and 266 nm) and in a wide energy density range (1 - 10{sup 3} J cm{sup -2}). The ablation rates were measured for different geometries of the irradiation surface [a shallow crater and a channel with a high (up to 10) aspect ratio]. The ablation rates (in a shallow crater) and the morphologies of the irradiated surface were compared for femtosecond and longer (220 ps, 7 ns) pulses. The role of the laser-generated plasma in the ablation of materials by subpicosecond pulses as well as the prospects for the practical application of ultrashort laser pulses in the processing of materials are analysed. (interaction of laser radiation with matter. laser plasma)

  20. Ultrasonic characterization of laser ablation

    NASA Astrophysics Data System (ADS)

    Smith, J. A.; Telschow, K. L.

    When a pulsed laser beam strikes the surface of an absorbing material, ultrasonic waves are generated due to thermoelectric expansion and, at higher laser power densities, ablation of the material. These sound generation mechanisms have been the subject of numerous theoretical and experimental studies and are now fairly well understood. In particular, it has been established that at low power densities the thermoelastic mechanism is well described by a surface center of expansion. This mechanism produces a characteristic waveform whose amplitude is proportional to the energy absorbed from the laser pulse and also dependent on the thermal and elastic properties of the material. The ablation ultrasonic source can be described by a point normal force acting on the material surface. For laser power densities near the ablation onset, the time dependence of the source is that of the laser pulse. The resultant waveform recorded on epicenter (source and detector collinear) has a sharp peak determined by the momentum impulse delivered to the material by the ablation process. Particularly in the near ablation onset region, this ultrasonic displacement peak can be used to characterize the ablation process occurring at the material surface. The onset power density for ablation and subsequent ablation dependence on power density are material dependent and thought to be a function of the heat capacity and thermal conductivity of the material. With this in mind, it is possible that these ablation signals could be used to characterize material microstructures, and perhaps material mechanical properties such as hardness, through microstructural changes of the material thermal parameters. This paper explores this question for samples of Type 304 stainless steel with microstructures controlled through work hardening and annealing.

  1. Laser ablation methods for analysis of urinary calculi: Comparison study based on calibration pellets

    NASA Astrophysics Data System (ADS)

    Štěpánková, K.; Novotný, K.; Vašinová Galiová, M.; Kanický, V.; Kaiser, J.; Hahn, D. W.

    2013-03-01

    Methods based on laser ablation, such as Laser-Induced Breakdown Spectroscopy (LIBS) and Laser-Ablation Inductively Coupled Plasma Mass/Optical Emission Spectrometry (LA-ICP-MS/OES) are particularly suitable for urinary calculi bulk and micro analysis. Investigation of spatial distribution of matrix and trace elements can help to explain their emergence and growth. However, quantification is still very problematic and these methods are often used only for qualitative elemental mapping. There are no commercially available standards, which would correspond to the urinary calculi matrix. Internal standardization is also difficult, mainly due to different crystalline phases in one kidney stone. The aim of this study is to demonstrate the calibration capabilities and examine the limitations of laser ablation based techniques. Calibration pellets were prepared from powdered human urinary calculi with phosphate, oxalate and urate matrix. For this comparative study, the most frequently used laser-ablation based analytical techniques were chosen, such as LIBS and LA-ICP-MS. Moreover, some alternative techniques such as simultaneous LIBS-LA-ICP-OES and laser ablation LA-LIBS were also utilized.

  2. Numerical Study of Thrust Generation in the Process of Laser Ablated Doped Polymer

    NASA Astrophysics Data System (ADS)

    Li, Nanlei; Hong, Yanji; Li, Xiuqian

    2011-11-01

    Recoil impulse of ablation products is a dominant source of thrust during laser ablation of polymers in vacuum. Based on the experiment phenomenon, put forward the threshold energy model to described ablation process, used laser deposition energy in polymer as ablation criterion, and calculated the fluence of energy generation from polymer chemolysis. Take the doped polymer PVC as research object, analyzed and computed interested parameter in process of laser ablated polymer, such as exhaust velocities of ablated product, ablated mass of polymer, recoil momentum gained by polymer target. Consulted experiment data, the numerical model well revealed the propulsion capability of different polymers.

  3. Study of polymer ablation products obtained by ultraviolet laser ablation — inductively coupled plasma atomic emission spectrometry

    NASA Astrophysics Data System (ADS)

    Todolí, J.-L.; Mermet, J.-M.

    1998-10-01

    A study of the nature of aerosols following polymer laser ablation was performed. A glass sample was used for comparison. Aerosol fractions were analyzed by using simple methods based on transport efficiency and filters. Three different tube lengths, i.e. 4, 29 and 54 m, were inserted between the ablation cell and the inductively coupled plasma atomic emission spectrometry (ICP-AES) injector. For the glass sample, 10 elements were studied. Only Na and K exhibited different results as the particle size, i.e. tube length, was varied. The polymers used were poly(vinyl chloride), PVC, and poly(ethylene), PE. Three elements (Ca, Ti and Sn) under different chemical forms were measured. Unlike Ti and Sn the ablated aerosol particle size (mass) seemed to depend on the Ca chemical form. Another PVC sample containing 11 elements was also studied. Na, Al and C exhibited a different behavior with particle size with respect to the remaining elements. Then, the carbon signal was studied after a 0.3 μm pore size filter had been placed between the ablation cell and the ICP torch. The results indicated that carbon was mainly present under gaseous form and particles smaller than 0.3 μm size. The analysis of the aerosol gaseous phase by thermal desorption GC-MS confirmed the presence of polymer volatile thermal degradation products. These results explained why carbon could not be applied as an efficient internal standard.

  4. Laser Paint Interactions Studied by Optical Emission Spectroscopy and Pump and Probe Analysis of the Ablation Plume

    NASA Astrophysics Data System (ADS)

    Rebollar, E.; Oujja, M.; Martín, M.; Castillejo, M.

    The ablation plumes resulting from the laser irradiation of pigments in the form of pellets and as tempera paints were studied by optical spectroscopic methods including optical emission spectroscopy (OES) and laser induced fluorescence (LIF), using a probe laser, delayed with respect to the ablation laser. The differences observed between emissions from pellets and from tempera paints of a given pigment, and between organic and inorganic pigments, serve to discuss the mechanisms operating in the laser irradiation of the paint systems.

  5. Parametric Study of Carbon Nanotube Production by Laser Ablation Process

    NASA Technical Reports Server (NTRS)

    Arepalli, Sivaram; Nikolaev, Pavel; Holmes, William; Hadjiev, Victor; Scott, Carl

    2002-01-01

    Carbon nanotubes form a new class of nanomaterials that are presumed to have extraordinary mechanical, electrical and thermal properties. The single wall nanotubes (SWNTs) are estimated to be 100 times stronger than steel with 1/6th the weight; electrical carrying capacity better than copper and thermal conductivity better than diamond. Applications of these SWNTs include possible weight reduction of aerospace structures, multifunctional materials, nanosensors and nanoelectronics. Double pulsed laser vaporization process produces SWNTs with the highest percentage of nanotubes in the output material. The normal operating conditions include a green laser pulse closely followed by an infrared laser pulse. Lasers ab late a metal-containing graphite target located in a flow tube maintained in an oven at 1473K with argon flow of 100 sccm at a 500 Torr pressure. In the present work a number of production runs were carried out, changing one operating condition at a time. We have studied the effects of nine parameters, including the sequencing of the laser pulses, pulse separation times, laser energy densities, the type of buffer gas used, oven temperature, operating pressure, flow rate and inner flow tube diameters. All runs were done using the same graphite target. The collected nanotube material was characterized by a variety of analytical techniques including scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman and thermo gravimetric analysis (TGA). Results indicate trends that could be used to optimize the process and increase the efficiency of the production process.

  6. 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.

  7. Ablation of atheroma by laser energy: a comparative study of the efficacy of different temporal rates of energy deposition

    NASA Astrophysics Data System (ADS)

    Ramsay, Donald J.; Walker, Philip J.; Dadswell, Nicola G.; May, James; Piper, James A.; Wacher, Christine

    1990-06-01

    Laser angioplasty continues to attract interest as a potential method for treating atherosclerotic arterial disease. Current efforts are aimed at finding the most effective combination of laser and delivery system. High energy pulsed ultraviolet or infrared lasers demonstrate good photoablative properties but there remain practical difficulties with the optical fibre delivery. Continuous wave lasers are widely used in conjunction with "hot-tip" fibres for thermal ablation but their direct (optical) ablation efficiency is low, causing significant surrounding thermal damage in soft tissue. While considerable attention has been directed previously at the ablative effects for different laser wavelengths, little systematic study has been made of the efficacy for different temporal rates of energy deposition. We have compared the efficacy for tissue ablation in cadaveric human aorta of three different laser systems with similar wavelengths in the visible (green) but different temporal rates of energy deposition. The laser sources were the continuous wave argon ion laser (514.5 nm), the high pulse energy, frequency doubled Nd:YAG laser (532 nm) and the copper vapour laser. The copper vapour laser is a high repetition rate, high average power, pulsed laser emitting in the green (511 nm) and yellow (578 nm) which has temporal characteristics intermediate between those of the Nd:YAG laser and the argon ion laser, and has the potential to be effective both for direct optical ablation and hot-tip thermal ablation.

  8. A study of laser ablation propulsion using polyoxymethelyne and a high power diode laser

    NASA Astrophysics Data System (ADS)

    Kolesar, Michael D.

    With an increased interest by universities, government and commercial groups in using constellations of pico and nano satellites, the need for micro-thrusters to aid in the station-keeping capabilities has become strong. This report examines using polymers and a laser to ablate material as a potential propulsion option for station-keeping. Homopolymer polyoxymethelyne (POM), commonly known as Delrin(TM), was tested as a fuel for a high powered (20 Watt 980 nm) solid state diode laser ablation thruster to be used for station-keeping on pico and nano sized satellites. The experiments required a partial vacuum to reduce the effects of air decomposition and remove water vapor during the ablation event. The vacuum chamber, shadowgraph, and an impulse measurement system were all designed and built around the 20-Watt laser. Three different sample thicknesses were tested (.005", .010", and .020") to determine the behavior of the polymer. The laser was focused onto the POM sample, which was mounted to a load cell and calibrated to measure the impulse of the system imparted by the laser pulse. The calculated thrust values ranged from 600 microN to 1300 microN with a high uncertainty due to the small sample size. The exhaust plume from the ablation event was captured using a shadowgraph. A low velocity was recorded because the chamber was not a complete vacuum, causing the exhaust plume to collide with the air molecules in the test chamber. However the load cell results suggested that 1.30 mN per burst can be produced with an uncertainty of 30%. With the work outlined in this paper, POM shows the promise and challenge of being a good candidate as a fuel material. POM warrants further development and investment as a fuel to be used with a laser ablation micro-thruster.

  9. 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.

  10. Computational study of nanosecond pulsed laser ablation and the application to momentum coupling

    SciTech Connect

    Yuan Hong; Tong Huifeng; Li Mu; Sun Chengwei

    2012-07-15

    During the evaporation and ablation of a matter induced by intensive laser radiation, the vapor plasma is ejected from the surface of the target which induces the recoil pressure and impulse in the target. Impulse coupling of laser beams with matter has been extensively studied as the basis of laser propulsion and laser clearing space debris. A one-dimensional (1D) bulk absorption model to simulate the solid target ablated directly by the laser beam is presented; numerical calculation of impulse acting on the target in vacuum with different laser parameters is performed with fluid dynamics theory and 1D Lagrange difference scheme. The calculated results of the impulse coupling coefficients are in good agreement with the experimental results and Phipps' empirical value. The simulated results show that the mechanical coupling coefficients decrease with the increment of laser intensity when the laser pulses generate plasma. The present model can be applied when the laser intensity is 10{sup 8} - 10{sup 10} W/cm{sup 2}, which will provide a guide to the study of momentum coupling of laser beams with matter.

  11. Ultraviolet femtosecond and nanosecond laser ablation of silicon: Ablation efficiency and laser-induced plasma expansion

    SciTech Connect

    Zeng, Xianzhong; Mao, Xianglei; Greif, Ralph; Russo, Richard E.

    2004-03-23

    Femtosecond laser ablation of silicon in air was studied and compared with nanosecond laser ablation at ultraviolet wavelength (266 nm). Laser ablation efficiency was studied by measuring crater depth as a function of pulse number. For the same number of laser pulses, the fs-ablated crater was about two times deeper than the ns-crater. The temperature and electron number density of the pulsed laser-induced plasma were determined from spectroscopic measurements. The electron number density and temperature of fs-pulse plasmas decreased faster than ns-pulse plasmas due to different energy deposition mechanisms. Images of the laser-induced plasma were obtained with femtosecond time-resolved laser shadowgraph imaging. Plasma expansion in both the perpendicular and the lateral directions to the laser beam were compared for femtosecond and nanosecond laser ablation.

  12. Echocardiography-guided percutaneous per-ventricular laser ablation of ventricular septum: in vivo study in a canine model.

    PubMed

    He, Guangbin; Sun, Chao; Zhang, Xiangkong; Zuo, Lei; Qin, Haiying; Zheng, Minjuan; Zhou, Xiaodong; Liu, Liwen

    2016-05-01

    Surgical myectomy and ethanol ablation are established intervention strategies for left ventricular outflow obstruction in hypertrophic cardiomyopathy. Safety and efficacy limitations of these interventions call for a minimally invasive, potentially safer, and more efficacious strategy. In this study, we aimed to evaluate the feasibility of echocardiography-guided percutaneous per-ventricular laser ablation of a ventricular septum in a canine model. Six domestic dogs were chosen for the study. A 21G needle was inserted into the right ventricle with its tip reaching the targeted basal to mid-septum, after which laser ablation was performed as follows: 1-W laser for 3 min (180 J) at the basal segment and 5 min (300 J) at middle segment of the septum, respectively. Echocardiography, blood chemistry tests, and pathology examination were performed to assess the results of laser ablation. No death or major complications, i.e., tamponade, pericardial effusion, or ventricular fibrillation, occurred. The laser-ablated areas were well demarcated in the results of the pathological examination. The diameters of the ablated regions were 4.42 ± 0.57 and 5.28 ± 0.83 mm for 3 and 5 min ablation, respectively. Pre-ablation and post-ablation, cardiac enzymes were found to increase significantly while no significant differences were found among M-mode, 2D (LVEF), pulsed-wave (PW) Doppler, and tissue Doppler imaging (TDI) measurements. Contrast echocardiography confirmed the perfusion defects in the ablated regions. Microscopically, the ablated myocardium showed coagulative changes and a sparse distribution of disappearing nuclei and an increase in eosinophil number were observed. Our study suggests that percutaneous and per-ventricular laser ablation of the septum is feasible, potentially safe and efficacious, and warrants further investigation and validation. PMID:26861985

  13. Dynamics of Femtosecond Laser Ablation Plume Studied With Ultrafast X-ray Absorption Fine Structure Imaging

    SciTech Connect

    Oguri, Katsuya; Okano, Yasuaki; Nishikawa, Tadashi; Nakano, Hidetoshi

    2010-10-08

    We investigated the dynamic process of an expanding femtosecond laser ablation plume of aluminum generated in an irradiation intensity range of 10{sup 13}-10{sup 15} W/cm{sup 2} with the ultrafast x-ray absorption fine structure (XAFS) imaging technique. The XAFS spectra of the aluminum L{sub II,III} edge of the plume revealed that the plume consists of doubly and singly charged ions, neutral atoms, liquid particles, and possible atomic clusters. Scanning electron microscopy of deposited ablation particles confirmed that the liquid particles corresponds to the spherical nanoparticles with a size ranging from several tens nanometers to approximately 200 nm. The spatiotemporal evolution of the XAFS image of the plume shows the sequential appearance of each ablation particle from aluminum surface according to its ejection velocity. The result suggests that the photomechanical fragmentation process, which was theoretically proposed, is dominant mechanism for the nanoparticle ejection under the irradiation intensity far from the ablation threshold of aluminum. This study clearly demonstrates the potential of our technique for measuring the ultrafast dynamics of femtosecond laser ablation process.

  14. Excimer laser ablation of ferrites

    NASA Astrophysics Data System (ADS)

    Tam, A. C.; Leung, W. P.; Krajnovich, D.

    1991-02-01

    Laser etching of ferrites was previously done by scanning a focused continuous-wave laser beam on a ferrite sample in a chemical environment. We study the phenomenon of photo-ablation of Ni-Zn or Mn-Zn ferrites by pulsed 248-nm KrF excimer laser irradiation. A transfer lens system is used to project a grating pattern of a mask irradiated by the pulsed KrF laser onto the ferrite sample. The threshold fluence for ablation at the ferrite surface is about 0.3 J/cm2. A typical fluence of 1 J/cm2 is used. The etched grooves produced are typically 20-50 μm wide, with depths achieved as deep as 70 μm . Groove straightness is good as long as a sharp image is projected onto the sample surface. The wall angle is steeper than 60 degrees. Scanning electron microscopy of the etched area shows a ``glassy'' skin with extensive microcracks and solidified droplets being ejected that is frozen in action. We found that this skin can be entirely removed by ultrasonic cleaning. A fairly efficient etching rate of about 10 nm/pulse for a patterned area of about 2 mm×2 mm is obtained at a fluence of 1 J/cm2. This study shows that projection excimer laser ablation is useful for micromachining of ferrite ceramics, and indicates that a hydrodynamic sputtering mechanism involving droplet emission is a cause of material removal.

  15. Time-resolved studies of particle effects in laser ablation inductively coupled plasma-mass spectrometry

    SciTech Connect

    Perdian, D.; Bajic, S.; Baldwin, D.; Houk, R.

    2007-11-13

    Time resolved signals in laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) are studied to determine the influence of experimental parameters on ICP-induced fractionation effects. Differences in sample composition and morphology, i.e., ablating brass, glass, or dust pellets, have a profound effect on the time resolved signal. Helium transport gas significantly decreases large positive signal spikes arising from large particles in the ICP. A binder for pellets also reduces the abundance and amplitude of spikes in the signal. MO{sup +} ions also yield signal spikes, but these MO{sup +} spikes generally occur at different times from their atomic ion counterparts.

  16. Study of ablation by laser irradiation of plane targets at wavelengths 1. 05, 0. 53, and 0. 35. mu. m

    SciTech Connect

    Key, M.H.; Toner, W.T.; Goldsack, T.J.; Kilkenny, J.D.; Veats, S.A.; Cunningham, P.F.; Lewis, C.L.S.

    1983-07-01

    Ablation by laser irradiation at wavelengths lambda = 1.05, 0.53, and 0.35 ..mu..m has been studied from analysis of time-resolved x-ray spectra of layered targets and of ion emission. Irradiance was varied in the range 2 x 10/sup 13/ to 2 x 10/sup 15/ W cm/sup -2/ with constant laser power and variable focal spot size. Deductions include the effect of lateral energy transport from small focal spots and ablation rates and ablation pressures obtained both in the limit of negligible transport and when lateral transport is significant. Advantages of short wavelengths for ablatively driven implosions are quantified.

  17. Er:YAG laser ablation: 5-11 years prospective study

    NASA Astrophysics Data System (ADS)

    Dostalova, Tatjana; Jelinkova, Helena; Nemec, Michal; Sulc, Jan; Miyagi, Mitsunobu

    2005-03-01

    The Er:YAG laser at 2940 nm has been proposed for use in dental cavity preparation and removal of carious enamel and dentin. The purpose of the present study was to determine the effect of the Er:YAG laser ablation in treating dental caries after a period from 5 to 11 years. For this study, 133 cavities were chosen, and for their reparation of it the three restorative materials were used. Baseline examination was made in the following intervals: one week, 1 year, and from 5 to 11 years after cavity preparation and placement of filling material. Clinical assessments were carried out in accordance with the US Public Health Service System. The follow-up included: the marginal ridge, marginal adaptation, anatomic form, caries, color match, cavo surface margin discoloration, surface smoothness, and postoperative sensitivity. Er:YAG laser ablation is an excellent method for treating frontal teeth, i.e., incisors, canines, premolars, and initial occlusal caries of molars. However, visual control of non-contact therapy is necessary. Er:YAG laser ablation is safe, and it strongly reduces pain. The laser treatment markedly decreases the unpleasant sound and vibration.

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

    NASA Astrophysics Data System (ADS)

    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.

  19. Synthesis of silver nanoparticles by laser ablation in ethanol: A pulsed photoacoustic study

    NASA Astrophysics Data System (ADS)

    Valverde-Alva, M. A.; García-Fernández, T.; Villagrán-Muniz, M.; Sánchez-Aké, C.; Castañeda-Guzmán, R.; Esparza-Alegría, E.; Sánchez-Valdés, C. F.; Llamazares, J. L. Sánchez; Herrera, C. E. Márquez

    2015-11-01

    The pulsed photoacoustic (PA) technique was used to study the synthesis by laser ablation of silver nanoparticles (Ag-NPs) in ethanol. PA technique allowed to determine the production rate per laser pulse and concentration of synthesized Ag-NPs. The samples were produced by using a pulsed Nd:YAG laser with 1064 nm of wavelength and 7 ns of pulse duration. The laser pulse energy varied from 10 to 100 mJ. Transmission electron microscopy micrographs demonstrated that the obtained nanoparticles were spherical with an average size close to 10 nm. The absorption spectra of the colloids showed a plasmon absorption peak around 400 nm. The PA analyses showed a significant reduction of the production rate of Ag-NPs during the first hundreds of laser pulses. For a higher number of pulses this rate was kept almost constant. Finally, we found that the root mean square (RMS) value of the PA signal was proportional to the laser pulse fluence on the target surface. Thus PA technique was useful to monitor the ablation process.

  20. The impact of laser ablation on optical soft tissue differentiation for tissue specific laser surgery-an experimental ex vivo study

    PubMed Central

    2012-01-01

    Background Optical diffuse reflectance can remotely differentiate various bio tissues. To implement this technique in an optical feedback system to guide laser surgery in a tissue-specific way, the alteration of optical tissue properties by laser ablation has to be taken into account. It was the aim of this study to evaluate the general feasibility of optical soft tissue differentiation by diffuse reflectance spectroscopy under the influence of laser ablation, comparing the tissue differentiation results before and after laser intervention. Methods A total of 70 ex vivo tissue samples (5 tissue types) were taken from 14 bisected pig heads. Diffuse reflectance spectra were recorded before and after Er:YAG-laser ablation. The spectra were analyzed and differentiated using principal component analysis (PCA), followed by linear discriminant analysis (LDA). To assess the potential of tissue differentiation, area under the curve (AUC), sensitivity and specificity was computed for each pair of tissue types before and after laser ablation, and compared to each other. Results Optical tissue differentiation showed good results before laser exposure (total classification error 13.51%). However, the tissue pair nerve and fat yielded lower AUC results of only 0.75. After laser ablation slightly reduced differentiation results were found with a total classification error of 16.83%. The tissue pair nerve and fat showed enhanced differentiation (AUC: 0.85). Laser ablation reduced the sensitivity in 50% and specificity in 80% of the cases of tissue pair comparison. The sensitivity of nerve–fat differentiation was enhanced by 35%. Conclusions The observed results show the general feasibility of tissue differentiation by diffuse reflectance spectroscopy even under conditions of tissue alteration by laser ablation. The contrast enhancement for the differentiation between nerve and fat tissue after ablation is assumed to be due to laser removal of the surrounding lipid-rich nerve

  1. Deposition of hydroxyapatite thin films by Nd:YAG laser ablation: a microstructural study

    SciTech Connect

    Nistor, L.C.; Ghica, C.; Teodorescu, V.S.; Nistor, S.V. . E-mail: snistor@alpha1.infim.ro; Dinescu, M.; Matei, D.; Frangis, N.; Vouroutzis, N.; Liutas, C.

    2004-11-02

    Hydroxyapatite (HA) thin films has been successfully deposited by Nd:YAG laser ablation at {lambda} = 532 nm. The morphology and microstructure of the deposited layers was studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and high resolution electron microscopy (HREM). Polycrystalline HA films were directly obtained with the substrate at 300 deg. C and without introducing water vapors in the deposition chamber. Electron paramagnetic resonance (EPR) measurements show that the oxygen stoichiometry in the HA films is also maintained. Depositions performed at {lambda} = 335 nm laser wavelength and 300 deg. C substrate temperature resulted in polycrystalline layers of mixed composition of HA and tricalciumphosphate (TCP)

  2. INTERACTION OF LASER RADIATION WITH MATTER. LASER PLASMA: Comparative study of the ablation of materials by femtosecond and pico- or nanosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Kononenko, Taras V.; Konov, Vitalii I.; Garnov, Sergei V.; Danielius, R.; Piskarskas, A.; Tamosauskas, G.; Dausinger, F.

    1999-08-01

    A series of studies was carried out on the ablation of steel, Si3N4 ceramic, and diamond in air by femtosecond (200 and 900 fs) pulses of different wavelengths (532 and 266 nm) and in a wide energy density range (1 — 103 J cm-2 ). The ablation rates were measured for different geometries of the irradiation surface [a shallow crater and a channel with a high (up to 10) aspect ratio]. The ablation rates (in a shallow crater) and the morphologies of the irradiated surface were compared for femtosecond and longer (220 ps, 7 ns) pulses. The role of the laser-generated plasma in the ablation of materials by subpicosecond pulses as well as the prospects for the practical application of ultrashort laser pulses in the processing of materials are analysed.

  3. Experimental studies of laser-ablated zirconium carbide plasma plumes: Fuel corrosion diagnostic development

    SciTech Connect

    Wantuck, P.J.; Butt, D.P.; Sappey, A.D.

    1992-01-01

    Understanding the corrosion behavior of nuclear fuel materials, such as refractory carbides, in a high temperature hydrogen environment is critical for several proposed nuclear thermal propulsion (NTP) concepts. Monitoring the fuel corrosion products is important not only for understanding corrosion characteristics, but to assess the performance of an actual, operating nuclear propulsion system as well. In this paper, we describe an experimental study initiated to develop, test, and subsequently utilize non-intrusive, laser-based diagnostics to characterize the gaseous product species which are expected to evolve during the exposure of representative fuel samples to hydrogen. Laser ablation is used to produce high temperature, vapor plumes from solid solution, uranium-free, zirconium carbide (ZrC) forms for probing by other laser diagnostic methods; predominantly laser-induced fluorescence (LIF). We discuss the laser ablation technique, results of plume emission measurements, as well as the use of planar LIF to image both the ZrC plumes and actual NTP fuel corrosion constituents.

  4. Experimental and computational study of complex shockwave dynamics in laser ablation plumes in argon atmosphere

    SciTech Connect

    Harilal, S. S.; Miloshevsky, G. V.; Diwakar, P. K.; LaHaye, N. L.; Hassanein, A.

    2012-08-15

    We investigated spatio-temporal evolution of ns laser ablation plumes at atmospheric pressure, a favored condition for laser-induced breakdown spectroscopy and laser-ablation inductively coupled plasma mass-spectrometry. The 1064 nm, 6 ns pulses from a Nd:YAG laser were focused on to an Al target and the generated plasma was allowed to expand in 1 atm Ar. The hydrodynamic expansion features were studied using focused shadowgraphy and gated 2 ns self-emission visible imaging. Shadowgram images showed material ejection and generation of shock fronts. A secondary shock is observed behind the primary shock during the time window of 100-500 ns with instabilities near the laser cone angle. By comparing the self-emission images obtained using fast photography, it is concluded that the secondary shocks observed in the shadowgraphy were generated by fast moving target material. The plume front estimates using fast photography exhibited reasonable agreement with data obtained from shadowgraphy at early times {<=}400 ns. However, at later times, fast photography images showed plume confinement while the shadowgraphic images showed propagation of the plume front even at greater times. The structure and dynamics of the plume obtained from optical diagnostic tools were compared to numerical simulations. We have shown that the main features of plume expansion in ambient Ar observed in the experiments can be reproduced using a continuum hydrodynamics model which provided valuable insight into the expansion dynamics and shock structure of the plasma plume.

  5. Time-resolved imaging for the dynamic study of ablative laser propulsion

    NASA Astrophysics Data System (ADS)

    Lin, Jun

    Time-resolved imaging techniques have been developed and used for a study of plasma dynamics in Ablative Laser Propulsion (ALP), an advanced propulsion technique utilizing the momentum of laser-ablated solid propellants for rocket thrust. We used a gated Intensified Charge Coupled Device camera to record light emission from laser-induced plasma. The plasma was ignited by 100-ps wide laser pulses, of energy 35 mJ at 532 nm wavelength. The required algorithms for processing 2-D digital images of the plasma and deriving the plasma edge velocities were also developed. The 2-D angular distribution functions for both plasma velocity and emission intensity were deduced from these measurements for the first time. The fitting functions for observed angular distributions were derived for a wide range of elements, such as C (graphite), Al, Si, Cu, Fe, Zn, Sn and Pb. Results show that the specific impulses (I sp) vary between 2.6 x 103 s (carbon) and 1.2 x 103 s (zinc), which are in excellent agreement with previously conducted Force Measurements. We also developed a digital video imaging (DVI) technique to study the dynamics of a ballistic pendulum driven by TEA CO2 laser pulses. The pulses had 200 ns pulsewidth and 10.6 J energy at 10.6 mum wavelength. The experiment using the DVI technique in the range of pressures from 3.5 mTorr to 1 atmosphere has been developed for the first time. Coupling coefficients (Cm) and mass removal rates as functions of pressure were deduced from these measurements. The technique allowed the addressing of the partition of the energy and momentum between air breakdown and target ablation. The study was performed on Aluminum targets. The partition functions show a sharp transition region between 1.0 and 10 Torr, where the momentum and energy imparted to the target via ablation appear comparable to those due to air breakdown. Our observations show that currently developing air-breathing laser-propulsion schemes would hardly support launching

  6. Multiple target laser ablation system

    DOEpatents

    Mashburn, Douglas N.

    1996-01-01

    A laser ablation apparatus and method are provided in which multiple targets consisting of material to be ablated are mounted on a movable support. The material transfer rate is determined for each target material, and these rates are stored in a controller. A position detector determines which target material is in a position to be ablated, and then the controller controls the beam trigger timing and energy level to achieve a desired proportion of each constituent material in the resulting film.

  7. Multiple target laser ablation system

    DOEpatents

    Mashburn, D.N.

    1996-01-09

    A laser ablation apparatus and method are provided in which multiple targets consisting of material to be ablated are mounted on a movable support. The material transfer rate is determined for each target material, and these rates are stored in a controller. A position detector determines which target material is in a position to be ablated, and then the controller controls the beam trigger timing and energy level to achieve a desired proportion of each constituent material in the resulting film. 3 figs.

  8. Optical time of flight studies of lithium plasma in double pulse laser ablation: Evidence of inverse Bremsstrahlung absorption

    SciTech Connect

    Sivakumaran, V.; Joshi, H. C.; Singh, R. K.; Kumar, Ajai

    2014-06-15

    The early stage of formation of lithium plasma in a collinear—double pulse laser ablation mode has been studied using optical time of flight (OTOF) spectroscopy as a function of inter-pulse delay time, the distance from the target surface and the fluence of the ablation lasers. The experimental TOF measurements were carried out for lithium neutral (670.8 nm and 610.3 nm), and ionic (548.4 nm and 478.8 nm) lines. These experimental observations have been compared with that for single pulse laser ablation mode. It is found that depending on the fluence and laser pulse shape of the first pre-ablation laser and the second main ablation laser, the plasma plume formation and its characteristic features can be described in terms of plume-plume or laser-plume interaction processes. Moreover, the enhancement in the intensity of Li neutral and ionic lines is observed when the laser-plume interaction is the dominant process. Here, we see the evidence of the role of inverse Bremsstrahlung absorption process in the initial stage of formation of lithium plasma in this case.

  9. The effects of laser repetition rate on femtosecond laser ablation of dry bone: a thermal and LIBS study.

    PubMed

    Gill, Ruby K; Smith, Zachary J; Lee, Changwon; Wachsmann-Hogiu, Sebastian

    2016-01-01

    The aim of this study is to understand the effect of varying laser repetition rate on thermal energy accumulation and dissipation as well as femtosecond Laser Induced Breakdown Spectroscopy (fsLIBS) signals, which may help create the framework for clinical translation of femtosecond lasers for surgical procedures. We study the effect of repetition rates on ablation widths, sample temperature, and LIBS signal of bone. SEM images were acquired to quantify the morphology of the ablated volume and fsLIBS was performed to characterize changes in signal intensity and background. We also report for the first time experimentally measured temperature distributions of bone irradiated with femtosecond lasers at repetition rates below and above carbonization conditions. While high repetition rates would allow for faster cutting, heat accumulation exceeds heat dissipation and results in carbonization of the sample. At repetition rates where carbonization occurs, the sample temperature increases to a level that is well above the threshold for irreversible cellular damage. These results highlight the importance of the need for careful selection of the repetition rate for a femtosecond laser surgery procedure to minimize the extent of thermal damage to surrounding tissues and prevent misclassification of tissue by fsLIBS analysis. PMID:26260774

  10. Study of superalloy topography during ultrahigh intensity nanosecond ultraviolet laser ablation

    NASA Astrophysics Data System (ADS)

    Wu, Qihong; Jie, Jiansheng; Ma, Yurong; Yu, Qingxuan; Miao, Bin; Wang, Guanzhong; Liao, Yuan; Fang, Rongchuan; Chen, Xiangli; Wang, Kelvin

    2002-05-01

    We report on the topography of holes ablated by an ultrahigh intensity 355 and 266 nm laser with 8 ns pulse width in Ni-base superalloy Inconel 718. The origin of droplets, micropores, and microcracks on the surface of hole is identified. Qualitative differences in the characteristics of microcracks indicate that the dominant continuous microcracks result from thermal effects in 355 nm laser ablation, and the dominant island-chain microcrack result from photochemical effects in 266 nm laser ablation. In ultrahigh intensity laser ablation (>200 GW/cm2), the mechanical load on the surface is very significant to the resulting topography, and the grain boundary plays an important role in the origin of the micropores.

  11. Synthesis and magnetic study of carbon coated iron oxide nanoparticles by laser ablation in solution

    NASA Astrophysics Data System (ADS)

    Prajapat, C. L.; Sharma, P.; Gonal, M. R.; Vatsa, R. K.; Singh, M. R.; Ravikumar, G.

    2016-05-01

    Magnetic Iron oxides nanoparticles (NPs) were prepared by Laser Ablation in Solution method. Formation and average size of iron oxide NPs (~8 nm) is confirmed by XRD pattern and magnetization studies. Detailed magnetic studies have been carried out using SQUID magnetometer. The saturation magnetization for the iron oxide NPs was found to be 60.07 emu/g. Below the blocking temperature of 150 K the hysteresis loop shows ferromagnetic nature, whereas it shows superparamagnetic behavior at 300 K, for the synthesized NPs.

  12. Spectroscopic studies on diamond like carbon films synthesized by pulsed laser ablation

    NASA Astrophysics Data System (ADS)

    Panda, Madhusmita; Krishnan, R.; Ravindran, T. R.; Das, Arindam; Mangamma, G.; Dash, S.; Tyagi, A. K.

    2016-05-01

    Hydrogen free Diamond like Carbon (DLC) thin films enriched with C-C sp3 bonding were grown on Si (111) substrates at laser pulse energies varying from 100 to 400 mJ (DLC-100, DLC-200, DLC-300, DLC-400), by Pulsed Laser Ablation (PLA) utilizing an Nd:YAG laser operating at fundamental wavelength. Structural, optical and morphological evolutions as a function of laser pulse energy were studied by micro Raman, UV-Vis spectroscopic studies and Atomic Force Microscopy (AFM), respectively. Raman spectra analysis provided critical clues for the variation in sp3 content and optical energy gap. The sp3 content was estimated using the FWHM of the G peak and found to be in the range of 62-69%. The trend of evolution of sp3 content matches well with the evolution of ID/IG ratio with pulse energy. UV-Vis absorption study of DLC films revealed the variation of optical energy gap with laser pulse energy (1.88 - 2.23 eV), which matches well with the evolution of G-Peak position of the Raman spectra. AFM study revealed that roughness, size and density of particulate in DLC films increase with laser pulse energy.

  13. Chemically assisted laser ablation ICP mass spectrometry.

    PubMed

    Hirata, Takafumi

    2003-01-15

    A new laser ablation technique combined with a chemical evaporation reaction has been developed for elemental ratio analysis of solid samples using an inductively coupled plasma mass spectrometer (ICPMS). Using a chemically assisted laser ablation (CIA) technique developed in this study, analytical repeatability of the elemental ratio measurement was successively improved. To evaluate the reliability of the CLA-ICPMS technique, Pb/U isotopic ratios were determined for zircon samples that have previously been analyzed by other techniques. Conventional laser ablation for Pb/U shows a serious elemental fractionation during ablation mainly due to the large difference in elemental volatility between Pb and U. In the case of Pb/U ratio measurement, a Freon R-134a gas (1,1,1,2-tetrafluoroethane) was introduced into the laser cell as a fluorination reactant. The Freon gas introduced into the laser cell reacts with the ablated sample U, and refractory U compounds are converted to a volatile U fluoride compound (UF6) under the high-temperature condition at the ablation site. This avoids the redeposition of U around the ablation pits. Although not all the U is reacted with Freon, formation of volatile UF compounds improves the transmission efficiency of U. Typical precision of the 206Pb/238U ratio measurement is 3-5% (2sigma) for NIST SRM 610 and Nancy 91500 zircon standard, and the U-Pb age data obtained here show good agreement within analytical uncertainties with the previously reported values. Since the observed Pb/U ratio for solid samples is relatively insensitive to laser power and ablation time, optimization of ablation conditions or acquisition parameters no longer needs to be performed on a sample-to-sample basis. PMID:12553756

  14. Experimental study on 785 nm femtosecond laser ablation of sapphire in air

    NASA Astrophysics Data System (ADS)

    Shaheen, M. E.; Gagnon, J. E.; Fryer, B. J.

    2015-06-01

    Changes in surface morphology and ablation rate induced on sapphire were investigated after interaction with femtosecond laser pulses in air at variable fluence (2 to 77 J cm-2) and repetition rate (10 to 1000 Hz). Multiple laser pulses at a wavelength of 785 nm and pulse width of 130 fs were fired at the surface of sapphire to produce craters whose depth, size and morphology were evaluated using optical and scanning electron microscopy. Ablation rate was found to depend on laser fluence, number of laser pulses and repetition rate. A rapid increase in ablation rate with fluence was observed for fluences lower than 5.9 J cm-2, followed by a slow increase up to fluence of 40.7 J cm-2. A drop in ablation rate occurred at fluence greater than 40.7 J cm-2. Craters produced at high repetition rate (1000 Hz) at fluence of 11.8 J cm-2 were deeper than those produced at low repetition rate (10 Hz) during the first 40 to 50 pulses. The situation was reversed for craters produced by greater than 50 laser pulses. The drop in ablation rate observed at high fluence and repetition rate can be attributed to attenuation of the laser energy due to plasma and particle shielding that result from interactions with the laser-generated particles that cannot be completely removed from the ablated crater. Defocusing effects associated with the non-equilibrium ionization of air which causes a divergence to the laser beam and consequently a reduction in the laser intensity at the sample surface can be another reason for the observed drop in the ablation rate at high fluence.

  15. Nd:YAG laser cleaning of ablation debris from excimer-laser-ablated polyimide

    NASA Astrophysics Data System (ADS)

    Gu, Jianhui; Low, Jason; Lim, Puay K.; Lim, Pean

    2001-10-01

    In the processing of excimer laser ablation of nozzles on polyimide in air, both gases like CO2, CO and HCN and solid debris including C2 approximately C12 are produced in laser ablation area. In this paper, we reported for the first time a Nd:YAG laser cleaning of ablation debris generated in excimer laser ablation of polyimide. It demonstrated effective cleaning with the advantages of shortening cleaning cycle time and simplifying cleaning process. The laser used for the cleaning was a Q-switched and frequency doubled Nd:YAG laser with wavelength of 532 nm and repetition rate of 10 Hz. The laser cleaning effect was compared with conventional plasma ashing. AFM measurement showed that the Nd:YAG laser cleaning had no damage to the substrate. XPS results indicated that the polyimide surface cleaned with laser beam had a lower oxygen/carbon ratio than that of plasma ashing. The study shows that frequency doubled Nd:YAG laser cleaning is effective in ablation debris removal from excimer laser ablated polyimide.

  16. Subpicosecond laser ablation of dental enamel

    NASA Astrophysics Data System (ADS)

    Rode, A. V.; Gamaly, E. G.; Luther-Davies, B.; Taylor, B. T.; Dawes, J.; Chan, A.; Lowe, R. M.; Hannaford, P.

    2002-08-01

    Laser ablation of dental enamel with subpicosecond laser pulses has been studied over the intensity range of (0.1-1.4) x1014 W/cm2 using 95 and 150 fs pulses at a pulse repetition rate of 1 kHz. The experimentally determined ablation threshold of 2.2plus-or-minus0.1 J/cm2 was in good agreement with theoretical predictions based on an electrostatic ablation model. The ablation rate increased linearly with the laser fluence for up to 15 times the ablation threshold. The absence of collateral damage was observed using optical and scanning electron microscopy. Pulpal temperature measurements showed an increase of about 10 degC during the 200 s course of ablation. However, air cooling at a rate of 5 l/min resulted in the intrapulpal temperature being maintained below the pulpal damage threshhold of 5.5 degC. The material removal rates for subpicosecond precision laser ablation of dental enamel are compared with other techniques.

  17. Ablation of femural bone with femtosecond laser pulses--a feasibility study.

    PubMed

    Liu, Yifei; Niemz, Markolf

    2007-09-01

    Although lasers are nowadays widely accepted as a popular scalpel of minimally invasive surgery (MIS), one of the most common orthopedic surgeries-the replacement of the knee joint-is still performed using an ordinary oscillating saw. Since ultra-short laser pulses are usually considered to be inefficient regardless of their high precision, the newest development of femtosecond laser systems has not yet been clinically applied to any mass ablation situation. However, thin disk Yb:KYW lasers meanwhile provide sufficient output power to ablate bone tissue within a reasonable time frame. Our results mainly focus on ablation rates obtained at different spot distances, repetition rates and pulse energies. It is shown that femtosecond laser pulses at high repetition rates are a promising tool for orthopedic surgery. PMID:17242869

  18. Basic ablation phenomena during laser thrombolysis

    NASA Astrophysics Data System (ADS)

    Sathyam, Ujwal S.; Shearin, Alan; Prahl, Scott A.

    1997-05-01

    This paper presents studies of microsecond ablation phenomena that take place during laser thrombolysis. The main goals were to optimize laser parameters for efficient ablation, and to investigate the ablation mechanism. Gelatin containing an absorbing dye was used as the clot model. A parametric study was performed to identify the optimal wavelength, spot size, pulse energies, and repetition rate for maximum material removal. The minimum radiant exposures to achieve ablation at any wavelength were measured. The results suggest that most visible wavelengths were equally efficient at removing material at radiant exposures above threshold. Ablation was initiated at surface temperatures just above 100 degrees Celsius. A vapor bubble was formed during ablation. Less than 5% of the total pulse energy is coupled into the bubble energy. A large part of the delivered energy is unaccounted for and is likely released partly as acoustic transients from the vapor expansion and partly wasted as heat. The current laser and delivery systems may not be able to completely remove large clot burden that is sometimes encountered in heart attacks. However, laser thrombolysis may emerge as a favored treatment for strokes where the occlusion is generally smaller and rapid recanalization is of paramount importance. A final hypothesis is that laser thrombolysis should be done at radiant exposures close to threshold to minimize any damaging effects of the bubble dynamics on the vessel wall.

  19. High-speed photographic studies of dye-assisted pulsed Nd:YAG laser ablation of dental hard tissues

    NASA Astrophysics Data System (ADS)

    Lu, Quiang; Wallace, David B.; Hayes, Donald J.

    1997-06-01

    We have been evaluating the use of a pulsed Nd:YAG laser for ablating hard dental tissue. For this application we apply dye-drops of an IR absorptive fluid on the enamel, then irradiate with a laser pulse from the laser. By using ink- jet technology to deliver the dye-drops, we can attain micron- and millisecond-scale precision in drop delivery, with a 'burst' of drops preceding each laser pulse. To gain better understanding of the ablation process we have used a high- speed CCD camera system with 1 microsecond(s) exposure and 1 microsecond(s) inter-exposure-interval capability. Fast photography of the ablation process showed the following typical events. (i) The laser induced plasma plume erupts immediately after pulse onset, expands to maximum within 50 microsecond(s) , and lasts up to 200 microsecond(s) . (ii) Ejected particles flying away from the site of laser pulse/dye-drop impact are detected within 30 microsecond(s) of laser pulse onset, and continue up to 10 ms. These particles attain velocities up to 50 m/s with lower velocities from lower pulse power. (iii) The plasma plume has a peak height that increases with increasing laser fluence, ranging up to 10 mm for a fluence of 242 J/cm2 on enamel. From this study, the dye-assisted ablation mechanisms are inferred to be plasma-mediated and explosion- mediated tissue removal.

  20. Laser ablation of human tooth

    NASA Astrophysics Data System (ADS)

    Franklin, Sushmita R.; Chauhan, P.; Mitra, A.; Thareja, R. K.

    2005-05-01

    We report the measurements of ablation threshold of human tooth in air using photo-thermal deflection technique. A third harmonic (355nm) of Nd:YAG (yttrium aluminum garnet) laser was used for irradiation and a low power helium neon laser as a probe beam. The experimental observations of ablation threshold in conjunction with theoretical model based on heat conduction equations for simulating the interaction of a laser radiation with a calcified tissue are used to estimate the absorption coefficient of human tooth.

  1. Laser ablation based fuel ignition

    DOEpatents

    Early, J.W.; Lester, C.S.

    1998-06-23

    There is provided a method of fuel/oxidizer ignition comprising: (a) application of laser light to a material surface which is absorptive to the laser radiation; (b) heating of the material surface with the laser light to produce a high temperature ablation plume which emanates from the heated surface as an intensely hot cloud of vaporized surface material; and (c) contacting the fuel/oxidizer mixture with the hot ablation cloud at or near the surface of the material in order to heat the fuel to a temperature sufficient to initiate fuel ignition. 3 figs.

  2. Laser ablation based fuel ignition

    DOEpatents

    Early, James W.; Lester, Charles S.

    1998-01-01

    There is provided a method of fuel/oxidizer ignition comprising: (a) application of laser light to a material surface which is absorptive to the laser radiation; (b) heating of the material surface with the laser light to produce a high temperature ablation plume which emanates from the heated surface as an intensely hot cloud of vaporized surface material; and (c) contacting the fuel/oxidizer mixture with the hot ablation cloud at or near the surface of the material in order to heat the fuel to a temperature sufficient to initiate fuel ignition.

  3. Confocal microscopy to guide Erbium:yttrium aluminum garnet laser ablation of basal cell carcinoma: an ex vivo feasibility study

    PubMed Central

    Larson, Bjorg A.; Chen, Chih-Shan Jason; Rajadhyaksha, Milind

    2013-01-01

    Abstract. For the removal of superficial and nodular basal cell carcinomas (BCCs), laser ablation provides certain advantages relative to other treatment modalities. However, efficacy and reliability tend to be variable because tissue is vaporized such that none is available for subsequent histopathological examination for residual BCC (and to confirm complete removal of tumor). Intra-operative reflectance confocal microscopy (RCM) may provide a means to detect residual tumor directly on the patient and guide ablation. However, optimization of ablation parameters will be necessary to control collateral thermal damage and preserve sufficient viability in the underlying layer of tissue, so as to subsequently allow labeling of nuclear morphology with a contrast agent and imaging of residual BCC. We report the results of a preliminary study of two key parameters (fluence, number of passes) vis-à-vis the feasibility of labeling and RCM imaging in human skin ex vivo, following ablation with an erbium:yttrium aluminum garnet laser. PMID:24045654

  4. Comparative study of CO2- and Er:YAG laser ablation of multiple cutaneous neurofibromas in von Recklinghausen's disease.

    PubMed

    Kriechbaumer, Lukas K; Susani, Martin; Kircher, Susanne G; Distelmaier, Klaus; Happak, Wolfgang

    2014-05-01

    With a prevalence of 1 in 3,000 births, neurofibromatosis type 1 (NF1) is one of the most common genetic disorders and is characterized by an uninhibited expansion of neural tissue. Occasionally, severe deformities occur, but frequently considerable cosmetic disfigurement is caused by the development of hundreds of benign cutaneous neurofibromas. The objective of this study was to evaluate the erbium:yttrium-aluminium-garnet (Er:YAG) laser as a therapeutic option for the removal of multiple cutaneous neurofibromas. In this prospective, comparative, in vivo study, 15,580 neurofibromas (44 operations on 21 patients) were removed via electrosurgery, CO2- or Er:YAG laser ablation. In 12 adjacent test areas, we compared the zone of thermal necrosis, the postoperative pain, the time to reepithelialization, the duration of postoperative erythema and the cosmetic outcome of these surgical methods. When compared to electrosurgery and CO2 laser ablation, the Er:YAG laser ablation outperformed the other methods of tumor removal. Rapid healing by second intention as well as the minimal discomfort and scar formation following Er:YAG laser ablation were noted. After 36 months of follow-up, permanent dyspigmentation was rare and hypertrophic scarring was not observed. Er:YAG laser vaporization of multiple cutaneous neurofibromas is a simple and rapid procedure that results in significantly better cosmetic results than CO2 laser treatment or electrosurgery. PMID:24189926

  5. Excimer laser ablation of the lens.

    PubMed

    Nanevicz, T M; Prince, M R; Gawande, A A; Puliafito, C A

    1986-12-01

    Ablation of the bovine crystalline lens was studied using radiation from an excimer laser at four ultraviolet wave lengths as follows: 193 nm (argon fluoride), 248 nm (krypton fluoride), 308 nm (xenon chloride), and 351 nm (xenon fluoride). The ablation process was quantitated by measuring mass ablated with an electronic balance, and characterized by examining ablation craters with scanning electron microscopy. The highest ablation rate was observed at 248 nm with lower rates at 193 and 308 nm. No ablation was observed at 351 nm. Scanning electron microscopy revealed the smoothest craters at 193 nm while at 248 nm there was vacuolization in the crater walls and greater disruption of surrounding tissue. The craters made at 308 nm did not have as smooth a contour as the 193-nm lesions. The spectral absorbance of the bovine lens was calculated at the wavelengths used for ablation and correlated with ablation rates and thresholds. High peak-power, pulsed ultraviolet laser radiation may have a role in surgical removal of the lens. PMID:3789982

  6. Laser ablation in analytical chemistry.

    PubMed

    Russo, Richard E; Mao, Xianglei; Gonzalez, Jhanis J; Zorba, Vassilia; Yoo, Jong

    2013-07-01

    In 2002, we wrote an Analytical Chemistry feature article describing the Physics of Laser Ablation in Microchemical Analysis. In line with the theme of the 2002 article, this manuscript discusses current issues in fundamental research, applications based on detecting photons at the ablation site (LIBS and LAMIS) and by collecting particles for excitation in a secondary source (ICP), and directions for the technology. PMID:23614661

  7. Nanochemical effects in femtosecond laser ablation of metals

    SciTech Connect

    Vorobyev, A. Y.; Guo, Chunlei

    2013-02-18

    We study chemical energy released from the oxidation of aluminum in multipulse femtosecond laser ablation in air and oxygen. Our study shows that the released chemical energy amounts to about 13% of the incident laser energy, and about 50% of the ablated material is oxidized. The ablated material mass per laser pulse is measured to be on the nanogram scale. Our study indicates that femtosecond laser ablation is capable of inducing nanochemical reactions since the femtosecond laser pulse can controllably produce nanoparticles, clusters, and atoms from a solid target.

  8. Studying ultrafast laser parameters to deter self-focusing for deep tissue ablation

    NASA Astrophysics Data System (ADS)

    Martin, Chris; Ben-Yakar, Adela

    2016-03-01

    Ultrafast pulsed lasers are a promising tool for precise and noninvasive tissue surgery. The high peak intensity of the pulses allows nonlinear interaction with tissue, causing three-dimensional confined ablation without thermal damage. However, deep tissue ablation has been limited to a few scattering lengths due to laser beam extinction. As pulse energies are increased to overcome attenuation, unwanted side effects can occur such as self-focusing, where the highly intense pulse alters the refractive index of the material, causing a lensing effect and long filaments of damage or complete beam collapse before the focus. Here, we examine laser parameters to overcome self-focusing for deep tissue ablation. Through imaging ablation voids with third harmonic generation, we show that increasing the pulse width from 200-fs to 2-ps reduces self-focusing induced focal plane shifting and avoids multiple filamentation altogether, resulting in deeper ablation without extended axial damage. Additionally, we simulate beam propagation for pulses of different central wavelengths, and show that longer wavelengths can ablate deeper because of decreased scattering in tissue and a subsequent reduction in self-focusing.

  9. Determination of energy density threshold for laser ablation of bacteria. An in vitro study.

    PubMed

    Coffelt, D W; Cobb, C M; MacNeill, S; Rapley, J W; Killoy, W J

    1997-01-01

    The Nd:YAG and CO2 lasers have been shown to be bactericidal at relative low energy densities. However, at energy densities exceeding 120 J/cm2 (CO2) and 200 J/cm2 (Nd:YAG), laser irradiation also causes irreparable root surface damage. The purpose of this study was to determine, in vitro, the energy density threshold at which microbial ablation could be achieved while inflicting the least amount of damage to the root surfaces of human teeth. Pairs of Escherichia coli colonies cultured on broth agar were treated with a CO2 laser using a pulsed waveform at approximate energy densities ranging from 3 to 110 J/cm2. One of each colony-pair was then examined by scanning electron microscopy (SEM) and the other subcultured for viable microbes. Roots of extracted teeth were lightly scaled and treated by CO2 laser, again with pulsed beam using approximate energy densities of 3 to 110 J/cm2: and examined by SEM. Regardless of the level of energy density, residual bacteria could be subcultured from all laser treated microbial colonies. The inability of the laser to completely obliterate microbial colonies was likely due to: depth of energy penetration, difficulty in precisely overlapping beam focal spots, irregular beam profile, and presence of microbes at the periphery of the beam focal spot. The threshold energy density for bacterial obliteration was determined to be 11 J/cm2 and that for root damage was 41 J/cm2. Root damage was evident by charring, crater formation, melt-down and resolidification surface mineral, and increasing surface porosity. The results of this in vitro study indicate that when used at an energy density between 11 and 41 J/cm2 the CO2 laser may destroy microbial colonies without inflicting undue damage to the tooth root surface. PMID:9049791

  10. Photothermal ablation of liver tissue with 1940-nm thulium fiber laser: an ex vivo study on lamb liver

    NASA Astrophysics Data System (ADS)

    Alagha, Heba Z.; Gülsoy, Murat

    2016-01-01

    The purpose of this study was to investigate the ablation efficiency of 1940-nm thulium fiber laser on liver tissue, while utilizing a real-time measurement system to monitor the temperature rise in adjacent tissues. Thulium fiber laser was delivered to lamb liver tissue samples via 400-μm bare tip fiber in contact mode. Eight different laser parameter combinations [power, continuous-wave (cw)/pulsed-modulated (pm) mode, and exposure time] were used. Exposure times were chosen to give the same total applied energy of 4 J for comparative purposes. Following laser irradiations, tissues were processed and stained with hematoxylin and eosin for macroscopic evaluation of ablation areas and total altered areas, and ablation efficiencies were calculated. Temperature of the nearby tissue at a distance of 1 mm from the fiber was measured, and rate of temperature change was calculated. A strong correlation between the rate of temperature change and ablation area was noted. Thermal effects increased with increasing power for both modes. The continuous-wave mode yielded higher ablation efficiencies than the pulse-modulated mode. Histological evaluation revealed a narrow vacuolization zone and negligible carbonization for higher-power values.

  11. Infrared laser ablation study of pressed soil pellets with inductively coupled plasma atomic emission spectrometry.

    PubMed

    Mikolás, J; Musil, P; Stuchliková, V; Novotný, K; Otruba, V; Kanický, V

    2002-09-01

    Potential of infrared laser ablation (LA) coupled with ICP-AES as a technique suitable for the determination of trace elements (Zn, Cu, Ni, Cr, and V) in agricultural soils was studied. Operating parameters such as laser beam energy, laser beam focusing with respect to the sample surface, and velocity of the sample translation in the plane perpendicular to the laser beam were optimized. Soil samples were mixed with powdered Ag as a binder, and an internal standard (GeO(2)), and pressed into pellets. Calibration samples were prepared by adding known amounts of oxides of elements of interest into soils of known elemental composition and then processed in the same way as the analyzed samples. Calibration curves were found to be linear at least up to several hundreds of mg kg(-1) for the elements of interest. The elemental contents obtained by using LA-ICP-AES were compared with those obtained by analysis using wet chemistry followed by ICP-AES with pneumatic nebulization (PN). The results were in good agreement. Accuracy was also tested using certified reference soils with a bias not exceeding 10% relative. PMID:12324844

  12. Study on the Long-Term Results of Endovenous Laser Ablation for Treating Varicose Veins.

    PubMed

    Go, Seung Je; Cho, Byung Sun; Mun, Yun Su; Kang, Yoon Jung; Ahn, Hye Young

    2016-06-01

    Background Endovenous laser ablation (EVLA) is widely performed since the early 2000s, but there are few long-term results. Objectives The aim of this study was to evaluate the long-term results of EVLA employed for treating varicose veins of the lower limbs by duplex ultrasonographic study. Methods A total of 24 limbs of 17 patients who underwent EVLA between 2004 and 2007 were examined with duplex ultrasonographic scans. The mean follow-up period was 66.1 months. Results There were five recurrences of saphenofemoral junction reflux. The occlusion rate was 79.2% at a mean follow-up of 66.1 months. There were 14 recanalizations and 5 recurrences of the great saphenous vein. Five partial and nine total recanalizations were observed. Conclusions EVLA is an effective and minimally invasive treatment for varicose veins. Our long-term result was acceptable, but the result was not outstanding. PMID:27231428

  13. In vivo study of necrosis on the liver tissue of Wistar rats: a combination of photodynamic therapy and carbon dioxide laser ablation

    NASA Astrophysics Data System (ADS)

    Rego, R. F.; Nicolodelli, G.; Araujo, M. T.; Tirapelli, L. F.; Araujo-Moreira, F. M.; Bagnato, V. S.

    2013-07-01

    Photodynamic therapy (PDT) is known to be limited to applications in large volume tumors due to its limited penetration. Therefore, a combination of PDT and carbon dioxide (CO2) laser ablation may constitute a potential protocol to destroy bulk tumors because it involves an association of these two techniques allowing the removal of visible lesions with a high selectivity of destruction of remnant tumors. The main aim of this study is to investigate the most appropriate procedure to combine use of a CO2 laser and PDT on livers of healthy rats, and to analyze different techniques of this treatment using three types of photosensitizers (PSs). Forty eight animals were separated to form six groups: (1) only CO2 laser ablation, (2) drug and CO2 laser ablation, (3) only PDT, (4) drug and light (PDT) followed by CO2 laser ablation, (5) ablated with CO2 laser followed by PDT, and (6) drug followed by CO2 laser ablation and light. For each group, three types of photosensitization were used: topical 5-aminolevulinic acid (ALA), intravenous ALA and intravenous Photogem®. Thirty hours after the treatments, the animals were sacrificed and the livers removed. The depth of necrosis was analyzed and measured, considering microscopic and macroscopic aspects. The results show that the effects of the PDT were considerably enhanced when combined with CO2 laser ablation, especially when the PDT was performed before the CO2 laser ablation.

  14. Time-Resolved Force and Schlieren Visualization Study of TEA CO2 Laser Ablation of Water Droplets

    NASA Astrophysics Data System (ADS)

    Li, Xiuqian; Hong, Yanji; Wen, Ming; Ye, Jifei; Cui, Cunyan

    2011-11-01

    Time-resolved force sensing technique was applied to the study of propulsive characteristics of water droplets for multi-pulse TEA (transversely excited at atmospheric pressure) CO2 laser propulsion. Laser-driven blast waves and associated flow dynamics in the impulse generation processes of ablation of water droplets were studied by Schlieren visualization. Experimental results showed that coupling coefficient and specific impulse decreased as the interval between laser pulses and pulse numbers was increased. The maximum speed of the blast wave in the opposite and same direction of laser propagation was respectively 10 km/s and 7 km/s.

  15. Time-resolved studies of particle effects in laser ablation inductively coupled plasma-mass spectrometry

    SciTech Connect

    Perdian, D.; Bajic, S.; Baldwin, D.; Houk, R.

    2007-11-13

    Transient signal responses for ablated samples as a function of particle size and laser parameters are characterized. Data are acquired with time resolution of 5 or 6 ms per data point. Large positive spikes in signal are observed and increase in both amplitude and frequency with increasing particle size. Particle sizes are selected using a differential mobility analyzer. Spikes in the signal also increase with decreasing laser rastering rates. A comparison of lasers with pulse widths of 370 fs and 5 ns shows that shortening the pulse width significantly reduces the frequency and amplitude of positive spikes in signal. These large positive spikes are attributed to the vaporization, atomization, and ionization of individual large intact particles, which are considered to be a major cause of fractionation in laser ablation ICP-MS.

  16. Possible evidence of Coulomb explosion in the femtosecond laser ablation of metal at low laser fluence

    NASA Astrophysics Data System (ADS)

    Li, Shuchang; Li, Suyu; Zhang, Fangjian; Tian, Dan; Li, He; Liu, Dunli; Jiang, Yuanfei; Chen, Anmin; Jin, Mingxing

    2015-11-01

    We use a computational model to study the ablation mechanism of metal target irradiated by femtosecond pulse laser. It is confirmed that the Coulomb explosion can occur during femtosecond laser ablation of metal. The influence of thermal ablation and Coulomb explosion on the ablation depth is respectively investigated. Comparing the calculated results with the experimental ones, we find that the theoretical results which consider the thermal ablation only agree well with the experimental ones at high laser fluence, and those which take the Coulomb explosion into account fit well with the experimental ones at lower laser fluence, which exactly explains the ablation mechanism. In contrast with the previous theoretical results which only consider the thermal ablation, our theoretical simulation describes the ablation mechanism straightforward by making comparison of ablation depth, and provides a more reasonable explanation that fits with the actual ablation process.

  17. Dynamics of femtosecond laser ablation studied with time-resolved x-ray absorption fine structure imaging

    SciTech Connect

    Oguri, Katsuya; Okano, Yasuaki; Nishikawa, Tadashi; Nakano, Hidetoshi

    2009-04-01

    We studied the dynamics of the femtosecond laser ablation of aluminum in an energy range well above the ablation threshold with the ultrafast time-resolved x-ray-absorption fine structure imaging technique. Analyzing the spectral structures near the L absorption edge that appeared in one-dimensional images of soft-x-ray absorbance, we successfully identified doubly and singly charged ions, neutral atoms, liquid nanoparticles, and possible atomic clusters in the expanding ablation plume. We also clarified that the ejected particles depend strongly on the laser irradiation intensity. The spatiotemporal evolution of the ablation particles allows us to estimate the spatial distribution of atomic density and the ejection velocity of each type of particle. In particular, we discuss the temporal sequence of the particle ejection in the early stages of plume expansion. Our experimental results strongly support the idea that photomechanical fragmentation and vaporization are dominant mechanisms for the production of liquid nanoparticles and neutral atoms, respectively, in femtosecond laser ablation induced in an irradiation intensity range of 10{sup 14}-10{sup 15} W/cm{sup 2}.

  18. Laser ablation in titanium implants followed by biomimetic hydroxyapatite coating: Histomorphometric study in rabbits.

    PubMed

    Faeda, Rafael Silveira; Spin-Neto, Rubens; Marcantonio, Elcio; Guastaldi, Antonio Carlos; Marcantonio, Elcio

    2012-07-01

    Titanium surface texture and chemistry modification successfully improves the host response and consequently the bone-to-implant contact surrounding dental implants. The aim of the present study was to investigate, using histomorphometrical-analysis, the effects of titanium surface modification by laser-ablation (Nd:YAG) followed by thin chemical deposition of HA. Forty-eight rabbits received one implant by tibiae of AS-machined (MS), laser-modified (LMS), or biomimetic hydroxyapatite-coated (HA) surface. Bone-to-implant contact (BIC) and bone area (BBT) were evaluated after 4, 8, and 12 weeks, at cortical and cancellous regions. Average BIC in the cortical region was higher (P < 0.001) on the LMS and HA implants for all periods, with no differences between LMS and HA. For the cancellous area, the LMS and HA implants showed higher (P < 0.01) BIC than MS at the initial periods. The LMS and HA showed similar values in the cortical region, but a tendency of higher values for HA in the cancellous region was observed in all periods. For the BBT, the differences were found only between HA and MS after 4 weeks in the cortical region (P < 0.05), and after 12 weeks in the cancellous area (P < 0.05). Our results showed that HA biomimetic coating preceded by laser treatment induced the contact osteogenesis and allowed the formation of a more stable bone-implant interface, even in earlier periods. PMID:22389308

  19. Laser Ablation Molecular Isotopic Spectrometry

    NASA Astrophysics Data System (ADS)

    Russo, Richard E.; Bol'shakov, Alexander A.; Mao, Xianglei; McKay, Christopher P.; Perry, Dale L.; Sorkhabi, Osman

    2011-02-01

    A new method of performing optical isotopic analysis of condensed samples in ambient air and at ambient pressure has been developed: Laser Ablation Molecular Isotopic Spectrometry (LAMIS). The technique uses radiative transitions from molecular species either directly vaporized from a sample or formed by associative mechanisms of atoms or ions in a laser ablation plume. This method is an advanced modification of a known atomic emission technique called laser-induced breakdown spectroscopy (LIBS). The new method — LAMIS — can determine not only chemical composition but also isotopic ratios of elements in the sample. Isotopic measurements are enabled by significantly larger isotopic shifts found in molecular spectra relative to atomic spectra. Analysis can be performed from a distance and in real time. No sample preparation or pre-treatment is required. Detection of the isotopes of hydrogen, boron, carbon, and oxygen are discussed to illustrate the technique.

  20. 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.

  1. Laser ablation-ICP-MS depth profiling to study ancient glass surface degradation.

    PubMed

    Panighello, Serena; Van Elteren, Johannes T; Orsega, Emilio F; Moretto, Ligia M

    2015-05-01

    In general the analysis of archeological glass represents a challenge for a wide variety of objects because of the presence of physical and/or chemical damage on the surface of the artifact, also known as weathering or corrosion. To retrieve accurate bulk elemental information by laser ablation-inductively coupled plasma-mass spectrometry (ICP-MS), the original, pristine glass needs to be "reached", thereby penetrating the alteration layer which is often more than 10 μm thick. To study this alteration layer the laser was operated in the drilling mode, either with a low (1 Hz) or a high (10 Hz) pulse repetition rate for a period of 50 s yielding detailed spatial information for ca. 20 elements over a shallow depth (ca. 5 μm) or less-detailed spatial information for 50-60 elements over a greater depth (ca. 50 μm). Quantitative elemental depth profiles (in wt%) were obtained with the so-called sum normalization calibration protocol, based on summation of the elements as their oxides to 100 wt%. We were able to associate the increase of SiO2 (in wt%) in the alteration layer to the volumetric mass density change in the glass as a result of depletion of Na2O and K2O. Also the interaction of the number of laser shots with the alteration layer is shown experimentally via depth measurements using profilometry. Chemical and physical changes in four ancient glass artifacts, directly and indirectly measureable by laser drilling, were studied as a function of internal and external factors such as age, composition, and exposure conditions. PMID:25716469

  2. Experimental study on double-pulse laser ablation of steel upon multiple parallel-polarized ultrashort-pulse irradiations

    NASA Astrophysics Data System (ADS)

    Schille, Joerg; Schneider, Lutz; Kraft, Sebastian; Hartwig, Lars; Loeschner, Udo

    2016-07-01

    In this paper, double-pulse laser processing is experimentally studied with the aim to explore the influence of ultrashort pulses with very short time intervals on ablation efficiency and quality. For this, sequences of 50 double pulses of varied energy and inter-pulse delay, as adjusted between 400 fs and 18 ns by splitting the laser beam into two optical paths of different length, were irradiated to technical-grade stainless steel. The depth and the volume of the craters produced were measured in order to evaluate the efficiency of the ablation process; the crater quality was analyzed by SEM micrographs. The results obtained were compared with craters produced with sequences of 50 single pulses and energies equal to the double pulse. It is demonstrated that double-pulse processing cannot exceed the ablation efficiency of single pulses of optimal fluence, but the ablation crater surface formed smoother if inter-pulse delay was in the range between 10 ns and 18 ns. In addition, the influence of pulse duration and energy distribution between the individual pulses of the double pulse on ablation was studied. For very short inter-pulse delay, no significant effect of energy variation within the double pulse on removal rate was found, indicating that the double pulse acts as a big single pulse of equal energy. Further, the higher removal efficiency was achieved when double-pulse processing using femtosecond pulses instead of picosecond pulses.

  3. A Study of Burst-Mode Ultrafast-Pulse Laser Ablation on Soft Tissues and Tissue-Proxies

    NASA Astrophysics Data System (ADS)

    Qian, Zuoming

    This thesis research presents an experimental study of both the physics mechanisms and biological effects of burst-mode ultrafast-pulse laser ablation. A 3D living-cell-culture tissue-proxy based on agar hydrogel was developed, and this tissue-proxy was used to quantify the cellular necrosis range, to identify the types of cellular death, and to measure the volume of material removal post burst-mode laser ablation. The potential hazards of cellular DNA damage were also evaluated. A time-resolving energy-partition diagnostics system was designed and built for characterizing the dynamic scattering and absorption of pulses during burst-mode ablation. Such characterizations were carried out on soda-lime glass, aluminum, porcine tissues, distilled water, and agar gels using this diagnostic system. Each type of target materials displayed distinct features in their absorption patterns. An array of characteristics of the absorption and their relation to the ablation dynamics were analyzed, and valuable insight about the burst-mode ablation process was gained. The characterization of the dynamic absorptions allowed the evaluation of the roles of different physics mechanisms in the resulting cellular damage and material removal.

  4. Excimer laser ablation of ferrite ceramics

    NASA Astrophysics Data System (ADS)

    Tam, A. C.; Leung, W. P.; Krajnovich, D.

    We study the ablation of Ni-Zn or Mn-7n ferrites by 248-nm KrF excimer laser irradiation for high-resolution patterning. A transfer lens system is used to project the image of a mask irradiated by the pulsed KrF laser onto the ferrite sample. The threshold fluente for ablation of the ferrite surface is about 0.3 J/cm2. A typical fluente of 1 J/cm2 is used to produce good-quality patterning. Scanning electron microscopy of the ablated area shows a "glassy" skin with extensive microcracks and solidified droplets being ejected that is frozen in action. This skin can be removed by ultrasonic cleaning.

  5. Femtosecond lasers for machining of transparent, brittle materials: ablative vs. non-ablative femtosecond laser processing

    NASA Astrophysics Data System (ADS)

    Hendricks, F.; Matylitsky, V. V.

    2016-03-01

    This paper focuses on precision machining of transparent materials by means of ablative and non-ablative femtosecond laser processing. Ablation technology will be compared with a newly developed patent pending non-ablative femtosecond process, ClearShapeTM, using the Spectra-Physics Spirit industrial femtosecond laser.

  6. Numerical study of the ablative Richtmyer-Meshkov instability of laser-irradiated deuterium and deuterium-tritium targets

    NASA Astrophysics Data System (ADS)

    Marocchino, Alberto; Atzeni, Stefano; Schiavi, Angelo

    2010-11-01

    The Richtmyer-Meshkov instability (RMI) at the ablation front of laser-irradiated planar targets is investigated by two-dimensional numerical hydrodynamics simulations. The linear evolution of perturbations seeded either by surface roughness or target inhomogeneity is studied for perturbation wavelengths in the range 10≤λ≤400 μm and laser intensity 4×1012≤I≤4×1014 W/cm2 (with laser wavelength λlaser=0.35 μm). Thin and thick cryogenic deuterium or deuterium-tritium (DT) planar targets are considered. For targets irradiated at constant intensity, it is found that perturbations with wavelength below a given threshold perform damped oscillations, while perturbations above such a threshold are unstable and oscillate with growing amplitude. This is qualitatively in agreement with theoretical predictions by Goncharov et al. [Phys. Plasmas 13, 012702 (2006)], according to which ablation related processes stabilize perturbations with kDc≫1, where Dc is the distance between the ablation front and critical density for laser propagation. For kDc<1 a weakly growing Landau-Darrieus instability (LDI) is instead excited. The stability threshold increases substantially with laser intensity, given the dependence of Dc on laser intensity I (roughly Dc∝I, according to the present simulations). Direct-drive laser fusion targets are irradiated by time-shaped pulses, with a low intensity initial foot. In this case, perturbations with wavelengths below some threshold (about 10 μm, for typical ignition-class all-DT targets) are damped after an initial growth. In a thin target, initial perturbations, either damped or amplified by RMI and LDI, seed the subsequent Rayleigh-Taylor instability. Finally, it is shown that RMI growth of fusion targets can be reduced by using laser pulses including an initial adiabat-shaping picket (originally proposed to reduce the growth of Rayleigh-Taylor instability).

  7. A study of phase explosion of metal using high power Nd:YAG laser ablation

    SciTech Connect

    Yoh, Jack J.; Lee, H. H.; Choi, J. H.; Lee, K. C.; Kim, K. H.

    2007-12-12

    The interaction of high-power pulsed-laser beam with metal targets in air from 1.06 {mu}m, 5 ns, 3 J/pulse max, Nd:YAG pulsed laser is investigated together with hydrodynamic theories of laser-supported detonation (LSD) wave and multi-material reactive Euler equations. The high speed blast wave generated by the laser ablation of metal reaches maximum velocity of several thousand meters per second. The apparently similar flow conditions to those of reactive shock wave allow one to apply the equations of motion for energetic materials and to understand the explosive behavior of metal vaporization upon laser ablation. The characteristic time at which planar to spherical wave transition occurs is confirmed at low (20 mJ/pulse) to higher (200 mJ/pulse) beam intensities. The flow structure behind the leading shock wave during the early planar shock state is confirmed by the high-resolution multi-material hydrocode originally developed for shock compression of condensed matter.

  8. a Study of Phase Explosion of Metal Using High Power Nd:YAG Laser Ablation

    NASA Astrophysics Data System (ADS)

    Yoh, Jack J.; Lee, H. H.; Choi, J. H.; Lee, K. C.; Kim, K. H.

    2007-12-01

    The interaction of high-power pulsed-laser beam with metal targets in air from 1.06 μm, 5 ns, 3 J/pulse max, Nd:YAG pulsed laser is investigated together with hydrodynamic theories of laser-supported detonation (LSD) wave and multi-material reactive Euler equations. The high speed blast wave generated by the laser ablation of metal reaches maximum velocity of several thousand meters per second. The apparently similar flow conditions to those of reactive shock wave allow one to apply the equations of motion for energetic materials and to understand the explosive behavior of metal vaporization upon laser ablation. The characteristic time at which planar to spherical wave transition occurs is confirmed at low (20 mJ/pulse) to higher (200 mJ/pulse) beam intensities. The flow structure behind the leading shock wave during the early planar shock state is confirmed by the high-resolution multi-material hydrocode originally developed for shock compression of condensed matter.

  9. Study of the fragmentation phenomena of TiO2 nanoparticles produced by femtosecond laser ablation in aqueous media

    NASA Astrophysics Data System (ADS)

    Alnassar, S. I.; Akman, E.; Oztoprak, B. G.; Kacar, E.; Gundogdu, O.; Khaleel, A.; Demir, A.

    2013-10-01

    Since last decade, Pulsed Laser Ablation in Liquid (PLAL) has become an increasingly important technique for the production of the nanoparticles (NPs) since it usually provides high purity nanoparticle systems. This paper reports on the production and fragmentation of titanium oxide TiO2 nanoparticles by pulsed laser ablation of a titanium target immersed in Sodium Dodecyl Sulfate (SDS) solution using an ultrafast Ti:Sapphire laser. After the production of TiO2 nanoparticles for 30 min of laser irradiation, second harmonics of the laser wavelength are re-applied for different energies (180,120, 60 µJ) to SDS solution containing TiO2 colloids in order to fragment relatively large pieces to obtain smaller ones. It was found that size of nanoparticles after the treatment is independent of the initial characteristics of colloids, but depends strongly on laser parameters especially pulse energy and on the presence of chemically active species in the solution. It was reported that particle size and size distribution range can be decreased using second harmonics of Ti:Sapphire laser wavelengths by using different values of energy. Re-irradiation process at average energy value of 180 μJ decreased average particle size from 185 nm to 110 nm. Characterization of the NPs was studied by applying various techniques such as UV-visible (UV-vis.), Transmission Electron Microscope (TEM), Dynamic Light Scattering (DLS) and Fourier Transform Infra-Red (FTIR).

  10. Synthesis of Ag@Silica Nanoparticles by Assisted Laser Ablation

    NASA Astrophysics Data System (ADS)

    González-Castillo, Jr.; Rodriguez, E.; Jimenez-Villar, E.; Rodríguez, D.; Salomon-García, I.; de Sá, Gilberto F.; García-Fernández, T.; Almeida, DB; Cesar, CL; Johnes, R.; Ibarra, Juana C.

    2015-10-01

    This paper reports the synthesis of silver nanoparticles coated with porous silica (Ag@Silica NPs) using an assisted laser ablation method. This method is a chemical synthesis where one of the reagents (the reducer agent) is introduced in nanometer form by laser ablation of a solid target submerged in an aqueous solution. In a first step, a silicon wafer immersed in water solution was laser ablated for several minutes. Subsequently, an AgNO3 aliquot was added to the aqueous solution. The redox reaction between the silver ions and ablation products leads to a colloidal suspension of core-shell Ag@Silica NPs. The influence of the laser pulse energy, laser wavelength, ablation time, and Ag+ concentration on the size and optical properties of the Ag@Silica NPs was investigated. Furthermore, the colloidal suspensions were studied by UV-VIS-NIR spectroscopy, X-Ray diffraction, and high-resolution transmission electron microscopy (HRTEM).

  11. Synthesis of Ag@Silica Nanoparticles by Assisted Laser Ablation.

    PubMed

    González-Castillo, J R; Rodriguez, E; Jimenez-Villar, E; Rodríguez, D; Salomon-García, I; de Sá, Gilberto F; García-Fernández, T; Almeida, D B; Cesar, C L; Johnes, R; Ibarra, Juana C

    2015-12-01

    This paper reports the synthesis of silver nanoparticles coated with porous silica (Ag@Silica NPs) using an assisted laser ablation method. This method is a chemical synthesis where one of the reagents (the reducer agent) is introduced in nanometer form by laser ablation of a solid target submerged in an aqueous solution. In a first step, a silicon wafer immersed in water solution was laser ablated for several minutes. Subsequently, an AgNO3 aliquot was added to the aqueous solution. The redox reaction between the silver ions and ablation products leads to a colloidal suspension of core-shell Ag@Silica NPs. The influence of the laser pulse energy, laser wavelength, ablation time, and Ag(+) concentration on the size and optical properties of the Ag@Silica NPs was investigated. Furthermore, the colloidal suspensions were studied by UV-VIS-NIR spectroscopy, X-Ray diffraction, and high-resolution transmission electron microscopy (HRTEM). PMID:26464175

  12. Depth profile studies of ZrTiN coatings by laser ablation inductively coupled plasma mass spectrometry.

    PubMed

    Kanický, Viktor; Kuhn, Hans-Rudolf; Guenther, Detlef

    2004-09-01

    The feasibility of depth profiling was studied by using a 193-nm ArF* excimer laser ablation system (GeoLas, MicroLas, Goettingen, Germany) with a lens array-based beam homogenizer in combination with an ICP-QMS Agilent 7500. Two ablation cells (20 and 1.5 cm3) were compared at the laser repetition rate of 1 Hz, laser beam energy of 135 mJ and the carrier gas flow rate 1.5 L min(-1) He + 0.78 L min(-1) Ar. The ablation cell dimensions are important parameters for signal tailing; however, very small cell volumes (e.g. 1.5 cm3) may cause memory effects, which can be probably explained by dominant inertial losses of aerosol on cell walls with its delayed mobilization. The 20-cm3 ablation cell seems to be appropriate for depth profiling by continuous single-hole drilling. The study of the influence of the pit diameter magnitude on the waning and emerging signals under small crater depth/diameter aspect ratios, which range between 0.75 and 0.0375 for the 3-microm-thick coatings and pit diameters 4-80 microm, revealed that the steady-state signals of pure coating and pure substrate (out of interface) were obtained at crater diameters between 20 and 40 microm. Depth resolution defined by means of slopes of tangents in the layer interface region depend on the pit diameter and has an optimum value between 20 and 40 microm and gives 0.6 microm for the 20-microm pit. In-depth variation of concentration of coating constituent (Ti) was proved to be almost identical with two different laser/ICP systems. PMID:15551076

  13. Femtosecond laser ablation of brass in air and liquid media

    NASA Astrophysics Data System (ADS)

    Shaheen, M. E.; Gagnon, J. E.; Fryer, B. J.

    2013-06-01

    Laser ablation of brass in air, water, and ethanol was investigated using a femtosecond laser system operating at a wavelength of 785 nm and a pulse width less than 130 fs. Scanning electron and optical microscopy were used to study the efficiency and quality of laser ablation in the three ablation media at two different ablation modes. With a liquid layer thickness of 3 mm above the target, ablation rate was found to be higher in water and ethanol than in air. Ablation under water and ethanol showed cleaner surfaces and less debris re-deposition compared to ablation in air. In addition to spherical particles that are normally formed from re-solidified molten material, micro-scale particles with varying morphologies were observed scattered in the ablated structures (craters and grooves) when ablation was conducted under water. The presence of such particles indicates the presence of a non-thermal ablation mechanism that becomes more apparent when ablation is conducted under water.

  14. Endometrial ablation

    MedlinePlus

    Hysteroscopy-endometrial ablation; Laser thermal ablation; Endometrial ablation-radiofrequency; Endometrial ablation-thermal balloon ablation; Rollerball ablation; Hydrothermal ablation; Novasure ablation

  15. PULSED LASER ABLATION OF CEMENT AND CONCRETE

    EPA Science Inventory

    Laser ablation was investigated as a means of removing radioactive contaminants from the surface and near-surface regions of concrete from nuclear facilities. We present the results of ablation tests on cement and concrete samples using a pulsed Nd:YAG laser with fiber optic beam...

  16. Magnetic Colloids By Pulsed Laser Ablation

    NASA Astrophysics Data System (ADS)

    Pandey, B. K.; Singh, M. K.; Agarwal, A.; Gopal, R.

    2011-06-01

    Colloidal magnetic nanoparticles have been successfully synthesized by nano second pules laser ablation of a cobalt slice immersed in liquid (distilled water) medium. The focused output of 1064 nm wavelength of pulsed Nd: YAG laser operating at 40 mJ/pulse is used for ablation. The liquid enviorment allows formation of colloids with nanoparticles in uniform particle diameter. Synchrotron X-ray powder diffraction (XRD) is used for the study of structural property of synthesized nanoparticles. The magnetic properties of cobalt nanoparticles are also investigated. The coercivity of is found to be 73 Oe. The optical properties have been determined by UV-visible absorption spectroscopy and band gap found to be 2.16 and 3.60 eV.

  17. Resonant holographic measurements of laser ablation plume expansion in vacuum and argon gas backgrounds

    SciTech Connect

    Lindley, R.A.

    1993-10-01

    This thesis discusses the following on resonant holographic measurements of laser ablation plume expansion: Introduction to laser ablation; applications of laser ablation; The study of plume expansion; holographic interferometry; resonant holographic interferometry; accounting for finite laser bandwidth; The solution for doppler broadening and finite bandwidth; the main optical table; the lumonics laser spot shape; developing and reconstructing the holograms; plume expansion in RF/Plasma Environments; Determining {lambda}{sub o}; resonant refraction effects; fringe shift interpretation; shot-to-shot consistency; laser ablation in vacuum and low pressure, inert, background gas; theoretically modeling plume expansion in vacuum and low pressure, inert, background gas; and laser ablation in higher pressure, inert, background gas.

  18. Laser ablation ICP-MS elemental analysis of individual fluid inclusions: An evaluation study

    NASA Astrophysics Data System (ADS)

    Shepherd, T. J.; Chenery, S. R.

    1995-10-01

    Details are given of the elemental analysis of single fluid inclusions using a UV laser ablation microprobe interfaced to an inductively coupled plasma mass spectrometer. The UV laser, a frequency quadrupled Nd:YAG operating at 266 run, allows higher spatial resolution (<2 μm) than can be achieved using near-IR or visible wavelengths. Tests have been carried out on 10-100 μm diameter aqueous (liquid + vapour) inclusions in fluorite, quartz, and halite up to 60 μm beneath the surface. A key feature of the system is a novel high temperature ablation cell which substantially improves the efficiency and reproducibility of fluid release. Calibration was carried out using a dual gas flow system that allowed use of standard solutions and NIST glasses for tuning the instrument and for obtaining relative sensitivity factors. As an alternative to synthetic fluid inclusions, a new calibration approach is described involving the encapsulation of microdroplets of standard solutions in hydrophobic epoxy resins fluid inclusion analogues. To illustrate the scope and performance of the instrument, data are reported for Ba, Ca, Cs, Cu, K, Mg, Mn, Na, Pb, Rb, Sr, and Zn in saline aqueous inclusions associated with evaporite and low temperature base metal deposits. Element detection limits vary according to the mass of material released for analysis and are thus related to the volume and composition of each inclusion. Precision is estimated to be better than 30%.

  19. Ablation of crystalline oxides by infrared femtosecond laser pulses

    SciTech Connect

    Watanabe, Fumiya; Cahill, David G.; Gundrum, Bryan; Averback, R. S.

    2006-10-15

    We use focused laser pulses with duration of 180 fs and wavelength of 800 nm to study the interactions of high power near-infrared light with the surfaces of single-crystal transparent oxides (sapphire, LaAlO{sub 3}, SrTiO{sub 3}, yttria-stabilized ZrO{sub 2}, and MgO); the morphologies of the ablation craters are studied by atomic force microscopy and scanning electron microscopy. With the exception of LaAlO{sub 3}, the high temperature annealing of these oxide crystals produces atomically flat starting surfaces that enable studies of the morphology of ablation craters with subnanometer precision. The threshold fluence for ablation is determined directly from atomic-force microscopy images and increases approximately linearly with the band gap of the oxide. For all oxides except sapphire, the depth of the ablation crater increases approximately as the square root of the difference between the peak laser fluence and the threshold fluence for ablation. Sapphire shows unique behavior: (i) at laser fluences within 1 J/cm{sup 2} of the threshold for ablation, the depth of the ablation crater increases gradually instead of abruptly with laser fluence, and (ii) the rms roughness of the ablation crater shows a pronounced minimum of <0.2 nm at a laser fluence of 1 J/cm{sup 2} above the threshold.

  20. Influence of water environment on holmium laser ablation performance for hard tissues.

    PubMed

    Lü, Tao; Xiao, Qing; Li, Zhengjia

    2012-05-01

    This study clarifies the ablation differences in air and in water for hard biological tissues, which are irradiated by fiber-guided long-pulsed holmium lasers. High-speed photography is used to record the dynamic characteristics of ablation plumes and vaporization bubbles induced by pulsed holmium lasers. The ablation morphologies and depth of hard tissues are quantitatively measured by optical coherence microscopy. Explosive vaporization effects in water play a positive role in the contact ablation process and are directly responsible for significant ablation enhancement. Furthermore, water layer depth can also contribute to ablation performance. Under the same laser parameters for fiber-tissue contact ablation in air and water, ablation performances are comparable for a single-laser pulse, but for more laser pulses the ablation performances in water are better than those in air. Comprehensive knowledge of ablation differences under various environments is important, especially in medical procedures that are performed in a liquid environment. PMID:22614434

  1. [Research on cells ablation characters by laser plasma].

    PubMed

    Han, Jing-hua; Zhang, Xin-gang; Cai, Xiao-tang; Duan, Tao; Feng, Guo-ying; Yang, Li-ming; Zhang, Ya-jun; Wang, Shao-peng; Li, Shi-wen

    2012-08-01

    The study on the mechanism of laser ablated cells is of importance to laser surgery and killing harmful cells. Three radiation modes were researched on the ablation characteristics of onion epidermal cells under: laser direct irradiation, focused irradiation and the laser plasma radiation. Based on the thermodynamic properties of the laser irradiation, the cell temperature rise and phase change have been analyzed. The experiments show that the cells damage under direct irradiation is not obvious at all, but the focused irradiation can cause cells to split and moisture removal. The removal shape is circular with larger area and rough fracture edges. The theoretical analysis found out that the laser plasma effects play a key role in the laser ablation. The thermal effects, radiation ionization and shock waves can increase the deposition of laser pulses energy and impact peeling of the cells, which will greatly increase the scope and efficiency of cell killing and is suitable for the cell destruction. PMID:23156745

  2. Pulsed Laser Ablation of Soft Biological Tissues

    NASA Astrophysics Data System (ADS)

    Vogel, Alfred; Venugopalan, Vasan

    In this chapter we focus on the key elements that form our current understanding of the mechanisms of pulsed laser ablation of soft biological tissues. We present a conceptual framework providing mechanistic links between various ablation applications and the underlying thermodynamic and phase change processes [1]. We define pulsed laser ablation as the use of laser pulses with duration of ~1 ms or less for the incision or removal of tissue regardless of the photophysical or photochemical processes involved. However, we will confine this presentation to pulsed ablation performed on a tissue level that does not involve laser-induced plasma formation. Ablation processes within transparent tissues or cells resulting from non-linear absorption have been considered in reviews by Vogel and Venugopalan [1] and by Vogel and co-workers [2].

  3. Laser ablation dynamics in metals: The thermal regime

    SciTech Connect

    Mezzapesa, F. P.; Brambilla, M.; Dabbicco, M.; Scamarcio, G.; Columbo, L. L.; Ancona, A.; Sibillano, T.

    2012-07-02

    We studied the laser ablation dynamics of steel in the thermal regime both experimentally and theoretically. The real-time monitoring of the process shows that the ablation rate depends on laser energy density and ambient pressure during the exposure time. We demonstrated that the ablation efficiency can be enhanced when the pressure is reduced with respect to the atmospheric pressure for a given laser fluence, reaching an upper limit despite of high-vacuum conditions. An analytical model based on the Hertz-Knudsen law reproduces all the experimental results.

  4. A study of ablation, spatial, and temporal characteristics of laser-induced plasmas generated by multiple collinear pulses.

    PubMed

    Galbács, G; Jedlinszki, N; Herrera, K; Omenetto, N; Smith, B W; Winefordner, J D

    2010-02-01

    Multi-pulse laser-induced breakdown spectroscopy (LIBS) in the collinear pulse configuration with time-integrating detection was performed on metallic samples in ambient air in an effort to clarify the contributing processes responsible for the signal enhancement observed in comparison with single-pulse excitation. Complementary experiments were also carried out on another LIBS setup using detection by an imaging spectrograph with high time resolution. The effects of laser bursts consisting of up to seven ns-range pulses from Nd-doped solid-state lasers operating at their fundamental wavelength and separated by 8.5-50 micros time gaps was studied. The ablation and emission characteristics of the generated plasmas were investigated using light profilometry, microscopy, plasma imaging, emission distribution mapping, time-resolved line emission monitoring, and plasma temperature calculations. The experimental data suggest that the two contributing processes mainly responsible for the signal enhancement effect are the plume reheating caused by the sequential laser pulses and, more dominantly, the increased material ablation attributed to the lower breakdown threshold for the preheated (molten) sample surface and/or the reduced background gas pressure behind the shockwave of preceding pulses. PMID:20149277

  5. Gas dynamic and time resolved imaging studies of single-wall carbon nanotubes growth in the laser ablation process

    NASA Astrophysics Data System (ADS)

    Sen, Rahul; Suzuki, S.; Kataura, H.; Achiba, Y.

    2001-10-01

    Single-wall carbon nanotubes (SWNTs) were synthesized by laser ablation of Ni-Co-graphite composite targets at 1200 °C under flowing argon. The effects of the temperature gradient near the target and the gas flow rate on the diameter distribution of SWNTs were studied in order to understand their growth dynamics. The diameter distribution of the SWNTs, analyzed by Raman spectroscopy, was dependent on the gas flow rate when there was a temperature gradient around the target. Time resolved scattering images from the ablated species at different flow rates indicated that velocities of backward moving species increased with increasing flow rate. These findings are used to estimate the time required for nucleation and the growth of SWNTs.

  6. Creation of silicon nanocrystals using the laser ablation in liquid

    NASA Astrophysics Data System (ADS)

    Perminov, P. A.; Dzhun, I. O.; Ezhov, A. A.; Zabotnov, S. V.; Golovan, L. A.; Ivlev, G. D.; Gatskevich, E. I.; Malevich, V. L.; Kashkarov, P. K.

    2011-04-01

    The method for the formation of silicon nanoparticles by picosecond laser pulses is studied upon the surface irradiation of the single-crystal silicon in various liquids. The ablation products are investigated using the atomic-force microscopy and Raman spectroscopy. The experimental results indicate the crystal-line structure of nanoparticles and the dependence of their size on the ablation medium.

  7. Precision ablation of dental enamel using a subpicosecond pulsed laser.

    PubMed

    Rode, A V; Gamaly, E G; Luther-Davies, B; Taylor, B T; Graessel, M; Dawes, J M; Chan, A; Lowe, R M; Hannaford, P

    2003-12-01

    In this study we report the use of ultra-short-pulsed near-infrared lasers for precision laser ablation of freshly extracted human teeth. The laser wavelength was approximately 800nm, with pulsewidths of 95 and 150fs, and pulse repetition rates of 1kHz. The laser beam was focused to an approximate diameter of 50microm and was scanned over the tooth surface. The rise in the intrapulpal temperature was monitored by embedded thermocouples, and was shown to remain below 5 degrees C when the tooth was air-cooled during laser treatment. The surface preparation of the ablated teeth, observed by optical and electron microscopy, showed no apparent cracking or heat effects, and the hardness and Raman spectra of the laser-treated enamel were not distinguishable from those of native enamel. This study indicates the potential for ultra-short-pulsed lasers to effect precision ablation of dental enamel. PMID:14738125

  8. Optical Effects on Laser Ablated Polymer Surfaces

    NASA Astrophysics Data System (ADS)

    Prabhu, R. D.; Govinthasamy, R.; Murthy, N. S.

    2006-03-01

    Laser ablation of poly (ethylene terephthalate) and polyimide films were investigated using Excimer-UV laser. SEM analyses indicate the presence of rings for a wide range of ablation parameters (fluence, frequency and number of pulses). It is proposed that the particles present in the plasma plume could cause the incident laser light to diffract, similar to the optical effects observed in the femtosecond laser ablation of solids. The polymer surface provides a perfect medium to register the optical signatures as seen in the SEM images. The fringe-spacings observed in the images are compared with the theoretical diffraction patterns and the height of the plasma particles above the surface is estimated using an optimization scheme. The results of the analysis are consistent with experimentally observed dynamics of the plasma plume. It is proposed that such optical effects could be a routine feature in the laser ablation of polymers. The significance of such artifacts for lithography is discussed.

  9. Laser ablation in analytical chemistry - A review

    SciTech Connect

    Russo, Richard E.; Mao, Xianglei; Liu, Haichen; Gonzalez, Jhanis; Mao, Samuel S.

    2001-10-10

    Laser ablation is becoming a dominant technology for direct solid sampling in analytical chemistry. Laser ablation refers to the process in which an intense burst of energy delivered by a short laser pulse is used to sample (remove a portion of) a material. The advantages of laser ablation chemical analysis include direct characterization of solids, no chemical procedures for dissolution, reduced risk of contamination or sample loss, analysis of very small samples not separable for solution analysis, and determination of spatial distributions of elemental composition. This review describes recent research to understand and utilize laser ablation for direct solid sampling, with emphasis on sample introduction to an inductively coupled plasma (ICP). Current research related to contemporary experimental systems, calibration and optimization, and fractionation is discussed, with a summary of applications in several areas.

  10. Studies of aluminum oxide thin films deposited by laser ablation technique

    NASA Astrophysics Data System (ADS)

    Płóciennik, P.; Guichaoua, D.; Korcala, A.; Zawadzka, A.

    2016-06-01

    This paper presents the structural and optical investigations of the aluminum oxide nanocrystalline thin films. Investigated films were fabricated by laser ablation technique in high vacuum onto quartz substrates. The films were deposited at two different temperatures of the substrates equal to room temperature and 900 K. X-ray Diffraction spectra proved nanocrystalline character and the corundum phase of the film regardless on the substrate temperature during the deposition process. Values of the refractive indices, extinction and absorption coefficients were calculated by using Transmission and Reflection Spectroscopy in the UV-VIS-NIR range of the wavelength. Coupling Prism Method was used for films thickness estimations. Experimental measurements and theoretical calculations of the Third Harmonic Generation were also reported. Obtained results show that the lattice strain may affect obtained values of the third order nonlinear optical susceptibility.

  11. Photoemission Studies of Metallic Photocathodes Prepared by Pulsed Laser Ablation Deposition Technique

    SciTech Connect

    Fasano, V.; Lorusso, A.; Perrone, A.; De Rosa, H.; Cultrera, L.

    2010-11-10

    We present the results of our investigation on metallic films as suitable photocathodes for the production of intense electron beams in RF photoinjector guns. Pulsed laser ablation deposition technique was used for growing Mg and Y thin films onto Si and Cu substrates in high vacuum and at room temperature.Different diagnostic methods were used to characterize the thin films deposited on Si with the aim to optimize the deposition process. Photoelectron performances were investigated on samples deposited on Cu substrate in an ultra high vacuum photodiode chamber at 10{sup -7} Pa. Relatively high quantum efficiencies have been obtained for the deposited films, comparable to those of corresponding bulks. Samples could stay for several months in humid open air before being tested in a photodiode cell. The deposition process and the role of the photocathode surface contamination and its influence on the photoelectron performances are presented and discussed.

  12. Features of the synthesis of nanocolloid oxides by laser ablation of bulk metal targets in solutions

    NASA Astrophysics Data System (ADS)

    Lapin, Ivan N.; Svetlichnyi, Valery A.

    2015-12-01

    Laser ablation of bulk targets in a fluid -- a promising new method for the synthesis of "pure" nanocolloids. Nanocrystalline materials produced by laser ablation are widely used in biology, medicine, and catalysis. High local temperature during ablation and large surface area of the particles promote chemical reactions and the formation of a complex composition of nanoparticles. In this paper the characteristics of the process of ablation and the obtaining of nanoparticles in a liquid by laser ablation of active materials (Zn, Ce, Ti, Si) were studied. Ways of increasing the productivity of laser ablation were discussed. Characterization of nanocolloids and nanocrystalline powders were performed.

  13. Osteoid Osteoma: Experience with Laser- and Radiofrequency-Induced Ablation

    SciTech Connect

    Gebauer, Bernhard Tunn, Per-Ulf; Gaffke, Gunnar; Melcher, Ingo; Felix, Roland; Stroszczynski, Christian

    2006-04-15

    The purpose of this study was to analyze the clinical outcome of osteoid osteoma treated by thermal ablation after drill opening. A total of 17 patients and 20 procedures were included. All patients had typical clinical features (age, pain) and a typical radiograph showing a nidus. In 5 cases, additional histological specimens were acquired. After drill opening of the osteoid osteoma nidus, 12 thermal ablations were induced by laser interstitial thermal therapy (LITT) (9F Power-Laser-Set; Somatex, Germany) and 8 ablations by radiofrequency ablation (RFA) (RITA; StarBurst, USA). Initial clinical success with pain relief has been achieved in all patients after the first ablation. Three patients had an osteoid osteoma recurrence after 3, 9, and 10 months and were successfully re-treated by thermal ablation. No major complication and one minor complication (sensible defect) were recorded. Thermal ablation is a safe and minimally invasive therapy option for osteoid osteoma. Although the groups are too small for a comparative analysis, we determined no difference between laser- and radiofrequency-induced ablation in clinical outcome after ablation.

  14. Numerical study of the influence of picosecond laser spot size on ablated depth and threshold fluence of metal

    NASA Astrophysics Data System (ADS)

    Zhang, Yiming; Lauer, Benjamin; Neuenschwander, Beat; Romano, Valerio

    2016-03-01

    Picosecond laser systems have been widely used in industrial microprocessing applications since they are a cost-effective tool to achieve high throughput. To better understand the ablation process, firstly the dependence of the ablation depth and the threshold fluence on the laser spot size were determined experimentally by performing ablation with a 10ps pulsed laser system. Further, a 2D axisymmetric model was established to demonstrate the possible mechanism of the phenomena. Three sets of spot radii, namely 15.5μm, 31.5μm and 49.6μm, respectively with equal laser peak fluences ranging from 0.6J/cm2 to 4.5J/cm2 were applied on copper. It was found that the laser ablation depth increases while the threshold fluence decreases with decreasing spot size at identical peak fluence. A 2D axisymmetric thermomechanical model was developed to qualitatively illustrate the mechanism behind these phenomena. The numerical results of the position where the tensile stress exceed to ultimate tensile strength (UTS) of copper show the same trend as the experimental ones. The longitudinal tensile stress was seen to play a more crucial role than the radial tensile/compressive stress on laser ablation process. The impact of the thermal stress on the ablation depth and threshold fluence is derived from the lattice temperature gradient along the surface of the material, leading to spallation and possible modifications of the mechanical properties already at lower laser peak fluences. This is elucidated numerically and analytically. The deviation of the experimental results from the simulation might be attributed to the fact that this simulation model is static. Nevertheless, at low laser fluences, this static approach can provide good explanations of the cold ablation with ultrashort pulsed laser. The limitation of this model is also illustrated.

  15. Theoretical study on line source laser-induced surface acoustic waves in two-layer structure in ablative regime

    NASA Astrophysics Data System (ADS)

    Shen, Z. H.; Xu, B. Q.; Ni, X. W.; Lu, J.; Zhang, S. Y.

    2004-03-01

    The generation of ultrasound in film-substrate system by a laser line source is studied in the case of ablation mechanism, which can be realized by adding a liquid layer at the excitation point. The time domain displacement can be yielded by the numerical jointed inversed Laplace-Fourier transformation technique. The typical surface acoustic waves (SAW) of two layer structures, slow film on fast substrate and fast film on slow substrate, are obtained and the effect of the propagation distance and the thickness of the film on the SAW are given.

  16. Ablation characteristics of quantum square pulse mode dental erbium laser

    NASA Astrophysics Data System (ADS)

    Lukač, Nejc; Suhovršnik, Tomaž; Lukač, Matjaž; Jezeršek, Matija

    2016-01-01

    Erbium lasers are by now an accepted tool for performing ablative medical procedures, especially when minimal invasiveness is desired. Ideally, a minimally invasive laser cutting procedure should be fast and precise, and with minimal pain and thermal side effects. All these characteristics are significantly influenced by laser pulse duration, albeit not in the same manner. For example, high cutting efficacy and low heat deposition are characteristics of short pulses, while vibrations and ejected debris screening are less pronounced at longer pulse durations. We report on a study of ablation characteristics on dental enamel and cementum, of a chopped-pulse Er:YAG [quantum square pulse (QSP)] mode, which was designed to reduce debris screening during an ablation process. It is shown that in comparison to other studied standard Er:YAG and Er,Cr:YSGG laser pulse duration modes, the QSP mode exhibits the highest ablation drilling efficacy with lowest heat deposition and reduced vibrations, demonstrating that debris screening has a considerable influence on the ablation process. By measuring single-pulse ablation depths, we also show that tissue desiccation during the consecutive delivery of laser pulses leads to a significant reduction of the intrinsic ablation efficacy that cannot be fully restored under clinical settings by rehydrating the tooth using an external water spray.

  17. Spectroscopic characterization of laser ablated silicon plasma

    NASA Astrophysics Data System (ADS)

    Shakeel, Hira; Mumtaz, M.; Shahzada, S.; Nadeem, A.; Haq, S. U.

    2014-06-01

    We report plasma parameters of laser ablated silicon plasma using the fundamental (1064 nm) and second harmonics (532 nm) of a Nd : YAG laser. The electron temperature and electron number density are evaluated using the Boltzmann plot method and Stark broadened line profile, respectively. The electron temperature and electron number density are deduced using the same laser irradiance 2-16 GW cm-2 for 1064 nm and 532 nm as 6350-7000 K and (3.42-4.44) × 1016 cm-3 and 6000-6400 K and (4.20-5.72) × 1016 cm-3, respectively. The spatial distribution of plasma parameters shows a decreasing trend of 8200-6300 K and (4.00-3.60) × 1016 cm-3 for 1064 nm and 6400-5500 K and (5.10-4.50) × 1016 cm-3 for 532 nm laser ablation. Furthermore, plasma parameters are also investigated at low pressure from 45 to 550 mbar, yielding the electron temperature as 4580-5535 K and electron number density as (1.51-2.12) × 1016 cm-3. The trend of the above-mentioned results is in good agreement with previous investigations. However, wavelength-dependent studies and the spatial evolution of plasma parameters have been reported for the first time.

  18. Laser-ablation-induced refractive index fields studied using pulsed digital holographic interferometry

    NASA Astrophysics Data System (ADS)

    Amer, Eynas; Gren, Per; Sjödahl, Mikael

    2009-07-01

    Pulsed digital holographic interferometry has been used to investigate the plume and the shock wave generated in the ablation process of a Q-switched Nd-YAG ( λ=1064 nm and pulse duration=12 ns) laser pulse on a polycrystalline boron nitride (PCBN) target under atmospheric air pressure. A special setup based on two synchronised wavelengths from the same laser for simultaneous processing and measurement has been used. Digital holograms were recorded for different time delays using collimated laser light ( λ=532 nm) passed through the volume along the target. Numerical data of the integrated refractive index field were calculated and presented as phase maps showing the propagation of the shock wave and the plume generated by the process. Radon inversion has been used to estimate the 3D refractive index fields measured from the projections assuming rotational symmetry. The shock wave density has been calculated using the point explosion model and the shock wave condition equation and its behaviour with time at different power densities ranging from 1.4 to 9.1 GW/cm 2 is presented. Shock front densities have been calculated from the reconstructed refractive index fields using the Gladstone-Dale equation. A comparison of the shock front density calculated from the reconstructed data and that calculated using the point explosion model at different time delays has been done. The comparison shows quite good agreement between the model and the experimental data. Finally the reconstructed refractive index field has been used to estimate the electron number density distribution within the laser-induced plasma. The electron number density behaviour with distance from the target at different power densities and its behaviour with time are shown. The electron number densities are found to be in the order of 10 18 cm -3 and decay at a rate of 3×10 15 electrons/cm 3 ns.

  19. Femtosecond laser ablation of the stapes

    PubMed Central

    McCaughey, Ryan G.; Sun, Hui; Rothholtz, Vanessa S.; Juhasz, Tibor; Wong, Brian J. F.

    2014-01-01

    A femtosecond laser, normally used for LASIK eye surgery, is used to perforate cadaveric human stapes. The thermal side effects of bone ablation are measured with a thermocouple in an inner ear model and are found to be within acceptable limits for inner ear surgery. Stress and acoustic events, recorded with piezoelectric film and a microphone, respectively, are found to be negligible. Optical microscopy, scanning electron microscopy, and optical coherence tomography are used to confirm the precision of the ablation craters and lack of damage to the surrounding tissue. Ablation is compared to that from an Er:YAG laser, the current laser of choice for stapedotomy, and is found to be superior. Ultra-short-pulsed lasers offer a precise and efficient ablation of the stapes, with minimal thermal and negligible mechanical and acoustic damage. They are, therefore, ideal for stapedotomy operations. PMID:19405768

  20. Femtosecond laser ablation of the stapes

    NASA Astrophysics Data System (ADS)

    McCaughey, Ryan G.; Sun, Hui; Rothholtz, Vanessa S.; Juhasz, Tibor; Wong, Brian J. F.

    2009-03-01

    A femtosecond laser, normally used for LASIK eye surgery, is used to perforate cadaveric human stapes. The thermal side effects of bone ablation are measured with a thermocouple in an inner ear model and are found to be within acceptable limits for inner ear surgery. Stress and acoustic events, recorded with piezoelectric film and a microphone, respectively, are found to be negligible. Optical microscopy, scanning electron microscopy, and optical coherence tomography are used to confirm the precision of the ablation craters and lack of damage to the surrounding tissue. Ablation is compared to that from an Er:YAG laser, the current laser of choice for stapedotomy, and is found to be superior. Ultra-short-pulsed lasers offer a precise and efficient ablation of the stapes, with minimal thermal and negligible mechanical and acoustic damage. They are, therefore, ideal for stapedotomy operations.

  1. Laser ablation inductively coupled plasma mass spectrometry

    SciTech Connect

    Durrant, S.F.

    1996-07-01

    Laser ablation for solid sample introduction to inductively coupled plasma mass spectrometry for bulk and spatially-resolved elemental analysis is briefly reviewed. {copyright} {ital 1996 American Institute of Physics.}

  2. Reflection of femtosecond laser light in multipulse ablation of metals

    SciTech Connect

    Vorobyev, A. Y.; Guo Chunlei

    2011-08-15

    The shot-to-shot reflectance of high-intensity laser light is studied as a function of both the number of laser shots and laser fluence in multipulse ablation of a metal when the irradiated surface undergoes structural changes from an initially smooth surface to a deep crater. Our study shows that the reflectance of the irradiated surface significantly decreases due to the high intensity of laser pulses and the laser-induced surface structures in ablation regimes typically used for femtosecond laser processing of materials. The high-intensity effect dominates in the reflection reduction at low numbers of laser shots when laser-induced surface structures do not cause the reflectance to decrease noticeably. With increasing the number of laser shots, the structural effect comes into play, and both high-intensity and structural effects quickly reduce the reflectance of the sample to a low value.

  3. Laser Ablation of Alumina in Water

    SciTech Connect

    Musaev, O.; Midgley, A; Wrobel, J; Kruger, M

    2010-01-01

    Bulk {alpha}-alumina immersed in distilled water was ablated by pulsed UV laser radiation. The resulting colloidal solution contained micron and submicron size particles. X-ray diffraction and Raman spectra of the ablated and original material are similar. Hence, most of the ablated material is {alpha}-alumina. From transmission electron microscope images, most of the submicron and all of the micron-sized particles have sharp edges and do not have spherical shapes, indicating that the dominant ablation mechanism is due to crack propagation. Some spherical particles of diameter less than 100 nm are observed, indicating that they were formed from the liquid state.

  4. Optodynamic aspect of a pulsed laser ablation process

    NASA Astrophysics Data System (ADS)

    Hrovatin, Rok; Možina, Janez

    1995-02-01

    A study of a pulsed laser ablation process is presented from a novel, optodynamic aspect. By quantitative analysis of laser-induced bulk ultrasonic and blast waves in the air the ablation dynamics is characterized. In this way the influence of the laser pulse parameters and of the interacting material on the ablation process was assessed. By the analysis of the laser drilling process of thin layered samples the material influence was demonstrated. Besides the ultrasonic evaluation of the laser pulse power density the plasma shielding for 10 ns laser pulses was analyzed by the same method. All measurements were noncontact. Bulk waves in the solid and blast waves in the air were measured simultaneously, an interferometric and a probe beam deflection method were used, respectively.

  5. Novel Laser Ablation Technology for Surface Decontamination

    SciTech Connect

    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 liquid 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.

  6. Near-infrared laser ablation of poly tetrafluoroethylene (Teflon) sensitized by nanoenergetic materials

    SciTech Connect

    Yang Yanqiang; Wang Shufeng; Sun Zhaoyong; Dlott, Dana D.

    2004-08-30

    Laser ablation of Teflon doped with size-selected (30-250 nm) Al nanoparticles is studied. Unlike pure Teflon, which requires a vacuum-ultraviolet or femtosecond excimer laser for ablation, this sensitized Teflon can be ablated with a near-infrared laser. Using 100 ps duration pulses, near-infrared ablation thresholds are lower by about a factor of 10 from excimer ablation of pure Teflon. A mechanism is discussed that involves Teflon decomposition by spherical shock fronts originating at each irradiated nanoparticle. Studies of the distance dependence of this process as a function of particle diameter and oxide layer thickness suggest ways of optimizing the ablation process.

  7. 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.

  8. Laser ablation of a turbid medium: Modeling and experimental results

    SciTech Connect

    Brygo, F.; Semerok, A.; Weulersse, J.-M.; Thro, P.-Y.; Oltra, R.

    2006-08-01

    Q-switched Nd:YAG laser ablation of a turbid medium (paint) is studied. The optical properties (absorption coefficient, scattering coefficient, and its anisotropy) of a paint are determined with a multiple scattering model (three-flux model), and from measurements of reflection-transmission of light through thin layers. The energy deposition profiles are calculated at wavelengths of 532 nm and 1.064 {mu}m. They are different from those described by a Lambert-Beer law. In particular, the energy deposition of the laser beam is not maximum on the surface but at some depth inside the medium. The ablated rate was measured for the two wavelengths and compared with the energy deposition profile predicted by the model. This allows us to understand the evolution of the ablated depth with the wavelength: the more the scattering coefficient is higher, the more the ablated depth and the threshold fluence of ablation decrease.

  9. 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.

  10. 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.

  11. 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.

  12. Pulse laser ablation at water-air interface

    NASA Astrophysics Data System (ADS)

    Utsunomiya, Yuji; Kajiwara, Takashi; Nishiyama, Takashi; Nagayama, Kunihito; Kubota, Shiro

    2010-06-01

    We studied a new pulse laser ablation phenomenon on a liquid surface layer, which is caused by the difference between the refractive indices of the two materials involved. The present study was motivated by our previous study, which showed that laser ablation can occur at the interface between a transparent material and a gas or liquid medium when the laser pulse is focused through the transparent material. In this case, the ablation threshold fluence is reduced remarkably. In the present study, experiments were conducted in water and air in order to confirm this phenomenon for a combination of two fluid media with different refractive indices. This phenomenon was observed in detail by pulse laser shadowgraphy. A high-resolution film was used to record the phenomenon with a Nd:YAG pulse laser with 10-ns duration as a light source. The laser ablation phenomenon on the liquid surface layer caused by a focused Nd:YAG laser pulse with 1064-nm wavelength was found to be followed by the splashing of the liquid surface, inducing a liquid jet with many ligaments. The liquid jet extension velocity was around 1000 m/s in a typical case. The liquid jet decelerated drastically due to rapid atomization at the tips of the ligaments. The liquid jet phenomenon was found to depend on the pulse laser parameters such as the laser fluence on the liquid surface, laser energy, and laser beam pattern. The threshold laser fluence for the generation of a liquid jet was 20 J/cm2. By increasing the incident laser energy with a fixed laser fluence, the laser focused area increased, which eventually led to an increase in the size of the plasma column. The larger the laser energy, the larger the jet size and the longer the temporal behavior. The laser beam pattern was found to have significant effects on the liquid jet’s velocity, shape, and history.

  13. Laser Ablation of Biological Tissue Using Pulsed CO{sub 2} Laser

    SciTech Connect

    Hashishin, Yuichi; Sano, Shu; Nakayama, Takeyoshi

    2010-10-13

    Laser scalpels are currently used as a form of laser treatment. However, their ablation mechanism has not been clarified because laser excision of biological tissue occurs over a short time scale. Biological tissue ablation generates sound (laser-induced sound). This study seeks to clarify the ablation mechanism. The state of the gelatin ablation was determined using a high-speed video camera and the power reduction of a He-Ne laser beam. The aim of this study was to clarify the laser ablation mechanism by observing laser excision using the high-speed video camera and monitoring the power reduction of the He-Ne laser beam. We simulated laser excision of a biological tissue by irradiating gelatin (10 wt%) with radiation from a pulsed CO{sub 2} laser (wavelength: 10.6 {mu}m; pulse width: 80 ns). In addition, a microphone was used to measure the laser-induced sound. The first pulse caused ablation particles to be emitted in all directions; these particles were subsequently damped so that they formed a mushroom cloud. Furthermore, water was initially evaporated by laser irradiation and then tissue was ejected.

  14. Cleaning of large area by excimer laser ablation

    NASA Astrophysics Data System (ADS)

    Sentis, Marc L.; Delaporte, Philippe C.; Marine, Wladimir I.; Uteza, Olivier P.

    2000-01-01

    Surface removal technologies are being challenged from environmental and economic perspectives. This paper is concerned with laser ablation applied to large surface cleaning with an automatized excimer laser unit. The study focused on metallic surfaces that are oxidized and are representative of contaminated surfaces with radionuclides in a context of nuclear power plant maintenance. The whole system is described: laser, beam deliver, particle collection cell, real time control of cleaning processes. Results concerning surface laser interaction and substrate modifications are presented.

  15. Near infrared femtosecond laser ablation of urinary calculi in water

    NASA Astrophysics Data System (ADS)

    Qiu, Jinze; Teichman, Joel M.; Kuranov, Roman V.; McElroy, Austin B.; Wang, Tianyi; Paranjape, Amit S.; Milner, Thomas E.

    2009-02-01

    Pulsed light emitted from a near infrared (λ=800nm) femtosecond laser is capable of plasma induced photodisruption of various materials. We used femtosecond laser pulses to ablate human urinary calculi. Femtosecond pulsed laser interaction with urinary calculi was investigated with various stone compositions, different incident fluences and number of applied pulses. Spectral-domain optical coherence tomography was used to image cross sections of ablation craters on the surface of urinary calculi. Our results indicate that femtosecond laser pulses can ablate various calculi compositions. Crater diameter and depth varies from tens of microns to several hundred microns when up to 1000 pulses were applied. Future studies are required to determine if pulsed near infrared femtosecond laser pulses can be applied clinically for lithotripsy of urinary calculi.

  16. A parametric study of single-wall carbon nanotube growth by laser ablation

    NASA Technical Reports Server (NTRS)

    Arepalli, Sivaram; Holmes, William A.; Nikolaev, Pavel; Hadjiev, Victor G.; Scott, Carl D.

    2004-01-01

    Results of a parametric study of carbon nanotube production by the double-pulse laser oven process are presented. The effect of various operating parameters on the production of single-wall carbon nanotubes (SWCNTs) is estimated by characterizing the nanotube material using analytical techniques, including scanning electron microscopy, transmission electron microscopy, thermo gravimetric analysis and Raman spectroscopy. The study included changing the sequence of the laser pulses, laser energy, pulse separation, type of buffer gas used, operating pressure, flow rate, inner tube diameter, as well as its material, and oven temperature. It was found that the material quality and quantity improve with deviation from normal operation parameters such as laser energy density higher than 1.5 J/cm2, pressure lower than 67 kPa, and flow rates higher than 100 sccm. Use of helium produced mainly small diameter tubes and a lower yield. The diameter of SWCNTs decreases with decreasing oven temperature and lower flow rates.

  17. Improved laser ablation model for asteroid deflection

    NASA Astrophysics Data System (ADS)

    Vasile, Massimiliano; Gibbings, Alison; Watson, Ian; Hopkins, John-Mark

    2014-10-01

    This paper presents an improved laser ablation model and compares the performance - momentum coupling and deflection system mass - of laser ablation against contactless deflection methods based on ion-propulsion. The deflection of an asteroid through laser ablation is achieved by illuminating the surface of the asteroid with high intensity laser light. The absorbed energy induces the sublimation of the surface material and the generation of a plume of gas and ejecta. Similar to a rocket engine, the flow of expelled material produces a continuous and controllable thrust that could be used to modify the trajectory and tumbling motion of the asteroid. Recent results gained from a series of laser ablation experiments were used to improve the sublimation and deflection models. In each experiment a terrestrial olivine sample was ablated, under vacuum, with a 90 W continuous wave laser. The paper presents a model that better fits the outcomes of the experimental campaign, in particular in terms of mass flow rate and spot temperature.

  18. Studies on linear, nonlinear optical and excited state dynamics of silicon nanoparticles prepared by picosecond laser ablation

    NASA Astrophysics Data System (ADS)

    Hamad, Syed; Krishna Podagatlapalli, G.; Mounika, R.; Nageswara Rao, S. V. S.; Pathak, A. P.; Venugopal Rao, S.

    2015-12-01

    We report results from our studies on the fabrication and characterization of silicon (Si) nanoparticles (NPs) and nanostructures (NSs) achieved through the ablation of Si target in four different liquids using ˜2 picosecond (ps) pulses. The consequence of using different liquid media on the ablation of Si target was investigated by studying the surface morphology along with material composition of Si based NPs. The recorded mean sizes of these NPs were ˜9.5 nm, ˜37 nm, ˜45 nm and ˜42 nm obtained in acetone, water, dichloromethane (DCM) and chloroform, respectively. The generated NPs were characterized by selected area electron diffraction (SAED), high resolution transmission microscopy (HRTEM), Raman spectroscopic techniques and Photoluminescence (PL) studies. SAED, HRTEM and Raman spectroscopy data confirmed that the material composition was Si NPs in acetone, Si/SiO2 NPs in water, Si-C NPs in DCM and Si-C NPs in chloroform and all of them were confirmed to be polycrystalline in nature. Surface morphological information of the fabricated Si substrates was obtained using the field emission scanning electron microscopic (FESEM) technique. FESEM data revealed the formation of laser induced periodic surface structures (LIPSS) for the case of ablation in acetone and water while random NSs were observed for the case of ablation in DCM and chloroform. Femtosecond (fs) nonlinear optical properties and excited state dynamics of these colloidal Si NPs were investigated using the Z-scan and pump-probe techniques with ˜150 fs (100 MHz) and ˜70 fs (1 kHz) laser pulses, respectively. The fs pump-probe data obtained at 600 nm consisted of single and double exponential decays which were tentatively assigned to electron-electron collisional relaxation (<1 ps) and non-radiative transitions (>1 ps). Large third order optical nonlinearities (˜10-14 e.s.u.) for these colloids have been estimated from Z-scan data at an excitation wavelength of 680 nm suggesting that the

  19. Studies on linear, nonlinear optical and excited state dynamics of silicon nanoparticles prepared by picosecond laser ablation

    SciTech Connect

    Hamad, Syed; Nageswara Rao, S. V. S.; Pathak, A. P.; Krishna Podagatlapalli, G.; Mounika, R.; Venugopal Rao, S. E-mail: soma-venu@uohyd.ac.in

    2015-12-15

    We report results from our studies on the fabrication and characterization of silicon (Si) nanoparticles (NPs) and nanostructures (NSs) achieved through the ablation of Si target in four different liquids using ∼2 picosecond (ps) pulses. The consequence of using different liquid media on the ablation of Si target was investigated by studying the surface morphology along with material composition of Si based NPs. The recorded mean sizes of these NPs were ∼9.5 nm, ∼37 nm, ∼45 nm and ∼42 nm obtained in acetone, water, dichloromethane (DCM) and chloroform, respectively. The generated NPs were characterized by selected area electron diffraction (SAED), high resolution transmission microscopy (HRTEM), Raman spectroscopic techniques and Photoluminescence (PL) studies. SAED, HRTEM and Raman spectroscopy data confirmed that the material composition was Si NPs in acetone, Si/SiO{sub 2} NPs in water, Si-C NPs in DCM and Si-C NPs in chloroform and all of them were confirmed to be polycrystalline in nature. Surface morphological information of the fabricated Si substrates was obtained using the field emission scanning electron microscopic (FESEM) technique. FESEM data revealed the formation of laser induced periodic surface structures (LIPSS) for the case of ablation in acetone and water while random NSs were observed for the case of ablation in DCM and chloroform. Femtosecond (fs) nonlinear optical properties and excited state dynamics of these colloidal Si NPs were investigated using the Z-scan and pump-probe techniques with ∼150 fs (100 MHz) and ∼70 fs (1 kHz) laser pulses, respectively. The fs pump-probe data obtained at 600 nm consisted of single and double exponential decays which were tentatively assigned to electron-electron collisional relaxation (<1 ps) and non-radiative transitions (>1 ps). Large third order optical nonlinearities (∼10{sup −14} e.s.u.) for these colloids have been estimated from Z-scan data at an excitation wavelength of 680 nm

  20. Ultrashort laser ablation of PMMA and intraocular lenses

    NASA Astrophysics Data System (ADS)

    Serafetinides, A. A.; Makropoulou, M.; Fabrikesi, E.; Spyratou, E.; Bacharis, C.; Thomson, R. R.; Kar, A. K.

    2008-10-01

    The use of intraocular lenses (IOLs) is the most promising method to restore vision after cataract surgery. Several new materials, techniques, and patterns have been studied for forming and etching IOLs to improve their optical properties and reduce diffractive aberrations. This study is aimed at investigating the use of ultrashort laser pulses to ablate the surface of PMMA and intraocular lenses, and thus provide an alternative to conventional techniques. Ablation experiments were conducted using various polymer substrates (PMMA samples, hydrophobic acrylic IOL, yellow azo dye doped IOL, and hydrophilic acrylic IOL consist of 25% H2O). The irradiation was performed using 100 fs pulses of 800 nm radiation from a regeneratively amplified Ti:sapphire laser system. We investigated the ablation efficiency and the phenomenology of the ablated patterns by probing the ablation depth using a profilometer. The surface modification was examined using a high resolution optical microscope (IOLs) or atomic force microscope—AFM (PMMA samples). It was found that different polymers exhibited different ablation characteristics, a result that we attribute to the differing optical properties of the materials. In particular, it was observed that the topography of the ablation tracks created on the hydrophilic intraocular lenses was smoother in comparison to those created on the PMMA and hydrophobic lens. The yellow doped hydrophobic intraocular lenses show higher ablation efficiency than undoped hydrophobic acrylic lenses.

  1. Resonant laser ablation: Mechanisms and applications

    SciTech Connect

    Anderson, J.E.; Bodla, R.; Eiden, G.C.; Nogar, N.S.; Smith, C.H.

    1994-06-01

    Ever since the first report of laser action, it has been recognized that laser ablation (evaporation/volatilization) may provide a useful sampling mechanism for chemical analysis. In particular, laser ablation is rapidly gaining popularity as a method of sample introduction for mass spectrometry. While most laser ablation/mass spectrometry has been performed with fixed frequency lasers operating at relatively high intensities/fluences ({ge}10{sup 8} W/cm{sup 2}, {ge}1 J/cm{sup 2}), there has been some recent interest in the use of tunable lasers to enhance the ionization yield of selected components in an analytical sample. This process has been termed resonant laser ablation (RLA), and typically relies on irradiation of a sample in a mass spectrometer with modest intensity laser pulses tuned to a one- or two-photon resonant transition in the analyte of interest. Potential advantages of RLA include: (1) simplification of the mass spectrum, by enhancement of signal from the analyte of interest; (2) improvement of the absolute detection limits by improving the ionization efficiency, and (3) improvement in relative sensitivity. The sensitivity enhancement results from reduction of spurious signal, and accompanying noise, in the detection channel. This spurious signal may be due to bleed through from adjacent mass channels, or from isobaric interferences. RLA tends to produce higher mass resolution because of minimal spatial spread in the ion source and small space charge effects. In this manuscript we present a survey of RLA attributes and applications.

  2. [Laser ablation of intervertebral disc: animal experiment].

    PubMed

    Qi, Q; Dang, G D; Cai, Q L

    1994-03-01

    The lumbar intervertebral discs (L3-6) were ablated through a transperitoneal approach in 12 adult dogs by using Nd: YAG laser (1.06 microns) with a 600 microns quartz fiber. The status of limbs motion and sphincter (bladder, bowel) was observed for evaluating the safety of laser irradiation. After irradiation, the animals were sacrificed at prescribed intervals of up to 40 weeks (2, 4, 8, 12 and 40 weeks after operation). The lumbar intervertebral discs were harvested and subjected to light microscopic observation. No dog had suffered from neurogenic dysfunction of limb motion and sphincter. Histological findings immediately after the irradiation showed the disc was vaporized and a cavity was made. After 2 and 4 weeks, fibrous tissues began to proliferate, but cartilaginous tissues replaced the fibrous tissues 12 weeks after the laser irradiation. No new bone formation was found within 40 weeks after operation. On the basis of this study and our previous cadaveric study, percutaneous laser disc decompression (PLDD) was applied in clinical practice in march of 1993. 10 patients underwent PLDD utilizing the same laser equipment. The average follow-up was 3 months. According to the Macnab's criteria, there was an excellent response in 7 patients and a good response in 3. PMID:7842915

  3. Ablation enhancement of silicon by ultrashort double-pulse laser ablation

    SciTech Connect

    Zhao, Xin; Shin, Yung C.

    2014-09-15

    In this study, the ultrashort double-pulse ablation of silicon is investigated. An atomistic simulation model is developed to analyze the underlying physics. It is revealed that the double-pulse ablation could significantly increase the ablation rate of silicon, compared with the single pulse ablation with the same total pulse energy, which is totally different from the case of metals. In the long pulse delay range (over 1 ps), the enhancement is caused by the metallic transition of melted silicon with the corresponding absorption efficiency. At ultrashort pulse delay (below 1 ps), the enhancement is due to the electron excitation by the first pulse. The enhancement only occurs at low and moderate laser fluence. The ablation is suppressed at high fluence due to the strong plasma shielding effect.

  4. Saturation effects in femtosecond laser ablation of silicon-on-insulator

    SciTech Connect

    Zhang Hao; Oosten, D. van; Krol, D. M.; Dijkhuis, J. I.

    2011-12-05

    We report a surface morphology study on single-shot submicron features fabricated on silicon on insulator by tightly focused femtosecond laser pulses. In the regime just below single-shot ablation threshold nano-tips are formed, whereas in the regime just above single-shot ablation threshold, a saturation in the ablation depth is found. We attribute this saturation by secondary laser absorption in the laser-induced plasma. In this regime, we find excellent agreement between the measured depths and a simple numerical model. When the laser fluence is further increased, a sharp increase in ablation depth is observed accompanied by a roughening of the ablated hole.

  5. 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.

  6. Resonant laser ablation: Mechanisms and applications

    SciTech Connect

    Anderson, J.E.; Allen, T.M.; Garrett, A.W.; Gill, C.G.; Hemberger, P.H.; Kelly, P.B.; Nogar, N.S.

    1997-01-01

    We will report on aspects of resonant laser ablation (RLA) behavior for a number of sample types: metals, alloys, thin films, zeolites and soil. The versatility of RLA is demonstrated, with results on a variety of samples and in several mass spectrometers. In addition, the application to depth profiling of thin films is described; absolute removal rates and detection limits are also displayed. A discussion of possible mechanisms for low-power ablation are presented. {copyright} {ital 1997 American Institute of Physics.}

  7. UV laser ablation patterns in intraocular lenses

    NASA Astrophysics Data System (ADS)

    Lagiou, D. P.; Evangelatos, Ch.; Apostolopoulos, A.; Spyratou, E.; Bacharis, C.; Makropoulou, M.; Serafetinides, A. A.

    2013-03-01

    The aim of this work is to investigate the effect of UV solid state laser radiation on intraocular lens (IOL) polymer surfaces as an alternative method to conventional surface shaping techniques for IOLs customization. Laser ablation experiments were performed on PMMA plates and commercially available hydrophobic and hydrophilic acrylic IOLs with the 5th harmonic of a Q-switched Nd:YAG laser (λ=213 nm). Circular arrays of holes were drilled on the polymer surface, covering the centre and the peripheries of the IOL. The morphology of the ablated IOL surface was examined with a conventional optical microscope (Leitz GMBH Wetzlar) and with a scanning electron microscope (SEM, Fei - Innova Nanoscope) at various laser parameters. Quantitative measurements of ablation rates were performed with a contact profilometer (Dektak-150), in which a mechanical stylus scanned across the surface of gold-coated IOLs (after SEM imaging) to measure variationsF in surface height. Laser interaction with IOLs depends on optical and mechanical material properties, in addition to laser radiation parameters. The exact ablation mechanism is discussed. Some polymer materials, depending on their properties, are more susceptible to the photothermal mechanism than the photochemical one or vice versa. In summary, every IOL polymer exhibits specific attributes in its interaction with the 5th harmonic of Nd:YAG laser.

  8. A Simulation of Laser Ablation During the Laser Pulse

    NASA Astrophysics Data System (ADS)

    Suzuki, Motoyuki; Ventzek, Peter L. G.; Sakai, Y.; Date, H.; Tagashira, H.; Kitamori, K.

    1996-10-01

    Charge damage considerations in plasma assisted etching are prompting the development of neutral beam sources. Already, anisotropic etching of has been demonstrated by neutral beams generated by exhausting heated ecthing gases into vacuum via a nozzle. Laser ablation of condensed etching gases may also be an attractive alternative means of generating neutral beams. Laser ablation coupled with electrical breakdown of the ablation plume may afford some degree of control over a neutral beam's dissociation fraction and ion content. Results from a Monte Carlo simulation of the laser ablation plume as it expands into vacuum at time-scales during the laser pulse will be presented. The model includes both heavy particle interactions and photochemistry. In particular, the influence of the initial particle angular distribution on the beam spread will be demonstrated as will the relationship between laser beam energy and initial ionization and dissociation fraction.

  9. Femtosecond laser lithotripsy: feasibility and ablation mechanism

    NASA Astrophysics Data System (ADS)

    Qiu, Jinze; Teichman, Joel M. H.; Wang, Tianyi; Neev, Joseph; Glickman, Randolph D.; Chan, Kin Foong; Milner, Thomas E.

    2010-03-01

    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 (λ=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 μm, 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 μm, 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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

    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.

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

    PubMed Central

    Chen, H.; Li, H.; Sun, YC.; Wang, Y.; Lü, PJ.

    2016-01-01

    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. PMID:26864679

  12. Optical properties measurement of the laser-ablated tissues for the combined laser ablation with photodynamic therapy

    NASA Astrophysics Data System (ADS)

    Honda, Norihiro; Ishii, Katsunori; Awazu, Kunio

    2012-03-01

    Laser ablation therapy combined with photodynamic therapy (PDT) is studied for treatment of advanced cancers. The clinical outcome of PDT may be improved by the accurate knowledge about the light distribution within tissue. Optical properties [absorption coefficient (μa), scattering coefficient (μs), anisotropy factor (g), refractive index, etc.] of tissues help us realizing a light propagation through the tissue. It is important to understand of the effect of laser coagulation formed by laser ablation to PDT. The aim of this study is to estimate of influence of coagulated region to PDT for effective PDT combined laser ablation therapy. We evaluated the optical property of mouse tumor tissue in native and coagulated state using a double integrating sphere system and an inverse Monte Carlo method in the wavelength range from 350 to 1000 nm. After laser ablation, the μa and reduced scattering coefficient spectra of coagulated tissues were increased in the wavelength range from 350 to 1000 nm. The optical penetration depth of coagulated tissues is 1.2-2.9 times lower than the native state in the wavelength range from 350 to 1000 nm. The intensity of the light energy inside the coagulated tissue falls to about 60% of its original value at the end of coagulated layer. The evaluation of light energy distribution by the determination of the tissues optical properties could be useful for optimization of the treatment procedure in combined laser ablation with PDT.

  13. Plasma mediated ablation of biological tissues with ultrashort laser pulses

    SciTech Connect

    Oraevsky, A.A. |; DaSilva, L.B.; Feit, M.D.

    1995-03-08

    Plasma mediated ablation of collagen gels and porcine cornea was studied at various laser pulse durations in the range from 350 fs to 1 ns at 1,053 nm wavelength. A time resolved stress detection technique was employed to measure transient stress profiles and amplitudes. Optical microscopy was used to characterize ablation craters qualitatively, while a wide band acoustic transducer helped to quantify tissue mechanical response and the ablation threshold. The ablation threshold was measured as a function of laser pulse duration and linear absorption coefficient. For nanosecond pulses the ablation threshold was found to have a strong dependence on the linear absorption coefficient of the material. As the pulse length decreased into the subpicosecond regime the ablation threshold became insensitive to the linear absorption coefficient. The ablation efficiency was found to be insensitive to both the laser pulse duration and the linear absorption coefficient. High quality ablation craters with no thermal or mechanical damage to surrounding material were obtained with 350 fs laser pulses. The mechanism of optical breakdown at the tissue surface was theoretically investigated. In the nanosecond regime, optical breakdown proceeds as an electron collisional avalanche ionization initiated by thermal seed electrons. These seed electrons are created by heating of the tissue by linear absorption. In the ultrashort pulse range, optical breakdown is initiated by the multiphoton ionization of the irradiated medium (6 photons in case of tissue irradiated at 1,053 nm wavelength), and becomes less sensitive to the linear absorption coefficient. The energy deposition profile is insensitive to both the laser pulse duration and the linear absorption coefficient.

  14. Laser ablated hard coating for microtools

    DOEpatents

    McLean, II, William; Balooch, Mehdi; Siekhaus, Wigbert J.

    1998-05-05

    Wear-resistant coatings composed of laser ablated hard carbon films, are deposited by pulsed laser ablation using visible light, on instruments such as microscope tips and micro-surgical tools. Hard carbon, known as diamond-like carbon (DLC), films produced by pulsed laser ablation using visible light enhances the abrasion resistance, wear characteristics, and lifetimes of small tools or instruments, such as small, sharp silicon tips used in atomic probe microscopy without significantly affecting the sharpness or size of these devices. For example, a 10-20 nm layer of diamond-like carbon on a standard silicon atomic force microscope (AFM) tip, enables the useful operating life of the tip to be increased by at least twofold. Moreover, the low inherent friction coefficient of the DLC coating leads to higher resolution for AFM tips operating in the contact mode.

  15. Laser ablated hard coating for microtools

    DOEpatents

    McLean, W. II; Balooch, M.; Siekhaus, W.J.

    1998-05-05

    Wear-resistant coatings composed of laser ablated hard carbon films, are deposited by pulsed laser ablation using visible light, on instruments such as microscope tips and micro-surgical tools. Hard carbon, known as diamond-like carbon (DLC), films produced by pulsed laser ablation using visible light enhances the abrasion resistance, wear characteristics, and lifetimes of small tools or instruments, such as small, sharp silicon tips used in atomic probe microscopy without significantly affecting the sharpness or size of these devices. For example, a 10--20 nm layer of diamond-like carbon on a standard silicon atomic force microscope (AFM) tip, enables the useful operating life of the tip to be increased by at least twofold. Moreover, the low inherent friction coefficient of the DLC coating leads to higher resolution for AFM tips operating in the contact mode. 12 figs.

  16. Laser systems for ablative fractional resurfacing.

    PubMed

    Paasch, Uwe; Haedersdal, Merete

    2011-01-01

    Ablative fractional resurfacing (AFR) creates microscopic vertical ablated channels that are surrounded by a thin layer of coagulated tissue, constituting the microscopic treatment zones (MTZs). AFR induces epidermal and dermal remodeling, which raises new possibilities for the treatment of a variety of skin conditions, primarily chronically photodamaged skin, but also acne and burn scars. In addition, it is anticipated that AFR can be utilized in the laser-assisted delivery of topical drugs. Clinical efficacy coupled with minimal downtime has driven the development of various fractional ablative laser systems. Fractionated CO(2) (10,600-nm), erbium yttrium aluminum garnet, 2940-nm and yttrium scandium gallium garnet, 2790-nm lasers are available. In this article, we present an overview of AFR technology, devices and histopathology, and we summarize the current clinical possibilities with AFR incorporating our personal experience. AFR is still in the exploratory era, and systematic investigations of clinical outcomes related to various system settings are needed. PMID:21158542

  17. Laser ablation of optically thin absorbing liquid layer predeposited onto a transparent solid substrate

    SciTech Connect

    Kudryashov, S. I.; Lyon, K.; Shukla, S.; Murry, D.; Allen, S. D.

    2006-09-01

    Ablation of optically thin liquid 2-propanol layers of variable thickness on IR-transparent solid Si substrate by a nanosecond CO{sub 2} laser has been experimentally studied using time-resolved optical interferometric and microscopy techniques. Basic ablation parameters - threshold fluences for surface vaporization and explosive homogeneous boiling of the superheated liquid, ablation depths, vaporization (ablation) rates, and characteristic ablation times versus laser fluence - were measured as a function of alcohol layer thickness. The underlying ablation mechanisms, their thermodynamics, and microscopic details are discussed.

  18. Fractional Erbium laser in the treatment of photoaging: randomized comparative, clinical and histopathological study of ablative (2940nm) vs. non-ablative (1540nm) methods after 3 months*

    PubMed Central

    Borges, Juliano; Cuzzi, Tullia; Mandarim-de-Lacerda, Carlos Alberto; Manela-Azulay, Mônica

    2014-01-01

    BACKGROUND Fractional non-ablative lasers keep the epidermis intact, while fractional ablative lasers remove it, making them theoretically more effective. OBJECTIVES To evaluate the clinical and histological alterations induced by fractional photothermolysis for treating photoaging, comparing the possible equivalence of multiple sessions of 1540nm Erbium, to one session of 2940nm Erbium. METHODS Eighteen patients (mean age 55.9) completed the treatment with three sessions of 1540nm fractional Erbium laser on one side of the face (50 mJ/mB, 15ms, 2 passes), and one session of 2940nm on the other side (5mJ/mB, 0.25ms, 2 passes). Biopsies were performed before and 3 months after treatment. Clinical, histological and morphometric evaluations were carried out. RESULTS All patients presented clinical improvement with no statistically significant difference (p> 0.05) between the treated sides. Histopathology revealed a new organization of collagen and elastic fibers, accompanied by edema, which was more evident with the 2940nm laser. This finding was confirmed by morphometry, which showed a decrease in collagen density for both treatments, with a statistical significance for the 2940nm laser (p > 0.001). CONCLUSIONS Three 1540nm sessions were clinically equivalent to one 2940nm session. The edema probably contributed to the positive results after three months, togheter with the new collagen and elastic fibers organization. The greater edema after the 2940nm session indicates that dermal remodeling takes longer than with 1540nm. It is possible that this histological superiority relates to a more prolonged effect, but a cohort longer than three months is needed to confirm that supposition. PMID:24770501

  19. Dissolution in a supercritical liquid as a mechanism of laser ablation of sapphire

    SciTech Connect

    Dolgaev, Sergei I; Karasev, M E; Kulevskii, L A; Simakin, Aleksandr V; Shafeev, Georgii A

    2001-07-31

    The laser ablation of sapphire is studied by irradiating its interface with water and aqueous solutions of KOH, KCl and Na{sub 2}CO{sub 3} by 2.92-{mu}m 130-ns holmium laser pulses. The ablation rate depends on the concentration and type of the dissolved substance. The highest ablation rate is 2.5{mu}m per pulse for a laser fluence of 120 J cm{sup -2}. The ablation of sapphire is attributed to its dissolution in water or in aqueous solutions in the supercritical state. (interaction of laser radiation with matter. laser plasma)

  20. Laser Ablation for Small Hepatocellular Carcinoma

    PubMed Central

    Pacella, Claudio Maurizio; Francica, Giampiero; Di Costanzo, Giovanni Giuseppe

    2011-01-01

    Hepatocellular carcinoma (HCC) is one of the most common malignancies worldwide and is increasingly detected at small size (<5 cm) owing to surveillance programmes in high-risk patients. For these cases, curative therapies such as resection, liver transplantation, or percutaneous ablation have been proposed. When surgical options are precluded, image-guided tumor ablation is recommended as the most appropriate therapeutic choice in terms of tumor local control, safety, and improvement in survival. Laser ablation (LA) represents one of currently available loco-ablative techniques: light is delivered via flexible quartz fibers of diameter from 300 to 600 μm inserted into tumor lesion through either fine needles (21g Chiba needles) or large-bore catheters. The thermal destruction of tissue is achieved through conversion of absorbed light (usually infrared) into heat. A range of different imaging modalities have been used to guide percutaneous laser ablation, but ultrasound and magnetic resonance imaging are most widely employed, according to local experience and resource availability. Available clinical data suggest that LA is highly effective in terms of tumoricidal capability with an excellent safety profile; the best results in terms of long-term survival are obtained in early HCC so that LA can be proposed not only in unresectable cases but, not differently from radiofrequency ablation, also as the first-line treatment. PMID:22191028

  1. Update On CO{sub 2} Laser Ablation Of Polyoxymethylene At 101 kPa

    SciTech Connect

    Sinko, John E.; Scharring, Stefan; Eckel, Hans-Albert; Ogita, Naoya; Sasoh, Akihiro; Roeser, Hans-Peter

    2010-10-08

    Recent work has brought about a renewed interest in CO{sub 2} laser ablation studies of polyoxymethylene, due to its potential as a test target for enhancing modern understanding of the laser ablation process. In this paper, new results taken in air at atmosphere pressure are reported, including data measured at institutions in Germany and Japan, which increase the body of literature data on CO{sub 2} laser ablation of polyoxymethylene. The results are discussed in terms of aerospace parameters such as the momentum coupling coefficient and specific impulse, and are compared to a previous literature study. The threshold fluence is specified for ablation of polyoxymethylene by CO{sub 2} laser radiation. Fluences higher (and lower) than previously tested for CO{sub 2} laser ablation were studied herein, and record specific impulse values for CO{sub 2} laser ablation of flat polyoxymethylene are also reported here.

  2. Comparison of soft and hard tissue ablation with sub-ps and ns pulse lasers

    SciTech Connect

    Da Silva, L.B.; Stuart, B.C.; Celliers, P.M.; Feit, M.D.; Glinsky, M.E.; Heredia, N.J.; Herman, S.; Lane, S.M.; London, R.A.; Matthews, D.L.; Perry, M.D.; Rubenchik, A.M.; Chang, T.D.; Neev, J.

    1996-05-01

    Tissue ablation with ultrashort laser pulses offers several unique advantages. The nonlinear energy deposition is insensitive to tissue type, allowing this tool to be used for soft and hard tissue ablation. The localized energy deposition lead to precise ablation depth and minimal collateral damage. This paper reports on efforts to study and demonstrate tissue ablation using an ultrashort pulse laser. Ablation efficiency and extent of collateral damage for 0.3 ps and 1000 ps duration laser pulses are compared. Temperature measurements of the rear surface of a tooth section is also presented.

  3. A new perspective of ablative pulsed laser propulsion: study on different morphologies of nano-structured ZnO

    NASA Astrophysics Data System (ADS)

    Ahmad, Muhammad Raza; Jamil, Yasir; Saeed, Humaima; Hussain, Tousif

    2015-05-01

    We report for the first time a new application of four different morphologies including nano-noodles of zinc oxide as a laser ablation micro-thruster. Nano-noodles represent a unique class of materials in which the electrons are confined near the surface owing to the majority of the near surface atoms. The synthesized samples of ZnO were of single phase, having a wurtzite hexagonal structure. Three different morphologies, viz. initial (nanoparticles), intermediate (nano-noodles) and final (complete nano-noodles) of zinc oxide were ablated using a Nd : YAG laser operating at 1064 nm for the measurement of propulsion parameters. The momentum coupling coefficient (Cm) and the specific impulse (Isp) were evaluated using the non-contact optical triangulation method. It has been observed that the morphology of the material affects the laser ablation propulsion (LAP) parameters. For each sample, the laser fluence for the optimum coupling coefficient owing to the plasma shielding effect has also been found. The synthesized nanostructured zinc oxide samples have been found useful as efficient laser propellants that can be used in a variety of applications due to diversity in their momentum coupling coefficient and specific impulse values.

  4. Dynamical modeling of laser ablation processes

    SciTech Connect

    Leboeuf, J.N.; Chen, K.R.; Donato, J.M.; Geohegan, D.B.; Liu, C.L.; Puretzky, A.A.; Wood, R.F.

    1995-09-01

    Several physics and computational approaches have been developed to globally characterize phenomena important for film growth by pulsed laser deposition of materials. These include thermal models of laser-solid target interactions that initiate the vapor plume; plume ionization and heating through laser absorption beyond local thermodynamic equilibrium mechanisms; gas dynamic, hydrodynamic, and collisional descriptions of plume transport; and molecular dynamics models of the interaction of plume particles with the deposition substrate. The complexity of the phenomena involved in the laser ablation process is matched by the diversity of the modeling task, which combines materials science, atomic physics, and plasma physics.

  5. 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.

  6. Nanoscale patterning of graphene through femtosecond laser ablation

    SciTech Connect

    Sahin, R.; Akturk, S.; Simsek, E.

    2014-02-03

    We report on nanometer-scale patterning of single layer graphene on SiO{sub 2}/Si substrate through femtosecond laser ablation. The pulse fluence is adjusted around the single-pulse ablation threshold of graphene. It is shown that, even though both SiO{sub 2} and Si have more absorption in the linear regime compared to graphene, the substrate can be kept intact during the process. This is achieved by scanning the sample under laser illumination at speeds yielding a few numbers of overlapping pulses at a certain point, thereby effectively shielding the substrate. By adjusting laser fluence and translation speed, 400 nm wide ablation channels could be achieved over 100 μm length. Raster scanning of the sample yields well-ordered periodic structures, provided that sufficient gap is left between channels. Nanoscale patterning of graphene without substrate damage is verified with Scanning Electron Microscope and Raman studies.

  7. Ablative Laser Propulsion Using Multi-Layered Material Systems

    NASA Technical Reports Server (NTRS)

    Nehls, Mary; Edwards, David; Gray, Perry; Schneider, T.

    2002-01-01

    Experimental investigations are ongoing to study the force imparted to materials when subjected to laser ablation. When a laser pulse of sufficient energy density impacts a material, a small amount of the material is ablated. A torsion balance is used to measure the momentum produced by the ablation process. The balance consists of a thin metal wire with a rotating pendulum suspended in the middle. The wire is fixed at both ends. Recently, multi-layered material systems were investigated. These multi-layered materials were composed of a transparent front surface and opaque sub surface. The laser pulse penetrates the transparent outer surface with minimum photon loss and vaporizes the underlying opaque layer.

  8. Innovative Laser Ablation Technology for Surface Decontamination

    SciTech Connect

    Chen, Winston C. H.

    2003-06-01

    The objective of this project is to develop a novel laser ablation in liquid for surface decontamination. It aims to achieve more efficient surface decontamination without secondary contamination. Another aim is to make this surface decontamination technology becomes economically feasible for large scale decontamination.

  9. NOVEL LASER ABLATION TECHNOLOGY FOR SURFACE DECONTAMINATION

    EPA Science Inventory

    The objective of this project is to develop a novel Laser Ablation Decontamination in Liquid (LADIL) technology for surface decontamination and safe removal of radioactive and/or toxic contaminants. It aims to achieve more efficient surface decontamination without secondary conta...

  10. Laser Ablation Inductively Coupled Plasma Mass Spectrometry

    PubMed Central

    Hutchinson, Robert W.; McLachlin, Katherine M.; Riquelme, Paloma; Haarer, Jan; Broichhausen, Christiane; Ritter, Uwe; Geissler, Edward K.; Hutchinson, James A.

    2015-01-01

    ABSTRACT New analytical techniques for multiparametric characterisation of individual cells are likely to reveal important information about the heterogeneity of immunological responses at the single-cell level. In this proof-of-principle study, laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was applied to the problem of concurrently detecting 24 lineage and activation markers expressed by human leucocytes. This approach was sufficiently sensitive and specific to identify subpopulations of isolated T, B, and natural killer cells. Leucocyte subsets were also accurately detected within unfractionated peripheral blood mononuclear cells preparations. Accordingly, we judge LA-ICP-MS to be a suitable method for assessing expression of multiple tissue antigens in solid-phase biological specimens, such as tissue sections, cytospins, or cells grown on slides. These results augur well for future development of LA-ICP-MS–based bioimaging instruments for general users. PMID:27500232

  11. Dynamics of laser ablated colliding plumes

    SciTech Connect

    Gupta, Shyam L.; Pandey, Pramod K.; Thareja, Raj K.

    2013-01-15

    We report the dynamics of single and two collinearly colliding laser ablated plumes of ZnO studied using fast imaging and the spectroscopic measurements. Two dimensional imaging of expanding plume and temporal evolution of various species in interacting zones of plumes are used to calculate plume front velocity, electron temperature, and density of plasma. The two expanding plumes interact with each other at early stage of expansion ({approx}20 ns) resulting in an interaction zone that propagates further leading to the formation of stagnation layer at later times (>150 ns) at the lateral collision front of two plumes. Colliding plumes have larger concentration of higher ionic species, higher temperature, and increased electron density in the stagnation region. A one-to-one correlation between the imaging and optical emission spectroscopic observations in interaction zone of the colliding plumes is reported.

  12. Laser ablated zirconium plasma: A source of neutral zirconium

    SciTech Connect

    Yadav, Dheerendra; Thareja, Raj K.

    2010-10-15

    The authors report spectroscopic investigations of laser produced zirconium (Zr) plasma at moderate laser fluence. At low laser fluence the neutral zirconium species are observed to dominate over the higher species of zirconium. Laser induced fluorescence technique is used to study the velocity distribution of ground state neutral zirconium species. Two-dimensional time-resolved density distributions of ground state zirconium is mapped using planner laser induced fluorescence imaging and total ablated mass of neutral zirconium atoms is estimated. Temporal and spatial evolutions of electron density and temperature are discussed by measuring Stark broadened profile and ratio of intensity of emission lines, respectively.

  13. Laser ablation of GaAs in liquid: the role of laser pulse duration

    NASA Astrophysics Data System (ADS)

    De Bonis, Angela; Galasso, Agostino; Santagata, Antonio; Teghil, Roberto

    2016-01-01

    The synthesis of gallium arsenide (GaAs) nanoparticles has attracted wide scientific and technological interest due to the possibility of tuning the GaAs NP (nanoparticle) band gap across the visible spectrum and their consequent use in optoelectronic devices. In recent years, laser ablation in liquid (LAL) has been widely used for the preparation of colloidal solutions of semiconducting and metallic nanoparticles, thanks to its flexibility. With the aim of highlighting the key role played by laser pulse duration on the ablation mechanism and on the properties of the obtained materials, laser ablation of a gallium arsenide target in acetone was performed using laser sources operating in two different temporal regimes: Nd:glass laser (λ   =  527 nm, pulse duration of 250 fs and frequency repetition rate of 10 Hz) and Nd:YAG laser (λ   =  532 nm, pulse duration of 7 ns and frequency repetition rate of 10 Hz). The ablation process was studied following the dynamics of the laser induced shock waves (SWs) and cavitation bubbles (CBs) by fast shadowgraphy, showing that CB dimension and lifetime is related to the laser pulse length. A characterization of the obtained materials by TEM (transmission electron microscopy) and microRaman spectroscopy have shown that quite spherical gallium oxide/GaAs nanoparticles can be obtained by nanosecond laser ablation. On the other hand, pure polycrystalline GaAs nanoparticles can be produced by using an ultrashort laser source.

  14. Microwave ablation versus laser ablation in occluding lateral veins in goats.

    PubMed

    Wang, Xu-hong; Wang, Xiao-ping; Su, Wen-juan; Yuan, Yuan

    2016-02-01

    Increasing number of endovenous techniques are available for the treatment of saphenous vein reflux and endovenous laser ablation (EVLA) is a frequently used method. A newly developed alternative, based on thermal therapy, is endovenous microwave ablation (EMA). This study evaluated the effect of the two procedures, in terms of coagulation and histological changes, in occluding lateral veins in goats. Twelve animals were randomized into two group, with 6 treated with EMA (EMA group), and the rest 6 with EVLA (EVLA group). Results of coagulation, including coagulation, fibrinolysis and platelet activation, were assessed at three or four different time points: before, immediately after, 24 h (and 48 h) after ablation. The diameter change, a measure of efficacy, was ultrasonographically measured before and 1 month after the ablation. Histological changes were grossly and microscopically evaluated immediately, 1 and 3 month(s) after the ablation. The length of the ablated vein and preoperative average diameter were comparable between the two groups. In both EMA and EVLA groups, several coagulation parameters, fibrinolysis and platelet activation parameters only underwent slight changes. Ultrasound imaging displayed that the diameter reduction of the veins treated by EMA was significantly larger than by EVLA, in consistent with the results of macroscopic examination. Microscopic examination revealed necrosis and thickening of the vein wall, and occlusion of the lumen within 3 months after ablation in both EMA and EVLA groups. It is concluded that EMA is a minimally invasive therapy, which appears to be safe and effective for treatment of lateral veins in goats. PMID:26838749

  15. Deposition of potassium oxygen on silicon surfaces by pulsed laser ablation of potassium superoxide: Study of work function changes

    NASA Astrophysics Data System (ADS)

    Choo, Cheow-Keong; Suzawa, Daisuke; Tanaka, Katsumi

    2006-04-01

    Potassium-oxygen species were deposited on pure, Si nanoparticles coated and H-terminated Si nanoparticles coated p-Si(1 0 0) surfaces by pulsed laser ablation of potassium superoxide (KO 2) target. The deposition properties, composition and the work function changes of the deposited species were investigated in situ using an X-ray photoelectron spectroscopy (XPS) and a Kelvin probe measurement. The deposited species were assigned to K 2O 2 and KO 2, and they can be selectively deposited by controlling the laser fluence: i.e., at 200 mJ/cm 2 and at those more than 300 mJ/cm 2, respectively. Experimental results showed that the work function decreased drastically with depositing of KO x ( x = 1 or 2), and the minimum work function values observed were 1.0 eV and 0.7 eV for pure p-Si(1 0 0) and Si nanoparticles coated substrates, respectively. The study demonstrates the formation of the surface species with minimum work function can be identified by XPS.

  16. Picosecond laser ablation of porcine sclera

    NASA Astrophysics Data System (ADS)

    Góra, Wojciech S.; Harvey, Eleanor M.; Dhillon, Baljean; Parson, Simon H.; Maier, Robert R. J.; Hand, Duncan P.; Shephard, Jonathan D.

    2013-03-01

    Lasers have been shown to be successful in certain medical procedures and they have been identified as potentially making a major contribution to the development of minimally invasive procedures. However, the uptake is not as widespread and there is scope for many other applications where laser devices may offer a significant advantage in comparison to the traditional surgical tools. The purpose of this research is to assess the potential of using a picosecond laser for minimally invasive laser sclerostomy. Experiments were carried out on porcine scleral samples due to the comparable properties to human tissue. Samples were prepared with a 5mm diameter trephine and were stored in lactated Ringer's solution. After laser machining, the samples were fixed in 3% glutaraldehyde, then dried and investigated under SEM. The laser used in the experiments is an industrial picosecond TRUMPF TruMicro laser operating at a wavelength of 1030nm, pulse length of 6ps, repetition rate of 1 kHz and a focused spot diameter of 30μm. The laser beam was scanned across the samples with the use of a galvanometer scan head and various ablation patterns were investigated. Processing parameters (pulse energy, spot and line separation) which allow for the most efficient laser ablation of scleral tissue without introducing any collateral damage were investigated. The potential to create various shapes, such as linear incisions, square cavities and circular cavities was demonstrated.

  17. Comparative study of femtosecond and nanosecond laser ablation for propulsion applications

    NASA Astrophysics Data System (ADS)

    Ionin, A. A.; Kudryashov, S. I.; Makarov, S. V.; Seleznev, L. V.; Sinitsyn, D. V.

    2012-07-01

    Dependences of absolute vapor/plasma pressure on femtosecond and nanosecond laser intensities were obtained for graphitic materials using a non-contact broadband ultrasonic technique, and propulsion prospects of femtosecond and nanosecond laser launching approaches are discussed.

  18. A Review of Laser Ablation Propulsion

    SciTech Connect

    Phipps, Claude; Bohn, Willy; Lippert, Thomas; Sasoh, Akihiro; Schall, Wolfgang; Sinko, John

    2010-10-08

    Laser Ablation Propulsion is a broad field with a wide range of applications. We review the 30-year history of laser ablation propulsion from the transition from earlier pure photon propulsion concepts of Oberth and Saenger through Kantrowitz's original laser ablation propulsion idea to the development of air-breathing 'Lightcraft' and advanced spacecraft propulsion engines. The polymers POM and GAP have played an important role in experiments and liquid ablation fuels show great promise. Some applications use a laser system which is distant from the propelled object, for example, on another spacecraft, the Earth or a planet. Others use a laser that is part of the spacecraft propulsion system on the spacecraft. Propulsion is produced when an intense laser beam strikes a condensed matter surface and produces a vapor or plasma jet. The advantages of this idea are that exhaust velocity of the propulsion engine covers a broader range than is available from chemistry, that it can be varied to meet the instantaneous demands of the particular mission, and that practical realizations give lower mass and greater simplicity for a payload delivery system. We review the underlying theory, buttressed by extensive experimental data. The primary problem in laser space propulsion theory has been the absence of a way to predict thrust and specific impulse over the transition from the vapor to the plasma regimes. We briefly discuss a method for combining two new vapor regime treatments with plasma regime theory, giving a smooth transition from one regime to the other. We conclude with a section on future directions.

  19. Spectroscopic measurements of ablation plasma generated with laser-driven intense extreme ultraviolet (EUV) light

    NASA Astrophysics Data System (ADS)

    Tanaka, N.; Hane, K.; Shikata, H.; Masuda, M.; Nagatomi, K.; Sunahara, A.; Yoshida, M.; Fujioka, S.; Nishimura, H.

    2016-03-01

    Material ablation by a focused Extreme ultraviolet (EUV) light is studied by comparing expanding ion properties and plasma parameters with laser ablation. The kinetic energy distributions of expanding ions from EUV and laser ablation showed different spectra implying different geometries of plasma expansion. The calculation results of plasma parameters showed that EUV energy is mostly deposited in high electron density region close to the solid density, while laser energy is deposited in low energy density region. Plasma parameters experimentally obtained from visible spectra did not show noticeable difference between EUV and laser ablation due to the corresponding low cut off density.

  20. Laser-ablation processes (Invited Paper)

    NASA Astrophysics Data System (ADS)

    Dingus, Ronald S.

    1992-06-01

    The physical mechanisms associated with ablation of matter by laser irradiation are quite different in different regions of parameter space. The important parameters are the laser wavelength; the laser flux versus time, position, and angle of incidence at the target; and the target properties as well as the properties of the laser-transport medium adjacent to the irradiated target surface. Important target properties include surface contour, laser reflectivity and absorption depth, thermal diffusively, vaporization energy, Gruneisen coefficient, spall strength, ionization energies and plasma opacity versus temperature and density. As the flux increases, the process becomes less dependent on most of these target properties. Depending on the values of these various parameters, at relatively low fluxes targets can be vaporized and these vapors can be transparent to the laser beam. If a transparent liquid or solid transport medium exists in front of the vaporized target material, then a complicated contained- vaporization process takes place and the work done on the target by the vapors can be several orders of magnitude larger than with a gas or vacuum transport medium; the degree of work enhancement can depend strongly on the vapor condensability and condensed matter thermal conductivity. For short-pulselength irradiations of semi-transparent targets with a low- acoustic-impedance-laser-transport medium adjacent to the target, ablation needs to be a vacuum in order for the beam to be able to propagate to the target. For targets in a vacuum exposed to fluxes of this order (and considerably higher) and for long pulselengths, most of the laser energy will be absorbed (before reaching the critical surface) by inverse bremsstrahlung in material blown off from the target; at higher fluxes, the beam will be stopped at the critical surface producing localized absorption along with much higher energy densities and non-thermal equilibrium behavior. When the combination of

  1. Laser ablation of a platinum target in water. II. Ablation rate and nanoparticle size distributions

    SciTech Connect

    Nichols, William T.; Sasaki, Takeshi; Koshizaki, Naoto

    2006-12-01

    This is the second in a series of three papers examining nanomaterial formation in laser ablation in liquids (LAL). Here we study the effect of the laser wavelength and fluence on the mass yield and size distribution of nanoparticles prepared by laser ablation of a platinum target immersed in water. For all wavelengths tested, laser fluences in the range of 10-70 J/cm{sup 2} resulted in spheroidal, nonagglomerated platinum nanoparticles with sizes ranging from 1 to 30 nm. Nanoparticle size distributions are found to be composed of two modes that are attributed to thermal vaporization and explosive boiling mechanisms. The peak of the smaller size mode remains nearly constant at 3 nm for all laser conditions, which is suggested to be due to the strong confinement of the vapor plume by the liquid. The larger size mode peaks in the range of 5-15 nm with a population that is strongly dependent on the laser parameters. It is concluded that changes in the mean size reported in many earlier studies on LAL of metal targets are a result of the relative quantity of nanoparticles from each mechanism rather than direct control over the ablation process. Additionally, it was observed that the yield of platinum nanoparticles was significantly larger for 1064 nm wavelength at fluences greater than 10 J/cm{sup 2}. The maximum ablation rate was approximately 4.4 mg/h, with an estimated ablation and collection efficiency of 0.9 {mu}g/J. Dependence of the mass yield on wavelength and fluence is seen to be dependent primarily on the extent of the explosive mechanism.

  2. Ultra-short pulsed laser tissue ablation using focused laser beam

    NASA Astrophysics Data System (ADS)

    Jaunich, Megan K.; Raje, Shreya; Mitra, Kunal; Grace, Michael S.; Fahey, Molly; Spooner, Greg

    2008-02-01

    Short pulse lasers are used for a variety of therapeutic applications in medicine. Recently ultra-short pulse lasers have gained prominence due to the reduction in collateral thermal damage to surrounding healthy tissue during tissue ablation. In this paper, ultra-short pulsed laser ablation of mouse skin tissue is analyzed by assessing the extent of damage produced due to focused laser beam irradiation. The laser used for this study is a fiber-based desktop laser (Raydiance, Inc.) having a wavelength of 1552 nm and a pulse width of 1.3 ps. The laser beam is focused on the sample surface to a spot size on the order of 10 microns, thus producing high peak intensity necessary for precise clean ablation. A parametric study is performed on in vitro mouse tissue specimens and live anaesthetized mice with mammary tumors through variation of laser parameters such as time-averaged laser power, repetition rate, laser scanning rate and irradiation time. Radial temperature distribution is measured using thermal camera to analyze the heat affected zone. Temperature measurements are performed to assess the peak temperature rise attained during ablation. A detailed histological study is performed using frozen section technique to observe the nature and extent of laser-induced damages.

  3. 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.

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

    NASA Technical Reports Server (NTRS)

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

    1990-01-01

    High temperature superconducting films of YBa2Cu3O(7-x) (YBCO) were grown on SrTiO3, LaAl03, 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 = 0) = 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-evaporated films was much lower than the value reported for single crystals, and was sample dependent.

  5. Small glass particle cloud generation induced by laser ablation

    NASA Astrophysics Data System (ADS)

    Nagayama, Kunihito; Kotsuka, Yuriko; Nakahara, Motonao; Kubota, Shiro

    2005-03-01

    Burst of small fragments of glass has been evidenced in the present study, when ground glass surface is laser ablated. Production of macro particles by laser ablation is an inherent characteristic of ground glass, and no similar phenomena have been observed in case of metal or polymer ablation. In this case, no additional metal coating has been made to further enhance absorption of laser pulse. Pulse laser shadowgraph has been taken to study the details of the phenomena in air and in vacuum. At least in vacuum, particle burst is found almost normal to the surface. By using ns-duration Nd:YAG laser of 100 mJ/pulse, observed particle velocity ranges 0.5 km/s to 1.5 km/s in case of in air and the maximum velocity is extended up to 1.5-2 km/s in vacuum. SEM observation of the ground surface reveals that glass surface is covered with micro cracks with several microns deep, which might attribute to macro particle production. In this sense, not surface roughness but also surface structure will be important in the ablation phenomena of glass. It is plausible that absorption of laser beam at the glass surface causes spallation like phenomena as well as production of an amount of plasma, and the plasma production might be responsible for the acceleration of broken fragments of glass. We applied the phenomena to ignite PETN powder explosive, and succeeded in igniting PETN powder only by laser ablation of ground glass.

  6. Thermal melting and ablation of silicon by femtosecond laser radiation

    SciTech Connect

    Ionin, A. A.; Kudryashov, S. I. Seleznev, L. V.; Sinitsyn, D. V.; Bunkin, A. F.; Lednev, V. N.; Pershin, S. M.

    2013-03-15

    The space-time dynamics of thermal melting, subsurface cavitation, spallative ablation, and fragmentation ablation of the silicon surface excited by single IR femtosecond laser pulses is studied by timeresolved optical reflection microscopy. This dynamics is revealed by monitoring picosecond and (sub)nanosecond oscillations of probe pulse reflection, which is modulated by picosecond acoustic reverberations in the dynamically growing surface melt subjected to ablation and having another acoustic impedance, and by optical interference between the probe pulse replicas reflected by the spalled layer surface and the layer retained on the target surface. The acoustic reverberation periods change during the growth and ablation of the surface melt film, which makes it possible to quantitatively estimate the contributions of these processes to the thermal dynamics of the material surface. The results on the thermal dynamics of laser excitation are supported by dynamic measurements of the ablation parameters using noncontact ultrasonic diagnostics, scanning electron microscopy, atomic force microscopy, and optical interference microscopy of the modified regions appearing on the silicon surface after ablation.

  7. Thermal melting and ablation of silicon by femtosecond laser radiation

    NASA Astrophysics Data System (ADS)

    Ionin, A. A.; Kudryashov, S. I.; Seleznev, L. V.; Sinitsyn, D. V.; Bunkin, A. F.; Lednev, V. N.; Pershin, S. M.

    2013-03-01

    The space-time dynamics of thermal melting, subsurface cavitation, spallative ablation, and fragmentation ablation of the silicon surface excited by single IR femtosecond laser pulses is studied by timeresolved optical reflection microscopy. This dynamics is revealed by monitoring picosecond and (sub)nanosecond oscillations of probe pulse reflection, which is modulated by picosecond acoustic reverberations in the dynamically growing surface melt subjected to ablation and having another acoustic impedance, and by optical interference between the probe pulse replicas reflected by the spalled layer surface and the layer retained on the target surface. The acoustic reverberation periods change during the growth and ablation of the surface melt film, which makes it possible to quantitatively estimate the contributions of these processes to the thermal dynamics of the material surface. The results on the thermal dynamics of laser excitation are supported by dynamic measurements of the ablation parameters using noncontact ultrasonic diagnostics, scanning electron microscopy, atomic force microscopy, and optical interference microscopy of the modified regions appearing on the silicon surface after ablation.

  8. Formation and characterization of nanoparticles via laser ablation in solution

    NASA Astrophysics Data System (ADS)

    Golightly, Justin Samuel

    isopropyl alcohol. Ablation in n-hexane also showed diffraction patterns correlating with carbides, and water showed oxygen incorporation. These results showed the ability to utilize the solvent in tailoring nanoparticles to achieve desired properties. Zirconium and nickel were ablated with the Nd:YAG at 532 nm. These studies utilized a stainless steel chamber designed and built to improve control over the experimental variables. The nickel study showcased the new chamber's ability for reproducibility in a size dependence study based upon laser fluence. The results of ablation with the Nd:YAG were compared to femtosecond ablation experiments performed with a titanium:sapphire femtosecond laser system. The Ti:sapphire femtosecond laser operated at 10 Hz, produced femtosecond pulses centered at ˜795 nm. The pulse duration was varied from 100 fs to 390 fs, the nanoparticles created from each condition were characterized, and the results are presented in chapters 5 and 6. Aluminum nanoparticles were made using both nanosecond and femtosecond laser ablation techniques. Aluminum nanoparticles have a great deal of potential for use as fuel additives as well as in paints and coatings. The nanosecond ablation process rendered large nanoparticles (over 200 nm) and the results are briefly shown in Appendix A. The femtosecond system produced a much smaller distribution of nanoparticles, with nanoparticles remaining in suspension for over a month's time, as evidenced by their unique UV-Vis absorbance. These nanoparticles were produced in isopropyl alcohol, and were stabilized by the solvent, as TEM analysis showed nanoparticles with very little oxygen incorporation. The solvent is bound to the nanoparticles as a result of the formation process and as a result forms a protective coating, which prevents further oxidation over time. The remarkable stability of these aluminum nanoparticles is a testament of employing the high energy scheme of the laser ablation process in a manner to

  9. Fundamentals and applications of polymers designed for laser ablation

    NASA Astrophysics Data System (ADS)

    Lippert, T.; Hauer, M.; Phipps, C. R.; Wokaun, A.

    The ablation characteristics of various polymers were studied at low and high fluences for an irradiation wavelength of 308 nm. The polymers can be divided into three groups, i.e. polymers containing triazene groups, designed ester groups, and reference polymers, such as polyimide. The polymers containing the photochemically most active group (triazene) exhibit the lowest thresholds of ablation (as low as 25 mJcm-2) and the highest etch rates (e.g. 250 nm/pulse at 100 mJcm-2), followed by the designed polyesters and then polyimide. Neither the linear nor the effective absorption coefficients have a clear influence on the ablation characteristics. The different behavior of polyimide might be explained by a pronounced thermal part in the ablation mechanism. The laser-induced decomposition of the designed polymers was studied by nanosecond interferometry and shadowgraphy. The etching of the triazene polymer starts and ends with the laser pulse, indicating photochemical ablation. Shadowgraphy reveals mainly gaseous products and a pronounced shockwave in air. The designed polymers were tested for an application as the polymer fuel in laser plasma thrusters.

  10. Femtosecond laser ablation of cadmium tungstate for scintillator arrays

    NASA Astrophysics Data System (ADS)

    Richards, S.; Baker, M. A.; Wilson, M. D.; Lohstroh, A.; Seller, P.

    2016-08-01

    Ultrafast pulsed laser ablation has been investigated as a technique to machine CdWO4 single crystal scintillator and segment it into small blocks with the aim of fabricating a 2D high energy X-ray imaging array. Cadmium tungstate (CdWO4) is a brittle transparent scintillator used for the detection of high energy X-rays and γ-rays. A 6 W Yb:KGW Pharos-SP pulsed laser of wavelength 1028 nm was used with a tuneable pulse duration of 10 ps to 190 fs, repetition rate of up to 600 kHz and pulse energies of up to 1 mJ was employed. The effect of varying the pulse duration, pulse energy, pulse overlap and scan pattern on the laser induced damage to the crystals was investigated. A pulse duration of ≥500 fs was found to induce substantial cracking in the material. The laser induced damage was minimised using the following operating parameters: a pulse duration of 190 fs, fluence of 15.3 J cm-2 and employing a serpentine scan pattern with a normalised pulse overlap of 0.8. The surface of the ablated surfaces was studied using scanning electron microscopy, energy dispersive X-ray spectroscopy, atomic force microscopy and X-ray photoelectron spectroscopy. Ablation products were found to contain cadmium tungstate together with different cadmium and tungsten oxides. These laser ablation products could be removed using an ammonium hydroxide treatment.

  11. Effect of liquid properties on laser ablation of aluminum and titanium alloys

    NASA Astrophysics Data System (ADS)

    Ouyang, Peixuan; Li, Peijie; Leksina, E. G.; Michurin, S. V.; He, Liangju

    2016-01-01

    In order to study the effect of liquid properties on laser ablation in liquids, aluminum 5A06 and titanium TB5 targets were irradiated by single-pulse infrared laser in isopropanol, distilled water, glycerin and as a comparison, in air, respectively. Craters induced by laser ablation were characterized using scanning electron and white-light interferometric microscopies. The results show that for liquid-mediated ablation, craters with porous surface structures were formed in aluminum target through phase explosion, while no micro-cavities were formed in titanium target owing to high critical temperature of titanium. In addition, ablation rates of aluminum and titanium targets vary with types of ambient media in accordance with such sequence: air < isopropanol < water < glycerin. Further, the influence of liquid properties on material-removal mechanisms for laser ablation in liquid is discussed. It is concluded that the density, thermal conductivity and acoustical impedance of liquid play a dominant role in laser ablation efficiency.

  12. Simulation of Double-Pulse Laser Ablation

    SciTech Connect

    Povarnitsyn, Mikhail E.; Khishchenko, Konstantin V.; Levashov, Pavel R.; Itina, Tatian E.

    2010-10-08

    We investigate the physical reasons of a strange decrease in the ablation depth observed in femtosecond double-pulse experiments with increasing delay between the pulses. Two ultrashort pulses of the same energy produce the crater which is less than that created by a single pulse. Hydrodynamic simulation shows that the ablation mechanism is suppressed when the delay between the pulses exceeds the electron-ion relaxation time. In this case, the interaction of the second laser pulse with the expanding target material leads to the formation of the second shock wave suppressing the rarefaction wave created by the first pulse. The modeling of the double-pulse ablation for different delays between pulses confirms this explanation.

  13. Specific Impulse Definition for Ablative Laser Propulsion

    NASA Technical Reports Server (NTRS)

    Herren, Kenneth A.; Gregory, Don A.

    2004-01-01

    The term "specific impulse" is so ingrained in the field of rocket propulsion that it is unlikely that any fundamental argument would be taken seriously for its removal. It is not an ideal measure but it does give an indication of the amount of mass flow (mass loss/time), as in fuel rate, required to produce a measured thrust over some time period This investigation explores the implications of being able to accurately measure the ablation rate and how the language used to describe the specific impulse results may have to change slightly, and recasts the specific impulse as something that is not a time average. It is not currently possible to measure the ablation rate accurately in real time so it is generally just assumed that a constant amount of material will be removed for each laser pulse delivered The specific impulse dependence on the ablation rate is determined here as a correction to the classical textbook definition.

  14. Cluster Generation Under Pulsed Laser Ablation Of Compound Semiconductors

    SciTech Connect

    Bulgakov, Alexander V.; Evtushenko, Anton B.; Shukhov, Yuri G.; Ozerov, Igor; Marine, Wladimir

    2010-10-08

    A comparative experimental study of pulsed laser ablation in vacuum of two binary semiconductors, zinc oxide and indium phosphide, has been performed using IR- and visible laser pulses with particular attention to cluster generation. Neutral and cationic Zn{sub n}O{sub m} and In{sub n}P{sub m} particles of various stoichiometry have been produced and investigated by time-of-flight mass spectrometry. At ZnO ablation, large cationic (n>9) and all neutral clusters are mainly stoichiometric in the ablation plume. In contrast, indium phosphide clusters are strongly indium-rich with In{sub 4}P being a magic cluster. Analysis of the plume composition upon laser exposure has revealed congruent vaporization of ZnO and a disproportionate loss of phosphorus by the irradiated InP surface. Plume expansion conditions under ZnO ablation are shown to be favorable for stoichiometric cluster formation. A delayed vaporization of phosphorus under InP ablation has been observed that results in generation of off-stoichiometric clusters.

  15. Femtosecond laser ablation elemental mass spectrometry.

    PubMed

    Hergenröder, Roland; Samek, Ota; Hommes, Vanja

    2006-01-01

    Laser ablation mass spectrometry (LA-MS) has always been an interesting method for the elemental analysis of solid samples. Chemical analysis with a laser requires small amounts of material. Depending on the analytical detection system, subpicogram quantities may be sufficient. In addition, a focused laser beam permits the spatial characterization of heterogeneity in solid samples typically with micrometer resolution in terms of lateral and depth dimensions. With the advent of high-energy, ultra-short pulse lasers, new possibilities arise. The task of this review is to discuss the principle differences between the ablation process of short (>1 ps) and ultra-short (<1 ps) pulses. Based on the timescales and the energy balance of the process that underlies an ablation event, it will be shown that ultra-short pulses are less thermal and cause less collateral damages than longer pulses. The confinement of the pulse energy to the focal region guarantees a better spatial resolution in all dimensions and improves the analytical figures of merit (e.g., fractionation). Applications that demonstrate these features and that will be presented are in-depth profiling of multi-layer samples and the elemental analysis of biological materials. PMID:16477613

  16. Phase transitions in femtosecond laser ablation

    NASA Astrophysics Data System (ADS)

    Povarnitsyn, Mikhail E.; Khishchenko, Konstantin V.; Levashov, Pavel R.

    2009-03-01

    In this study we simulate an interaction of femtosecond laser pulses (100 fs, 800 nm, 0.1-10 J/cm 2) with metal targets of Al, Au, Cu, and Ni. For analysis of laser-induced phase transitions, melting and shock waves propagation as well as material decomposition we use an Eulerian hydrocode in conjunction with a thermodynamically complete two-temperature equation of state with stable and metastable phases. Isochoric heating, material evaporation from the free surface of the target and fast propagation of the melting and shock waves are observed. On rarefaction the liquid phase becomes metastable and its lifetime is estimated using the theory of homogeneous nucleation. Mechanical spallation of the target material at high strain rates is also possible as a result of void growth and confluence. In our simulation several ablation mechanisms are taken into account but the main issue of the material is found to originate from the metastable liquid state. It can be decomposed either into a liquid-gas mixture in the vicinity of the critical point, or into droplets at high strain rates and negative pressure. The simulation results are in agreement with available experimental findings.

  17. Study of Ablation and Implosion Stages of 1-MA Wire Array Z-Pinch using X-ray Laser-Based Backlighting

    NASA Astrophysics Data System (ADS)

    Anderson, Austin; Ivanov, Vladimir; Papp, Daniel; Talbot, Bjorn; Astanovitskiy, Alexey

    2013-10-01

    The ablation and implosion stages of wire array z-pinches were studied using laser-based x-ray imaging at the 1-MA Zebra pulse power generator at the University of Nevada, Reno. X-ray backlighting at the wavelength of 6.65 Å was provided by hitting a Si target with the 50 TW Leopard laser. Laser-based radiography allows flexibility in both the timing and the position of the x-ray source. The issue of the method is the small energy of the laser pulse compared to radiation of the Z pinch. A spherically bent quartz crystal can give spatial resolution <10 microns and spectral linewidth of the x-ray on the order of 10-4. X-ray imaging allows viewing of the dense core of plasma column during the ablation stage. Wires with diameters 7.6-15 were resolved in test shots. Images of the wire-array at the ablation stage are discussed. Work was supported by the DOE grant DE-SC0008824 and DOE/NNSA UNR grant DE-FC52-06NA27616.

  18. In vitro investigation on Ho:YAG laser-assisted bone ablation underwater.

    PubMed

    Zhang, Xianzeng; Chen, Chuanguo; Chen, Faner; Zhan, Zhenlin; Xie, Shusen; Ye, Qing

    2016-07-01

    Liquid-assisted hard tissue ablation by infrared lasers has extensive clinical application. However, detailed studies are still needed to explore the underlying mechanism. In the present study, the dynamic process of bubble evolution induced by Ho:YAG laser under water without and with bone tissue at different thickness layer were studied, as well as its effects on hard tissue ablation. The results showed that the Ho:YAG laser was capable of ablating hard bone tissue effectively in underwater conditions. The penetration of Ho:YAG laser can be significantly increased up to about 4 mm with the assistance of bubble. The hydrokinetic forces associated with the bubble not only contributed to reducing the thermal injury to peripheral tissue, but also enhanced the ablation efficiency and improve the ablation crater morphology. The data also presented some clues to optimal selection of irradiation parameters and provided additional knowledge of the bubble-assisted hard tissue ablation mechanism. PMID:27056700

  19. Pulsed CO2 laser ablation of graphite and polymers

    NASA Astrophysics Data System (ADS)

    Wong, K. H.; Tou, T. Y.; Low, K. S.

    1998-02-01

    Spectroscopic analysis of the emission plumes of graphite, polyimide, polyethylene terepthalate, and polymethylmethacrylate that have been ablated by using a pulsed CO2 laser operating at 10.6 μm shows the presence of CN and C2, species not previously reported for CO2 laser ablation. The gross dynamics of the luminous plume, which was studied by using a streak camera, compares favorably with predictions from the snowplow model, which also accurately forecasts the time history of the plume expansion for a wide range of background gas pressures and laser fluences. Framing shadowgraphy reveals the onset of laser-supported detonation waves at approximately 50 mbar Ar, thus somewhat limiting the validity of this model.

  20. Subcellular analysis by laser ablation electrospray ionization mass spectrometry

    DOEpatents

    Vertes, Akos; Stolee, Jessica A; Shrestha, Bindesh

    2014-12-02

    In various embodiments, a method of laser ablation electrospray ionization mass spectrometry (LAESI-MS) may generally comprise micro-dissecting a cell comprising at least one of a cell wall and a cell membrane to expose at least one subcellular component therein, ablating the at least one subcellular component by an infrared laser pulse to form an ablation plume, intercepting the ablation plume by an electrospray plume to form ions, and detecting the ions by mass spectrometry.

  1. Modeling CO{sub 2} Laser Ablative Impulse with Polymers

    SciTech Connect

    Sinko, John E.; Phipps, Claude R.; Sasoh, Akihiro

    2010-10-08

    Laser ablation vaporization models have usually ignored the spatial dependence of the laser beam. Here, we consider effects from modeling using a Gaussian beam for both photochemical and photothermal conditions. The modeling results are compared to experimental and literature data for CO{sub 2} laser ablation of the polymer polyoxymethylene under vacuum, and discussed in terms of the ablated mass areal density and momentum coupling coefficient. Extending the scope of discussion, laser ablative impulse generation research has lacked a cohesive strategy for linking the vaporization and plasma regimes. Existing models, mostly formulated for ultraviolet laser systems or metal targets, appear to be inappropriate or impractical for applications requiring CO{sub 2} laser ablation of polymers. A recently proposed method for linking the vaporization and plasma regimes for analytical modeling is addressed here along with the implications of its use. Key control parameters are considered, along with the major propulsion parameters needed for laser ablation propulsion modeling.

  2. Particle analysis using laser ablation mass spectroscopy

    DOEpatents

    Parker, Eric P.; Rosenthal, Stephen E.; Trahan, Michael W.; Wagner, John S.

    2003-09-09

    The present invention provides a method of quickly identifying bioaerosols by class, even if the subject bioaerosol has not been previously encountered. The method begins by collecting laser ablation mass spectra from known particles. The spectra are correlated with the known particles, including the species of particle and the classification (e.g., bacteria). The spectra can then be used to train a neural network, for example using genetic algorithm-based training, to recognize each spectra and to recognize characteristics of the classifications. The spectra can also be used in a multivariate patch algorithm. Laser ablation mass specta from unknown particles can be presented as inputs to the trained neural net for identification as to classification. The description below first describes suitable intelligent algorithms and multivariate patch algorithms, then presents an example of the present invention including results.

  3. Endovenous laser ablation with TM-fiber laser

    NASA Astrophysics Data System (ADS)

    Somunyudan, Meral Filiz; Topaloglu, Nermin; Ergenoglu, Mehmet Umit; Gulsoy, Murat

    2011-03-01

    Endovenous Laser Ablation (EVLA) has become a popular minimally invasive alternative to stripping in the treatment of saphenous vein reflux. Several wavelengths have been proposed; of which 810, 940 and 980- nm are the most commonly used. However, the most appropriate wavelength is still the subject of debate. Thermal shrinkage of collagenous tissue during EVLA plays a significant role in the early and late results of the treatment. The aim of this study is to compare the efficacy of 980 and 1940-nm laser wavelengths in the treatment of varicose veins. In this study, 980 and 1940-nm lasers at different power settings (8/10W for 980-nm, 2/3W for 1940-nm) were used to irradiate stripped human veins. The most prominent contraction and narrowing in outer and inner diameter were observed with the 1940-nm at 2W, following 980-nm at 8W, 1940-nm at 3W and finally 980-nm at 10W. The minimum carbonization was observed with the 1940-nm at 2W. As a conclusion, 1940-nm Tm-fiber laser which has a significant effect in the management of varicose veins due to more selective energy absorption in water and consequently in the vein is a promising method in the management of varicose veins.

  4. Pulsed dye laser application in ablation of vascular ectasias of the larynx: a preliminary animal study

    NASA Astrophysics Data System (ADS)

    Woo, Peak; Wang, Zhi; Perrault, Donald F., Jr.; McMillan, Kathleen; Pankratov, Michail M.

    1995-05-01

    Vascular ectasias (dilatation) and vascular lesions of the larynx are difficult to treat with exciting modalities. Varix (enlarged vessel) of the vocal folds, vocal fold hemorrhage, vascular polyp, hemangioma, intubation or contact granuloma are common problems which disturb voice. Current applications of CO2 laser and cautery often damage the delicate vocal fold cover. The 585 nm dermatologic pulsed dye laser may be an ideal substitute. Two adult canines were examined under anesthesia via microlaryngoscopy technique. Pulsed dye laser (SPTL-1a, Candela Laser Corp., Wayland, MA) energy was delivered via the micromanipulator with the 3.1-mm spot size in single pulses of 6, 8, and 10 Joules/cm2 and applied to the vessels of the vocal folds, epiglottis, and arytenoid cartilage. Endoscopic examination was carried out immediately after the treatment and at 4 weeks postoperatively. The animals were sacrificed at 3 weeks, larynges excised, and whole organ laryngeal section were prepared for histology. Pulsed dye laser thrombosed vessels of the vocal fold using 6 or 8 Joules/cm2. Vascular break and leakage occurred at 10 Joules/cm2. Follow up examination showed excellent vessel obliteration or thrombosis without scarring or injury to the overlying tissues. Histologic examination shows vascular thrombosis without inflammation and fibrosis in the vocal fold cover. Pulsed dye laser may have promise in treatment of vascular lesions of the larynx and upper airway.

  5. Comparative study of magnetite (Fe3O4) thin films grown by pulsed laser ablation and sputtering

    NASA Astrophysics Data System (ADS)

    Bohra, Murtaza; Varun Karthik Y., S.; Haveesh, G.; Tarun Y. S., N.; Prasad, D. V. B.; Chowdhury, D. Roy; Prasad, K. Eswar

    2016-05-01

    Comparative study of magnetite (Fe3O4) thin films grown by pulsed laser ablation (PLD) and radio frequency (RF)-sputtering of α-Fe2O3 target have been investigated. We have found strong correlation between RF power (P) of sputtering and substrate temperature (Ts) of PLD films on their structural and magnetic properties. Films grown at low P and Ts are dominated by antiferromagnetic α-Fe2O3 phase while ferrimagnetic Fe3O4 phase is dominant at high P and Ts Post-annealing in H2/H2O atmosphere at 450 °C, these films show single phase Fe3O4 but RF power and substrate temperature still play a significant role. With increasing P and Ts values, the orientation of Fe3O4 films change from (110) to (111) followed by complete randomizations. These (110) to (111) orientations affect magnetic properties differently above Verwey transition temperature of 120 K. The RF-power and substrate temperature have the same influence on the physical properties of Fe3O4 films, as both are related to thermal energy.

  6. Mathematical Modeling of Laser Ablation in Liquids with Applications to Laser Ultrasonics

    SciTech Connect

    Conant, R. J.; Telschow, Kenneth Louis; Walter, John Bradley

    2002-12-01

    The use of laser ablation as a means of generating ultrasonic waves in liquid metals is studied in this paper. A mathematical model for predicting the onset of ablation is developed, as is a model of the ablation process based on steady state, one-dimensional gas dynamics in which the vapor phase is treated as an ideal gas. The results of this model are then used in a quasi-two-dimensional model of laser ablation that accounts for the spatial distribution of intensity in the laser beam. Model predictions are compared with experiments conducted on liquid mercury and excellent agreement is obtained. Based on these results, a simplified model is developed that shows excellent agreement with both the theory and the experiments.

  7. Resolving Bias in Laser Ablation Geochronology

    NASA Astrophysics Data System (ADS)

    Bowring, James; Horstwood, Matthew; Gehrels, George

    2013-06-01

    Increasingly, scientific investigations requiring geochronology utilize laser ablation (LA)-inductively coupled plasma mass spectrometry (ICPMS), taking advantage of the efficiency and throughput possible for uranium-thorium-lead (U-Th-Pb) dating. A number of biases exist when comparing data among laboratories and an ongoing community-based effort is working to resolve and eliminate these biases to improve the accuracy of scientific interpretation based on these data.

  8. Size properties of colloidal nanoparticles produced by nanosecond pulsed laser ablation and studying the effects of liquid medium and laser fluence

    NASA Astrophysics Data System (ADS)

    Mahdieh, Mohammad Hossein; Fattahi, Behzad

    2015-02-01

    In this paper, pulsed laser ablation method was used for synthesis of colloidal nanoparticles of aluminum and titanium targets in distilled water, ethanol, and acetone as liquid environments. Ultraviolet-visible (UV-vis) absorption spectrophotometer and scanning electron microscope (SEM) were used for characterization of produced nanoparticles. Using image processing technique and analyzing the SEM images, nanoparticles' mean size and size distribution were achieved. The results show that liquid medium has strong effect on size properties of produced nanoparticles. From the results, it was found that ablation of both metal targets in ethanol medium leads to formation of smaller size nanoparticles with narrower size distributions. The influence of laser fluence was also investigated. According to the results, higher laser fluence produces larger mean size nanoparticles with broader size distribution.

  9. KTP-532 laser ablation of urethral strictures

    NASA Astrophysics Data System (ADS)

    Malloy, Terrence R.

    1991-07-01

    In 1988, the KTP-532 laser was used to ablate a series of benign urethral strictures. Rather than using a single incision, as in urethrotomy, strictures were treated with a 360$DEG contact photoradiation. Thirty-one males, average age 53.2 years, received 37 treatments. Six patients underwent a second laser treatment. Stricture etiology was commonly iatrogenic (32%), traumatic (16%), and post-gonococcal (10%). Stricture location included mainly bulbar (49%), membranous (20%), and penile (12%) areas. The surgical technique consisted of a circumferential ablation followed by foley catheter placement (mean 10 days). Follow-up on 29 of 31 patients ranged from 1 to 16 months (mean 9.7) Complete success occurred in 17 patients (59%) who had no further symptoms or instrumentation. Partial success was seen in 6 patients (20.5%) with symptoms but no stricture recurrence. Six patients (20.5%) failed therapy requiring additional surgery or regular dilatations. No complications were encountered. Although longer assessment is required, KTP-532 laser ablation of urethral strictures appears efficacious.

  10. Investigating Age Resolution in Laser Ablation Geochronology

    NASA Astrophysics Data System (ADS)

    Horstwood, Matt; Kosler, Jan; Jackson, Simon; Pearson, Norman; Sylvester, Paul

    2009-02-01

    Workshop on Data Handling in LA-ICP-MS U-Th-Pb Geochronology; Vancouver, British Columbia, Canada, 12-13 July 2008; Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) uranium-thorium-lead (U-Th-Pb) dating is an increasingly popular approach for determining the age of mineral grains and the timing of geological events. The spatial resolution offered by this technique allows detailed investigations of complex igneous and metamorphic processes, and the speed of data capture allows vast amounts of information to be gathered rapidly. Laser ablation U-Th-Pb dating is therefore becoming an increasingly influential technique to the geochronology community, providing cost-effective and ready access to age data for laboratories and end users worldwide. However, complications in acquiring, processing, and interpreting data can lead to inaccurate age information entering the literature. With the numbers of practitioners expanding rapidly, the need to standardize approaches and resolve difficulties (particularly involving the subjectivity in processing laser ablation U-Th-Pb data) is becoming important.

  11. KTP-532 laser ablation of urethral strictures.

    PubMed

    Turek, P J; Malloy, T R; Cendron, M; Carpiniello, V L; Wein, A J

    1992-10-01

    In 1988 the KTP-532 laser was used to ablate a series of benign urethral strictures. Rather than using a single incision as in urethrotomy, strictures were treated with 360-degree contact photoradiation. Thirty-one male patients, average age 53.2 years, received thirty-seven treatments; 6 patients underwent a second laser treatment. Stricture etiology was commonly iatrogenic (32%), traumatic (16%), and postgonococcal (10%). Stricture location included mainly bulbar (49%), membranous (20%), and penile (12%) areas. The surgical technique consisted of circumferential ablation, followed by Foley catheter placement (mean, 10 days). Follow-up on 29 of 31 patients ranged from one to sixteen months (mean 9.7). Complete success occurred in 17 patients (59%) who had no further symptoms or instrumentation. Partial success was seen in 6 patients (20.5%) with symptom, but not stricture, recurrence. Six patients (20.5%) failed therapy, requiring additional surgery or regular dilations. No complications were seen. Although longer assessment is required, KTP-532 laser ablation of urethral strictures appears efficacious. PMID:1413350

  12. FINAL REPORT. WASTE VOLUME REDUCTION USING SURFACE CHARACTERIZATION AND DECONTAMINATION BY LASER ABLATION

    EPA Science Inventory

    Laser ablation was studied as a method for removing contaminated surface layers from concrete. The objectives of this research were to determine the mechanism and efficacy of laser ablation, to understand the chemistry of contaminated concrete surfaces, and to chemically and phys...

  13. Endovenous Laser Ablation of Incompetent Perforator Veins: A New Technique in Treatment of Chronic Venous Disease

    SciTech Connect

    Ozkan, Ugur

    2009-09-15

    The aim of this study was to assess the feasibility of endovenous laser ablation of incompetent perforator veins in a patient with incompetency of the small saphenous vein and multiple perforator veins. Two different methods were used to ablate seven perforator veins with a laser giving 50-60 J/cm energy. Total occlusion was observed in six perforators, and partial ablation in one perforator, at 1-month follow-up. To our knowledge, endovenous laser ablation of incompetent perforator veins is easy and a good therapeutic method.

  14. Solar cell contact formation using laser ablation

    DOEpatents

    Harley, Gabriel; Smith, David D.; Cousins, Peter John

    2014-07-22

    The formation of solar cell contacts using a laser is described. A method of fabricating a back-contact solar cell includes forming a poly-crystalline material layer above a single-crystalline substrate. The method also includes forming a dielectric material stack above the poly-crystalline material layer. The method also includes forming, by laser ablation, a plurality of contacts holes in the dielectric material stack, each of the contact holes exposing a portion of the poly-crystalline materiat layer; and forming conductive contacts in the plurality of contact holes.

  15. Solar cell contact formation using laser ablation

    DOEpatents

    Harley, Gabriel; Smith, David D.; Cousins, Peter John

    2015-07-21

    The formation of solar cell contacts using a laser is described. A method of fabricating a back-contact solar cell includes forming a poly-crystalline material layer above a single-crystalline substrate. The method also includes forming a dielectric material stack above the poly-crystalline material layer. The method also includes forming, by laser ablation, a plurality of contacts holes in the dielectric material stack, each of the contact holes exposing a portion of the poly-crystalline material layer; and forming conductive contacts in the plurality of contact holes.

  16. Solar cell contact formation using laser ablation

    DOEpatents

    Harley, Gabriel; Smith, David; Cousins, Peter

    2012-12-04

    The formation of solar cell contacts using a laser is described. A method of fabricating a back-contact solar cell includes forming a poly-crystalline material layer above a single-crystalline substrate. The method also includes forming a dielectric material stack above the poly-crystalline material layer. The method also includes forming, by laser ablation, a plurality of contacts holes in the dielectric material stack, each of the contact holes exposing a portion of the poly-crystalline material layer; and forming conductive contacts in the plurality of contact holes.

  17. Effect of Laser Wavelength and Ablation Time on Pulsed Laser Ablation Synthesis of AL Nanoparticles in Ethanol

    NASA Astrophysics Data System (ADS)

    Baladi, A.; Mamoory, R. Sarraf

    Aluminum nanoparticles were synthesized by pulsed laser ablation of Al targets in ethanol for 5-15 minutes using the 1064 and 533 nm wavelengths of a Nd:YAG laser with energies of 280-320 mJ per pulse. It has been found that higher wavelength leads to significantly higher ablation efficiency, and finer spherical nanoparticles are also synthesized. Besides, it was obvious that higher ablation time resulted in higher ablated mass, while lower ablation rate was observed. Finer nanoparticles, moreover, are synthesized in higher ablation times.

  18. Picosecond and femtosecond laser ablation of hard tissues

    NASA Astrophysics Data System (ADS)

    Serafetinides, Alexander A.; Makropoulou, Mersini I.; Kar, Ajoy K.; Khabbaz, Marouan

    1996-12-01

    In this study, the interaction of picosecond and femtosecond pulsed laser radiation with human dental tissue was investigated experimentally, as this unexplored field is expected to be a potential alternative in powerful laser processing of biomedical structures. Dentin ablation rate experiments were performed by using teeth sections of different thickness. Dental tissue samples were irradiated in air with i) a regenerative amplifier laser at 1064 nm, pulse duration 110 ps, ii) the second harmonic laser at 532 nm, pulse duration 100 ps, and iii) a picosecond tunable dye amplifier at 595 nm, pulse width 800 fs. In all the experiments the pulse repetition rate was 10 Hz. The ablation rate per pulse at different energy fluence settings was calculated by measuring the time needed for the perforation of the whole dental sample thickness. Short laser pulses can confine thermal energy within the optical zone, which maximizes photothermal and photomechanical mechanisms of interaction. Tissue ablation rates were found to be comparable to or better than other nanosecond lasers, and left smooth surfaces, free of thermal damage.

  19. CO2 Laser Absorption in Ablation Plasmas

    SciTech Connect

    Eckel, Hans-Albert; Tegel, Jochen; Schall, Wolfgang O.

    2006-05-02

    The impulse formation by laser ablation is limited by the premature absorption of the incident laser radiation in the initially produced cloud of ablation products. The power fraction of a CO2 laser pulse transmitted through a small hole in a POM sample for pulse energies of 35 to 150 J focused on a spot of 2 cm2 has been compared with the incident power. The plasma formation in vacuum and in air of 3500 Pa and the spread of the shock wave with velocities of 1.6 to 2.4 km/s in the low pressure air was observed by Schlieren photography. A sharp edged dark zone with a maximum extension of 10 to 12 mm away from the target surface develops within 5 {mu}s independently of the pressure and is assumed to be a plasma. In order to find out, if this is also the zone where the majority of the incident laser radiation is absorbed, a CO2 probe laser beam was directed through the expansion cloud parallel to and at various distances from the sample surface. The time behavior of the absorption signal of the probe beam has been measured and an absorption wave could be observed.

  20. Recent advances in laser ablation modelling for asteroid deflection methods

    NASA Astrophysics Data System (ADS)

    Thiry, Nicolas; Vasile, Massimiliano

    2014-09-01

    Over the past few years, a series of studies have demonstrated the theoretical benefits of using laser ablation in order to mitigate the threat of a potential asteroid on a collision course with earth. Compared to other slow-push mitigation strategies, laser ablation allows for a significant reduction in fuel consumption since the ablated material is used as propellant. A precise modelling of the ablation process is however difficult due to the high variability in the physical parameters encountered among the different asteroids as well as the scarcity of experimental studies available in the literature. In this paper, we derive a new thermal model to simulate the efficiency of a laser-based detector. The useful material properties are first derived from thermochemical tables and equilibrium thermodynamic considerations. These properties are then injected in a 3D axisymetrical thermal model developed in Matlab. A temperature-dependent conduction flux is imposed on the exterior boundary condition that takes into account the balance between the incident power and the power losses due to the vaporization process across the Knudsen layer and the radiations respectively. A non-linear solver is finally used and the solution integrated over the ablation front to reconstruct the net thrust and the global mass flow. Compared to an initial 1D model, this new approach shows the importance of the parietal radiation losses in the case of a CW laser. Despite the low energy conversion efficiency, this new model still demonstrates the theoretical benefit of using lasers over more conventional low-thrust strategies.

  1. Ablation processing of biomedical materials by ultrashort laser pulse ranging from 50 fs through 2 ps

    NASA Astrophysics Data System (ADS)

    Ozono, Kazue; Obara, Minoru; Sakuma, Jun

    2003-06-01

    In recent years, femtosecond laser processing of human hard/soft tissues has been studied. Here, we have demonstrated ablation etching of hydroxyapatite. Hydroxyapatite (Ca10(PO4)6(OH)2) is a key component of human tooth and human bone. The human bone is mainly made of hydroxyapatite oriented along the collagen. The micromachining of hydroxyapatite is highly required for orthopedics and dentistry. The important issue is to preserve the chemical property of the ablated surface. If chemical properties of hydroxyapatite change once, the human bone or tooth cannot grow again after laser processing. As for nanosecond laser ablation (for example excimer laser ablation), the relative content of calcium and phosphorus in (Ca10(PO4)6(OH)2) is found to change after laser ablation. We used here pulsewidth tunable output from 50 fs through 2 ps at 820 nm and 1 kpps. We measured calcium spectrum and phosphorus spectrum of the ablated surface of hydroxyapatite by XPS. As a result, the chemical content of calcium and phosphorus is kept unchanged before and after 50-fs - 2-ps laser ablation. We also demonstrated ablation processing of human tooth with Ti:sapphire laser, and precise ablation processing and microstructure fabrication are realized.

  2. A review of Thulium fiber laser ablation of kidney stones

    NASA Astrophysics Data System (ADS)

    Fried, Nathaniel M.; Blackmon, Richard L.; Irby, Pierce B.

    2011-02-01

    The clinical solid-state Holmium:YAG laser lithotripter (λ=2120 nm) is capable of operating at high pulse energies, but its efficient operation is limited to low pulse rates during lithotripsy. The diode-pumped experimental Thulium Fiber Laser (λ=1908 nm) is limited to low pulse energies, but can operate at high pulse rates. This review compares stone ablation threshold, ablation rate, and retropulsion effects for Ho:YAG and TFL. Laser lithotripsy complications also include optical fiber bending failure resulting in endoscope damage and low irrigation rates leading to poor visibility. Both problems are related to fiber diameter and limited by Ho:YAG laser multimode spatial beam profile. This study exploits TFL spatial beam profile for higher power transmission through smaller fibers. A short taper is also studied for expanding TFL beam at the distal tip of a small-core fiber. Stone mass loss, stone crater depths, fiber transmission losses, fiber burn-back, irrigation rates, and deflection through a flexible ureteroscope were measured for tapered fiber and compared with conventional fibers. The stone ablation threshold for TFL was four times lower than for Ho:YAG. Stone retropulsion with Ho:YAG increased linearly with pulse energy. Retropulsion with TFL was minimal at pulse rates < 150 Hz, then rapidly increased at higher pulse rates. TFL beam profile provides higher laser power through smaller fibers than Ho:YAG laser, potentially reducing fiber failure and endoscope damage and allowing greater irrigation rates for improved visibility and safety. Use of a short tapered distal fiber tip also allows expansion of the laser beam, resulting in decreased fiber tip damage compared to conventional fibers, without compromising fiber bending, stone ablation efficiency, or irrigation rates.

  3. Laser ablation of Al-Ni alloys and multilayers

    NASA Astrophysics Data System (ADS)

    Roth, Johannes; Trebin, Hans-Rainer; Kiselev, Alexander; Rapp, Dennis-Michael

    2016-05-01

    Laser ablation of Al-Ni alloys and multilayers has been studied by molecular dynamics simulations. The method was combined with a two-temperature model to describe the interaction between the laser beam, the electrons, and the atoms. As a first step, electronic parameters for the alloys had to be found and the model developed originally for pure metals had to be generalized to multilayers. The modifications were verified by computing melting depths and ablation thresholds for pure Al and Ni. Here known data could be reproduced. The improved model was applied to the alloys Al_3Ni, AlNi and AlNi_3. While melting depths and ablation thresholds for AlNi behave unspectacular, sharp drops at high fluences are observed for Al_3Ni and AlNi_3. In both cases, the reason is a change in ablation mechanism from phase explosion to vaporization. Furthermore, a phase transition occurs in Al_3Ni. Finally, Al layers of various thicknesses on a Ni substrate have been simulated. Above threshold, 8 nm Al films are ablated as a whole while 24 nm Al films are only partially removed. Below threshold, alloying with a mixture gradient has been observed in the thin layer system.

  4. Ablation dynamics in laser sclerotomy ab externo

    NASA Astrophysics Data System (ADS)

    Brinkmann, Ralf; Droege, Gerit; Mohrenstecher, Dirk; Scheu, M.; Birngruber, Reginald

    1996-01-01

    Laser sclerostomy ab externo with flashlamp excited mid-IR laser systems emitting in the 2-3 micrometer spectral range is in phase II clinical trials. Although acutely high success rates were achieved, the restenosis rate after several months is about 40%. Laser pulses of several hundreds of microseconds, known to induce thermo-mechanical explosive evaporation were used for this procedure. We investigated the ablation dynamics in tissue and the cavitation bubble dynamics in water by means of an Er:YAG laser system to estimate the extent of mechanical damage zones in the sclera and in the anterior chamber, which may contribute to the clinical failure. We found substantial mechanical tissue deformation during the ablation process caused by the cavitation effects. Stress waves up to several bar generated by explosive evaporization were measured. The fast mechanical stretching and collapsing of the scleral tissue induced by cavitation resulted in tissue dissection as could be proved by flash photography and histology. The observed high restenosis might be a result of a subsequent enhanced wound healing process. Early fistula occlusions due to iris adherences, observed in about 20% of the clinical cases may be attributed to intraocular trauma induced by vapor bubble expansion through the anterior chamber after scleral perforation. An automatic feedback system minimizing adverse effects by steering and terminating the laser process during scleral fistulization is demonstrated. Moreover, a new approach in laser sclerostomy ab externo is presented using a cw-IR laser diode system emitting at the 1.94 micrometer mid-IR water absorption peak. This system was used in vitro and showed smaller damage zones compared to the pulsed laser radiation.

  5. Nanosecond laser ablation for pulsed laser deposition of yttria

    NASA Astrophysics Data System (ADS)

    Sinha, Sucharita

    2013-09-01

    A thermal model to describe high-power nanosecond pulsed laser ablation of yttria (Y2O3) has been developed. This model simulates ablation of material occurring primarily through vaporization and also accounts for attenuation of the incident laser beam in the evolving vapor plume. Theoretical estimates of process features such as time evolution of target temperature distribution, melt depth and ablation rate and their dependence on laser parameters particularly for laser fluences in the range of 6 to 30 J/cm2 are investigated. Calculated maximum surface temperatures when compared with the estimated critical temperature for yttria indicate absence of explosive boiling at typical laser fluxes of 10 to 30 J/cm2. Material ejection in large fragments associated with explosive boiling of the target needs to be avoided when depositing thin films via the pulsed laser deposition (PLD) technique as it leads to coatings with high residual porosity and poor compaction restricting the protective quality of such corrosion-resistant yttria coatings. Our model calculations facilitate proper selection of laser parameters to be employed for deposition of PLD yttria corrosion-resistive coatings. Such coatings have been found to be highly effective in handling and containment of liquid uranium.

  6. Laser ablation of copper and aluminium in air

    NASA Astrophysics Data System (ADS)

    Xia, Yueyuan; Mei, Liangmo; Tan, Chunyu; Liu, Xiangdong; Wang, Qingpu; Yue, Shubin

    1991-06-01

    The ablation behavior of copper alloy and aluminium irradiated in air by 1.06 μm, 10 ns pulsed laser with power density of 6.4×109W/cm2 was studied using scanning electron microscopy (SEM), MCS-RBS and X-ray microanalysis. Evidence of bulk vaporization via bubble formation was observed for the copper alloy under the laser irradiation. Silver-enrichment microregions were found in the ablation crater created by the laser shots on the copper alloy sample. Material removal rates of these materials were determined by crater shape-profile measurement. Using self-similar solutions of the gas-dynamic equations, gas-dynamic parameters of the vaporization waves are obtained. These parameters are used to calculate material removal rates and impulse coupling coefficients of these materials under the pulsed laser irradiation. The calculated mass removal rates and the coupling coefficients are compared with the corresponding experimentally determined values. The surface kinetic energy of the irradiated area on the Al sample is estimated. Possible mechanisms for laser ablation of the materials under study are discussed.

  7. Ablation by ultrashort laser pulses: Atomistic and thermodynamic analysis of the processes at the ablation threshold

    SciTech Connect

    Upadhyay, Arun K.; Inogamov, Nail A.; Rethfeld, Baerbel; Urbassek, Herbert M.

    2008-07-15

    Ultrafast laser irradiation of solids may ablate material off the surface. We study this process for thin films using molecular-dynamics simulation and thermodynamic analysis. Both metals and Lennard-Jones (LJ) materials are studied. We find that despite the large difference in thermodynamical properties between these two classes of materials--e.g., for aluminum versus LJ the ratio T{sub c}/T{sub tr} of critical to triple-point temperature differs by more than a factor of 4--the values of the ablation threshold energy E{sub abl} normalized to the cohesion energy, {epsilon}{sub abl}=E{sub abl}/E{sub coh}, are surprisingly universal: all are near 0.3 with {+-}30% scattering. The difference in the ratio T{sub c}/T{sub tr} means that for metals the melting threshold {epsilon}{sub m} is low, {epsilon}{sub m}<{epsilon}{sub abl}, while for LJ it is high, {epsilon}{sub m}>{epsilon}{sub abl}. This thermodynamical consideration gives a simple explanation for the difference between metals and LJ. It explains why despite the universality in {epsilon}{sub abl}, metals thermomechanically ablate always from the liquid state. This is opposite to LJ materials, which (near threshold) ablate from the solid state. Furthermore, we find that immediately below the ablation threshold, the formation of large voids (cavitation) in the irradiated material leads to a strong temporary expansion on a very slow time scale. This feature is easily distinguished from the acoustic oscillations governing the material response at smaller intensities, on the one hand, and the ablation occurring at larger intensities, on the other hand. This finding allows us to explain the puzzle of huge surface excursions found in experiments at near-threshold laser irradiation.

  8. Calcified lesion modeling for excimer laser ablation

    NASA Astrophysics Data System (ADS)

    Scott, Holly A.; Archuleta, Andrew; Splinter, Robert

    2009-06-01

    Objective: Develop a representative calcium target model to evaluate penetration of calcified plaque lesions during atherectomy procedures using 308 nm Excimer laser ablation. Materials and Methods: An in-vitro model representing human calcified plaque was analyzed using Plaster-of-Paris and cement based composite materials as well as a fibrinogen model. The materials were tested for mechanical consistency. The most likely candidate(s) resulting from initial mechanical and chemical screening was submitted for ablation testing. The penetration rate of specific multi-fiber catheter designs and a single fiber probe was obtained and compared to that in human cadaver calcified plaque. The effects of lasing parameters and catheter tip design on penetration speed in a representative calcified model were verified against the results in human cadaver specimens. Results: In Plaster of Paris, the best penetration was obtained using the single fiber tip configuration operating at 100 Fluence, 120 Hz. Calcified human lesions are twice as hard, twice as elastic as and much more complex than Plaster of Paris. Penetration of human calcified specimens was highly inconsistent and varied significantly from specimen to specimen and within individual specimens. Conclusions: Although Plaster of Paris demonstrated predictable increases in penetration with higher energy density and repetition rate, it can not be considered a totally representative laser ablation model for calcified lesions. This is in part due to the more heterogeneous nature and higher density composition of cadaver intravascular human calcified occlusions. Further testing will require a more representative model of human calcified lesions.

  9. Excimer laser photorefractive keratectomy with different ablation zones.

    PubMed

    Hassan, Z; Lampé, Z; Békési, L; Berta, A

    1997-01-01

    In this study we would like to introduce the excimer laser, and to demonstrate our results and complications by using different ablation zones during photorefractive keratectomy (PRK) in the correction of myopia and astigmatismus. In 1996 we performed photorefractive keratectomy on 100 myopic eyes of 52 patients (28 females, 24 males). Mean age was 26.21 years (ranged from 19 to 54 years). The preoperative refraction ranged from -1.0 D to -18.0 Diopters. The diameter of the ablation zones were between 5 and 6.5 mm. We evaluated the results and the complications of the surgeries of 100 eyes which were performed with Schwind keratom F excimer laser. After 2 days, 1 week, 1 month, 3 months, and 6 months postoperatively we tested the best uncorrected and corrected visual acuities, and performed intraocular pressure measurement, slit lamp examination as well as corneal topography. The postoperative refractions were between +/- 0.5 to +/- 1.0 Diopters. After six months postoperatively the slit lamp examination showed that 80% of the patients had no corneal haze while 20% had stage I (Hanna) corneal haze. The smaller the diameter of the ablation zone was, the more pronounced the corneal haze and the night-glare were. The photorefractive excimer laser keratectomy is judged to be a safe method, although it might have some side-effects. The different ablation zones of this treatment means an important modification, that not only allows the method to meet the individual requirements, but reduces the chance of the complications as well. Based on the authors' experiences PRK for moderate myopia with large diameter ablation zones appears more predictable than than with smaller ablation zone diameters. PMID:9408312

  10. Effect of nanosecond pulse laser ablation on the surface morphology of Zr-based metallic glass

    NASA Astrophysics Data System (ADS)

    Zhu, Yunhu; Fu, Jie; Zheng, Chao; Ji, Zhong

    2016-09-01

    In this study, we investigated the ripple patterns formation on the surface of Zr41.2Ti13.8Cu12.5Ni10Be22.5 (vit1) bulk metallic glass using a nanosecond pulse laser ablation in air with a wavelength of 1064 nm. The strong thermal ablation phenomenon could be observed on vit1 BMG surface at laser energy of 200 mJ as a result of the adhibition of confining overlay. Many periodic ripples had formed on the edge of the ablated area at laser energy of 400 mJ because of the high intensity pulsed laser beam. The underlying mechanism of the periodic ripples formation could be explained by the K-H hydrodynamic instability theory. It had been shown that laser ablation with 600 mJ and 200 pulses results in the formation of many micro-cracks on the ablated area. Further analysis showed that the spatial occupation of the laser ablated area and the spacing between two adjacent ripples increased as the laser energy and the number of incident laser pulses increasing. The surface ripples feature on the edge of ablated area became more obvious with increasing laser pulses, but it was not correlated closely with the laser energies variation.

  11. Infrared laser ablation atmospheric pressure photoionization mass spectrometry.

    PubMed

    Vaikkinen, Anu; Shrestha, Bindesh; Kauppila, Tiina J; Vertes, Akos; Kostiainen, Risto

    2012-02-01

    In this paper we introduce laser ablation atmospheric pressure photoionization (LAAPPI), a novel atmospheric pressure ion source for mass spectrometry. In LAAPPI the analytes are ablated from water-rich solid samples or from aqueous solutions with an infrared (IR) laser running at 2.94 μm wavelength. Approximately 12 mm above the sample surface, the ablation plume is intercepted with an orthogonal hot solvent (e.g., toluene or anisole) jet, which is generated by a heated nebulizer microchip and directed toward the mass spectrometer inlet. The ablated analytes are desolvated and ionized in the gas-phase by atmospheric pressure photoionization using a 10 eV vacuum ultraviolet krypton discharge lamp. The effect of operational parameters and spray solvent on the performance of LAAPPI is studied. LAAPPI offers ~300 μm lateral resolution comparable to, e.g., matrix-assisted laser desorption ionization. In addition to polar compounds, LAAPPI efficiently ionizes neutral and nonpolar compounds. The bioanalytical application of the method is demonstrated by the direct LAAPPI analysis of rat brain tissue sections and sour orange (Citrus aurantium) leaves. PMID:22242626

  12. Deposition, characterization, and laser ablation patterning of YBCO thin films

    NASA Astrophysics Data System (ADS)

    Vase, Per; Yueqiang, Shen; Freltoft, Torsten

    1990-12-01

    High quality epitaxial thin films of YBa 2Cu 3O 7 have been deposited on single-crystal MgO(001) substrates by 355 nm Nd:YAG laser ablation. Through a systematic optimization of the deposition parameters, it was found that for a target-substrate distance of 30 mm, the optimal laser intensity, substrate temperature, and deposition oxygen pressure were 300 MW/cm 2, 750 ° C, and 0.5-1.0 mbar, respectively. Microstrips with dimensions down to 10 μm across were fabricated using both a photoresist technique and laser ablation through a metal mask. The superconducting transition takes place over 1 K, and the critical temperature is reproducible within ±1.5 K, the best result being Tc,0 = 90 K. The highest critical current density measured on a 10 X 0.15 μm 2 strips was 4 X 10 6 A/cm 2 at 77 K . Film patterning using laser ablation through a metal mask was studied in detail to investigate the applicability of this method. Etch rates as a function of laser intensity were measured, and the process was followed in situ by on-line monitoring of the film resistivity.

  13. Laser ablation and high precision patterning of biomaterials and intraocular lenses

    NASA Astrophysics Data System (ADS)

    Serafetinides, A. A.; Spyratou, E.; Makropoulou, M.

    2010-10-01

    The use of intraocular lenses (IOL) is the most promising method for restoring excellent vision in cataract surgery. In addition, multifocal intraocular lenses for good distant and near vision are investigated. Several new materials, techniques and patterns are studied for the formation and etching of intraocular lenses in order to improve their optical properties and reduce the diffractive aberrations. As pulsed laser ablation is well established as a universal tool for surface processing of organic polymer materials, this study was focused in using laser ablation with short and ultra short laser pulses for surface modification of PMMA and intraocular lenses, instead of using other conventional techniques. The main advantage of using very short laser pulses, e.g. of ns, ps or fs duration, is that heat diffusion into the polymer material is negligible. As a result high precision patterning of the sample, without thermal damage of the surroundings, becomes possible. In this study, laser ablation was performed using commercially available hydrophobic acrylic IOLs, hydrophilic acrylic IOLs, and PMMA IOLs, with various diopters. We investigated the ablation efficiency and the phenomenology of the etched patterns by testing the ablation rate, versus laser energy fluence, at several wavelengths and the surface modification with atomic force microscopy (AFM), or scanning electron microscopy (SEM). The irradiated polymers have different optical properties, at the applied wavelengths, and therefore, present different ablation behaviour and morphology of the laser ablated crater walls and surrounding surfaces. The experimental results, some theoretical assumptions for mathematical modeling of the relevant ablation mechanisms are discussed.

  14. Ablation algorithms and corneal asphericity in myopic correction with excimer lasers

    NASA Astrophysics Data System (ADS)

    Iroshnikov, Nikita G.; Larichev, Andrey V.; Yablokov, Michail G.

    2007-06-01

    The purpose of this work is studying a corneal asphericity change after a myopic refractive correction by mean of excimer lasers. As the ablation profile shape plays a key role in the post-op corneal asphericity, ablation profiles of recent lasers should be studied. The other task of this research was to analyze operation (LASIK) outcomes of one of the lasers with generic spherical ablation profile and to compare an asphericity change with theoretical predictions. The several correction methods, like custom generated aspherical profiles, may be utilized for mitigation of unwanted effects of asphericity change. Here we also present preliminary results of such correction for one of the excimer lasers.

  15. 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.

  16. Spectroscopic characterization approach to study surfactants effect on ZnO 2 nanoparticles synthesis by laser ablation process

    NASA Astrophysics Data System (ADS)

    Drmosh, Q. A.; Gondal, M. A.; Yamani, Z. H.; Saleh, T. A.

    2010-05-01

    Zinc peroxide nanoparticles having grain size less than 5 nm were synthesized using pulsed laser ablation in aqueous solution in the presence of different surfactants and solid zinc target in 3% H 2O 2. The effect of surfactants on the optical and structure of ZnO 2 was studied by applying different spectroscopic techniques. Structural properties and grain size of the synthesized nanoparticles were studied using XRD method. The presence of the cubic phase of zinc peroxide in all samples was confirmed with XRD, and the grain sizes were 4.7, 3.7, 3.3 and 2.8 nm in pure H 2O 2, and H 2O 2 mixed with SDS, CTAB and OGM respectively. For optical characterization, FTIR transmittance spectra of ZnO 2 nanoparticles prepared with and without surfactants show a characteristic ZnO 2 absorption at 435-445 cm -1. FTIR spectrum revealed that the adsorbed surfactants on zinc peroxide disappeared in case of CTAB and OGM while it appears in case of SDS. This could be due to high critical micelles SDS concentration comparing with others which is attributed to the adsorption anionic nature of this surfactant. Both FTIR and UV-vis spectra show a red shift in the presence of SDS and blue shift in the presence of CTAB and OGM. The blue shift in the absorption edge indicates the quantum confinement property of nanoparticles. The zinc peroxide nanoparticles prepared in additives-free media was also characterized by Raman spectra which show the characteristic peaks at 830-840 and 420-440 cm -1.

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

    SciTech Connect

    Zheng, Buxiang; Jiang, Gedong; Wang, Wenjun Wang, Kedian; Mei, Xuesong

    2014-03-15

    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 alloy 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}.

  18. Surface-enhanced Raman scattering study of organic pigments using silver and gold nanoparticles prepared by pulsed laser ablation

    NASA Astrophysics Data System (ADS)

    Fazio, E.; Trusso, S.; Ponterio, R. C.

    2013-05-01

    The identification of pigments used in ancient times represents an interesting task in order to discriminate a production of a precise geographic area or to trace out the ancient commercial networks. Conventional micro-Raman spectroscopy (MRS), being a non-destructiveness technique, has been largely used for the analysis of dyes. Nevertheless several pigments, especially of organic origin, show weak Raman activity beside a strong a fluorescence that prevents their identification. Surface enhanced Raman scattering (SERS) can address such difficulties. The presence of noble metal nanoparticles induces a giant amplification of the Raman signal beside the fluorescence quenching. In this work we present the use of gold and silver nanoparticles to enhance the Raman signal of some commercial red organic dyes: bazilwood, dragon's blood, carmine and madder lake. The nanoparticles were prepared adopting two approaches: (1) ablating metallic targets in water using a pulsed Nd:YAG laser at 532 nm and (2) depositing the nanoparticles on glass substrates by means of a KrF excimer laser ablation process, performed in a controlled argon atmosphere.

  19. Polarization of plastic targets by laser ablation

    NASA Astrophysics Data System (ADS)

    Giuffreda, E.; Delle Side, D.; Krasa, J.; Nassisi, V.

    2016-05-01

    Charge separation in plasmas produced on plastic targets by low laser irradiance, structure of the ion front, and the current of fast electrons expanding into the vacuum chamber ahead of ions are characterized. Of particular interest is the negative current flowing through the plastic targets to the grounded vacuum chamber during the period of laser-target interaction. The subsequent multi - peaked structure of positive target current is correlated with occurrence of double sheet layers. The late-time negative charging of targets provides evidence for production of very slow ions by ionization of neutrals ablated at the target crater by radiation from plasma produced by 23 ns excimer KrF laser. The experimental setting allowing the target current observation is discussed.

  20. Subsurface ablation of atherosclerotic plaque using ultrafast laser pulses

    PubMed Central

    Lanvin, Thomas; Conkey, Donald B.; Frobert, Aurelien; Valentin, Jeremy; Goy, Jean-Jacques; Cook, Stéphane; Giraud, Marie-Noelle; Psaltis, Demetri

    2015-01-01

    We perform subsurface ablation of atherosclerotic plaque using ultrafast pulses. Excised mouse aortas containing atherosclerotic plaque were ablated with ultrafast near-infrared (NIR) laser pulses. Optical coherence tomography (OCT) was used to observe the ablation result, while the physical damage was inspected in histological sections. We characterize the effects of incident pulse energy on surface damage, ablation hole size, and filament propagation. We find that it is possible to ablate plaque just below the surface without causing surface damage, which motivates further investigation of ultrafast ablation for subsurface atherosclerotic plaque removal. PMID:26203381

  1. Molecular dynamics study of nanoparticle evolution in a background gas under laser ablation conditions

    NASA Astrophysics Data System (ADS)

    Gouriet, K.; Zhigilei, L. V.; Itina, T. E.

    2009-03-01

    Long-time evolution of nanoparticles produced by short laser interactions is investigated for different materials. To better understand the mechanisms of the nanoparticle formation at a microscopic level, we use molecular dynamics (MD) simulations to analyse the evolution of a cluster in the presence of a background gas with different parameters (density and temperature). In particular, we compare the simulation results obtained for materials with different interaction potentials (Morse, Lennard-Jones, and Embedded Atom Model). Attention is focused on the evaporation and condensation processes of a cluster with different size and initial temperature. As a result of the MD calculations, we determinate the influence of both cluster properties and background gas parameters on the nanoparticle evolution. The role of the interaction potential is discussed based on the results of the simulations.

  2. Laser ablation of a platinum target in water. III. Laser-induced reactions

    SciTech Connect

    Nichols, William T.; Sasaki, Takeshi; Koshizaki, Naoto

    2006-12-01

    This is the third paper in our series studying the laser-target-liquid interactions occurring in laser ablation in liquids (LAL). Here, laser ablation of a platinum target in pure water at 355 nm wavelength is studied as a function of laser energy. We describe three distinct reaction regimes between the ablated target species and water at different laser focusing conditions. At low laser fluence (<10 J/cm{sup 2}), material removal is caused by laser heating of the platinum surface and the primary products are small clusters with a large percentage of platinum atoms in a nonzero oxidation state. At intermediate fluences (10-70 J/cm{sup 2}), platinum nanoparticles are the primary products. Our previous studies demonstrated that in this fluence regime ablation occurs through both thermal vaporization and explosive ejection of molten droplets. In both cases reactivity is small due to the low reactivity of platinum with water. At high fluences (>70 J/cm{sup 2}), we find large, faceted particles that are attributed to the drying of PtO{sub x} gels formed by reactive plasma etching of the target. Taken together these results demonstrate that significant tunability in the target-liquid interaction is possible during nanomaterial synthesis by LAL.

  3. Deflection of uncooperative targets using laser ablation

    NASA Astrophysics Data System (ADS)

    Thiry, Nicolas; Vasile, Massimiliano

    2015-09-01

    Owing to their ability to move a target in space without requiring propellant, laser-based deflection methods have gained attention among the research community in the recent years. With laser ablation, the vaporized material is used to push the target itself allowing for a significant reduction in the mass requirement for a space mission. Specifically, this paper addresses two important issues which are thought to limit seriously the potential efficiency of a laser-deflection method: the impact of the tumbling motion of the target as well as the impact of the finite thickness of the material ablated in the case of a space debris. In this paper, we developed a steady-state analytical model based on energetic considerations in order to predict the efficiency range theoretically allowed by a laser deflection system in absence of the two aforementioned issues. A numerical model was then implemented to solve the transient heat equation in presence of vaporization and melting and account for the tumbling rate of the target. This model was also translated to the case where the target is a space debris by considering material properties of an aluminium 6061-T6 alloy and adapting at every time-step the size of the computational domain along with the recession speed of the interface in order to account for the finite thickness of the debris component. The comparison between the numerical results and the analytical predictions allow us to draw interesting conclusions regarding the momentum coupling achievable by a given laser deflection system both for asteroids and space debris in function of the flux, the rotation rate of the target and its material properties. In the last section of this paper, we show how a reasonably small spacecraft could deflect a 56m asteroid with a laser system requiring less than 5kW of input power.

  4. Femtosecond laser bone ablation with a high repetition rate fiber laser source

    PubMed Central

    Mortensen, Luke J.; Alt, Clemens; Turcotte, Raphaël; Masek, Marissa; Liu, Tzu-Ming; Côté, Daniel C.; Xu, Chris; Intini, Giuseppe; Lin, Charles P.

    2014-01-01

    Femtosecond laser pulses can be used to perform very precise cutting of material, including biological samples from subcellular organelles to large areas of bone, through plasma-mediated ablation. The use of a kilohertz regenerative amplifier is usually needed to obtain the pulse energy required for ablation. This work investigates a 5 megahertz compact fiber laser for near-video rate imaging and ablation in bone. After optimization of ablation efficiency and reduction in autofluorescence, the system is demonstrated for the in vivo study of bone regeneration. Image-guided creation of a bone defect and longitudinal evaluation of cellular injury response in the defect provides insight into the bone regeneration process. PMID:25657872

  5. Femtosecond laser bone ablation with a high repetition rate fiber laser source.

    PubMed

    Mortensen, Luke J; Alt, Clemens; Turcotte, Raphaël; Masek, Marissa; Liu, Tzu-Ming; Côté, Daniel C; Xu, Chris; Intini, Giuseppe; Lin, Charles P

    2015-01-01

    Femtosecond laser pulses can be used to perform very precise cutting of material, including biological samples from subcellular organelles to large areas of bone, through plasma-mediated ablation. The use of a kilohertz regenerative amplifier is usually needed to obtain the pulse energy required for ablation. This work investigates a 5 megahertz compact fiber laser for near-video rate imaging and ablation in bone. After optimization of ablation efficiency and reduction in autofluorescence, the system is demonstrated for the in vivo study of bone regeneration. Image-guided creation of a bone defect and longitudinal evaluation of cellular injury response in the defect provides insight into the bone regeneration process. PMID:25657872

  6. Thermal Ablation for Benign Thyroid Nodules: Radiofrequency and Laser

    PubMed Central

    Lee, Jeong Hyun; Valcavi, Roberto; Pacella, Claudio M.; Rhim, Hyunchul; Na, Dong Gyu

    2011-01-01

    Although ethanol ablation has been successfully used to treat cystic thyroid nodules, this procedure is less effective when the thyroid nodules are solid. Radiofrequency (RF) ablation, a newer procedure used to treat malignant liver tumors, has been valuable in the treatment of benign thyroid nodules regardless of the extent of the solid component. This article reviews the basic physics, techniques, applications, results, and complications of thyroid RF ablation, in comparison to laser ablation. PMID:21927553

  7. Fabrication of silver nanoparticles dispersed in palm oil using laser ablation.

    PubMed

    Zamiri, Reza; Zakaria, Azmi; Ahangar, Hossein Abbastabar; Sadrolhosseini, Amir Reza; Mahdi, Mohd Adzir

    2010-01-01

    In this study we used a laser ablation technique for preparation of silver nanoparticles. The fabrication process was carried out by ablation of a silver plate immersed in palm oil. A pulsed Nd:YAG laser at a wavelength of 1064 nm was used for ablation of the plate at different times. The palm coconut oil allowed formation of nanoparticles with very small and uniform particle size, which are dispersed very homogeneously within the solution. The obtained particle sizes for 15 and 30 minute ablation times were 2.5 and 2 nm, respectively. Stability study shows that all of the samples remained stable for a reasonable period of time. PMID:21151470

  8. Single-shot ablation threshold of chromium using UV femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Banerjee, S. P.; Fedosejevs, R.

    2014-07-01

    Single-shot ablation threshold for thin chromium film was studied using 266 nm, femtosecond laser pulses. Chromium is a useful material in the nanotechnology industry and information on ablation threshold using UV femtosecond pulses would help in precise micromachining of the material. The ablation threshold was determined by measuring the ablation crater diameters as a function of incident laser pulse energy. Absorption of 266 nm light on the chromium film was also measured under our experimental conditions, and the absorbed energy single-shot ablation threshold fluence was 46 ± 5 mJ/cm2. The experimental ablation threshold fluence value was compared to time-dependent heat flow calculations based on the two temperature model for ultrafast laser pulses. The model predicts a value of 31.6 mJ/cm2 which is qualitatively consistent with the experimentally obtained value, given the simplicity of the model.

  9. Printable Nanophotonic Devices via Holographic Laser Ablation.

    PubMed

    Zhao, Qiancheng; Yetisen, Ali K; Sabouri, Aydin; Yun, Seok Hyun; Butt, Haider

    2015-09-22

    Holography plays a significant role in applications such as data storage, light trapping, security, and biosensors. However, conventional fabrication methods remain time-consuming, costly, and complex, limiting the fabrication of holograms and their extensive use. Here, we demonstrate a single-pulse laser ablation technique to write parallel surface gratings and Fresnel zone plates. We utilized a 6 ns high-energy green laser pulse to form interference patterns to record a surface grating with 820 nm periodicity and asymmetric zone plate holograms on 4.5 nm gold-coated substrates. The holographic recording process was completed within seconds. The optical characteristics of the interference patterns have been computationally modeled, and well-ordered polychromatic diffraction was observed from the fabricated holograms. The zone plate showed a significant diffraction angle of 32° from the normal incident for the focal point. The nanosecond laser interference ablation for rapid hologram fabrication holds great potential in a vast range of optical devices. PMID:26301907

  10. Application of laser microdissection ICP-MS for high resolution elemental mapping in mouse brain tissue: a comparative study with laser ablation ICP-MS.

    PubMed

    Sussulini, Alessandra; Becker, J Sabine

    2015-01-01

    Mapping of elements in biological tissue by laser induced mass spectrometry is a fast growing analytical methodology in life sciences. This method provides a multitude of useful information of metal, nonmetal, metalloid and isotopic distribution at major, minor and trace concentration ranges, usually with a lateral resolution of 12-160 µm. Selected applications in medical research require an improved lateral resolution of laser induced mass spectrometric technique at the low micrometre scale and below. The present work demonstrates the applicability of a recently developed analytical methodology - laser microdissection associated to inductively coupled plasma mass spectrometry (LMD ICP-MS) - to obtain elemental images of different solid biological samples at high lateral resolution. LMD ICP-MS images of mouse brain tissue samples stained with uranium and native are shown, and a direct comparison of LMD and laser ablation (LA) ICP-MS imaging methodologies, in terms of elemental quantification, is performed. PMID:25476347

  11. Sulphur selective ablation by UV laser

    NASA Astrophysics Data System (ADS)

    Lorusso, Antonella; Nassisi, Vincenzo; Belloni, Fabio; Buccolieri, Giovanni; Caretto, Giuseppe; Castellano, Alfredo

    2005-06-01

    In this work we report the preliminary experimental results on the selective ablation of sulphur in ancient stones. The sulphur concentration was reduced after laser action. For this goal an excimer laser operating at 308 nm wavelength and time duration of 20 ns was used. In order to estimate the sulphur concentration before and after laser cleaning, a portable apparatus for energy-dispersive X-ray fluorescence (EDXRF) was utilised. The processed sample were characterized by an initial sulphur concentration of 2.8% w/w. After the laser treatment, sulphur concentration decreased after a total deposited energy of about 30 J/cm2 up to 1.2% w/w value. Due to the porosity of the stone, in fact, it is difficult to eliminate completely the S presence in the composition of the stones. It was also observed that after a few laser shots the initial black area of the stone became white showing in this way the great potential of the laser action on the cleaning process of the pietra leccese.

  12. PREFACE AND CONFERENCE INFORMATION: Eighth International Conference on Laser Ablation

    NASA Astrophysics Data System (ADS)

    Hess, Wayne P.; Herman, Peter R.; Bäuerle, Dieter; Koinuma, Hideomi

    2007-04-01

    Laser ablation encompasses a wide range of delicate to extreme light interactions with matter that present considerably challenging problems for scientists to study and understand. At the same time, laser ablation also represents a basic process of significant commercial importance in laser material processing—defining a multi-billion dollar industry today. These topics were widely addressed at the 8th International Conference on Laser Ablation (COLA), held in Banff, Canada on 11-16 September 2005. The meeting took place amongst the majestic and natural beauty of the Canadian Rocky Mountains at The Banff Centre, where delegates enjoyed many inspiring presentations and discussions in a unique campus learning environment. The conference brought together world leading scientists, students and industry representatives to examine the basic science of laser ablation and improve our understanding of the many physical, chemical and/or biological processes driven by the laser. The multi-disciplinary research presented at the meeting underlies some of our most important trends at the forefront of science and technology today that are represented in the papers collected in this volume. Here you will find new processes that are producing novel types of nanostructures and nano-materials with unusual and promising properties. Laser processes are described for delicately manipulating living cells or modifying their internal structure with unprecedented degrees of control and precision. Learn about short-pulse lasers that are driving extreme physical processes on record-fast time scales and opening new directions from material processing applications. The conference papers further highlight forefront application areas in pulsed laser deposition, nanoscience, analytical methods, materials, and microprocessing applications. Laser ablation continues to grow and evolve, touching forefront areas in science and driving new technological trends in laser processing applications. Please

  13. Pre-ignition laser ablation of nanocomposite energetic materials

    SciTech Connect

    Stacy, S. C.; Massad, R. A.; Pantoya, M. L.

    2013-06-07

    Laser ignition of energetic material composites was studied for initiation with heating rates from 9.5 Multiplication-Sign 10{sup 4} to 1.7 Multiplication-Sign 10{sup 7} K/s. This is a unique heating rate regime for laser ignition studies because most studies employ either continuous wave CO{sub 2} lasers to provide thermal ignition or pulsed Nd:YAG lasers to provide shock ignition. In this study, aluminum (Al) and molybdenum trioxide (MoO{sub 3}) nanoparticle powders were pressed into consolidated pellets and ignited using a Nd:YAG laser (1064 nm wavelength) with varied pulse energy. Results show reduced ignition delay times corresponding to laser powers at the ablation threshold for the sample. Heating rate and absorption coefficient were determined from an axisymmetric heat transfer model. The model estimates absorption coefficients from 0.1 to 0.15 for consolidated pellets of Al + MoO{sub 3} at 1064 nm wavelength. Ablation resulted from fracturing caused by a rapid increase in thermal stress and slowed ignition of the pellet.

  14. Pre-ignition laser ablation of nanocomposite energetic materials

    NASA Astrophysics Data System (ADS)

    Stacy, S. C.; Massad, R. A.; Pantoya, M. L.

    2013-06-01

    Laser ignition of energetic material composites was studied for initiation with heating rates from 9.5 × 104 to 1.7 × 107 K/s. This is a unique heating rate regime for laser ignition studies because most studies employ either continuous wave CO2 lasers to provide thermal ignition or pulsed Nd:YAG lasers to provide shock ignition. In this study, aluminum (Al) and molybdenum trioxide (MoO3) nanoparticle powders were pressed into consolidated pellets and ignited using a Nd:YAG laser (1064 nm wavelength) with varied pulse energy. Results show reduced ignition delay times corresponding to laser powers at the ablation threshold for the sample. Heating rate and absorption coefficient were determined from an axisymmetric heat transfer model. The model estimates absorption coefficients from 0.1 to 0.15 for consolidated pellets of Al + MoO3 at 1064 nm wavelength. Ablation resulted from fracturing caused by a rapid increase in thermal stress and slowed ignition of the pellet.

  15. Dynamical Study of Femtosecond-Laser-Ablated Liquid-Aluminum Nanoparticles Using Spatiotemporally Resolved X-Ray-Absorption Fine-Structure Spectroscopy

    SciTech Connect

    Oguri, Katsuya; Okano, Yasuaki; Nishikawa, Tadashi; Nakano, Hidetoshi

    2007-10-19

    We study the temperature evolution of aluminum nanoparticles generated by femtosecond laser ablation with spatiotemporally resolved x-ray-absorption fine-structure spectroscopy. We successfully identify the nanoparticles based on the L-edge absorption fine structure of the ablation plume in combination with the dependence of the edge structure on the irradiation intensity and the expansion velocity of the plume. In particular, we show that the lattice temperature of the nanoparticles is estimated from the L-edge slope, and that its spatial dependence reflects the cooling of the nanoparticles during plume expansion. The results reveal that the emitted nanoparticles travel in a vacuum as a condensed liquid phase with a lattice temperature of about 2500 to 4200 K in the early stage of plume expansion.

  16. Practical Laser Ablation U-Th Thermochronology and Geochronology

    NASA Astrophysics Data System (ADS)

    Hodges, K.; Van Soest, M. C.; Tripathy, A.; Boyce, J. W.

    2012-12-01

    (U-Th)/He thermochronology of the accessory phases apatite and zircon has become an essential tool for many landscape evolution and tectonic studies. Moreover, new geochronologic applications of the (U-Th)/He method -dating impact events, young volcanic eruptions, and secondary hydrothermal mineralization, for example - are only recently being explored. A significant impediment to all applications of the method is a commonly observed scatter of replicate dates for different crystals from an individual sample, typically greater than that which can be explained by analytical imprecision alone. While several reasons for this have been proposed, three are certainly important: 1) the propensity for many accessory minerals to be strongly and complexly zoned in U and Th; 2) inclusions of other (U+Th)-rich minerals in dated grains; and 3) frequently ignored and generally unquantifiable uncertainties in the alpha ejection corrections applied to dated crystals. For nearly a decade, we have worked to establish a new technique that avoids or minimizes the impact of these factors. Individual crystals are mounted, polished, and imaged to resolve internal zonation and inclusion content as a means of selecting appropriate grains for analysis. A 193 nm ArF excimer laser is used to ablate sample from the center of the polished surface, sufficiently far from the crystal rim to eliminate the need for an alpha ejection correction. 4He is measured in the ablated material by magnetic sector, gas-source mass spectrometry. After precise measurement of the ablation pit to permit the determination of 4He concentration, the sample is removed and mounted for U + Th analysis by laser ablation inductively coupled, plasma mass spectrometry. For parent element analyses, the ablation pit is targeted so as to encompass the 4He ablation pit on a scale large enough to integrate intragranular U + Th zoning and account for recoil redistribution of 4He within grains. We have documented the efficacy of

  17. Comparison of 1470 nm Laser and Radial 2ring Fiber with 980 nm Laser and Bare-Tip Fiber in Endovenous Laser Ablation of Saphenous Varicose Veins: A Multicenter, Prospective, Randomized, Non-Blind Study

    PubMed Central

    Ogawa, Tomohiro; Sugawara, Hiromitsu; Shokoku, Shintaro; Sato, Shoji

    2015-01-01

    Objective: The aim of this study is to compare the clinical efficacy and safety of two laser wavelengths and fiber types in endovenous laser ablation (EVLA) of saphenous varicose veins of the lower limb. Design: Multi-center prospective randomized non-blind clinical trial. Patients and Methods: From January 2007 to December 2011, 113 patients (113 limbs) with primary varicose veins were randomized into two groups. They were treated with radial 2ring fiber and 1470 nm laser in Group I (57 limbs) and bare-tip fiber and 980 nm laser in Group E (56 limbs) in order to ablate the saphenous vein. Vein occlusion rates at 12 weeks and pain in treated region were recorded as primary endpoint. Visual analogue scale (VAS) for assessment of pain, rates of bruising, complications and equipment failure were recorded as secondary endpoint of safety. Results: Occlusion rates at 12 weeks were 100% in both groups. Rates of pain (0% vs. 25.0%) and bruising (7.0% vs. 57.1%) were significantly lower in Group I (p <0.0001). VAS of pain was significantly lower on postoperative day 1, day 5 and 2nd week in Group I. Conclusion: Treatment of saphenous varicose veins by EVLA using a 1470 nm laser and a radial 2ring fiber resulted in comparable occlusion rates at 12 weeks and less postoperative pain and bruising than EVLA with a 980 nm laser and a bare-tip fiber. (This article is a translation of Jpn J Vasc Surg 2014; 23: 964–971.) PMID:26730252

  18. Survey Of CO{sub 2} Laser Ablation Propulsion With Polyoxymethylene Propellant

    SciTech Connect

    Sinko, John E.; Sasoh, Akihiro

    2010-05-06

    Polyoxymethylene (POM) has been widely studied as a laser propulsion propellant paired to CO{sub 2} laser radiation. POM is a good test case for studying ablation properties of polymer materials, and within limits, for study of general trends in laser ablation-induced impulse. Despite many studies, there is no general understanding of POM ablation that takes into account the ambient pressure, spot area, fluence, and effects from confinement and combustion. This paper reviews and synthesizes CO{sub 2} laser ablation propulsion research using POM targets. Necessary directions for future study are indicated to address incomplete regions of the various parameter spaces. Literature data is compared in terms of propulsion parameters such as momentum coupling coefficient and specific impulse, within a range of fluences from about 1-500 J/cm{sup 2}, ambient pressures from about 10{sup -2}-10{sup 5} Pa, and laser spot areas from about 0.01-10 cm{sup 2}.

  19. Low-order harmonic generation in metal ablation plasmas in nanosecond and picosecond laser regimes

    SciTech Connect

    Lopez-Arias, M.; Oujja, M.; Sanz, M.; Castillejo, M.; Ganeev, R. A.; Boltaev, G. S.; Satlikov, N. Kh.; Tugushev, R. I.; Usmanov, T.

    2012-02-15

    Low-order harmonics, third and fifth, of IR (1064 nm) laser emission have been produced in laser ablation plasmas of the metals manganese, copper and silver. The harmonics were generated in a process triggered by laser ablation followed by frequency up-conversion of a fundamental laser beam that propagates parallel to the target surface. These studies were carried out in two temporal regimes by creating the ablation plasma using either nanosecond or picosecond pulses and then probing the plasma plume with pulses of the same duration. The spatiotemporal behavior of the generated harmonics was characterized and reveals the distinct composition and dynamics of the plasma species that act as nonlinear media, allowing the comparison of different processes that control the generation efficiency. These results serve to guide the choice of laser ablation plasmas to be used for efficient high harmonic generation of laser radiation.

  20. Special regime of liquid-assisted laser ablation of ceramics

    NASA Astrophysics Data System (ADS)

    Sinev, D. A.; Dobrina, D. A.; Strusevich, A. V.; Veiko, V. P.; Baranov, M. A.; Yakusheva, A. A.

    2016-05-01

    Results of experimental study the peculiarities of liquid-assisted laser ablation of alumina-silicate ceramics are reported giving attention particularly to effect of thin-wall glass macrosphere appearance at the end of irradiation onto a formed hole in bulk material. Typical times of formation, size and temperature dynamics, and chemical composition were determined; kinetics and mechanism of formation are discussed in presented paper.

  1. Laser ablation loading of a surface-electrode ion trap

    SciTech Connect

    Leibrandt, David R.; Clark, Robert J.; Labaziewicz, Jaroslaw; Antohi, Paul; Bakr, Waseem; Brown, Kenneth R.; Chuang, Isaac L.

    2007-11-15

    We demonstrate loading of {sup 88}Sr{sup +} ions by laser ablation into a mm-scale surface-electrode ion trap. The laser used for ablation is a pulsed, frequency-tripled Nd:YAG with pulse energies of 1-10 mJ and durations of 4 ns. An additional laser is not required to photoionize the ablated material. The efficiency and lifetime of several candidate materials for the laser ablation target are characterized by measuring the trapped ion fluorescence signal for a number of consecutive loads. Additionally, laser ablation is used to load traps with a trap depth (40 meV) below where electron impact ionization loading is typically successful (> or approx. 500 meV)

  2. Hydrogen alpha laser ablation plasma diagnostics.

    PubMed

    Parigger, C G; Surmick, D M; Gautam, G; El Sherbini, A M

    2015-08-01

    Spectral measurements of the H(α) Balmer series line and the continuum radiation are applied to draw inferences of electron density, temperature, and the level of self-absorption in laser ablation of a solid ice target in ambient air. Electron densities of 17 to 3.2×10(24) m(-3) are determined from absolute calibrated emission coefficients for time delays of 100-650 ns after generation of laser plasma using Q-switched Nd:YAG radiation. The corresponding temperatures of 4.5-0.95 eV were evaluated from the absolute spectral radiance of the continuum at the longer wavelengths. The redshifted, Stark-broadened hydrogen alpha line emerges from the continuum radiation after a time delay of 300 ns. The electron densities inferred from power law formulas agree with the values obtained from the plasma emission coefficients. PMID:26258326

  3. Laser-Ablation (U-Th)/He Geochronology

    NASA Astrophysics Data System (ADS)

    Hodges, K.; Boyce, J.

    2003-12-01

    Over the past decade, ultraviolet laser microprobes have revolutionized the field of 40Ar/39Ar geochronology. They provide unprecedented information about Ar isotopic zoning in natural crystals, permit high-resolution characterization of Ar diffusion profiles produced during laboratory experiments, and enable targeted dating of multiple generations of minerals in thin section. We have modified the analytical protocols used for 40Ar/39Ar laser microanalysis for use in (U-Th)/He geochronologic studies. Part of the success of the 40Ar/39Ar laser microprobe stems from fact that measurements of Ar isotopic ratios alone are sufficient for the calculation of a date. In contrast, the (U-Th)/He method requires separate analysis of U+Th and 4He. Our method employs two separate laser microprobes for this process. A target mineral grain is placed in an ultrahigh vacuum chamber fitted with a window of appropriate composition to transmit ultraviolet radiation. A focused ArF (193 nm) excimer laser is used to ablate tapered cylindrical pits on the surface of the target. The liberated material is scrubbed with a series of getters in a fashion similar to that used for 40Ar/39Ar geochronology, and the 4He abundance is determined using a quadrupole mass spectrometer with well-calibrated sensitivity. A key requirement for calculation of the 4He abundance in the target is a precise knowledge of the volume of the ablation pit. This is the principal reason why we employ the ArF excimer for 4He analysis rather than a less-expensive frequency-multiplied Nd-YAG laser; the excimer creates tapered cylindrical pits with extremely reproducible and easily characterized geometry. After 4He analysis, U and Th are measured on the same sample surface using the more familiar technique of laser-ablation inductively coupled plasma mass spectrometry (LA-ICPMS). Our early experiments have been done using a frequency-quintupled Nd-YAG microprobe (213nm), While the need to analyze U+Th and He in separate

  4. Laser ablation of electronic materials including the effects of energy coupling and plasma interactions

    SciTech Connect

    Zeng, Xianzhong

    2004-12-10

    Many laser ablation applications such as laser drilling and micromachining generate cavity structures. The study of laser ablation inside a cavity is of both fundamental and practical significance. In this dissertation, cavities with different aspect ratios (depth/diameter) were fabricated in fused silica by laser micromachining. Pulsed laser ablation in the cavities was studied and compared with laser ablation on a flat surface. The formation of laser-induced plasmas in the cavities and the effects of the cavities on the ablation processes were investigated. The temperatures and electron number densities of the resulting laser-induced plasmas in the cavities were determined from spectroscopic measurements. Reflection and confinement effects by the cavity walls and plasma shielding were discussed to explain the increased temperature and electron number density with respect to increasing cavity aspect ratio. The temporal variations of the plasma temperature and electron number density inside the cavity decreased more rapidly than outside the cavity. The effect of laser energy on formation of a plasma inside a cavity was also investigated. Propagation of the shock wave generated during pulsed laser ablation in cavities was measured using laser shadowgraph imaging and compared with laser ablation on a flat surface. It is found that outside the cavity, after about 30 ns the radius of the expanding shock wave was proportional to t2/5, which corresponds to a spherical blast wave. The calculated pressures and temperatures of the shocked air outside of the cavities were higher than those obtained on the flat surface. Lasers with femtosecond pulse duration are receiving much attention for direct fabrication of microstructures due to their capabilities of high-precision ablation with minimal damage to the sample. We have also performed experimental studies of pulsed femtosecond laser ablation on the flat surface of silicon samples and compared results with pulsed nanosecond

  5. Silver Nanoparticle Fabrication by Laser Ablation in Polyvinyl Alcohol Solutions

    NASA Astrophysics Data System (ADS)

    Halimah Mohamed., K.; Mahmoud Goodarz, Naseri; Amir, Reza Sadrolhosseini; Arash, Dehzangi; Ahmad, Kamalianfar; Elias, B. Saion; Reza, Zamiri; Hossein Abastabar, Ahangar; Burhanuddin, Y. Majlis

    2014-07-01

    A laser ablation technique is applied for synthesis of silver nanoparticles in different concentrations of polyvinyl alcohol (PVA) aqueous solution. The ablation of high pure silver plate in the solution is carried out by a nanosecond Q-switched Nd:YAG pulsed laser. X-ray diffraction and transmission electron microscopy are implemented to explore the particles sizes. The effects of PVA concentrations on the absorbance of the silver nanoparticles are studied as well, by using a UV-vis spectrophotometer. The preparation process is carried out for deionized water as a reference sample. The comparison of the obtained results with the reference sample shows that the formation efficiency of nanoparticles in PVA is much higher and the sizes of particles are also smaller.

  6. Dopant-enhanced ablation of nitrocellulose by a nitrogen laser

    NASA Astrophysics Data System (ADS)

    Kosmidis, C. E.; Skordoulis, C. D.

    1993-01-01

    The photoetching behavior of pure nitrocellulose and of nitrocellulose dyed with stilbene-420, coumarin-120 and rhodamine 6G by 337 nm nitrogen laser pulses has been studied. Ablation with a low power nitrogen laser is hereby reported for the first time. A two step photochemical mechanism is proposed to account for the ablation of the pure material. With the addition of dyes strongly absorbing at 337 nm the photoetching rate of nitrocellulose can be increased significantly. This increase is proportional to the molar extinction coefficient of the dye at 337 nm and its concentration in the polymer. The photoetching mechanism and the energy transfer processes from the dye to the polymer are discussed in detail.

  7. 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.

  8. Laser ablation of CFRP using picosecond laser pulses at different wavelengths from UV to IR

    NASA Astrophysics Data System (ADS)

    Wolynski, Alexander; Herrmann, Thomas; Mucha, Patrick; Haloui, Hatim; L'huillier, Johannes

    Laser processing of carbon fibre reinforced plastics (CFRP) has a great industrial relevance for high performance structural parts in airplanes, machine tools and cars. Through-holes drilled by nanosecond laser pulses show thermal induced molten layers and voids. Recently, picosecond lasers have demonstrated the ability to drill high-efficient and high-quality rivet through-holes. In this paper a high-power picosecond laser system operating at different wavelengths (355 nm, 532 nm and 1064 nm) has been used for CFRP ablation experiments to study the influence of different laser parameters in terms of machining quality and processing time.

  9. Laser ablation of liquid surface in air induced by laser irradiation through liquid medium

    NASA Astrophysics Data System (ADS)

    Utsunomiya, Yuji; Kajiwara, Takashi; Nishiyama, Takashi; Nagayama, Kunihito; Kubota, Shiro; Nakahara, Motonao

    2010-10-01

    The pulse laser ablation of a liquid surface in air when induced by laser irradiation through a liquid medium has been experimentally investigated. A supersonic liquid jet is observed at the liquid-air interface. The liquid surface layer is driven by a plasma plume that is produced by laser ablation at the layer, resulting in a liquid jet. This phenomenon occurs only when an Nd:YAG laser pulse (wavelength: 1064 nm) is focused from the liquid onto air at a low fluence of 20 J/cm2. In this case, as Fresnel’s law shows, the incident and reflected electric fields near the liquid surface layer are superposed constructively. In contrast, when the incident laser is focused from air onto the liquid, a liquid jet is produced only at an extremely high fluence, several times larger than that in the former case. The similarities and differences in the liquid jets and atomization processes are studied for several liquid samples, including water, ethanol, and vacuum oil. The laser ablation of the liquid surface is found to depend on the incident laser energy and laser fluence. A pulse laser light source and high-resolution film are required to observe the detailed structure of a liquid jet.

  10. Time-resolved diagnostics of excimer laser-generated ablation plasmas used for pulsed laser deposition

    SciTech Connect

    Geohegan, D.B.

    1994-09-01

    Characteristics of laser plasmas used for pulsed laser deposition (PLD) of thin films are examined with four in situ diagnostic techniques: Optical emission spectroscopy, optical absorption spectroscopy, ion probe studies, and gated ICCD (intensified charge-coupled-device array) fast photography. These four techniques are complementary and permit simultaneous views of the transport of ions, excited states, ground state neutrals and ions, and hot particulates following KrF laser ablation of YBCO, BN, graphite and Si in vacuum and background gases. The implementation and advantages of the four techniques are first described in order to introduce the key features of laser plasmas for pulsed laser deposition. Aspects of the interaction of the ablation plume with background gases (i.e., thermalization, attenuation, shock formation) and the collision of the plasma plume with the substrate heater are then summarized. The techniques of fast ICCD photography and gated photon counting are then applied to investigate the temperature, velocity, and spatial distribution of hot particles generated during KrF ablation of YBCO, BN, Si and graphite. Finally, key features of fast imaging of the laser ablation of graphite into high pressure rare gases are presented in order to elucidate internal reflected shocks within the plume, redeposition of material on a surface, and formation of hot nanoparticles within the plume.

  11. Underwater excimer laser ablation of polymers

    NASA Astrophysics Data System (ADS)

    Elaboudi, I.; Lazare, S.; Belin, C.; Talaga, D.; Labrugère, C.

    2008-09-01

    In this paper, we study the photoablation kinetic of poly (ethylene terephthalate) (PET), polycarbonate (PC), polyimide (PI) and polystyrene (PS) in both air and water. Compared to the results obtained in air, we highlight the decrease of the ablation threshold (AT) of polyesters in contact with water as a function of polymer chemical structure. In order to check the expected hydrolytic reaction of polyesters near the ablation threshold, the chemical modification of the polymer surfaces, as well the composition of the ablation products, were investigated after irradiation near the fluence of ablation threshold in air (air- F t ) by X-ray photoelectron spectroscopy (XPS) and confocal Raman microspectroscopy. The morphology of polymers obtained by underwater irradiation and near the air- F t was also examined using scanning electron microscopy (SEM). To understand the process and its dynamics in contact with water, we consider the model of temperature at the polymer-water interface based on the semi-analytical solution of the transit heat-diffusion equation.

  12. Research and application of surface heat treatment for multipulse laser ablation of materials

    NASA Astrophysics Data System (ADS)

    Cai, Song; Chen, Genyu; Zhou, Cong

    2015-11-01

    This study analysed a laser ablation platform and built heat transfer equations for multipulse laser ablation of materials. The equations include three parts: laser emission after the material melt and gasification; end of laser emission after the material melts and there is the presence of a super-hot layer and solid-phase heat transfer changes during material ablation. For each of the three parts, the effects of evaporation, plasma shielding and energy accumulation under the pulse interval were considered. The equations are reasonable, and all the required parameters are only related to the laser parameters and material properties, allowing the model to have a certain versatility and practicability. The model was applied for numerical simulation of the heat transfer characteristics in the multipulse laser ablation of bronze and diamond. Next, experiments were conducted to analyse the topography of a bronze-bonded diamond grinding wheel after multipulse laser ablation. The theoretical analysis and experimental results showed that multipulse laser can merge the truing and dressing on a bronze-bonded diamond grinding wheel. This study provides theoretical guidance for optimising the process parameters in the laser ablation of a bronze-bonded diamond grinding wheel. A comparative analysis showed that the numerical solution to the model is in good agreement with the experimental data, thus verifying the correctness and feasibility of the heat transfer model.

  13. Investigation of different liquid media and ablation times on pulsed laser ablation synthesis of aluminum nanoparticles

    NASA Astrophysics Data System (ADS)

    Baladi, Arash; Sarraf Mamoory, Rasoul

    2010-10-01

    Aluminum nanoparticles were synthesized by pulsed laser ablation of Al targets in ethanol, acetone, and ethylene glycol. Transmission Electron Microscope (TEM) and Scanning Electron Microscope (SEM) images, Particle size distribution diagram from Laser Particle Size Analyzer (LPSA), UV-visible absorption spectra, and weight changes of targets were used for the characterization and comparison of products. The experiments demonstrated that ablation efficiency in ethylene glycol is too low, in ethanol is higher, and in acetone is highest. Comparison between ethanol and acetone clarified that acetone medium leads to finer nanoparticles (mean diameter of 30 nm) with narrower size distribution (from 10 to 100 nm). However, thin carbon layer coats some of them, which was not observed in ethanol medium. It was also revealed that higher ablation time resulted in higher ablated mass, but lower ablation rate. Finer nanoparticles, moreover, were synthesized in higher ablation times.

  14. Analysis of fabric materials cut using ultraviolet laser ablation

    NASA Astrophysics Data System (ADS)

    Tsai, Hsin-Yi; Yang, Chih-Chung; Hsiao, Wen-Tse; Huang, Kuo-Cheng; Andrew Yeh, J.

    2016-04-01

    Laser ablation technology has widely been applied in the clothing industry in recent years. However, the laser mechanism would affect the quality of fabric contours and its components. Hence, this study examined carbonization and oxidation conditions and contour variation in nonwoven, cotton, and composite leather fabrics cut by using an ultraviolet laser at a wavelength of 355 nm. Processing parameters such as laser power, pulse frequency, scanning speed, and number of pulses per spot were adjusted to investigate component variation of the materials and to determine suitable cutting parameters for the fabrics. The experimental results showed that the weights of the component changed substantially by pulse frequency but slightly by laser power, so pulse frequency of 100 kHz and laser power of 14 W were the approximate parameters for three fabrics for the smaller carbonization and a sufficient energy for rapidly cutting, which the pulse duration of laser system was fixed at 300 μs and laser irradiance was 0.98 J/mm2 simultaneously. In addition, the etiolate phenomenon of nonwoven was reduced, and the component weight of cotton and composite leather was closed to the value of knife-cut fabric as the scanning speed increased. The approximate scanning speed for nonwoven and composite leather was 200 mm/s, and one for cotton was 150 mm/s, respectively. The sharper and firmer edge is obtained by laser ablation mechanism in comparison with traditional knife cutting. Experimental results can serve as the reference for laser cutting in the clothing industry, for rapidly providing smoother patterns with lower carbonization and oxidation edge in the fashion industry.

  15. Laser-induced back-ablation of aluminum thin films using picosecond laser pulses

    SciTech Connect

    BULLOCK, A B

    1999-05-26

    Experiments were performed to understand laser-induced back-ablation of Al film targets with picosecond laser pulses. Al films deposited on the back surface of BK-7 substrates are ablated by picosecond laser pulses propagating into the Al film through the substrate. The ablated Al plume is transversely probed by a time-delayed, two-color sub-picoseond (500 fs) pulse, and this probe is then used to produce self-referencing interferograms and shadowgraphs of the Al plume in flight. Optical emission from the Al target due to LIBA is directed into a time-integrated grating spectrometer, and a time-integrating CCD camera records images of the Al plume emission. Ablated Al plumes are also redeposited on to receiving substrates. A post-experimental study of the Al target and recollected deposit characteristics was also done using optical microscopy, interferometry, and profilometry. In this high laser intensity regime, laser-induced substrate ionization and damage strongly limits transmitted laser fluence through the substrate above a threshold fluence. The threshold fluence for this ionization-based transmission limit in the substrate is dependent on the duration of the incident pulse. The substrate ionization can be used as a dynamic control of both transmitted spatial pulse profile and ablated Al plume shape. The efficiency of laser energy transfer between the laser pulse incident on the Al film and the ablated Al plume is estimated to be of order 5% and is a weak function of laser pulsewidth. The Al plume is highly directed. Low plume divergence ({theta}{sub divergence} < 5{sup o}) shows the ablated plume temperature to be very low at long time delays ( T << 0.5 eV at delays of 255 ns). Spectroscopic observations and calculations indicate that, in early time (t < 100 ps), the Al film region near the substrate/metal interface is at temperatures of order 0.5 eV. Interferograms of Al plumes produced with 0.1 {micro}m films show these plumes to be of high neutral atom

  16. Plume collimation for laser ablation electrospray ionization mass spectrometry

    DOEpatents

    Vertes, Akos; Stolee, Jessica A.

    2016-06-07

    In various embodiments, a device may generally comprise a capillary having a first end and a second end; a laser to emit energy at a sample in the capillary to ablate the sample and generate an ablation plume in the capillary; an electrospray apparatus to generate an electrospray plume to intercept the ablation plume to produce ions; and a mass spectrometer having an ion transfer inlet to capture the ions. The ablation plume may comprise a collimated ablation plume. The device may comprise a flow cytometer. Methods of making and using the same are also described.

  17. Plume collimation for laser ablation electrospray ionization mass spectrometry

    SciTech Connect

    Vertes, Akos; Stolee, Jessica A.

    2014-09-09

    In various embodiments, a device may generally comprise a capillary having a first end and a second end; a laser to emit energy at a sample in the capillary to ablate the sample and generate an ablation plume in the capillary; an electrospray apparatus to generate an electrospray plume to intercept the ablation plume to produce ions; and a mass spectrometer having an ion transfer inlet to capture the ions. The ablation plume may comprise a collimated ablation plume. The device may comprise a flow cytometer. Methods of making and using the same are also described.

  18. Tracing the plasma interactions for pulsed reactive crossed-beam laser ablation

    SciTech Connect

    Chen, Jikun; Stender, Dieter; Pichler, Markus; Pergolesi, Daniele; Schneider, Christof W.; Wokaun, Alexander; Lippert, Thomas; Döbeli, Max

    2015-10-28

    Pulsed reactive crossed-beam laser ablation is an effective technique to govern the chemical activity of plasma species and background molecules during pulsed laser deposition. Instead of using a constant background pressure, a gas pulse with a reactive gas, synchronized with the laser beam, is injected into vacuum or a low background pressure near the ablated area of the target. It intercepts the initially generated plasma plume, thereby enhancing the physicochemical interactions between the gaseous environment and the plasma species. For this study, kinetic energy resolved mass-spectrometry and time-resolved plasma imaging were used to study the physicochemical processes occurring during the reactive crossed beam laser ablation of a partially {sup 18}O substituted La{sub 0.6}Sr{sub 0.4}MnO{sub 3} target using oxygen as gas pulse. The characteristics of the ablated plasma are compared with those observed during pulsed laser deposition in different oxygen background pressures.

  19. Tracing the plasma interactions for pulsed reactive crossed-beam laser ablation

    NASA Astrophysics Data System (ADS)

    Chen, Jikun; Stender, Dieter; Pichler, Markus; Döbeli, Max; Pergolesi, Daniele; Schneider, Christof W.; Wokaun, Alexander; Lippert, Thomas

    2015-10-01

    Pulsed reactive crossed-beam laser ablation is an effective technique to govern the chemical activity of plasma species and background molecules during pulsed laser deposition. Instead of using a constant background pressure, a gas pulse with a reactive gas, synchronized with the laser beam, is injected into vacuum or a low background pressure near the ablated area of the target. It intercepts the initially generated plasma plume, thereby enhancing the physicochemical interactions between the gaseous environment and the plasma species. For this study, kinetic energy resolved mass-spectrometry and time-resolved plasma imaging were used to study the physicochemical processes occurring during the reactive crossed beam laser ablation of a partially 18O substituted La0.6Sr0.4MnO3 target using oxygen as gas pulse. The characteristics of the ablated plasma are compared with those observed during pulsed laser deposition in different oxygen background pressures.

  20. Modeling Of Laser Ablation And Fragmentation Of Human Calculi

    NASA Astrophysics Data System (ADS)

    Gitomer, Steven J.; Jones, Roger D.; Howsare, Charles

    1989-09-01

    The large-scale radiation-hydrodynamics computer code LASNEX, has been used to model experimental results in the laser ablation and fragmentation of renal and biliary calculi. Recent experiments have demonstrated laser ablation and fragmentation of human calculi in vitro and in vivo. In the interaction, laser light incident upon the calculus is of sufficient intensity to produce a plasma (a hot ionized gas). The physical picture which emerges is as follows. The plasma couples to acoustic and shear waves which then propagate through the dense stone material, causing spall and fracture by reflection from material discontinuities or boundaries. Experiments have thus far yielded data on the interaction against which models can be tested. Data on the following have been published: (1) light emission, (2) absorption and emission spectra, (3) fragmentation efficiency, (4) cavitation bubble dynamics and (5) mass removal. We have performed one dimensional simulations of the laser-matter interaction to elucidate the im-portant physical mechanisms. We find that good quantitative fits between simulation and experiment are obtained for visible light emission, electron temperature, electron density, plasma pressure and cavitation bubble growth. With regard to mass removal, experiment and simulation are consistent with each other and give an excellent estimate of the ablation threshold. The modeling indicates that a very small ablation layer at the surface of the calulus is responsible for significant mass loss by fragmentation within the bulk of the calculus. With such quantitative fits in hand, we believe this type of modeling can now be applied to the study of other procedures involving plasma formation of interest to the medical community.

  1. [The incidence of ventricular arrhythmia following direct current ablation, high-frequency current ablation and laser photo-ablation].

    PubMed

    Hindricks, G; Haverkamp, W; Dute, U; Gülker, H

    1988-11-01

    Incidence and severity of ventricular arrhythmias (VA) following transvenous catheter ablation have so far not been fully elucidated. In the present study we evaluated the comparative incidence of postablation ventricular arrhythmias following high voltage-direct current electrical ablation (DCA), radiofrequency-ablation (RFA), and laser-photoablation (LPA). Experiments were performed on a total of 26 anesthetized mongrel dogs (BW: 20-30 kg). DCA (n = 14; 150-200 J) and RFA (n = 7; 38.5-72.5 J) were performed unipolarly via a 6F USCI catheter, LPA (n = 5; 40-80 J) was delivered through a quarz core fiber (diameter 0.4 mm) housed within a special designed catheter. Energies were delivered to various sites of free wall and apical endocardium of the left ventricle. Immediately after DCA fast runs of ventricular tachycardia (VT) developed in 13 out of 14 dogs degenerating into ventricular fibrillation in two animals. Mean cycle length of induced VT was 298 +/- 86 ms. Persistent VA, morphologically mainly characterized by an accelerated idioventricular rhythm interrupted by runs of ventricular salvoes, occurred in 12 animals (mean rate: 78 +/- 13 VPB/min 3 h after ablation). During VT early endocardial activations were recorded from the ablation site. No significant correlation between total applied energy (150-550 J) and incidence of arrhythmogenic effects was observed. RFA and LPA induced ventricular salvoes and runs of non-sustained ventricular tachycardia, in one animal ventricular fibrillation occurred during RFA; however, no persistent arrhythmic activity developed after RFA and LPA, respectively.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:3213137

  2. Renaissance of laser interstitial thermal ablation.

    PubMed

    Missios, Symeon; Bekelis, Kimon; Barnett, Gene H

    2015-03-01

    Laser interstitial thermal therapy (LITT) is a minimally invasive technique for treating intracranial tumors, originally introduced in 1983. Its use in neurosurgical procedures was historically limited by early technical difficulties related to the monitoring and control of the extent of thermal damage. The development of magnetic resonance thermography and its application to LITT have allowed for real-time thermal imaging and feedback control during laser energy delivery, allowing for precise and accurate provision of tissue hyperthermia. Improvements in laser probe design, surgical stereotactic targeting hardware, and computer monitoring software have accelerated acceptance and clinical utilization of LITT as a neurosurgical treatment alternative. Current commercially available LITT systems have been used for the treatment of neurosurgical soft-tissue lesions, including difficult to access brain tumors, malignant gliomas, and radiosurgery-resistant metastases, as well as for the ablation of such lesions as epileptogenic foci and radiation necrosis. In this review, the authors aim to critically analyze the literature to describe the advent of LITT as a neurosurgical, laser excision tool, including its development, use, indications, and efficacy as it relates to neurosurgical applications. PMID:25727222

  3. Comparison of holmium:YAG and thulium fiber laser lithotripsy: ablation thresholds, ablation rates, and retropulsion effects

    NASA Astrophysics Data System (ADS)

    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/cm2, 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.

  4. 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. PMID:21806249

  5. Metal particles produced by laser ablation for ICP-MSmeasurements

    SciTech Connect

    Gonzalez, Jhanis J.; Liu, Chunyi; Wen, Sy-Bor; Mao, Xianglei; Russo, Richard E.

    2007-06-01

    Pulsed laser ablation (266nm) was used to generate metal particles of Zn and Al alloys using femtosecond (150 fs) and nanosecond (4 ns) laser pulses with identical fluences of 50 J cm{sup -2}. Characterization of particles and correlation with Inductively Coupled Plasma Mass Spectrometer (ICP-MS) performance was investigated. Particles produced by nanosecond laser ablation were mainly primary particles with irregular shape and hard agglomerates (without internal voids). Particles produced by femtosecond laser ablation consisted of spherical primary particles and soft agglomerates formed from numerous small particles. Examination of the craters by white light interferometric microscopy showed that there is a rim of material surrounding the craters formed after nanosecond laser ablation. The determination of the crater volume by white light interferometric microscopy, considering the rim of material surrounding ablation craters, revealed that the volume ratio (fs/ns) of the craters on the selected samples was approximately 9 (Zn), 7 (NIST627 alloy) and 5 (NIST1711 alloy) times more ablated mass with femtosecond pulsed ablation compared to nanosecond pulsed ablation. In addition, an increase of Al concentration from 0 to 5% in Zn base alloys caused a large increase in the diameter of the particles, up to 65% while using nanosecond laser pulses. When the ablated particles were carried in argon into an ICP-MS, the Zn and Al signals intensities were greater by factors of {approx} 50 and {approx} 12 for fs vs. ns ablation. Femtosecond pulsed ablation also reduced temporal fluctuations in the {sup 66}Zn transient signal by a factor of ten compared to nanosecond laser pulses.

  6. Interferometric diagnostic suite for ultrafast laser ablation of metals

    SciTech Connect

    Clarke, S. A.; Rodriguez, G.; Taylor, Antoinette J.,; Forsman, A. C.

    2004-01-01

    We report on the development of a suite of novel techniques to measure important characteristics in intense ultrashort laser solid target experiments such as critical surface displacement, ablation depth, and plasma characteristics. Measurement of these important characteristics on an ultrafast ({approx}50 fs) time scale is important in understanding the primary event mechanisms in laser ablation of metal targets. Unlike traditional methods that infer these characteristics from spectral power shifts, phase shifts in frequency domain interferometry (FDI) or laser breakthrough studies of multiple shots on bulk materials, these techniques directly measure these characteristics from a single ultrafast heating pulse. These techniques are based on absolute displacement interferometry and nanotopographic applications of wavefront sensors. By applying all these femtosecond time-resolved techniques to a range of materials (Al, Au, and Au on plastic) over a range of pulse energies (10{sup 11} to 10{sup 16} W/cm{sup 2}) and pulse durations (50 to 700 fs), greater insight into the ablation mechanism and its pulse parameter dependencies can be determined. Comparison of these results with hydrocode software programs also reveals the applicability of hydrocode models.

  7. Holmium laser ablation of cartilage: effects of cavitation bubbles

    NASA Astrophysics Data System (ADS)

    Asshauer, Thomas; Jansen, Thomas; Oberthur, Thorsten; Delacretaz, Guy P.; Gerber, Bruno E.

    1995-05-01

    The ablation of fresh harvested porcine femur patellar groove cartilage by a 2.12 micrometers Cr:Tm:Ho:YAG laser in clinically used irradiation conditions was studied. Laser pulses were delivered via a 600 micrometers diameter fiber in isotonic saline. Ablation was investigated as a function of the angle of incidence of the delivery fiber with respect to the cartilage surface (0-90 degrees) and of radiant exposure. Laser pulses with energies of 0.5, 1.0 and 1.5 J and a duration of 250 microseconds were used. A constant fiber tip-tissue distance of 1 mm was maintained for all experiments. The dynamics of the induced vapor bubble and of the ablation process was monitored by time resolved flash videography with a 1 microseconds illumination. Acoustic transients were measured with a piezoelectric PVDF needle probe hydrophone. Bubble attachment to the cartilage surface during the collapse phase, leading to the direct exposition of the cartilage surface to the maximal pressure generated, was observed in all investigated irradiation conditions. Maximal pressure transients of up to 200 bars (at 1 mm distance from the collapse center) were measured at the bubble collapse at irradiation angles >= 60 degrees. No significant pressure variation was observed in perpendicular irradiation conditions as a function of radiant exposure. A significant reduction of the induced pressure for irradiation angles

  8. Temperature profiles of 980- and 1,470-nm endovenous laser ablation, endovenous radiofrequency ablation and endovenous steam ablation.

    PubMed

    Malskat, W S J; Stokbroekx, M A L; van der Geld, C W M; Nijsten, T E C; van den Bos, R R

    2014-03-01

    Endovenous thermal ablation (EVTA) techniques are very effective for the treatment of varicose veins, but their exact working mechanism is still not well documented. The lack of knowledge of mechanistic properties has led to a variety of EVTA protocols and a commercially driven dissemination of new or modified techniques without robust scientific evidence. The aim of this study is to compare temperature profiles of 980-and 1,470-nm endovenous laser ablation (EVLA), segmental radiofrequency ablation (RFA), and endovenous steam ablation (EVSA). In an experimental setting, temperature measurements were performed using thermocouples; raw potato was used to mimic a vein wall. Two laser wavelengths (980 and 1,470 nm) were used with tulip-tip fibers and 1,470 nm also with a radial-emitting fiber. Different powers and pullback speeds were used to achieve fluences of 30, 60, and 90 J/cm. For segmental RFA, 1 cycle of 20 s was analyzed. EVSA was performed with two and three pulses of steam per centimeter. Maximum temperature increase, time span of relevant temperature increase, and area under the curve of the time of relevant temperature increase were measured. In all EVLA settings, temperatures increased and decreased rapidly. High fluence is associated with significantly higher temperatures and increased time span of temperature rise. Temperature profiles of 980- and 1,470-nm EVLA with tulip-tip fibers did not differ significantly. Radial EVLA showed significantly higher maximum temperatures than tulip-tip EVLA. EVSA resulted in mild peak temperatures for longer durations than EVLA. Maximum temperatures with three pulses per centimeter were significantly higher than with two pulses. RFA temperature rises were relatively mild, resulting in a plateau-shaped temperature profile, similar to EVSA. Temperature increase during EVLA is fast with a high-peak temperature for a short time, where EVSA and RFA have longer plateau phases and lower maximum temperatures. PMID

  9. Evaluation of ablation efficiency and surface morphology of human teeth upon irradiation with femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Shaheen, M. E.; Gagnon, J. E.; Fryer, B. J.

    2014-11-01

    This study investigates changes in ablation efficiency and surface morphology induced in human dental enamel and dentin upon interaction with femtosecond laser pulses at variable energies and number of laser pulses. Craters were created using a Ti:sapphire femtosecond laser ablation system operating at a wavelength of 785 nm, pulse width of 130 fs, and repetition rate of 20 Hz. Various techniques, such as optical and scanning electron microscopy and inductively coupled plasma mass spectrometry (ICP-MS), were used to evaluate ablation depth, amount of material ablated, and surface morphology of the craters. Ablation rate (ablation depth per pulse) was found to be lower in enamel than dentin with the maximum rate occurring at fluence of 12.4 J cm-2 in both materials. A drop in ablation rate was observed for fluence greater than 12.4 J cm-2 and was attributed to attenuation of laser energy due to interaction with the laser-generated particles. Above this fluence, signs of thermal effects, such as melting and formation of droplets of molten material at the sample surface, were observed. The response of the ICP-MS indicated that the amount of ablated material removed from dentin is greater than that removed from enamel by a factor of 1.5 or more at all investigated fluence.

  10. Modeling of nanosecond-laser ablation: calculations based on a nonstationary averaging technique (spatial moments)

    NASA Astrophysics Data System (ADS)

    Arnold, N. D.; Luk'yanchuk, Boris S.; Bityurin, Nikita M.; Baeuerle, D.

    1998-09-01

    Semi-analytical approach to a quantitative analysis of thermal ns laser ablation is presented. It permits one to take into account: (1) Arbitrary temperature dependences of material parameters, such as the specific heat, thermal conductivity, absorptivity, absorption coefficient, etc. (2) Arbitrary temporal profiles of the laser pulse. (3) Strong (Arrhenius- type) dependence of the ablation velocity on the temperature of the ablation front, which leads to a non-steady movement of the ablation boundary during the (single) pulse. (4) Screening of the incoming radiation by the ablated products. (5) Influence of the ablation (vaporization) enthalpy on the heating process. (6) Influence of melting and/or other phase transformations. The nonlinear heat conduction equation is reduced to three ordinary differential equations which describe the evolution of the surface temperature, spatial width of the enthalpy distribution, and the ablated depth. Due to its speed and flexibility, the method provides powerful tool for the fast analysis of the experimental data. The influence of different factors onto ablation curves (ablated depth h vs. fluence (phi) ) is studied. Analytical formulas for (phi) th and h((phi) ) dependences are derived and discussed. The ablation curves reveal three regions of fluence: Arrhenius region, linear region, and screening region. Threshold fluence (phi) th and Arrhenius tails at (phi) less than (phi) th, are affected heavily by the temperature dependences in material parameters, surface evaporation rate, and pulse duration and shape. In contrast, the slope of the ablation curves at (phi) greater than (phi) th, is determined almost exclusively by the latent heat of vaporization, high temperature dependence of absorptivity, and, in the case of screening, by the absorption coefficient of the plume (alpha) g. In the screening region ablated depth increases logarithmically with fluence and its qualitative behavior is weakly affected by the temperature

  11. UV laser ablation of parylene films from gold substrates

    SciTech Connect

    O. R. Musaev, P. Scott, J. M. Wrobel, and M. B. Kruger

    2009-11-19

    Parylene films, coating gold substrates, were removed by laser ablation using 248 nm light from an excimer laser. Each sample was processed by a different number of pulses in one of three different environments: air at atmospheric pressure, nitrogen at atmospheric pressure, and vacuum. The laser-induced craters were analyzed by optical microscopy and x-ray photoelectron spectroscopy. Multi-pulse ablation thresholds of gold and parylene were estimated.

  12. Infra-red femtosecond laser ablation: Benefit for LA-ICP-MS elemental analysis?

    NASA Astrophysics Data System (ADS)

    Poitrasson, F.; d'Abzac, F.; Freydier, R.; Seydoux-Guillaume, A.; Chmeleff, J.; Chatel, B.

    2011-12-01

    Femtosecond (fs) laser ablation systems have now been used for about a decade for elemental analysis in chemical and geosciences laboratories. Published studies investigated the influence of various analytical parameters, such as laser pulsewidth, wavelength, energy or ablation duration, on the quality of the analytical data produced by fs Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS). It was rapidly found that under comparable analytical conditions, chemical fractionation effects that may occur during laser-induced particle production, transport and/or decomposition in the ICP-MS plasma torch become negligible in the fs laser ablation regime under 300 fs laser pulsewidth. Another major benefit of fs laser ablation is its restricted matrix-sensitive nature compared to ns laser ablation, thereby facilitating greatly LA-ICP-MS calibration for chemical analysis with a reference material having completely different optical and chemical properties compared to the sample to be analyzed (e.g., a standard glass to calibrate analyses of a phosphate mineral). This effect is particularly remarkable as it can be stated from both UV and IR fs laser ablation studies. Reproducible laser ablations of optical quality quartz can also be produced using such an IR laser. Precise, accurate and reproducible chemical analyses may be obtained using ns laser ablation systems. However, this is achieved under carefully controlled analytical conditions using state of the art ablation cells. Instead, it appears that fs laser ablation is making LA-ICP-MS analyses more reliable. More recently, analytical studies combined with high spatial resolution microscopic techniques allowed us to understand better the nature of fs laser-matter interaction through the direct examination of the laser-induced craters and of the particles produced. These investigations have shown the dominance of mechanical over thermal effects on the solids ablated using a fs laser. Whatever the

  13. 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. PMID:22565342

  14. Application of Laser Ablation Processing in Electric Power System Industries

    NASA Astrophysics Data System (ADS)

    Konagai, Chikara; Sano, Yuji; Nittoh, Koichi; Kuwako, Akira

    The present status of laser ablation processing applied in electric power system industries is reviewed. High average power LD-pumped Nd:YAG lasers with Q-switch have been developed and currently introduced into various applications. Optical fiber based laser beam delivery systems for Q-switched pulse laser are also being developed these years. Based on such laser and beam delivery technology, laser ablation processes are gradually introduced in maintenance of nuclear power plant, thermal power plant and electrical power distribution system. Cost effectiveness, robustness and reliability of the process is highly required for wide utilization in these fields.

  15. Mechanisms affecting kinetic energies of laser-ablated materials

    SciTech Connect

    Chen, K.R. |; Leboeuf, J.N.; Wood, R.F.; Geohegan, D.B.; Donato, J.M.; Liu, C.L.; Puretzky, A.A.

    1995-12-31

    Laser materials processing techniques are expected to have a dramatic impact on materials science and engineering in the near future and beyond. One of the main laser materials processing techniques is Pulsed Laser Deposition (PLD) for thin film growth. While experimentalists search for optimal approaches for thin film growth with pulsed laser deposition (PLD), a systematic effort in theory and modeling of various processes during PLD is needed. The quality of film deposited depends critically on the range and profile of the kinetic energy and density of the ablated plume. While it is to the advantage of pulsed laser deposition to have high kinetic energy, plumes that are too energetic causes film damage. A dynamic source effect was found to accelerate the plume expansion velocity much higher than that from a conventional free expansion model. A self-similar theory and a hydrodynamic model are developed to study this effect, which may help to explain experimentally observed high front expansion velocity. Background gas can also affect the kinetic energies. High background gas may cause the ablated materials to go backward. Experimentally observed plume splitting is also discussed.

  16. 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.

  17. Properties of zirconia thin films deposited by laser ablation

    SciTech Connect

    Cancea, V. N.; Filipescu, M.; Colceag, D.; Dinescu, M.; Mustaciosu, C.

    2013-11-13

    Zirconia thin films have been deposited by laser ablation of a ceramic ZrO{sub 2} target in vacuum or in oxygen background at 0.01 mbar. The laser beam generated by an ArF laser (λ=193 nm, ν=40 Hz) has been focalized on the target through a spherical lens at an incident angle of 45°. The laser fluence has been established to a value from 2.0 to 3.4 Jcm{sup −2}. A silicon (100) substrate has been placed parallel to the target, at a distance of 4 cm, and subsequently has been heated to temperatures ranging between 300 °C and 600 °C. Thin films morphology has been characterized by atomic force microscopy and secondary ion mass spectrometry. Biocompatibility of these thin films has been assessed by studying the cell attachment of L929 mouse fibroblasts.

  18. Properties of zirconia thin films deposited by laser ablation

    NASA Astrophysics Data System (ADS)

    Cancea, V. N.; Filipescu, M.; Colceag, D.; Mustaciosu, C.; Dinescu, M.

    2013-11-01

    Zirconia thin films have been deposited by laser ablation of a ceramic ZrO2 target in vacuum or in oxygen background at 0.01 mbar. The laser beam generated by an ArF laser (λ=193 nm, ν=40 Hz) has been focalized on the target through a spherical lens at an incident angle of 45°. The laser fluence has been established to a value from 2.0 to 3.4 Jcm-2. A silicon (100) substrate has been placed parallel to the target, at a distance of 4 cm, and subsequently has been heated to temperatures ranging between 300 °C and 600 °C. Thin films morphology has been characterized by atomic force microscopy and secondary ion mass spectrometry. Biocompatibility of these thin films has been assessed by studying the cell attachment of L929 mouse fibroblasts.

  19. 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.

  20. Laser Ablation of Polymer Microfluidic Devices

    NASA Astrophysics Data System (ADS)

    Killeen, Kevin

    2004-03-01

    Microfluidic technology is ideal for processing precious samples of limited volumes. Some of the most important classes of biological samples are both high in sample complexity and low in concentration. Combining the elements of sample pre-concentration, chemical separation and high sensitivity detection with chemical identification is essential for realizing a functional microfluidic based analysis system. Direct write UV laser ablation has been used to rapidly fabricate microfluidic devices capable of high performance liquid chromatography (HPLC)-MS. These chip-LC/MS devices use bio-compatible, solvent resistant and flexible polymer materials such as polyimide. A novel microfluidic to rotary valve interface enables, leak free, high pressure fluid switching between multiple ports of the microfluidic chip-LC/MS device. Electrospray tips with outer dimension of 50 um and inner of 15 um are formed by ablating the polymer material concentrically around a multilayer laminated channel structure. Biological samples of digested proteins were used to evaluate the performance of these microfluidic devices. Liquid chromatography separation and similar sample pretreatments have been performed using polymeric microfluidic devices with on-chip separation channels. Mass spectrometry was performed using an Agilent Technologies 1100 series ion trap mass spectrometer. Low fmol amounts of protein samples were positively and routinely identified by searching the MS/MS spectral data against protein databases. The sensitivity and separation performance of the chip-LC devices has been found to be comparable to state of the art nano-electrospray systems.

  1. Laser ablation in analytical chemistry-a review.

    PubMed

    Russo, Richard E; Mao, Xianglei; Liu, Haichen; Gonzalez, Jhanis; Mao, Samuel S

    2002-05-24

    Laser ablation is becoming a dominant technology for direct solid sampling in analytical chemistry. Laser ablation refers to the process in which an intense burst of energy delivered by a short laser pulse is used to sample (remove a portion of) a material. The advantages of laser ablation chemical analysis include direct characterization of solids, no chemical procedures for dissolution, reduced risk of contamination or sample loss, analysis of very small samples not separable for solution analysis, and determination of spatial distributions of elemental composition. This review describes recent research to understand and utilize laser ablation for direct solid sampling, with emphasis on sample introduction to an inductively coupled plasma (ICP). Current research related to contemporary experimental systems, calibration and optimization, and fractionation is discussed, with a summary of applications in several areas. PMID:18968642

  2. 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.

  3. Ablation characteristics of electrospun core-shell nanofiber by femtosecond laser.

    PubMed

    Park, ChangKyoo; Xue, Ruipeng; Lannutti, John J; Farson, Dave F

    2016-08-01

    This study examined the femtosecond laser ablation properties of core and shell polymers their relationship to the ablation characteristics of core-shell nanofibers. The single-pulse ablation threshold of bulk polycaprolactone (PCL) was measured to be 2.12J/cm(2) and that of bulk polydimethylsiloxane (PDMS) was 4.07J/cm(2). The incubation coefficients were measured to be 0.82±0.02 for PCL and 0.53±0.03 for PDMS. PDMS-PCL core-shell and pure PCL nanofibers were fabricated by electrospinning. The energy/volume of pure PCL and PDMS-PCL core-shell nanofiber ablation was investigated by measuring linear ablation grooves made at different scanning speeds. At large scanning speed, higher energy/volume was required for machining PDMS-PCL nanofiber than for PCL nanofiber. However, at small scanning speed, comparable energy/volume was measured for PDMS-PCL and PCL nanofiber ablation. Additionally, in linear scanned ablation of PDMS-PCL fibers at small laser pulse energy and large scanning speed, there were partially ablated fibers where the shell was ablated but the core remained. This was attributed to the lower ablation threshold of the shell material. PMID:27157748

  4. In situ Diagnostics During Carbon Nanotube Production by Laser Ablation

    NASA Technical Reports Server (NTRS)

    Arepalli, Sivaram

    1999-01-01

    The preliminary results of spectral analysis of the reaction zone during the carbon nanotube production by laser ablation method indicate synergetic dependence on dual laser setup. The emission spectra recorded from different regions of the laser ablated plume at different delay times from the laser pulses are used to map the temperatures of C2 and C3. These are compared with Laser Induced Fluorescence (LIF) spectra also obtained during production to model the growth mechanism of carbon nanotubes. Experiments conducted to correlate the spectral features with nanotube yields as a function of different production parameters will be discussed.

  5. Laser ablation synthesis and spectral characterization of ruby nanoparticles

    NASA Astrophysics Data System (ADS)

    Baranov, M. S.; Bardina, A. A.; Savelyev, A. G.; Khramov, V. N.; Khaydukov, E. V.

    2016-04-01

    The laser ablation method was implemented for synthesis of ruby nanoparticles. Nanoparticles were obtained by nanosecond ablation of bulk ruby crystal in 10% ethanol water solution. The nanoparticles enable water colloid stability and exhibit narrow photoluminescent line at 694 nm when pumped at blue-green spectral range. The ruby nanoparticles were characterized by SEM and Z-sizer.

  6. Surface Decontamination Using Laser Ablation Process - 12032

    SciTech Connect

    Moggia, Fabrice; Lecardonnel, Xavier; Damerval, Frederique

    2012-07-01

    A new decontamination method has been investigated and used during two demonstration stages by the Clean-Up Business Unit of AREVA. This new method is based on the use of a Laser beam to remove the contaminants present on a base metal surface. In this paper will be presented the type of Laser used during those tests but also information regarding the efficiency obtained on non-contaminated (simulated contamination) and contaminated samples (from the CEA and La Hague facilities). Regarding the contaminated samples, in the first case, the contamination was a quite thick oxide layer. In the second case, most of the contamination was trapped in dust and thin grease layer. Some information such as scanning electron microscopy (SEM), X-Ray scattering spectroscopy and decontamination factors (DF) will be provided in this paper. Laser technology appears to be an interesting one for the future of the D and D applications. As shown in this paper, the results in terms of efficiency are really promising and in many cases, higher than those obtained with conventional techniques. One of the most important advantages is that all those results have been obtained with no generation of secondary wastes such as abrasives, chemicals, or disks... Moreover, as mentioned in introduction, the Laser ablation process can be defined as a 'dry' process. This technology does not produce any liquid waste (as it can be the case with chemical process or HP water process...). Finally, the addition of a vacuum system allows to trap the contamination onto filters and thus avoiding any dissemination in the room where the process takes place. The next step is going to be a commercial use in 2012 in one of the La Hague buildings. (authors)

  7. Hydrocarbon level detection with nanosecond laser ablation

    NASA Astrophysics Data System (ADS)

    Bidin, Noriah; Hosseinian S, Raheleh; Nugroho, Waskito; Mohd Marsin, Faridah; Zainal, Jasman

    2013-12-01

    Nanosecond laser induced breakdown in liquid is used as a technique to detect hydrocarbon levels in water. A Q-switched Nd:YAG laser was focused to generate optical breakdown associated with shock wave generation. The shock wave was propagated at the speed of sound in the medium after travelling 1 μs outward from the center of optical breakdown. Different amplitudes of sound were traced with the aid of an ultrasonic probe. The optical properties of the hydrocarbon solution were quantified via fundamental refractive index measurement (the Snell law). A continuous mode diode pumped solid state laser with second harmonic generation was used as the illumination light source. A CCD video camera with Matrox version 4.2 software was utilized to analyze the recording image. Option line analysis was performed to analyze the intensity of optical breakdown at different input energies. Gray level analysis was also conducted on the scattering light after passing through the hydrocarbon solution at different concentrations. The hydrocarbon solution comprised impurities or particles that varied according to the concentration. The average of the gray level is assumed to present the size of the particle. Inherently, as the acoustic wave propagates outward, it transports the mass (particles or impurities) and impacts on the ultrasonic probe. As a result a higher concentration of hydrocarbons reveals a larger amplitude of sound waves. This phenomenon is identified as a finger print for hydrocarbon levels between 100 and 1000 ppm. The transient detection, without complicated sampling preparation and no hazardous chemical involvement, makes laser ablation a promising technique to detect in situ hydrocarbon levels in water.

  8. Ablation threshold and ablation mechanism transition of polyoxymethylene irradiated by CO2 laser.

    PubMed

    Li, Gan; Cheng, Mousen; Li, Xiaokang

    2016-09-01

    Polyoxymethylene (POM) decomposes gradually as it is heated up by the irradiation of CO2 laser; the long-chain molecules of POM are broken into short chains, which leads to the lowering of the melting point and the critical temperature of the ablation products. When the product temperature is above the melting point, ablation comes up in the way of vaporization; when the product temperature is higher than the critical temperature, all liquid products are transformed into gas instantly and the ablation mechanism is changed. The laser fluence at which significant ablation is observed is defined as the ablation threshold, and the fluence corresponding to the ablation mechanism changing is denoted as the flyover threshold. In this paper, random pyrolysis is adopted to describe the pyrolytic decomposition of POM, and consequently, the components of the pyrolysis products under different pyrolysis rates are acquired. The Group Contribution method is used to count the thermodynamic properties of the pyrolysis products, and the melting point and the critical temperature of the product mixture are obtained by the Mixing Law. The Knudsen layer relationship is employed to evaluate the ablation mass removal when the product temperature is below the critical temperature. The gas dynamics conservation laws associated with the Jouguet condition are used to calculate the mass removal when the product temperature is higher than the critical temperature. Based on the model, a set of simulations for various laser intensities and lengths are carried out to generalize the relationships between the thresholds and the laser parameters. Besides the ablated mass areal density, which fits the experimental data quite well, the ablation temperature, pyrolysis rate, and product components are also discussed for a better understanding of the ablation mechanism of POM. PMID:27607281

  9. IR laser ablation of doped poly(methyl methacrylate)

    NASA Astrophysics Data System (ADS)

    Gaspard, S.; Oujja, M.; Rebollar, E.; Walczak, M.; Díaz, L.; Santos, M.; Castillejo, M.

    2007-05-01

    We investigate the TEA CO 2 laser ablation of films of poly(methyl methacrylate), PMMA, with average MW 2.5, 120 and 996 kDa doped with photosensitive compounds iodo-naphthalene (NapI) and iodo-phenanthrene (PhenI) by examining the induced morphological and physicochemical modifications. The films casted on CaF 2 substrates were irradiated with a pulsed CO 2 laser (10P(20) line at 10.59 μm) in resonance with vibrational modes of PMMA and of the dopants at fluences up to 6 J/cm 2. Laser induced fluorescence probing of photoproducts in a pump and probe configuration is carried out at 266 nm. Formation of naphthalene (NapH) and phenanthrene (PhenH) is observed in NapI and PhenI doped PMMA, respectively, with relatively higher yields in high MW polymer, in similarity with results obtained previously upon irradiation in the UV at 248 nm. Above threshold, formation of photoproducts is nearly complete after 200 ms. As established via optical microscopy, bubbles are formed in the irradiated areas with sizes that depend on polymer MW and filaments are observed to be ejected out of the irradiated volume in the samples made with high MW polymer. The implications of these results for the mechanisms of polymer IR laser ablation are discussed and compared with UV range studies.

  10. [In vitro studies of shock wave effects during ablation of normal and atherosclerotic vascular wall by excimer laser].

    PubMed

    Haase, K K; Hanke, H; Baumbach, A; Wehrmann, M; Rose, C; Karsch, K R

    1993-02-01

    Ablation of atherosclerotic plaque and normal arterial wall was performed using a xenon-chloride-excimer laser with a wavelength of 308 nm and a pulse duration of 115 ns. The light was transmitted via a 600 micron fiber and adjusted to an energy density of 3.5 J/cm2. The acoustic signals generated by the laser pulse were measured with hydrophones consisting of polyvinylidenefluoride with active diameters of 0.3 mm and recorded on a dual-channel digital storage oscilloscope using either a 0.5 m coaxial cable or a broadband transmission system. From 19 cadavers human aortic tissue segments were excised and macroscopically classified as either normal or calcified atherosclerotic plaque. Approximately 500 measurements were performed in saline and blood each. Histological analysis was carried out after the experiments to verify the macroscopic diagnosis and to correlate the acoustic responses with the tissue characteristics. For "normal" arterial segments, maximum peak pressure was 1.25 MPa +/- 0.85 MPa, rise time 163 ns +/- 43 ns, and pressure increase 8.2 kPa +/- 5.4 kPa/ns in saline. For calcified, atheromatous segments a significantly higher maximum pressure (2.20 MPa +/- 1.16 MPa), a significantly shorter rise time (69.9 ns +/- 25.8 ns), and a significantly higher pressure increase (32.3 kPa +/- 21.3 kPa/ns) was found in saline (p < or = 0.0001). In blood, maximum peak pressure was 1.29 MPa +/- 0.43 MPa, rise time 93.3 ns +/- 27.7 ns, and pressure increase 14.6 kPa +/- 5.2 kPa/ns for "normal" arterial segments. Maximum peak pressure (2.28 MPa +/- 0.63 MPa) and pressure increase (32.8 kPa +/- Pa/ns) were significantly higher for calcified tissue segments.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:8465570

  11. Advantages of dual-laser ablation in the growth of multicomponent thin films

    NASA Astrophysics Data System (ADS)

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

    2012-07-01

    We report the use of a dual-laser deposition process to grow stoichiometric films of the piezoelectric material PbZr0.52Ti0.48O3 (PZT) and the thermoelectric material Ba8Ga16Ge30. High volatility of Pb and Ba in these materials leads to non-stoichiometric growth in conventional PLD processes. Dual-laser ablation process preserves the Pb and Ba stoichiometry while significantly reducing the thickness variation and particulate density on the deposited films. This lead to the growth of smooth uniform films with enhanced ferroelectric and electrical properties. The dual-laser ablation combines the pulses of a KrF excimer laser (248 nm wavelength, 30 ns pulse width) and a CO2 laser (10.6 μm wavelength, 250 ns pulse width) where the beams are spatially overlapped on the ablation target and temporally delayed. At an optimum delay that is dependent on the physical properties of the material, CO2 pulse energy is coupled into the plume, generating a high temperature plasma (>25,000K). Laser-target interaction studies have shown the evaporation to be stoichiometric. Emission spectroscopy studies have shown ten-fold increase in emission intensities in dual-laser ablation while time-gated 2D ICCD imaging studies revealed the plume expansion to be stoichiometric over a large cone-angle of the plume under these conditions. Time-of-flight investigations in concert with hydrodynamic modeling provided a clear understanding of the mechanism of dual-laser ablation. Furthermore, plasma generated in the process is highly ionized (>75%) leading to films with high density and crystallinity. This paper will show the enhancement in properties attainable by the dual-laser ablation process in comparison to the single laser ablation.

  12. Simulation of laser ablation of metals for nanoparticles production

    NASA Astrophysics Data System (ADS)

    Davydov, R. V.; Antonov, V. I.; Davydova, T. I.

    2016-03-01

    In this paper a mathematical model for femtosecond laser ablation of metals is proposed, based on standard two-temperature model connected with 1D hydrodynamic equations. Wide-range equation of state has been developed. The simulation results are compared with experimental data for aluminium and copper. A good agreement for both metals with numerical results and experiment shows that this model can be employed for choosing laser parameters to better accuracy in nanoparticles production by ablation of metals.

  13. A laser ablation source for offline ion production at LEBIT

    NASA Astrophysics Data System (ADS)

    Izzo, C.; Bollen, G.; Bustabad, S.; Eibach, M.; Gulyuz, K.; Morrissey, D. J.; Redshaw, M.; Ringle, R.; Sandler, R.; Schwarz, S.; Valverde, A. A.

    2016-06-01

    A laser ablation ion source has been developed and implemented at the Low-Energy Beam and Ion Trap (LEBIT) facility at the National Superconducting Cyclotron Laboratory. This offline ion source enhances the capabilities of LEBIT by providing increased access to ions used for calibration measurements and checks of systematic effects as well as stable and long-lived ions of scientific interest. The design of the laser ablation ion source and a demonstration of its successful operation are presented.

  14. Momentum Transfer by Laser Ablation of Irregularly Shaped Space Debris

    SciTech Connect

    Liedahl, D A; Libby, S B; Rubenchik, A

    2010-02-04

    Proposals for ground-based laser remediation of space debris rely on the creation of appropriately directed ablation-driven impulses to either divert the fragment or drive it into an orbit with a perigee allowing atmospheric capture. For a spherical fragment, the ablation impulse is a function of the orbital parameters and the laser engagement angle. If, however, the target is irregularly shaped and arbitrarily oriented, new impulse effects come into play. Here we present an analysis of some of these effects.

  15. Momentum Transfer by Laser Ablation of Irregularly Shaped Space Debris

    SciTech Connect

    Liedahl, Duane A.; Libby, Stephen B.; Rubenchik, Alexander

    2010-10-08

    Proposals for ground-based laser remediation of space debris rely on the creation of appropriately directed ablation-driven impulses to either divert the fragment or drive it into an orbit with a perigee allowing atmospheric capture. For a spherical fragment, the ablation impulse is a function of the orbital parameters and the laser engagement angle. If, however, the target is irregularly shaped and arbitrarily oriented, new impulse effects come into play. Here we present an analysis of some of these effects.

  16. 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.

  17. Preparation of platinum nanoparticles in liquids by laser ablation method

    NASA Astrophysics Data System (ADS)

    Binh Nguyen, The; Dinh Nguyen, Thanh; Nguyen, Quang Dong; Trinh Nguyen, Thi

    2014-09-01

    Platinum (Pt) nanoparticles were prepared in solutions of ethanol and TSC (trisodium citrate—Na3C6H5O7.nH2O) in water by laser ablation method using Nd:YAG laser. The role of laser fluence, laser wavelength and concentration of surfactant liquids in laser ablation process were investigated. The morphology, size distribution and optical properties of the Pt nanoparticles (NPs) were observed by transmission electron microscopy (TEM), UV-vis spectrometer and x-ray diffraction measurements. The average diameter of Pt NPs prepared in ethanol and TSC solutions ranges around 7-9 nm and 10-12 nm, respectively. The results showed advantages of the laser ablation method.

  18. Laser ablation for the synthesis of carbon nanotubes

    SciTech Connect

    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.

  19. 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.

  20. 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.

  1. Comparison of High Rate Laser Ablation and Resulting Structures Using Continuous and Pulsed Single Mode Fiber Lasers

    NASA Astrophysics Data System (ADS)

    Knebel, T.; Streek, A.; Exner, H.

    This paper compares high rate laser ablation and resulting structures of aluminum by using both a continuous wave and a ns-pulsed single mode fiber laser of high average laser power. Two different scan technologies were applied for fast deflection of the laser beams. In this work, 2.5D laser processing was studied by using a high aperture galvanometer scanner with a maximum scan speed of 18 m/s. By contrast, considerably higher scan speeds up to 1,000 m/s were achieved by using the in-house developed polygon scanner system. The ablation rates and the processing rates per unit area were analyzed by means of the depths of line-scan ablation tracks and laser processed cavities. In addition, SEM photograph of the machining samples will be presented in order to evaluate the machining quality. Finally the feasibility of this high rate technology for industrial application is demonstrated by machining examples.

  2. Preclinical Assessment of a 980-nm Diode Laser Ablation System in a Large Animal Tumor Model

    PubMed Central

    Ahrar, Kamran; Gowda, Ashok; Javadi, Sanaz; Borne, Agatha; Fox, Matthew; McNichols, Roger; Ahrar, Judy U.; Stephens, Clifton; Stafford, R. Jason

    2010-01-01

    Purpose To characterize the performance of a 980-nm diode laser ablation system in an in vivo tumor model. Materials and Methods This study was approved by the Institutional Animal Care and Use Committee. The ablation system consisted of a 15-W, 980-nm diode laser, flexible diffusing tipped fiber optic, and 17-gauge internally cooled catheter. Ten immunosuppressed dogs were inoculated subcutaneously with canine transmissible venereal tumor fragments in eight dorsal locations. Laser ablations were performed at 79 sites where inoculations were successful (99%) using powers of 10 W, 12.5 W, and 15 W, with exposure times between 60 and 180 seconds. In 20 cases, multiple overlapping ablations were performed. After the dogs were euthanized, the tumors were harvested, sectioned along the applicator track, measured and photographed. Measurements of ablation zone were performed on gross specimen. Histopathology and viability staining was performed using hematoxylin and eosin (H&E) and nicotinamide adenine dinucleotide hydrogen (NADH) staining. Results Gross pathology confirmed well-circumscribed ablation zone with sharp boundaries between thermally ablated tumor in the center surrounded by viable tumor tissue. When a single applicator was used, the greatest ablation diameters ranged from 12 mm at the lowest dose (10 W, 60 sec) to 26 mm at the highest dose (15 W, 180 sec). Multiple applicators created ablation zones of up to 42 mm in greatest diameter (with the lasers operating at 15 W for 120 sec). Conclusions The new 980-nm diode laser and internally cooled applicator effectively creates large ellipsoid thermal ablations in less than 3 minutes. PMID:20346883

  3. Comparison of the erbium-yttrium aluminum garnet and carbon dioxide lasers for in vitro bone and cartilage ablation

    SciTech Connect

    Gonzalez, C.; van de Merwe, W.P.; Smith, M.; Reinisch, L. )

    1990-01-01

    The in vitro bone- and cartilage-ablation characteristics of the solid-state erbium:yttrium aluminum garnet laser were compared to those of the carbon dioxide laser. Ablations of fresh, frozen cadaver septal cartilage and maxillary sinus bone were performed using total energies between 1 and 6 J. Specimens were studied using hematoxylin and eosin stain and digitized, computer-assisted measurements of 35-mm photographs. Erbium-yttrium aluminum garnet-ablated bone averaged 5 microns of adjacent tissue thermal injury, compared with 67 microns with carbon dioxide-ablated bone. Erbium-yttrium aluminum garnet-ablated cartilage averaged 2 microns of adjacent tissue thermal injury, compared with 21 microns with the carbon dioxide-ablated cartilage. The tissue-ablation characteristics of the erbium-yttrium aluminum garnet laser are promising for future otolaryngologic applications.

  4. Ablation of CsI by XUV Capillary Discharge Laser

    NASA Astrophysics Data System (ADS)

    Pira, Peter; Zelinger, Zdenek; Burian, Tomas; Vysin, Ludek; Wild, Jan; Juha, Libor; Lancok, Jan; Nevrly, Vaclav

    2015-09-01

    XUV capillary discharge laser (CDL) is suitable source for ablation of ionic crystals as material which is difficult to ablate by conventional laser. Single crystal of CsI was irradiated by 2.5 ns pulses of a 46.9 nm radiation at 2 Hz. The CDL beam was focused by Sc/Si multilayer spherical mirror. Attenuation length of CsI for this wavelength is 38 nm. Ablation rate was calculated after irradiation of 10, 20, 30, 50 and 100 pulses. Depth of the craters was measured by optical profiler (white light interferometry). Ablation threshold was determined from craters after irradiation with the changing fluence and compared with modeling by XUV-ABLATOR.

  5. 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

  6. Characterization of excimer laser ablation generated pepsin particles using multi-wavelength photoacoustic instrument

    NASA Astrophysics Data System (ADS)

    Hopp, B.; Kecskeméti, G.; Smausz, T.; Ajtai, T.; Filep, A.; Utry, N.; Kohut, A.; Bozóki, Z.; Szabó, G.

    2012-05-01

    Preparation of organic thin layers on various special substrates using the pulsed laser deposition (PLD) technique is an important task from the point of view of bioengineering and biosensor technologies. Earlier studies demonstrated that particle ejection starts during the ablating laser pulse resulting in significant shielding effects which can influence the real fluence on the target surface and consequently the efficiency of layer preparation. In this study, we introduce a photoacoustic absorption measurement technique for in-situ characterization of ablated particles during PLD experiments. A KrF excimer laser beam ( λ=248 nm, FWHM=18 ns) was focused onto pepsin targets in a PLD chamber; the applied laser fluences were 440 and 660 mJ/cm2. We determined the wavelength dependence of optical absorption and mass specific absorption coefficient of laser ablation generated pepsin aerosols in the UV-VIS-NIR range. On the basis of our measurements, we calculated the absorbance at the ablating laser wavelength, too. We demonstrated that when the laser ablation generated pepsin aerosols spread through the whole PLD chamber the effect of absorptivity is negligible for the subsequent pulses. However, the interaction of the laser pulse and the just formed particle cloud generated by the same pulse is more significant.

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

    SciTech Connect

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

    2009-08-01

    The ablation depth in planar Sn targets irradiated with a pulsed 1064 nm laser was investigated over laser intensities from 3x10{sup 11} to 2x10{sup 12} W/cm{sup 2}. 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.

  8. Control of laser-ablation plasma potential with external electrodes

    SciTech Connect

    Isono, Fumika Nakajima, Mitsuo; Hasegawa, Jun; Kawamura, Tohru; Horioka, Kazuhiko

    2015-08-15

    The potential of a laser-ablation plasma was controlled stably up to +2 kV by using external ring electrodes. A stable electron sheath was formed between the plasma and the external electrodes by placing the ring electrodes away from the boundary of the drifting plasma. The plasma kept the potential for a few μs regardless of the flux change of the ablation plasma. We also found that the plasma potential changed with the expansion angle of the plasma from the target. By changing the distance between the plasma boundary and the external electrodes, we succeeded in controlling the potential of laser-ablation plasma.

  9. Bubble formation induced by nanosecond laser ablation in water and its diagnosis by optical transmission technique

    NASA Astrophysics Data System (ADS)

    Mahdieh, M. H.; Akbari Jafarabadi, M.

    2014-09-01

    In this paper, bubble formation and ablation rate in laser ablation of a thin-film aluminum target are studied. The target was an aluminum thin-film coated on a quartz substrate and interacted by a nanosecond Nd:YAG laser beam in ambient air and distilled water. Measuring optical transmission of a He-Ne beam through the ablation region shows that the ablation rate in water is higher than that in ambient air. The results also show that an initial peak appears in the transmission signal which is an evidence for bubble formation in water. Analyzing the data is useful for monitoring the bubble formation in water and relatively estimating the ablation rate.

  10. Mechanisms of Carbon Nanotube Production by Laser Ablation Process

    NASA Technical Reports Server (NTRS)

    Scott, Carl D.; Arepalli, Sivaram; Nikolaev, Pavel; Smalley, Richard E.; Nocholson, Leonard S. (Technical Monitor)

    2000-01-01

    We will present possible mechanisms for nanotube production by laser oven process. Spectral emission of excited species during laser ablation of a composite graphite target is compared with that of laser irradiated C60 vapor. The similarities in the transient and spectral data suggest that fullerenes are intermediate precursors for nanotube formation. The confinement of the ablation products by means of a 25-mm diameter tube placed upstream of the target seems to improve the production and purity of nanotubes. Repeated laser pulses vaporize the amorphous/graphitic carbon and possibly catalyst particles, and dissociate fullerenes yielding additional feedstock for SWNT growth.

  11. Growth modes of ZnO nanostructures from laser ablation

    SciTech Connect

    Amarilio-Burshtein, I.; Tamir, S.; Lifshitz, Y.

    2010-03-08

    ZnO nanowires (NWs) and other nanostructures were grown by laser ablation of a ZnO containing target onto different substrates with and without the presence of an Au catalyst. The morphology and structure of the NWs were studied using high resolution scanning and transmission electron microscopes [including imaging, selected area electron diffraction (SAED), and energy dispersive x-ray spectroscopy (EDS)]. The different growth modes obtainable could be tuned by varying the Zn concentration in the vapor phase keeping other growth parameters intact. Possible growth mechanisms of these nanowires are suggested and discussed.

  12. Growth modes of ZnO nanostructures from laser ablation

    NASA Astrophysics Data System (ADS)

    Amarilio-Burshtein, I.; Tamir, S.; Lifshitz, Y.

    2010-03-01

    ZnO nanowires (NWs) and other nanostructures were grown by laser ablation of a ZnO containing target onto different substrates with and without the presence of an Au catalyst. The morphology and structure of the NWs were studied using high resolution scanning and transmission electron microscopes [including imaging, selected area electron diffraction (SAED), and energy dispersive x-ray spectroscopy (EDS)]. The different growth modes obtainable could be tuned by varying the Zn concentration in the vapor phase keeping other growth parameters intact. Possible growth mechanisms of these nanowires are suggested and discussed.

  13. MRI-guided laser ablation of neuroendocrine tumor hepatic metastases

    PubMed Central

    Perälä, Jukka; Klemola, Rauli; Kallio, Raija; Li, Chengli; Vihriälä, Ilkka; Salmela, Pasi I; Tervonen, Osmo

    2014-01-01

    Background Neuroendocrine tumors (NET) represent a therapeutically challenging and heterogeneous group of malignancies occurring throughout the body, but mainly in the gastrointestinal system. Purpose To describe magnetic resonance imaging (MRI)-guided laser ablation of NET liver metastases and assess its role within the current treatment options and methods. Material and Methods Two patients with NET tumor hepatic metastases were treated with MRI-guided interstitial laser ablation (LITT). Three tumors were treated. Clinical follow-up time was 10 years. Results Both patients were successfully treated. There were no local recurrences at the ablation site during the follow-up. Both patients had survived at 10-year follow-up. One patient is disease-free. Conclusion MRI-guided laser ablation can be used to treat NET tumor liver metastases but combination therapy and a rigorous follow-up schedule are recommended. PMID:24778794

  14. Combination of erbium and holmium laser radiation for tissue ablation

    NASA Astrophysics Data System (ADS)

    Pratisto, Hans S.; Frenz, Martin; Koenz, Flurin; Altermatt, Hans J.; Weber, Heinz P.

    1996-05-01

    Erbium lasers emitting at 2.94 micrometers and holmium lasers emitting at 2.1 micrometers are interesting tools for cutting, drilling, smoothing and welding of water containing tissues. The high absorption coefficient of water at these wavelengths leads to their good ablation efficiency with controlled thermally altered zones around the ablation sites. Combination of pulses with both wavelengths transmitted through one fiber were used to perform incisions in soft tissue and impacts in bone disks. Histological results and scanning electron microscope evaluations reveal the strong influence of the absorption coefficient on tissue effects, especially on the ablation efficiency and the zone of thermally damaged tissue. It is demonstrated that the combination of high ablation rates and deep coagulation zones can be achieved. The results indicate that this laser system can be considered as a first step towards a multi-functional medical instrument.

  15. Laser cutting of carbon fiber reinforced plastics (CFRP) by UV pulsed laser ablation

    NASA Astrophysics Data System (ADS)

    Niino, Hiroyuki; Kurosaki, Ryozo

    2011-03-01

    In this paper, we report on a micro-cutting of carbon fiber reinforced plastics (CFRP) by nanosecond-pulsed laser ablation with a diode-pumped solid state UV laser (DPSS UV laser, λ= 355nm). A well-defined cutting of CFRP which were free of debris and thermal-damages around the grooves, were performed by the laser ablation with a multiple-scanpass irradiation method. CFRP is a high strength composite material with a lightweight, and is increasingly being used various applications. UV pulsed laser ablation is suitable for laser cutting process of CFRP materials, which drastically reduces a thermal damage at cut regions.

  16. Excimer laser ablation of polymer-clay nanocomposites

    NASA Astrophysics Data System (ADS)

    Chang, I.-Ta

    The ablation behavior of Polystyrene-Organically Modified Montmorillonite (OMMT) nanocomposites was evaluated by measuring the weight loss induced by KrF excimer laser irradiation of the nanocomposite specimens under air atmosphere. The characteristic values of ablation, ablation threshold fluence and effective absorption coefficient for polystyrene and its naonocomposites were calculated based on the weight loss data. The effects of morphology due to spatial variation in injection molded samples are also discussed in this work. Results demonstrate that both the dispersion state and the concentration of clay play important roles in excimer laser ablation. The sensitivity of threshold fluence and absorption coefficient to dispersion state of OMMT depends on the clay concentration. The excimer laser induced surface micro/nano structure formation and modification of PS-Clay Nanocomposites at various OMMT concentrations were also investigated. Scanning electron microscopy, atomic force microscopy and Fourier Transform Infrared (FTIR) spectroscopy with attenuated total reflectance accessory were utilized to analyze the ablated surface. Results show that, in general, better dispersion of OMMT leads to less continuous surface structures and more pronounced carbonyl regions on FTIR spectra. Clay nanoparticles are exposed on ablated surfaces and affect surface structure formation after irradiation by laser. A mechanism for the formation of excimer laser induced surface structures on injection molded parts is thus proposed.

  17. YSGG 2790-nm superficial ablative and fractional ablative laser treatment.

    PubMed

    Smith, Kevin C; Schachter, G Daniel

    2011-05-01

    The 2790-nm wavelength YSGG laser was introduced for aesthetic purposes under the trade name Pearl by Cutera in 2007. In clinical use, the Pearl superficial resurfacing laser has proved effective and well tolerated for the correction of superficial brown epidermal dyschromia and superficial fine lines and scars, and the Pearl Fractional laser produces excellent improvement in both dyschromia and improvement of deeper lines and moderately deep acne scarring. The two laser treatments can be combined in a single treatment session on different parts of the face or on the entire face, depending on patient needs and priorities. PMID:21763987

  18. Improving Consistency in Laser Ablation Geochronology

    NASA Astrophysics Data System (ADS)

    Horstwood, Matt; Gehrels, George; Bowring, James

    2010-07-01

    Workshop on Data Handling in LA-ICP-MS U-Th-Pb Geochronology; San Francisco, California, 12-13 December 2009; The use of uranium-thorium-lead (U-Th-Pb) laser ablation-inductively coupled plasma mass spectrometry (LA-ICP-MS) geochronology involves rapid analysis of U-and Th-rich accessory minerals. It routinely achieves 1-2% precision for U-Th-Pb dates constituting detrital mineral age spectra and for dating igneous and metamorphic events. The speed and low setup and analysis cost of LA-ICP-MS U-Th-Pb geochronology has led to a proliferation of active laboratories. Tens of thousands of analyses are produced per month, but there is little agreement on how to transform these data into accurate U-Th-Pb dates. Recent interlaboratory blind comparisons of zircon samples indicate that resolvable biases exist among laboratories and the sources of bias are not fully understood. Common protocols of data reduction and reporting are essential for scientists to be able to compare and interpret these data accurately.

  19. Efficient space propulsion engines based on laser ablation

    SciTech Connect

    Phipps, C.R.

    1993-08-01

    Recent results have shown laser momentum transfer coefficients C{sub m} as large as 700 dynes/J from visible and near-infrared laser pulses with heterogeneous targets. Using inexpensive target materials, it is now possible to deliver a 1-tonne satellite from LEO to GEO in 21 days using a 10-kW onboard laser ablation engine, or to maintain several 1-tonne GEO satellites on station from Earth indefinitely using a laser with 100-W average power.

  20. Transmission of 1064 nm laser radiation during ablation with an ultra-short pulse laser (USPL) system

    NASA Astrophysics Data System (ADS)

    Schelle, Florian; Meister, Jörg; Oehme, Bernd; Frentzen, Matthias

    2012-01-01

    During ablation of oral hard tissue with an USPL system a small amount of the incident laser power does not contribute to the ablation process and is being transmitted. Partial transmission of ultra-short laser pulses could potentially affect the dental pulp. The aim of this study was to assess the transmission during ablation and to deduce possible risks for the patient. The study was performed with an Nd:YVO4 laser, emitting pulses with a duration of 8 ps at a wavelength of 1064 nm. A repetition rate of 500 kHz and an average power of 9 W were chosen to achieve high ablation efficiency. A scanner system created square cavities with an edge length of 1 mm. Transmission during ablation of mammoth ivory and dentin slices with a thickness of 2 mm and 5 mm was measured with a power meter, placed directly beyond the samples. Effects on subjacent blood were observed by ablating specimens placed in contact to pork blood. In a separate measurement the temperature increase during ablation was monitored using an infrared camera. The influence of transmission was assessed by tuning down the laser to the corresponding power and then directly irradiating the blood. Transmission during ablation of 2 mm specimens was about 7.7% (ivory) and 9.6% (dentin) of the incident laser power. Ablation of specimens directly in contact to blood caused coagulation at longer irradiation times (t~18s). Direct irradiation of blood with the transmitted power provoked bubbling and smoke formation. Temperature measurements identified heat generation as the main reason for the observed coagulation.

  1. Treatment planning for prostate focal laser ablation in the face of needle placement uncertainty

    SciTech Connect

    Cepek, Jeremy Fenster, Aaron; Lindner, Uri; Trachtenberg, John; Davidson, Sean R. H.; Haider, Masoom A.; Ghai, Sangeet

    2014-01-15

    Purpose: To study the effect of needle placement uncertainty on the expected probability of achieving complete focal target destruction in focal laser ablation (FLA) of prostate cancer. Methods: Using a simplified model of prostate cancer focal target, and focal laser ablation region shapes, Monte Carlo simulations of needle placement error were performed to estimate the probability of completely ablating a region of target tissue. Results: Graphs of the probability of complete focal target ablation are presented over clinically relevant ranges of focal target sizes and shapes, ablation region sizes, and levels of needle placement uncertainty. In addition, a table is provided for estimating the maximum target size that is treatable. The results predict that targets whose length is at least 5 mm smaller than the diameter of each ablation region can be confidently ablated using, at most, four laser fibers if the standard deviation in each component of needle placement error is less than 3 mm. However, targets larger than this (i.e., near to or exceeding the diameter of each ablation region) require more careful planning. This process is facilitated by using the table provided. Conclusions: The probability of completely ablating a focal target using FLA is sensitive to the level of needle placement uncertainty, especially as the target length approaches and becomes greater than the diameter of ablated tissue that each individual laser fiber can achieve. The results of this work can be used to help determine individual patient eligibility for prostate FLA, to guide the planning of prostate FLA, and to quantify the clinical benefit of using advanced systems for accurate needle delivery for this treatment modality.

  2. Ultrafast laser ablation for targeted atherosclerotic plaque removal

    NASA Astrophysics Data System (ADS)

    Lanvin, Thomas; Conkey, Donald B.; Descloux, Laurent; Frobert, Aurelien; Valentin, Jeremy; Goy, Jean-Jacques; Cook, Stéphane; Giraud, Marie-Noelle; Psaltis, Demetri

    2015-07-01

    Coronary artery disease, the main cause of heart disease, develops as immune cells and lipids accumulate into plaques within the coronary arterial wall. As a plaque grows, the tissue layer (fibrous cap) separating it from the blood flow becomes thinner and increasingly susceptible to rupturing and causing a potentially lethal thrombosis. The stabilization and/or treatment of atherosclerotic plaque is required to prevent rupturing and remains an unsolved medical problem. Here we show for the first time targeted, subsurface ablation of atherosclerotic plaque using ultrafast laser pulses. Excised atherosclerotic mouse aortas were ablated with ultrafast near-infrared (NIR) laser pulses. The physical damage was characterized with histological sections of the ablated atherosclerotic arteries from six different mice. The ultrafast ablation system was integrated with optical coherence tomography (OCT) imaging for plaque-specific targeting and monitoring of the resulting ablation volume. We find that ultrafast ablation of plaque just below the surface is possible without causing damage to the fibrous cap, which indicates the potential use of ultrafast ablation for subsurface atherosclerotic plaque removal. We further demonstrate ex vivo subsurface ablation of a plaque volume through a catheter device with the high-energy ultrafast pulse delivered via hollow-core photonic crystal fiber.

  3. Evaluation of explosive sublimation as the mechanism of nanosecond laser ablation of tungsten under vacuum conditions

    NASA Astrophysics Data System (ADS)

    Oderji, Hassan Yousefi; Farid, Nazar; Sun, Liying; Fu, Cailong; Ding, Hongbin

    2016-08-01

    A non-equilibrium mechanism for nanosecond laser ablation is suggested herein, and its predictions are compared to the results of W experiments performed under vacuum conditions. A mechanism of particle formation is explained via this model, with partial sublimation of the superheated irradiated zone of the target considered to be the mechanism of laser ablation. In this study, a mixture of vapor and particles was explosively generated and subsequently prevented the rest of a laser pulse from reaching its intended target. This mechanism was found to play an essential role in the ablation of W under vacuum conditions, and it provides a theoretical justification for particle formation. Moreover, special considerations were taken into account for the expansion of plasma into a vacuum. The model was evaluated by measuring the mass of ablated particles using a quartz crystal deposition monitor and time-resolved optical emission spectroscopy. The results of this model were found to be in good agreement with experimental values.

  4. Comparison of transcatheter laser and direct-current shock ablation of endocardium near tricuspid anulus

    NASA Astrophysics Data System (ADS)

    Zhang, Yu-Zhen; Wang, Shi-Wen; Li, Junheng

    1993-03-01

    Forty to eighty percent of the patients with accessory pathways (APs) manifest themselves by tachyarrhythmias. Many of these patients needed either life-long medical therapy or surgery. In order to avoid the discomfort and expenses in surgical procedures, closed chest percutaneous catheter ablation of APs became a potentially desirable therapeutic approach. Many investigations indicated that ablation of right APs by transcatheter direct current (dc) shock could cause life-threatening arrhythmias, right coronary arterical (RCA) spasm, etc. With the development of transcatheter laser technique, it has been used in drug-incurable arrhythmias. The results show that laser ablation is much safer than surgery and electric shock therapy. The purpose of this study is to explore the effectiveness, advantages, and complications with transcatheter Nd:YAG laser and dc shock in the ablation of right atrioventricular accessory pathways in the atrium near the tricuspid annulus (TA) in 20 dogs.

  5. ZnO nanoparticles obtained by pulsed laser ablation and their composite with cotton fabric: Preparation and study of antibacterial activity

    NASA Astrophysics Data System (ADS)

    Svetlichnyi, Valery; Shabalina, Anastasiia; Lapin, Ivan; Goncharova, Daria; Nemoykina, Anna

    2016-05-01

    A simple deposition method was used to prepare a ZnO/cotton fabric composite from water and ethanol dispersions of ZnO nanoparticles obtained by the pulsed laser ablation method. The structure and composition of the nanoparticles from dispersions and as-prepared composites were studied using electron microscopy, X-ray diffraction, and spectroscopy. The nanoparticles and composite obtained exhibited antibacterial activity to three different pathogenic microorganisms-Escherichia coli, Staphylococcus aureus, and Bacillus subtilis. An attempt to understand a mechanism of bactericidal effect of ZnO nanoparticles was made. It was shown that zinc ions and hydrogen peroxide were not responsible for antibacterial activity of the particles and the composite, and surface properties of nanoparticles played an important role in antibacterial activity of zinc oxide. The proposed composite is a promising material for use as an antibacterial bandage.

  6. Femtosecond laser ablation of polytetrafluoroethylene (Teflon) in ambient air

    NASA Astrophysics Data System (ADS)

    Wang, Z. B.; Hong, M. H.; Lu, Y. F.; Wu, D. J.; Lan, B.; Chong, T. C.

    2003-05-01

    Teflon, polytetrafluorethylene (PTFE), is an important material in bioscience and medical application due to its special characteristics (bio-compatible, nonflammable, antiadhesive, and heat resistant). The advantages of ultrashort laser processing of Teflon include a minimal thermal penetration region and low processing temperatures, precision removal of material, and good-quality feature definition. In this paper, laser processing of PTFE in ambient air by a Ti:sapphire femtosecond laser (780 nm, 110 fs) is investigated. It is found that the pulse number on each irradiated surface area must be large enough for a clear edge definition and the ablated depth increases with the pulse number. The air ionization effect at high laser fluences not only degrades the ablated structures quality but also reduces the ablation efficiency. High quality microstructures are demonstrated with controlling laser fluence below a critical fluence to exclude the air ionization effect. The ablated microstructures show strong adhesion property to liquids and clear edges that are suitable for bio-implantation applications. Theoretical calculation is used to analyze the evolution of the ablated width and depth at various laser fluences.

  7. Early plume and shock wave dynamics in atmospheric-pressure ultraviolet-laser ablation of different matrix-assisted laser ablation matrices

    SciTech Connect

    Schmitz, Thomas A.; Koch, Joachim; Guenther, Detlef; Zenobi, Renato

    2011-06-15

    Pulsed laser ablation of molecular solids is important for identification and quantification in (bio-)organic mass spectrometry, for example using matrix-assisted laser desorption/ionization (MALDI). Recently, there has been a major shift to using MALDI and related laser ablation/post-ionization methods at atmospheric pressure. However, the underlying laser ablation processes, in particular early plume formation and expansion, are still poorly understood. Here, we present a study of the early ablation processes on the ns-time scale in atmospheric pressure UV-laser ablation of anthracene as well as of different common MALDI matrices such as 2,5-dihydroxybenzoic acid (2,5-DHB), {alpha}-cyano-4-hydroxycinnamic acid and sinapinic acid. Material release as well as the formation and expansion of hemi-spherical shock waves were studied by shadowgraphy with high temporal resolution ({approx}5 ns). The applicability of the classical Taylor-Sedov model for expansion of strong shock waves ('point-blast model'), as well as the drag force model, were evaluated to mathematically describe the observed shock wave propagation. The time- and energy-dependent expansion of the shock waves could be described using a Taylor-Sedov scaling law of the form R {proportional_to} t{sup q}, when a q-exponent of {approx}0.5 instead of the theoretical value of q 0.4 was found, indicating a faster expansion than expected. The deviations from the ideal value of q were attributed to the non-negligible influence of ambient pressure, a weak versus strong shock regime, and additional acceleration processes present in laser ablation that surpass the limit of the point-blast model. The onset of shock wave formation at a fluence of {approx}15-30 mJ/cm{sup 2} for the compounds investigated coincides with the onset of bulk material release, whereas, pure desorption below this fluence threshold did not lead to features visible in shadowgraphy.

  8. [INVITED] Control of femtosecond pulsed laser ablation and deposition by temporal pulse shaping

    NASA Astrophysics Data System (ADS)

    Garrelie, Florence; Bourquard, Florent; Loir, Anne--Sophie; Donnet, Christophe; Colombier, Jean-Philippe

    2016-04-01

    This study explores the effects of temporal laser pulse shaping on femtosecond pulsed laser deposition (PLD). The potential of laser pulses temporally tailored on ultrafast time scales is used to control the expansion and the excitation degree of ablation products including atomic species and nanoparticles. The ablation plume generated by temporally shaped femtosecond pulsed laser ablation of aluminum and graphite targets is studied by in situ optical diagnostic methods. Taking advantage of automated pulse shaping techniques, an adaptive procedure based on spectroscopic feedback regulates the irradiance for the enhancement of typical plasma features. Thin films elaborated by unshaped femtosecond laser pulses and by optimized sequence indicate that the nanoparticles generation efficiency is strongly influenced by the temporal shaping of the laser irradiation. The ablation processes leading either to the generation of the nanoparticles either to the formation of plasma can be favored by using a temporal shaping of the laser pulse. Insights are given on the possibility to control the quantity of the nanoparticles. The temporal laser pulse shaping is shown also to strongly modify the laser-induced plasma contents and kinetics for graphite ablation. Temporal pulse shaping proves its capability to reduce the number of slow radicals while increasing the proportion of monomers, with the addition of ionized species in front of the plume. This modification of the composition and kinetics of plumes in graphite ablation using temporal laser pulse shaping is discussed in terms of modification of the structural properties of deposited Diamond-Like Carbon films (DLC). This gives rise to a better understanding of the growth processes involved in femtosecond-PLD and picosecond-PLD of DLC suggesting the importance of neutral C atoms, which are responsible for the subplantation process.

  9. Laser-solid interaction and dynamics of the laser-ablated materials

    SciTech Connect

    Chen, K.R.; Leboeuf, J.N.; Geohegan, D.B.; Wood, R.F.; Donato, J.M.; Liu, C.L.; Puretzky, A.A.

    1995-07-01

    Rapid transformations through the liquid and vapor phases induced by laser-solid interactions are described by the authors` thermal model with the Clausius-Clapeyron equation to determine the vaporization temperature under different surface pressure condition. Hydrodynamic behavior of the vapor during and after ablation is described by gas dynamic equations. These two models are coupled. Modeling results show that lower background pressure results lower laser energy density threshold for vaporization. The ablation rate and the amount of materials removed are proportional to the laser energy density above its threshold. The authors also demonstrate a dynamic source effect that accelerates the unsteady expansion of laser-ablated material in the direction perpendicular to the solid. A dynamic partial ionization effect is studied as well. A self-similar theory shows that the maximum expansion velocity is proportional to c{sub s}{alpha}, where 1 {minus} {alpha} is the slope of the velocity profile. Numerical hydrodynamic modeling is in good agreement with the theory. With these effects, {alpha} is reduced. Therefore, the expansion front velocity is significantly higher than that from conventional models. The results are consistent with experiments. They further study how the plume propagates in high background gas condition. Under appropriate conditions, the plume is slowed down, separates with the background, is backward moving, and hits the solid surface. Then, it splits into two parts when it rebounds from the surface. The results from the modeling will be compared with experimental observations where possible.

  10. UV solid state laser ablation of intraocular lenses

    NASA Astrophysics Data System (ADS)

    Apostolopoulos, A.; Lagiou, D. P.; Evangelatos, Ch.; Spyratou, E.; Bacharis, C.; Makropoulou, M.; Serafetinides, A. A.

    2013-06-01

    Commercially available intraocular lenses (IOLs) are manufactured from silicone and acrylic, both rigid (e.g. PMMA) and foldable (hydrophobic or hydrophilic acrylic biomaterials), behaving different mechanical and optical properties. Recently, the use of apodizing technology to design new diffractive-refractive multifocals improved the refractive outcome of these intraocular lenses, providing good distant and near vision. There is also a major ongoing effort to refine laser refractive surgery to correct other defects besides conventional refractive errors. Using phakic IOLs to treat high myopia potentially provides better predictability and optical quality than corneal-based refractive surgery. The aim of this work was to investigate the effect of laser ablation on IOL surface shaping, by drilling circular arrays of holes, with a homemade motorized rotation stage, and scattered holes on the polymer surface. In material science, the most popular lasers used for polymer machining are the UV lasers, and, therefore, we tried in this work the 3rd and the 5th harmonic of a Q-switched Nd:YAG laser (λ=355 nm and λ=213 nm respectively). The morphology of the ablated IOL surface was examined with a scanning electron microscope (SEM, Fei - Innova Nanoscope) at various laser parameters. Quantitative measurements were performed with a contact profilometer (Dektak-150), in which a mechanical stylus scanned across the surface of gold-coated IOLs (after SEM imaging) to measure variations in surface height and, finally, the ablation rates were also mathematically simulated for depicting the possible laser ablation mechanism(s). The experimental results and the theoretical modelling of UV laser interaction with polymeric IOLs are discussed in relation with the physical (optical, mechanical and thermal) properties of the material, in addition to laser radiation parameters (laser energy fluence, number of pulses). The qualitative aspects of laser ablation at λ=213 nm reveal a

  11. Laser ablation of basal cell carcinomas guided by confocal microscopy

    NASA Astrophysics Data System (ADS)

    Sierra, Heidy; Cordova, Miguel; Nehal, Kishwer; Rossi, Anthony; Chen, Chih-Shan Jason; Rajadhyaksha, Milind

    2016-02-01

    Laser ablation offers precise and fast removal of superficial and early nodular types of basal cell carcinomas (BCCs). Nevertheless, the lack of histological confirmation has been a limitation. Reflectance confocal microscopy (RCM) imaging combined with a contrast agent can offer cellular-level histology-like feedback to detect the presence (or absence) of residual BCC directly on the patient. We conducted an ex vivo bench-top study to provide a set of effective ablation parameters (fluence, number of passes) to remove superficial BCCs while also controlling thermal coagulation post-ablation to allow uptake of contrast agent. The results for an Er:YAG laser (2.9 um and pulse duration 250us) show that with 6 passes of 25 J/cm2, thermal coagulation can be effectively controlled, to allow both the uptake of acetic acid (contrast agent) and detection of residual (or absence) BCCs. Confirmation was provided with histological examination. An initial in vivo study on 35 patients shows that the uptake of contrast agent aluminum chloride) and imaging quality is similar to that observed in the ex vivo study. The detection of the presence of residual tumor or complete clearance was confirmed in 10 wounds with (additional) histology and in 25 lesions with follow-up imaging. Our results indicate that resolution is sufficient but further development and use of appropriate contrast agent are necessary to improve sensitivity and specificity. Advances in RCM technology for imaging of lateral and deep margins directly on the patient may provide less invasive, faster and less expensive image-guided approaches for treatment of BCCs.

  12. EUV nanosecond laser ablation of silicon carbide, tungsten and molybdenum

    NASA Astrophysics Data System (ADS)

    Frolov, Oleksandr; Kolacek, Karel; Schmidt, Jiri; Straus, Jaroslav; Choukourov, Andrei; Kasuya, Koichi

    2015-09-01

    In this paper we present results of study interaction of nanosecond EUV laser pulses at wavelength of 46.9 nm with silicon carbide (SiC), tungsten (W) and molybdenum (Mo). As a source of laser radiation was used discharge-plasma driver CAPEX (CAPillary EXperiment) based on high current capillary discharge in argon. The laser beam is focused with a spherical Si/Sc multilayer-coated mirror on samples. Experimental study has been performed with 1, 5, 10, 20 and 50 laser pulses ablation of SiC, W and Mo at various fluence values. Firstly, sample surface modification in the nanosecond time scale have been registered by optical microscope. And the secondly, laser beam footprints on the samples have been analyzed by atomic-force microscope (AFM). This work supported by the Czech Science Foundation under Contract GA14-29772S and by the Grant Agency of the Ministry of Education, Youth and Sports of the Czech Republic under Contract LG13029.

  13. Laser fiber migration into the pelvic cavity: A rare complication of endovenous laser ablation.

    PubMed

    Lun, Yu; Shen, Shikai; Wu, Xiaoyu; Jiang, Han; Xin, Shijie; Zhang, Jian

    2015-10-01

    Endovenous laser ablation is an established alternative to surgery with stripping for the treatment of varicose veins. Ecchymoses and pain are frequently reported side effects of endovenous laser ablation. Device-related complications are rare but serious. We describe here an exceptional complication, necessitating an additional surgical procedure to remove a segment of laser fiber that had migrated into the pelvic cavity. Fortunately, severe damage had not occurred. This case highlights the importance of checking the completeness of the guidewire, catheter, and laser fiber after endovenous laser ablation. PMID:24965101

  14. Laser ablation and target acceleration under the strong magnetic field

    NASA Astrophysics Data System (ADS)

    Nagatomo, H.; Matsuo, K.; Breil, J.; Nicolai, P.; Feugeas, J.-L.; Asahina, T.; Sunahara, A.; Johzaki, T.; Fujioka, S.; Sano, T.; Mima, K.

    2015-11-01

    Various discussion and experiments have been made about the laser plasma phenomena under the strong magnetic field recently. One of the advantage is guiding electron beam for heating core plasma in last phase of Fast Ignition scheme. However, the implosion dynamics in FI is influenced by the magnetic field due to the anisotropic of electron heat conduction. Some simple experiments where target is accelerated by laser driven ablation under the strong magnetic field were conducted to benchmark the simulation code. Related to the experiment, we focus on the early stage of the acceleration in this study. 2-D radiative MHD code (PINOCO-MHD) is used for the simulation. In the simulation magnetic field transport, diffusion and Braginskii coefficient for electron heat conduction are taken account. In preliminary simulation result suggests that the magnetic pressure may have an influence on the target surface and/or ablated plasma at very early phase. The effect of the magnetic pressure is very sensitive to the vacuum, initial and boundary conditions, and they should be treated carefully. These numerical conditions will be discussed as well. This study was partially supported by JSPS KAKENHI Grant No. 26400532.

  15. The role of laser wavelength on plasma generation and expansion of ablation plumes in air

    SciTech Connect

    Hussein, A. E.; Diwakar, P. K.; Harilal, S. S.; Hassanein, A.

    2013-04-14

    We investigated the role of excitation laser wavelength on plasma generation and the expansion and confinement of ablation plumes at early times (0-500 ns) in the presence of atmospheric pressure. Fundamental, second, and fourth harmonic radiation from Nd:YAG laser was focused on Al target to produce plasma. Shadowgraphy, fast photography, and optical emission spectroscopy were employed to analyze the plasma plumes, and white light interferometry was used to characterize the laser ablation craters. Our results indicated that excitation wavelength plays a crucial role in laser-target and laser-plasma coupling, which in turn affects plasma plume morphology and radiation emission. Fast photography and shadowgraphy images showed that plasmas generated by 1064 nm are more cylindrical compared to plasmas generated by shorter wavelengths, indicating the role of inverse bremsstrahlung absorption at longer laser wavelength excitation. Electron density estimates using Stark broadening showed higher densities for shorter wavelength laser generated plasmas, demonstrating the significance of absorption caused by photoionization. Crater depth analysis showed that ablated mass is significantly higher for UV wavelengths compared to IR laser radiation. In this experimental study, the use of multiple diagnostic tools provided a comprehensive picture of the differing roles of laser absorption mechanisms during ablation.

  16. The role of laser wavelength on plasma generation and expansion of ablation plumes in air

    NASA Astrophysics Data System (ADS)

    Hussein, A. E.; Diwakar, P. K.; Harilal, S. S.; Hassanein, A.

    2013-04-01

    We investigated the role of excitation laser wavelength on plasma generation and the expansion and confinement of ablation plumes at early times (0-500 ns) in the presence of atmospheric pressure. Fundamental, second, and fourth harmonic radiation from Nd:YAG laser was focused on Al target to produce plasma. Shadowgraphy, fast photography, and optical emission spectroscopy were employed to analyze the plasma plumes, and white light interferometry was used to characterize the laser ablation craters. Our results indicated that excitation wavelength plays a crucial role in laser-target and laser-plasma coupling, which in turn affects plasma plume morphology and radiation emission. Fast photography and shadowgraphy images showed that plasmas generated by 1064 nm are more cylindrical compared to plasmas generated by shorter wavelengths, indicating the role of inverse bremsstrahlung absorption at longer laser wavelength excitation. Electron density estimates using Stark broadening showed higher densities for shorter wavelength laser generated plasmas, demonstrating the significance of absorption caused by photoionization. Crater depth analysis showed that ablated mass is significantly higher for UV wavelengths compared to IR laser radiation. In this experimental study, the use of multiple diagnostic tools provided a comprehensive picture of the differing roles of laser absorption mechanisms during ablation.

  17. Interaction of extreme ultraviolet laser radiation with solid surface: ablation, desorption, nanostructuring

    NASA Astrophysics Data System (ADS)

    Kolacek, Karel; Schmidt, Jiri; Straus, Jaroslav; Frolov, Oleksandr; Juha, Libor; Chalupsky, Jaromir

    2015-02-01

    The area, where interaction of focused XUV laser radiation with solid surface takes place, can be divided according to local fluency into desorption region (if fluency is larger than zero and smaller than ablation threshold) and ablation region (if fluency is equal or larger than this threshold). It turned out that a direct nanostructuring (e.g. imprinting diffraction pattern created on edges of windows of proximity standing grid) is possible in the desorption region only. While for femtosecond pulses the particle (atom/molecule) removal-efficiency η in the desorption region is very small (η < 10%), and hence, it can be easily distinguished from the ablation region with η ~ 100%, for nanosecond pulses in desorption region this η rises at easily ablated materials from 0% at the periphery up to ~90% at the ablation contour and, therefore, the boundary between these two regions can be found with the help of nanostructuring only. This rise of removal efficiency could be explained by gradually increased penetration depth (due to gradually removed material) during laser pulse. This is a warning against blind using crater shape for fluency mapping in the case of long laser pulses. On the other hand it is a motivation to study an ablation plum (or ablation jet) and to create a knowledge bank to be used at future numerical modeling of this process.

  18. On the role of chemical reactions in initiating ultraviolet laser ablation in poly(methyl methacrylate)

    SciTech Connect

    Prasad, Manish; Conforti, Patrick F.; Garrison, Barbara J.

    2007-05-15

    The role of chemical reactions is investigated versus the thermal and mechanical processes occurring in a polymer substrate during irradiation by a laser pulse and subsequent ablation. Molecular dynamics simulations with an embedded Monte Carlo based reaction scheme were used to study ultraviolet ablation of poly(methyl methacrylate) at 157 nm. We discuss the onset of ablation, the mechanisms leading to ablation, and the role of stress relaxation of the polymer matrix during ablation. Laser induced heating and chemical decomposition of the polymer substrate are considered as ablation pathways. It is shown that heating the substrate can set off ablation via mechanical failure of the material only for very short laser pulses. For longer pulses, the mechanism of ejection is thermally driven limited by the critical number of bonds broken in the substrate. Alternatively, if the photon energy goes towards direct bond breaking, it initiates chemical reactions, polymer unzipping, and formation of gaseous products, leading to a nearly complete decomposition of the top layers of substrates. The ejection of small molecules has a hollowing out effect on the weakly connected substrates which can lead to lift-off of larger chunks. Excessive pressure buildup upon the creation of gaseous molecules does not lead to enhanced yield. The larger clusters are thermally ejected, and an entrainment of larger polymer fragments in gaseous molecules is not observed.

  19. 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.

  20. Diffraction modelling of laser ablation using transmission masks

    NASA Astrophysics Data System (ADS)

    Dyer, P. E.; Mackay, J.; Walton, C. D.

    2004-10-01

    We present an analysis of near-field diffraction effects in ablation with transmission masks, based on coupling a simplified form of the Fresnel-Kirchhoff diffraction integral with basic models for material removal. Modelling for square, hexagonal and circular proximity masks is described and compared with previously reported experiments on glass, silicon and polyimide using excimer, femtosecond and CO2 lasers. The model has general applicability and can provide useful insight into the effect of near-field diffraction in ablation patterning.

  1. Pulsed laser ablation and deposition of niobium carbide

    NASA Astrophysics Data System (ADS)

    Sansone, M.; De Bonis, A.; Santagata, A.; Rau, J. V.; Galasso, A.; Teghil, R.

    2016-06-01

    NbC crystalline films have been deposited in vacuum by ultra-short pulsed laser deposition technique. The films have been characterized by transmission and scanning electron microscopies and by X-ray diffraction. To clarify the ablation-deposition mechanism, the plasma produced by the ablation process has been characterized by optical emission spectroscopy and fast imaging. A comparison of the results with those obtained by ns pulsed deposition of the same target has been carried out.

  2. Laser ablation molecular isotopic spectrometry of carbon isotopes

    NASA Astrophysics Data System (ADS)

    Bol‧shakov, Alexander A.; Mao, Xianglei; Jain, Jinesh; McIntyre, Dustin L.; Russo, Richard E.

    2015-11-01

    Quantitative determination of carbon isotopes using Laser Ablation Molecular Isotopic Spectrometry (LAMIS) is described. Optical emission of diatomic molecules CN and C2 is used in these measurements. Two quantification approaches are presented: empirical calibration of spectra using a set of reference standards and numerical fitting of a simulated spectrum to the experimental one. Formation mechanisms of C2 and CN in laser ablation plasma are briefly reviewed to provide insights for implementation of LAMIS measurements. A simulated spectrum of the 12C2 Swan system was synthesized using four constituents within 473.5-476.5 nm. Simulation included three branches of 12C2 (1-0), branches R(0-0) and R(1-1), and branch P(9-8) of 12C2. Spectral positions of the tail lines in R(0-0) and R(1-1) were experimentally measured, since they were not accurately known before. The Swan band (1-0) of the isotopologue 13C12C was also simulated. Fitting to the experimental spectrum yielded the ratio 13C/12C = 1.08% in a good agreement with measurements by isotope ratio mass spectrometry. LAMIS promises to be useful in coal, oil and shale exploration, carbon sequestration monitoring, and agronomy studies.

  3. Laser ablation molecular isotopic spectrometry of carbon isotopes

    SciTech Connect

    Bol'shakov, Alexander A.; Jain, Jinesh; Russo, Richard E.; McIntyre, Dustin; Mao, Xianglei

    2015-08-28

    Quantitative determination of carbon isotopes using Laser Ablation Molecular Isotopic Spectrometry (LAMIS) is described. Optical emission of diatomic molecules CN and C2 is used in these measurements. Two quantification approaches are presented:empirical calibration of spectra using a set of reference standards and numerical fitting of a simulated spectrum to the experimental one. Formation mechanisms of C2 and CN in laser ablation plasma are briefly reviewed to provide insights for implementation of LAMIS measurements. A simulated spectrum of the 12C2 Swan system was synthesized using four constituents within 473.5–476.5 nm. Simulation included three branches of 12C2 (1-0), branches R(0-0) and R(1-1), and branch P(9-8) of 12C2. Spectral positions of the tail lines in R(0-0) and R(1-1) were experimentally measured, since they were not accurately known before. The Swan band (1-0) of the isotopologue 13C12C was also simulated. Fitting to the experimental spectrumyielded the ratio 13C/12C = 1.08% in a good agreement with measurements by isotope ratio mass spectrometry. LAMIS promises to be useful in coal, oil and shale exploration, carbon sequestration monitoring, and agronomy studies

  4. Neutral atomic jet generation by laser ablation of copper targets

    SciTech Connect

    Matos, J. B. de; Rodrigues, N. A. S.

    2014-08-15

    This work aimed the obtainment of a neutral atomic jet departing from a plume generated by laser ablation of copper targets. A pair of electrodes together with a transducer pressure sensor was used to study the ablated plume charge composition and also to measure the ion extraction from the plasma plume. The neutral beam was produced with this setup and the relative abundance of neutrals in the plasma was measured, it decreases from 30% to 8% when the laser fluence is varied from 20 J/cm{sup 2} to 32 J/cm{sup 2}. The necessary voltage to completely remove the ions from the plume varied from 10 V to 230 V in the same fluence range. TOF analysis resulted in center of mass velocities between 3.4 and 4.6 km/s, longitudinal temperature in the range from 1 × 10{sup 4} K to 2.4 × 10{sup 4} K and a Mach number of M = 2.36, calculated using purely hydrodynamic expansion approximation.

  5. Optimization of laser ablation and signal enhancement for nuclear material detection

    NASA Astrophysics Data System (ADS)

    LaHaye, Nicole L.

    The purpose of the study was to investigate the role of different laser parameters on laser ablation properties, specifically in terms of performance in laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). Many laser parameters affect laser ablation performance, including laser wavelength and pulse duration, as presented here. It was previously thought that wavelength plays no role in ultrafast laser ablation; however, it was found that shorter wavelength yields lower detection limits and ablation threshold. Our results also demonstrate that in the laser pulse duration range of 40 fs to 1 ps, negligible differences occur in signal intensity, elemental ratios, and detection limits. U/Pb and U/Th ratios, which were examined to ensure limited fractionation, give comparable results at all pulse widths investigated. A parametric study of plasma hydrodynamics will also be presented. An elemental detection method combining laser induced breakdown spectroscopy (LIBS) and LA-ICP-MS is developed, with plasma density and temperature actively monitored to investigate how plasma conditions affect ICP-MS results. The combination of these two methods will help to mitigate the disadvantages of using each technique individually. Depth and spatial analysis of thin films was performed using femtosecond LA-ICP-MS to study the stoichiometric distribution of the films. The thin film-substrate interface was probed, revealing intermixing between the two layers. Lastly, the persistence of uranium emission in laser-produced plasmas (LPP) was investigated under various Ar ambient environments. Plasma collisional effects and confinement play a very important role in emission intensity and persistence, yielding important results for future LIBS and laser absorption spectroscopy (LAS) research. Lastly, suggestions for future work are made, which include extension of the LIBS and LA-ICP-MS systems to other samples like oxide thin films and spatial and depth profiling of known

  6. Heat generation caused by ablation of dental restorative materials with an ultra short pulse laser (USPL) system

    NASA Astrophysics Data System (ADS)

    Braun, Andreas; Wehry, Richard; Brede, Olivier; Frentzen, Matthias; Schelle, Florian

    2011-03-01

    The aim of this study was to assess heat generation in dental restoration materials following laser ablation using an Ultra Short Pulse Laser (USPL) system. Specimens of phosphate cement (PC), ceramic (CE) and composite (C) were used. Ablation was performed with an Nd:YVO4 laser at 1064 nm and a pulse length of 8 ps. Heat generation during laser ablation depended on the thickness of the restoration material. A time delay for temperature increase was observed in the PC and C group. Employing the USPL system for removal of restorative materials, heat generation has to be considered.

  7. Processing condition influence on the characteristics of gold nanoparticles produced by pulsed laser ablation in liquids

    NASA Astrophysics Data System (ADS)

    Nikov, R. G.; Nikolov, A. S.; Nedyalkov, N. N.; Atanasov, P. A.; Alexandrov, M. T.; Karashanova, D. B.

    2013-06-01

    A study is presented of Au nanoparticles (NPs) created by nanosecond pulsed laser ablation of a solid target in double distilled water. The influence was examined of the laser wavelength on the size, shape and optical properties of the resulting NPs. Three different wavelengths: the fundamental (λ = 1064 nm), second (λSHG = 532) and third (λTHG = 355) harmonic of a Nd:YAG laser at the same fluence were utilized to produce various colloids. Ablation at the wavelength of 532 nm was investigated in more detail to reveal the influence of self-absorption by the already created NPs on their characteristics. The colloid produced was irradiated by λirrad = 532 nm (laser energy 40 mJ) at different times up to 25 min after the end of ablation. The initial structure of welded NPs forming wires was modified. Transmission electron microscopy and optical transmission measurements were used to evaluate the shape and size distribution of the NPs.

  8. Dynamics of Laser-Ablation Plume and Ambient Gas Visualized by Laser-Induced Fluorescence Imaging Spectroscopy

    NASA Astrophysics Data System (ADS)

    Sasaki, Koichi; Watarai, Hiroshi

    2006-04-01

    The dynamics of both a laser-ablation plume and ambient gas were studied by visualizing their density distributions by laser-induced fluorescence imaging spectroscopy. A deep dip was formed in the density distribution of the ambient gas. The depth of the dip was almost 100% immediately after irradiation of the ablation laser pulse. The size of the dip expanded with time. At a long delay time after the irradiation of the ablation laser pulse, the ambient gas returned to the dip and slowly filled it. The location of the dip corresponded to that of the plume ejected from the target. This means that the high pressure of the plume removed the ambient gas, and the plume and the ambient gas located exclusively. In addition, we observed the formation and propagation of a compressed layer around the dip.

  9. Determination of ablation threshold for composite resins and amalgam irradiated with femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Freitas, A. Z.; Freschi, L. R.; Samad, R. E.; Zezell, D. M.; Gouw-Soares, S. C.; Vieira, N. D., Jr.

    2010-03-01

    The use of laser for caries removal and cavity preparation is already a reality in the dental clinic. The objective of the present study was to consider the viability of ultrashort laser pulses for restorative material selective removal, by determining the ablation threshold fluence for composite resins and amalgam irradiated with femtosecond laser pulses. Lasers pulses centered at 830 nm with 50 fs of duration and 1 kHz of repetition rate, with energies in the range of 300 to 770 μJ were used to irradiate the samples. The samples were irradiated using two different geometrical methods for ablation threshold fluence determinations and the volume ablation was measured by optical coherence tomography. The shape of the ablated surfaces were analyzed by optical microscopy and scanning electron microscopy. The determined ablation threshold fluence is 0.35 J/cm2 for the composite resins Z-100 and Z-350, and 0.25 J/cm2 for the amalgam. These values are half of the value for enamel in this temporal regime. Thermal damages were not observed in the samples. Using the OCT technique (optical coherence tomography) was possible to determine the ablated volume and the total mass removed.

  10. Laser ablation and influence of Debye temperature and laser parameters on size and number of nanoparticles

    NASA Astrophysics Data System (ADS)

    Vaezzadeh, Majid; Saeidi, Mohammadreza; Zarei, Mohsen

    2010-03-01

    Dependence of size and number of nanoparticles on kind of material, power of laser and pulse duration of laser in laser ablation is investigated by presenting a model based on Debye model for specific heat capacity. Simulations from the theory demonstrate that there is a critical power of laser which is very important for controlling size of nanoparticles in laser ablation method. The critical power of laser depends on material Debye temperature and pulse duration of laser. Finally difference between experimental diagrams of zinc and carbon is explained by using results of the theory.

  11. Molecular signatures in femtosecond laser-induced organic plasmas: comparison with nanosecond laser ablation.

    PubMed

    Serrano, Jorge; Moros, Javier; Laserna, J Javier

    2016-01-28

    During the last few years, laser-induced breakdown spectroscopy (LIBS) has evolved significantly in the molecular sensing area through the optical monitoring of emissions from organic plasmas. Large efforts have been made to study the formation pathways of diatomic radicals as well as their connections with the bonding framework of molecular solids. Together with the structural and chemical-physical properties of molecules, laser ablation parameters seem to be closely tied to the observed spectral signatures. This research focuses on evaluating the impact of laser pulse duration on the production of diatomic species that populate plasmas of organic materials. Differences in relative intensities of spectral signatures from the plasmas of several organic molecules induced in femtosecond (fs) and nanosecond (ns) ablation regimes have been studied. Beyond the abundance and origin of diatomic radicals that seed the plasma, findings reveal the crucial role of the ablation regime in the breakage pattern of the molecule. The laser pulse duration dictates the fragments and atoms resulting from the vaporized molecules, promoting some formation routes at the expense of other paths. The larger amount of fragments formed by fs pulses advocates a direct release of native bonds and a subsequent seeding of the plasma with diatomic species. In contrast, in the ns ablation regime, the atomic recombinations and single displacement processes dominate the contribution to diatomic radicals, as long as atomization of molecules prevails over their progressive decomposition. Consequently, fs-LIBS better reflects correlations between strengths of emissions from diatomic species and molecular structure as compared to ns-LIBS. These new results entail a further step towards the specificity in the analysis of molecular solids by fs-LIBS. PMID:26695078

  12. Interstitial laser-induced thermotherapy of the lung: evaluation of the influence of ablation continuity on ablation size in a swine model

    PubMed Central

    Schoellnast, Helmut; Monette, Sebastien; Ezell, Paula C.; Keene, Andrew; Quehenberger, Franz; Erinjeri, Joseph P.

    2013-01-01

    Abstract The purpose of this study was to assess the relationship between size and the continuity of energy application in interstitial laser-induced thermotherapy. Percutaneous computed tomography-guided laser ablation (30 W, 600 nm diode) of the lung was performed in 7 Yorkshire pigs; a total of 42 ablation zones were created. Twenty ablations were performed using a continuous cycle of 2 min (protocol A) and 22 ablations were performed using 4 intermittent cycles with a duration of 1 min for each cycle interrupted by a 10-s stop between the cycles (protocol B). The lung was harvested immediately after euthanasia for gross pathology and histopathologic evaluation. Statistical analysis was performed using the Student t test and the Spearman correlation coefficient. Laser ablation resulted in complete necrosis of variable size of lung. The mean ablation zone dimensions (±SD) were 1.9 (±0.4) cm × 1.4 (±0.3) cm for protocol A and 2.2 (±0.5) cm × 1.4 (±0.4) cm for protocol B. The size of the necrosis is not significantly different when comparing a continuous 2-min ablation to a 4-cycle intermittent ablation for 1 min each cycle interrupted by a 10-s stop between the cycles (P = 0.98 and 0.53, respectively). PMID:23439016

  13. Direct coupling of a laser ablation cell to an AMS

    NASA Astrophysics Data System (ADS)

    Wacker, L.; Münsterer, C.; Hattendorf, B.; Christl, M.; Günther, D.; Synal, H.-A.

    2013-01-01

    In rare cases, cleaned samples can be directly inserted into a negative ion source of an AMS and still meet the requirements for long-term and stable measurements. We present the coupling of a laser ablation system to the gas ion source of an AMS system (MICADAS, ETH Zurich) for direct and continuous CO2 introduction. Solid carbonate samples like stalagmites or corals are suitable sample materials, which can be ablated and decomposed continuously using a pulsed laser focused onto the surface of a solid sample, which is placed in an airtight ablation cell. CO2 formed during the ablation of a CaCO3 sample is continually flushed with He into the gas ion source. The production rate of CO2 can be adjusted via the laser pulse repetition rate (1-20 Hz), the crater diameter (1-150 μm) and the energy density applied (0.2-3 mJ/pulse) of the laser (frequency quintupled Nd:YAG at 213 nm with 5 ns pulse duration). In our first test, measurements of one sample with known age were replicated within one sigma. Blanks showed 5% contamination of modern carbon of yet unknown origin. In order to develop LA-AMS into a routine sampling tool the ablation cell geometry and settings of the gas ion source have to be further optimized.

  14. Ultrathin sectioning with DUV-pulsed laser ablation: development of a laser ablation nano tome.

    PubMed

    Kanemaru, Takaaki; Oki, Yuji

    2015-08-01

    The electrically automated ultrathin sectioning apparatus, which has been developed in recent years, can produce consecutive ultrathin sections with a diamond knife and a gallium ion beam. These newly developed apparatuses, however, have several shortcomings, such as the limited block cutting area, thermal damage to the sample by the focused ion beam and a sample electronic charge. To overcome these faults and for easier scanning electron microscopy three-dimensional fine structural reconstruction, we have developed a new cutting method using a deep ultraviolet laser, which we have named the 'LANTome (Light Ablation Nanotome)'. Using this method, we confirmed the widening of sectioning areas, shortening of the sectioning time, automatic smoothing of rough surfaces, no sample electronic charge and minimal heat effects on the sample tissue, such as thermal denaturation. PMID:25888714

  15. Laser ablation of powdered samples and analysis by means of laser-induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Ctvrtnickova, T.; Cabalin, L.; Laserna, J.; Kanicky, V.; Nicolas, G.

    2009-03-01

    The presented work proves the capacities of laser-induced breakdown spectroscopy (LIBS) as a fast, universal, and versatile technique for analysis of complex materials as ceramics. This paper reports on the analysis of ceramic raw materials (brick clays and kaolin) submitted to laser ablation in the form of pressed pellets. Spectrographic study was provided by standard single-pulse LIBS technique and orthogonal reheating double-pulse LIBS. It was found that both methods are comparable in terms of analytical performance, if adequate experimental parameters and signal detection systems are used.

  16. Influence of film thickness on laser ablation threshold of transparent conducting oxide thin-films

    NASA Astrophysics Data System (ADS)

    Rung, S.; Christiansen, A.; Hellmann, R.

    2014-06-01

    We report on a comprehensive study of the laser ablation threshold of transparent conductive oxide thin films. The ablation threshold is determined for both indium tin oxide and gallium zinc oxide as a function of film thickness and for different laser wavelengths. By using a pulsed diode pumped solid state laser at 1064 nm, 532 nm, 355 nm and 266 nm, respectively, the relationship between optical absorption length and film thickness is studied. We find that the ablation threshold decreases with increasing film thickness in a regime where the absorption length is larger than the film thickness. In turn, the ablation threshold increases in case the absorption length is smaller than the film thickness. In particular, we observe a minimum of the ablation threshold in a region where the film thickness is comparable to the absorption length. To the best of our knowledge, this behaviour previously predicted for thin metal films, has been unreported for all three regimes in case of transparent conductive oxides, yet. For industrial laser scribing processes, these results imply that the efficiency can be optimized by using a laser where the optical absorption length is close to the film thickness.

  17. In-situ bioconjugation in stationary media and in liquid flow by femtosecond laser ablation

    NASA Astrophysics Data System (ADS)

    Sajti, Csaba László; Petersen, Svea; Menéndez-Manjón, Ana; Barcikowski, Stephan

    2010-11-01

    In-situ functionalization of gold nanoparticles with fluorophore-tagged oligonucleotides is studied by comparing femtosecond laser ablation in stationary liquid and in biomolecule flow. Femtosecond laser pulses induce significant degradation to sensitive biomolecules when ablating gold in a stationary solution of oligonucleotides. Contrary, in-situ conjugation of nanoparticles in biomolecule flow considerably reduces the degree of degradation studied by gel electrophoresis and UV-Vis spectrometry. Ablating gold with 100 μJ femtosecond laser pulses DNA sequence does not degrade, while the degree of fluorophore tag degradation was 84% in stationary solution compared to 5% for 1 mL/min liquid flow. It is concluded that femtosecond laser-induced degradation of biomolecules is triggered by absorption of nanoparticle conjugates suspended in the colloid and not by ablation of the target. Quenching of nanoparticle size appears from 0.5 μM biomolecule concentration for 0.3 μg/s nanoparticle productivity indicating the successful surface functionalization. Finally, increasing the liquid flow rate from stationary to 450 mL/min enhances nanoparticle productivity from 0.2 μg/s to 1.5 μg/s, as increasing liquid flow allows removal of light absorbing nanoparticles from the ablation zone, avoiding attenuation of subsequent laser photons.

  18. Fundamental Mechanisms of Pulsed Laser Ablation of Biological Tissue

    NASA Astrophysics Data System (ADS)

    Albagli, Douglas

    The ability to cut and remove biological tissue with short pulsed laser light, a process called laser ablation, has the potential to revolutionize many surgical procedures. Ablation procedures using short pulsed lasers are currently being developed or used in many fields of medicine, including cardiology, ophthalmology, dermatology, dentistry, orthopedics, and urology. Despite this, the underlying physics of the ablation process is not well understood. In fact, there is wide disagreement over whether the fundamental mechanism is primarily photothermal, photomechanical, or photochemical. In this thesis, both experimental and theoretical techniques are developed to explore this issue. The photothermal model postulates that ablation proceeds through vaporization of the target material. The photomechanical model asserts that ablation is initiated when the laser-induced tensile stress exceeds the ultimate tensile strength of the target. I have developed a three dimensional model of the thermoelastic response of tissue to short pulsed laser irradiation which allows the time dependent stress distribution to be calculated given the optical, thermal and mechanical properties of the target. A complimentary experimental technique has been developed to verify this model, measure the needed physical properties of the tissue, and record the thermoelastic response of the tissue at the onset of ablation. The results of this work have been widely disseminated to the international research community and have led to significant findings which support the photomechanical model of ablation of tissue. First, the energy deposited in tissue is an order of magnitude less than that required for vaporization. Second, unlike the one-dimensional thermoelastic model of laser-induced stress generation that has appeared in the literature, the full three-dimensional model predicts the development of significant tensile stresses on the surface of the target, precisely where ablation is observed to

  19. Below-Band-Gap Laser Ablation Of Diamond For TEM

    NASA Technical Reports Server (NTRS)

    George, Thomas; Foote, Marc C.; Vasquez, Richard P.; Fortier, Edward P.; Posthill, John B.

    1995-01-01

    Thin, electron-transparent layers of diamond for examination in transmission electron microscope (TEM) fabricated from thicker diamond substrates by using laser beam to ablate surface of substrate. Involves use of photon energy below band gap. Growing interest in use of diamond as bulk substrate and as coating material in variety of applications has given rise to increasing need for TEM for characterization of diamond-based materials. Below-band-gap laser ablation method helps to satisfy this need. Also applied in general to cutting and etching of diamonds.

  20. Aerospace Laser Ignition/Ablation Variable High Precision Thruster

    NASA Technical Reports Server (NTRS)

    Campbell, Jonathan W. (Inventor); Edwards, David L. (Inventor); Campbell, Jason J. (Inventor)

    2015-01-01

    A laser ignition/ablation propulsion system that captures the advantages of both liquid and solid propulsion. A reel system is used to move a propellant tape containing a plurality of propellant material targets through an ignition chamber. When a propellant target is in the ignition chamber, a laser beam from a laser positioned above the ignition chamber strikes the propellant target, igniting the propellant material and resulting in a thrust impulse. The propellant tape is advanced, carrying another propellant target into the ignition chamber. The propellant tape and ignition chamber are designed to ensure that each ignition event is isolated from the remaining propellant targets. Thrust and specific impulse may by precisely controlled by varying the synchronized propellant tape/laser speed. The laser ignition/ablation propulsion system may be scaled for use in small and large applications.

  1. An MRI guided system for prostate laser ablation with treatment planning and multi-planar temperature monitoring

    NASA Astrophysics Data System (ADS)

    Xu, Sheng; Agarwal, Harsh; Bernardo, Marcelino; Seifabadi, Reza; Turkbey, Baris; Partanen, Ari; Negussie, Ayele; Glossop, Neil; Choyke, Peter; Pinto, Peter; Wood, Bradford J.

    2016-03-01

    Prostate cancer is often over treated with standard treatment options which impact the patients' quality of life. Laser ablation has emerged as a new approach to treat prostate cancer while sparing the healthy tissue around the tumor. Since laser ablation has a small treatment zone with high temperature, it is necessary to use accurate image guidance and treatment planning to enable full ablation of the tumor. Intraoperative temperature monitoring is also desirable to protect critical structures from being damaged in laser ablation. In response to these problems, we developed a navigation platform and integrated it with a clinical MRI scanner and a side firing laser ablation device. The system allows imaging, image guidance, treatment planning and temperature monitoring to be carried out on the same platform. Temperature sensing phantoms were developed to demonstrate the concept of iterative treatment planning and intraoperative temperature monitoring. Retrospective patient studies were also conducted to show the clinical feasibility of the system.

  2. Femtosecond pulsed laser ablation of GaAs

    NASA Astrophysics Data System (ADS)

    Trelenberg, T. W.; Dinh, L. N.; Saw, C. K.; Stuart, B. C.; Balooch, M.

    2004-01-01

    The properties of femtosecond-pulsed laser deposited GaAs nanoclusters were investigated. Nanoclusters of GaAs were produced by laser ablating a single crystal GaAs target in vacuum or in a buffer gas using a Ti-sapphire laser with a 150 fs minimum pulse length. For in-vacuum deposition, X-ray diffraction (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM) revealed that the average cluster size was approximately 7 nm for laser pulse lengths between 150 fs and 25 ps. The average cluster size dropped to approximately 1.5 nm at a pulse length of 500 ps. It was also observed that film thickness decreased with increasing laser pulse length. A reflective coating, which accumulated on the laser admission window during ablation, reduced the amount of laser energy reaching the target for subsequent laser shots and developed more rapidly at longer pulse lengths. This observation indicates that non-stoichiometric (metallic) ablatants were produced more readily at longer pulse lengths. The angular distribution of ejected material about the target normal was well fitted to a bi-cosine distribution of cos 47 θ+ cos 4 θ for ablation in vacuum using 150 fs pulses. XPS and AES revealed that the vacuum-deposited films contained excess amorphous Ga or As in addition to the stoichiometric GaAs nanocrystals seen with XRD. However, films containing only the GaAs nanocrystals were produced when ablation was carried out in the presence of a buffer gas with a pressure in excess of 6.67 Pa. At buffer gas pressure on the order of 1 Torr, it was found that the stoichiometry of the ablated target was also preserved. These experiments indicate that both laser pulse length and buffer gas pressure play important roles in the formation of multi-element nanocrystals by laser ablation. The effects of gas pressure on the target's morphology and the size of the GaAs nanocrystals formed will also be discussed.

  3. Spatiotemporal evolution of plasma molecular emission following laser ablation of explosive analogs

    NASA Astrophysics Data System (ADS)

    Merten, Jonathan; Jones, Matthew; Sheppard, Cheyenne; Parigger, Christian; Allen, Susan

    2013-05-01

    The spatial and temporal evolution of the CN molecular emission following laser ablation of a TNT analog (3- nitrobenzoic acid) has been studied along with ablation of targets that contain neither nitro groups nor C-N bonds. At a fluence of ~104 J/cm2, behavior indicative of the ablation of native CN bonds has been observed in samples containing no native CN bonds. The recorded data show significant plasma background emissions that pose difficulties for direct spectral imaging. Spatially resolved images suggest that some of the observed phenomena are simply the result of the interaction of the plasma and the observation volume of the collection optics.

  4. Comparing ablation induced by fs, ps, and ns XUV-laser pulses

    NASA Astrophysics Data System (ADS)

    Bittner, Michal; Juha, Libor; Chvostova, Dagmar; Letal, Vit; Krasa, Josef; Otcenasek, Zdenek; Kozlova, Michaela; Polan, Jiri; Praeg, Ansgar R.; Rus, Bedrich; Stupka, Michal; Krzywinski, Jacek; Andrejczuk, Andrzej; Pelka, Jerzy B.; Sobierajski, Ryszard; Feldhaus, Josef; Boody, Frederick P.; Grisham, Michael E.; Vaschenko, Georgiy O.; Menoni, Carmen S.; Rocca, Jorge J.

    2004-09-01

    Ablation thresholds, etch rates, and quality of ablated structures often differ dramatically if a conventional, UV-Vis-IR laser delivers radiation energy onto a material surface in a short (nanosecond) or ultra-short (picosecond/femtosecond) pulses. Various short-wavelength (λ < 100 nm) lasers emitting pulses with durations ranging from ~ 10 fs to ~ 1 ns have recently been put into a routine operation. This makes possible to investigate how the ablation characteristics depends on the pulse duration in the XUV spectral region. 1.2-ns pulses of 46.9-nm radiation delivered from a capillary-discharge Ne-like Ar laser, focused by a spherical Sc/Si multilayer-coated mirror were used for an ablation of organic polymers and silicon. Various materials were irradiated with an ellipsoidal-mirror-focused XUV radiation (λ = 86 nm, τ = 30-100 fs) generated by the free-electron laser (FEL) operated at the TESLA Test Facility (TTF1 FEL) in Hamburg. The beam of the Ne-like Zn XUV laser (λ = 21.2 nm, τ < 100 ps) driven by the Prague Asterix Laser System (PALS) was also successfully focused by a spherical Si/Mo multilayer-coated mirror to ablate various materials. Based on the results of the experiment the etch rates for three different pulse durations are compared using the XUV-ABLATOR code to compensate for the wavelength difference. Comparing the values of etch rates calculated for short pulses with the measured ones for ultrashort pulses we may study the influence of pulse duration on the XUV ablation efficiency.

  5. Fabrication of a multilevel THz Fresnel lens by femtosecond laser ablation

    NASA Astrophysics Data System (ADS)

    Komlenok, M. S.; Volodkin, B. O.; Knyazev, B. A.; Kononenko, T. V.; Kononenko, V. V.; Konov, V. I.; Soifer, V. A.; Pavel'ev, V. S.; Tukmakov, K. N.; Choporova, Yu Yu

    2015-10-01

    The possibility of fabricating a silicon diffractive fourlevel THz Fresnel lens by laser ablation is studied. For a microrelief to be formed on the sample surface, use is made of a femtosecond Yb : YAG laser with a high pulse repetition rate (f = 200 kHz). Characteristics of the diffractive optical element are investigated in the beam of a 141-mm free-electron laser. The measured diffraction efficiency of the lens is in good agreement with the theoretical estimate.

  6. Extended transurethral resection and Nd:YAG laser ablation of the prostate (TURLAP) for carcinoma: a pilot study

    NASA Astrophysics Data System (ADS)

    Childs, Stacy J.

    1993-05-01

    Transurethral resection of the prostate (TURP) has been combined with Nd:YAG application for the treatment of prostatic carcinoma for a decade. The inability to deliver the energy at right angles has made the procedure technically difficult, but results have been encouraging. A pilot study was begun in 1991 on ten patients who refused or were not candidates for radical prostatectomy. The protocol consisted of transrectal ultrasound imaging (TRUS) during extended TURP (EXTURP) followed immediately by Nd:YAG energy applied to the prostate bed and capsule. A second laser application under real time TRUS followed in eight weeks and a third (or fourth in one patient) was undertaken eight weeks later. Energy of 30,000- 85,000 Joules was applied during each procedure with the right angle urolase fiber (Bard) at 60 watts. Lesions were created for 30-60 seconds in each area of remaining tissue documented on TRUS. A thermocoupler was used to monitor rectal temperature. Complications include urinary retention, gross hematuria, bladder neck contracture, early incontinence, late incontinence, and probable permanent incontinence. Of the only four potent patients preoperatively, all (100%) are impotent now. TURLAP appears to be a safe and effective method of killing prostate malignant tissue and should be further studied perhaps in combination with interstitial laser irradiation to increase efficacy and lessen complications.

  7. Microstructure and Optics of Laser Ablation Grown Si Clusters

    NASA Astrophysics Data System (ADS)

    Vijayalakshmi, S.; Federici, J.; Grebel, H.; Iqbal, Z.

    1998-03-01

    Nanoclusters of silicon grown by laser ablation on aluminum,quartz and KBr substrates were studied by micro-Raman spectroscopy at a spatial resolution of 1 micron. The cluster films consist of islands composed of nanocrystalline and microcrystalline silicon separated by a matrix showing the Raman spectrum of amorphous silicon.The crystallite sizes determined from the position of the Raman frequency ranged from below 10 nm to above this value(Z. Iqbal & S. Veprek, J.Phys. C15, 377 (1982)). HRTEM studies on clusters deposited on KBr confirmed this picture - and in addition revealed interesting architectures at the boundaries between the amorphous and crystalline domains, which may be relevant to the growth process. The results will be compared with AFM studies and correlated with the observed large optical non-linearity of the films (S. Vijayalakshmi, M. George & H. Grebel, Appl.Phys.Lett. 70, 708 (1997)).

  8. 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.

  9. CO{sub 2} Laser Ablation Propulsion Tractor Beams

    SciTech Connect

    Sinko, John E.; Schlecht, Clifford A.

    2010-05-06

    Manipulation of objects at a distance has already been achieved with no small measure of success in the realm of microscopic objects on the scale size of nanometers to micrometers in applications including laser trapping and laser tweezers. However, there has been relatively little effort to apply such remote control to macroscopic systems. A space tractor beam could be applied to a wide range of applications, including removal of orbital debris, facilitation of spacecraft docking, adjustment of satellite attitude or orbital position, etc. In this paper, an ablative laser propulsion tractor beam is demonstrated based on radiation from a CO{sub 2} laser. Cooperative, layered polymer targets were used for remote impulse generation using a CO{sub 2} laser. The use of a structured ablatant enabling switching between thrust directional parity (i.e., forward or reverse) and imparting torque to a remote target. Fluence-dependent results are presented in the context of polymer ablation modeling work and with consideration of confined ablation effects.

  10. The effect of film properties and laser processing parameters on the laser ablation of molybdenum thin films

    NASA Astrophysics Data System (ADS)

    Schneller, Eric; Rodrigues, Rafael; Dhere, Neelkanth G.; Kar, Aravinda

    2014-10-01

    Molybdenum is commonly used as the electrical back contact for Cu(In,Ga)(Se,S)2 thin-film solar cells. In order to create a monolithically interconnected device, scribing of the molybdenum layer is required. This scribe, known as the P1 scribe, is commonly carried out through laser processing. Optimization of this laser scribing has been carried out using a 532nm pulsed Nd:YAG laser. It was found that two specific regimes of processing resulted in defect free scribes. These regimes are low fluency and high pulse overlap, and high fluency and low pulse overlap. Film properties, including the microstructure, surface oxidation, and internal stress, were studied to understand their effect on the laser ablation process. It was observed that a thin layer of oxidation resulted in significant heat affected zone during the laser ablation process. A discussion of the optimal film properties and laser processing parameters is presented.

  11. Surface roughness and wettability of dentin ablated with ultrashort pulsed laser

    NASA Astrophysics Data System (ADS)

    Liu, Jing; Lü, Peijun; Sun, Yuchun; Wang, Yong

    2015-05-01

    The aim of this study was to evaluate the surface roughness and wettability of dentin following ultrashort pulsed laser ablation with different levels of fluence and pulse overlap (PO). Twenty-five extracted human teeth crowns were cut longitudinally into slices of approximately 1.5-mm thick and randomly divided into nine groups of five. Samples in groups 1 to 8 were ablated with an ultrashort pulsed laser through a galvanometric scanning system. Samples in group 9 were prepared using a mechanical rotary instrument. The surface roughness of samples from each group was then measured using a three-dimensional profile measurement laser microscope, and wettability was evaluated by measuring the contact angle of a drop of water on the prepared dentin surface using an optical contact angle measuring device. The results showed that both laser fluence and PO had an effect on dentin surface roughness. Specifically, a higher PO decreased dentin surface roughness and reduced the effect of high-laser fluence on decreasing the surface roughness in some groups. Furthermore, all ablated dentin showed a contact angle of approximately 0 deg, meaning that laser ablation significantly improved wettability. Adjustment of ultrashort pulsed laser parameters can, therefore, significantly alter dentin surface roughness and wettability.

  12. Direct femtosecond laser ablation of copper with an optical vortex beam

    NASA Astrophysics Data System (ADS)

    Anoop, K. K.; Fittipaldi, R.; Rubano, A.; Wang, X.; Paparo, D.; Vecchione, A.; Marrucci, L.; Bruzzese, R.; Amoruso, S.

    2014-09-01

    Laser surface structuring of copper is induced by laser ablation with a femtosecond optical vortex beam generated via spin-to-orbital conversion of the angular momentum of light by using a q-plate. The variation of the produced surface structures is studied as a function of the number of pulses, N, and laser fluence, F. After the first laser pulse (N = 1), the irradiated surface presents an annular region characterized by a corrugated morphology made by a rather complex network of nanometer-scale ridges, wrinkles, pores, and cavities. Increasing the number of pulses (2 < N < 100), the surface texture progressively evolves towards larger structures, while the central, non-ablated area is gradually decorated by nanoparticles produced during laser ablation. At large number of pulses (200 < N < 1000), a micro-tip with a nanostructured surface forms in the center of the irradiated area, which eventually disappears at still larger number of pulses (N > 1000) and a deep crater is formed. The nanostructure variation with the laser fluence, F, also evidences an interesting dependence, with a coarsening of the structure morphology as F increases. Our experimental findings demonstrate that direct femtosecond laser ablation with optical vortex beams produces interesting patterns not achievable by the more standard beams with a Gaussian intensity profile. They also suggest that appropriate tuning of the experimental conditions (F, N) can allow generating micro- and/or nano-structured surface for any specific application.

  13. Direct femtosecond laser ablation of copper with an optical vortex beam

    SciTech Connect

    Anoop, K. K.; Rubano, A.; Marrucci, L.; Bruzzese, R.; Amoruso, S.; Fittipaldi, R.; Vecchione, A.; Wang, X.; Paparo, D.

    2014-09-21

    Laser surface structuring of copper is induced by laser ablation with a femtosecond optical vortex beam generated via spin-to-orbital conversion of the angular momentum of light by using a q-plate. The variation of the produced surface structures is studied as a function of the number of pulses, N, and laser fluence, F. After the first laser pulse (N=1), the irradiated surface presents an annular region characterized by a corrugated morphology made by a rather complex network of nanometer-scale ridges, wrinkles, pores, and cavities. Increasing the number of pulses (2ablated area is gradually decorated by nanoparticles produced during laser ablation. At large number of pulses (2001000) and a deep crater is formed. The nanostructure variation with the laser fluence, F, also evidences an interesting dependence, with a coarsening of the structure morphology as F increases. Our experimental findings demonstrate that direct femtosecond laser ablation with optical vortex beams produces interesting patterns not achievable by the more standard beams with a Gaussian intensity profile. They also suggest that appropriate tuning of the experimental conditions (F, N) can allow generating micro- and/or nano-structured surface for any specific application.

  14. 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.

  15. Outcome of Endovenous Laser Ablation of Varicose Veins

    PubMed Central

    Rustempasic, Nedzad; Cvorak, Alemko; Agincic, Alija

    2014-01-01

    ABSTRACT Introduction: In Bosnia and Herzegovina according to available data, treatment of incompetent superficial lower extremity varicose veins by endovenous laser ablation (EVLA) has been introduced two years ago and so far no paper has been published regarding results of EVLA treatment of patients from our country. We wanted to present our results with EVLA treatment. Aim of study: to evaluate and compare primary posttreatment outcomes of endovenous laser ablation (EVLA) with classical surgical method of varicose vein treatment. Patients and methods: The study was clinical and prospective. It was carried out at Clinic for vascular surgery in Sarajevo where fifty-eight (58) patients received surgical treatment for varicose veins and in Aesthetic Surgery Center “Nasa mala klinika” in Sarajevo were sixty-one (61) patients with varicose veins were treated by endovenous laser ablation. Total 119 patients (limbs) with pathologic reflux only in great saphenous vein were evaluated between 1st of January 2013 and 31st of April 2014. Following primary outcome endpoints were evaluated smean day of return to normal everyday activities, patient subjective quantification of pain during first seven days after intervention, incidence of deep venous thrombosis (DVT), incidence of wound bleeding requiring surgical intervention, incidence of peri-saphenous vein hematoma and infection rate. Results: Mean of return to normal activities (expressed in days after intervention); EVLA vs. stripping (surgery) =1.21vs12.24, T test 13,619; p=0, 000, p<0,05. T test was used for comparing Mean value of visual pain analog scale for the first 7 days between groups, for all seven days pain was significantly higher in surgical group of patients as compared to EVLA group; p<0,05. Incidence of hematoma greater than 1% of total body surface area was significantly higher in patients receiving surgical treatment; Pearson Chi Square=23,830, p<0,05; odds ratio:10,453. Incidences of infection, deep

  16. Feasibility of ablative fractional laser-assisted drug delivery with optical coherence tomography.

    PubMed

    Yang, Chih-Hsun; Tsai, Meng-Tsan; Shen, Su-Chin; Ng, Chau Yee; Jung, Shih-Ming

    2014-11-01

    Fractional resurfacing creates hundreds of microscopic wounds in the skin without injuring surrounding tissue. This technique allows rapid wound healing owing to small injury regions, and has been proven as an effective method for repairing photodamaged skin. Recently, ablative fractional laser (AFL) treatment has been demonstrated to facilitate topical drug delivery into skin. However, induced fractional photothermolysis depends on several parameters, such as incident angle, exposure energy, and spot size of the fractional laser. In this study, we used fractional CO2 laser to induce microscopic ablation array on the nail for facilitating drug delivery through the nail. To ensure proper energy delivery without damaging tissue structures beneath the nail plate, optical coherence tomography (OCT) was implemented for quantitative evaluation of induced microscopic ablation zone (MAZ). Moreover, to further study the feasibility of drug delivery, normal saline was dripped on the exposure area of fingernail and the speckle variance in OCT signal was used to observe water diffusion through the ablative channels into the nail plate. In conclusion, this study establishes OCT as an effective tool for the investigation of fractional photothermolysis and water/drug delivery through microscopic ablation channels after nail fractional laser treatment. PMID:25426321

  17. Feasibility of ablative fractional laser-assisted drug delivery with optical coherence tomography

    PubMed Central

    Yang, Chih-Hsun; Tsai, Meng-Tsan; Shen, Su-Chin; Ng, Chau Yee; Jung, Shih-Ming

    2014-01-01

    Fractional resurfacing creates hundreds of microscopic wounds in the skin without injuring surrounding tissue. This technique allows rapid wound healing owing to small injury regions, and has been proven as an effective method for repairing photodamaged skin. Recently, ablative fractional laser (AFL) treatment has been demonstrated to facilitate topical drug delivery into skin. However, induced fractional photothermolysis depends on several parameters, such as incident angle, exposure energy, and spot size of the fractional laser. In this study, we used fractional CO2 laser to induce microscopic ablation array on the nail for facilitating drug delivery through the nail. To ensure proper energy delivery without damaging tissue structures beneath the nail plate, optical coherence tomography (OCT) was implemented for quantitative evaluation of induced microscopic ablation zone (MAZ). Moreover, to further study the feasibility of drug delivery, normal saline was dripped on the exposure area of fingernail and the speckle variance in OCT signal was used to observe water diffusion through the ablative channels into the nail plate. In conclusion, this study establishes OCT as an effective tool for the investigation of fractional photothermolysis and water/drug delivery through microscopic ablation channels after nail fractional laser treatment. PMID:25426321

  18. Fabrication of Random Microspikes on Mold Metal by Ultrashort Laser Ablation for Hydrophilic Surface

    NASA Astrophysics Data System (ADS)

    Noh, Jiwhan; Lee, Jae-Hoon; Lee, Sang-Yup; Na, Suckjoo

    2010-10-01

    Microsized spikes, which are smaller than laser focused spots, were fabricated by laser ablation in this study. The hydrophilic property of the surface with the microsize spikes was tested. Microspikes of 20 µm size were formed using a 50 µm laser focused spot size by optimizing the laser process parameters. Water drops were placed on the microspikes to measure the contact angle, which was 10° while that of the surface without microspikes was 80°. This shows that a surface can be processed to be hydrophilic with laser ablation, without applying hydrophilic chemical coating. Because the base material in this study was a mold metal, injection molding products with functional surfaces were produced economically by forming micropatterns on their surfaces. The economically micropatterns produced in this study will be applicable for controlling the friction of fluids on surfaces, as well as for producing hydrophilic surfaces.

  19. Laser ablation--reflections on a very complex technique for solid sampling.

    PubMed

    Niemax, K

    2001-06-01

    This paper is an attempt to point out the complex correlations between the experimental conditions in solid sampling by lasers. In particular, the influence of the laser properties, the surrounding gas, and the matrix on the analytical results of laser ablation techniques, such as laser induced breakdown spectrometry or laser ablation-ICP-MS, will be discussed. PMID:11495052

  20. High resolution selective multilayer laser processing by nanosecond laser ablation of metal nanoparticle films

    SciTech Connect

    Ko, Seung H.; Pan Heng; Hwang, David J.; Chung, Jaewon; Ryu, Sangil; Grigoropoulos, Costas P.; Poulikakos, Dimos

    2007-11-01

    Ablation of gold nanoparticle films on polymer was explored using a nanosecond pulsed laser, with the goal to achieve feature size reduction and functionality not amenable with inkjet printing. The ablation threshold fluence for the unsintered nanoparticle deposit was at least ten times lower than the reported threshold for the bulk film. This could be explained by the combined effects of melting temperature depression, lower conductive heat transfer loss, strong absorption of the incident laser beam, and the relatively weak bonding between nanoparticles. The ablation physics were verified by the nanoparticle sintering characterization, ablation threshold measurement, time resolved ablation plume shadowgraphs, analysis of ablation ejecta, and the measurement and calculation of optical properties. High resolution and clean feature fabrication with small energy and selective multilayer processing are demonstrated.

  1. Micro-ablation with high power pulsed copper vapor lasers.

    PubMed

    Knowles, M

    2000-07-17

    Visible and UV lasers with nanosecond pulse durations, diffraction-limited beam quality and high pulse repetition rates have demonstrated micro-ablation in a wide variety of materials with sub-micron precision and sub-micron-sized heat-affected zones. The copper vapour laser (CVL) is one of the important industrial lasers for micro-ablation applications. Manufacturing applications for the CVL include orifice drilling in fuel injection components and inkjet printers, micro-milling of micromoulds, via hole drilling in printed circuit boards and silicon machining. Recent advances in higher power (100W visible, 5W UV), diffraction-limited, compact CVLs are opening new possibilities for manufacturing with this class of nanosecond laser. PMID:19404369

  2. Emission spectroscopy analysis during Nopal cladodes dethorning by laser ablation

    NASA Astrophysics Data System (ADS)

    Peña-Díaz, M.; Ponce, L.; Arronte, M.; Flores, T.

    2007-04-01

    Optical emission spectroscopy of the pulsed laser ablation of spines and glochids from Opuntia (Nopal) cladodes was performed. Nopal cladodes were irradiated with Nd:YAG free-running laser pulses on their body, glochids and spines. Emission spectroscopy analyses in the 350-1000 nm region of the laser induced plasma were made. Plasma plume evolution characterization, theoretical calculations of plasma plume temperature and experiments varying the processing atmosphere showed that the process is dominated by a thermally activated combustion reaction which increases the dethorning process efficiency. Therefore, appropriate laser pulse energy for minimal damage of cladodes body and in the area beneath glochids and spines can be obtained.

  3. Production of nanoparticles from natural hydroxylapatite by laser ablation

    PubMed Central

    2011-01-01

    Laser ablation of solids in liquids technique has been used to obtain colloidal nanoparticles from biological hydroxylapatite using pulsed as well as a continuous wave (CW) laser. Transmission electron microscopy (TEM) measurements revealed the formation of spherical particles with size distribution ranging from few nanometers to hundred nanometers and irregular submicronic particles. High resolution TEM showed that particles obtained by the use of pulsed laser were crystalline, while those obtained by the use of CW laser were amorphous. The shape and size of particles are consistent with the explosive ejection as formation mechanism. PMID:21711800

  4. Laser ablation in a liquid-confined environment using a nanosecond laser pulse

    NASA Astrophysics Data System (ADS)

    Kang, Hyun Wook; Lee, Ho; Welch, Ashley J.

    2008-04-01

    Laser ablation of aluminum metal with 1ns, 800nm pulse at low radiant exposures was investigated in air (dry) and water (wet) environments. Compared to dry ablation, an approximately eight times increase in material removal rate was associated with wet ablation. Based on optical reflectance and scanning electron microscope images, bubble formation/collapse was responsible for augmented acoustic pressure and ablation performance. Numerically simulated temperature distributions during wet ablation were consistent with the occurrence of explosive water vaporization near the critical temperature of water. Strong pressure emission during liquid vaporization and jet formation can account for enhanced ablation process. Radial expansion of bubbles minimized the redeposition of debris, leading to improvements in energy coupling to the target and ablation performance.

  5. Endovenous Laser Ablation as a Treatment for Postsurgical Recurrent Saphenous Insufficiency

    SciTech Connect

    Anchala, Praveen R.; Wickman, Christopher; Chen, Richard; Faundeen, Tonya; Pearce, William; Narducy, Lisa; Resnick, Scott A.

    2010-10-15

    The purpose of this study was to investigate the safety and efficacy of endovenous laser ablation as a treatment for recurrent symptomatic saphenous insufficiency occurring after saphenous vein ligation and stripping. A single-center retrospective review of patients who received endovenous laser ablation as a treatment for recurrent symptomatic saphenous insufficiency after ligation and stripping between November 2003 and October 2006 was performed. Fifty-six insufficient saphenous systems were identified in 38 patients. Follow-up consisted of a clinical examination in all patients as well as selective lower-extremity duplex ultrasound as clinically indicated. All 38 patients demonstrated complete closure of the insufficient saphenous vein by clinical examination and/or duplex ultrasound evaluation. Preoperative symptoms resolved after treatment in all 38 patients. No major complications were identified. Endovenous laser ablation of recurrent symptomatic saphenous venous insufficiency is a safe and effective treatment in patients who develop recurrent symptoms after saphenous vein ligation and stripping.

  6. Formation of nanostructured solid-state carbon particles by laser ablation of graphite in isopropyl alcohol

    NASA Astrophysics Data System (ADS)

    Kitazawa, Sin-Iti; Abe, Hiroaki; Yamamoto, Shunya

    2005-02-01

    Nanostructured solid-state carbon particles with sizes of 1 10 μm are successfully formed from graphite target by applying laser ablation technique in isopropyl alcohol. In the laser ablation in liquid, the diffusion of the evaporated atomic carbon particles is prevented. It follows that the shock front is condensed in the high-density condition, and evaporated carbon particles are clustered and aggregated. Nanostructured solid-state carbon particles are formed by repeatedly gathering. In this study, the influence of laser ablation process on isopropyl alcohol solvent and graphite target is analyzed, and it is revealed that the possible influences on chemical reactions with isopropyl alcohol and the direct exfoliation from the target can be excluded in this condensation process.

  7. Nucleation and growth of nanoparticles in a plasma by laser ablation in liquid

    NASA Astrophysics Data System (ADS)

    Taccogna, Francesco

    2015-10-01

    > Modelling the nucleation and growth of nanoparticles in liquid-phase laser ablation is very important to optimize and control the size and the structure of nanoparticles. However, the detailed formation process of nanoparticles after laser ablation is still unclear. In the present study we investigated for the first time the kinetic growth of nanoparticles synthesized by laser ablation in water, emphasizing the leading role of the plasma medium and in particular the electrostatic agglomeration due to the charging of the nanoparticle in the plasma plume. The importance of the confining role of the liquid medium on the plasma plume is revealed, showing how an isothermal expansion is able to produce smaller nanoparticles compared to an adiabatic cooling.

  8. Infrared Laser Ablation Sample Transfer for MALDI and Electrospray

    NASA Astrophysics Data System (ADS)

    Park, Sung-Gun; Murray, Kermit King

    2011-08-01

    We have used an infrared laser to ablate materials under ambient conditions that were captured in solvent droplets. The droplets were either deposited on a MALDI target for off-line analysis by MALDI time-of-flight mass spectrometry or flow-injected into a nanoelectrospray source of an ion trap mass spectrometer. An infrared optical parametric oscillator (OPO) laser system at 2.94 μm wavelength and approximately 1 mJ pulse energy was focused onto samples for ablation at atmospheric pressure. The ablated material was captured in a solvent droplet 1-2 mm in diameter that was suspended from a silica capillary a few millimeters above the sample target. Once the sample was transferred to the droplet by ablation, the droplet was deposited on a MALDI target. A saturated matrix solution was added to the deposited sample, or in some cases, the suspended capture droplet contained the matrix. Peptide and protein standards were used to assess the effects of the number of IR laser ablation shots, sample to droplet distance, capture droplet size, droplet solvent, and laser pulse energy. Droplet collected samples were also injected into a nanoelectrospray source of an ion trap mass spectrometer with a 500 nL injection loop. It is estimated that pmol quantities of material were transferred to the droplet with an efficiency of approximately 1%. The direct analysis of biological fluids for off-line MALDI and electrospray was demonstrated with blood, milk, and egg. The implications of this IR ablation sample transfer approach for ambient imaging are discussed.

  9. 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

  10. The effect of ultrafast laser wavelength on ablation properties and implications on sample introduction in inductively coupled plasma mass spectrometry

    SciTech Connect

    LaHaye, N. L.; Harilal, S. S.; Diwakar, P. K.; Hassanein, A.; Kulkarni, P.

    2013-07-14

    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.

  11. Pulsed laser ablation of pepsin on an inorganic substrate

    NASA Astrophysics Data System (ADS)

    Cicco, N.; Lopizzo, T.; Marotta, V.; Morone, A.; Verrastro, M.; Viggiano, V.

    2009-03-01

    Pressed pepsin pellets used as targets were ablated with the pulses of the Nd-YAG laser. The activity of the pepsin thin layer, deposited on a glass substrate, was successfully detected by analyzing the proteolytic degradation areas on the polyacrylamide gel (PA-gel) copolymerized with albumin from the hen egg white (ovalbumin), used as an enzymatic substrate.

  12. Fractal Character of Titania Nanoparticles Formed by Laser Ablation

    SciTech Connect

    Musaev, O.; Midgley, A; Wrobel, J; Yan, J; Kruger, M

    2009-01-01

    Titania nanoparticles were fabricated by laser ablation of polycrystalline rutile in water at room temperature. The resulting nanoparticles were analyzed with x-ray diffraction, Raman spectroscopy, and transmission electron microscopy. The electron micrograph image of deposited nanoparticles demonstrates fractal properties.

  13. Laser Ablation of Materials for Propulsion of Spacecraft

    NASA Technical Reports Server (NTRS)

    Edwards, David L.; Carruth, Ralph; Campbell, Jonathan; Gray, Perry

    2004-01-01

    A report describes experiments performed as part of a continuing investigation of the feasibility of laser ablation of materials as a means of propulsion for small spacecraft. In each experiment, a specimen of ablative material was mounted on a torsion pendulum and irradiated with a laser pulse having an energy of 5 J. The amplitude of the resulting rotation of the torsion pendulum was taken to be an indication of the momentum transferred from the laser beam. Of the ablative materials tested, aluminum foils yielded the smallest rotation amplitudes of the order of 10 degrees. Black coating materials yielded rotation amplitudes of the order of 90 degrees. Samples of silver coated with a fluorinated ethylene propylene (FEP) copolymer yielded the largest rotation amplitudes 6 to 8 full revolutions. The report presents a theory involving heating of a confined plasma followed by escape of the plasma to explain the superior momentum transfer performance of the FEP specimens. It briefly discusses some concepts for optimizing designs of spacecraft engines to maximize the thrust obtainable by exploiting the physical mechanisms of the theory. Also discussed is the use of laser-ablation engines with other types of spacecraft engines.

  14. 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.

  15. Optical limiting properties of silver nanoparticles fabricated by laser ablation

    NASA Astrophysics Data System (ADS)

    Ong, T. S.; Lee, S. S.; Van, L. H.; Hong, Ming Hui; Chong, Tow Chong

    2004-10-01

    Silver nanoparticles have been fabricated by laser ablation of a silver metal foil in solution. The presence of sodium bis(2-ethylhexyl) sulfosuccinate increases the yield of the nanoparticles and enhances their stability. The optical limiting performance of the silver nanoparticles embedded in a PMMA film is compared to that in an aqueous solution.

  16. Superconducting properties of epitaxial laser ablated thin films

    NASA Astrophysics Data System (ADS)

    Berling, D.; Del Vecchio, A.; Leggieri, G.; Loegel, B.; Luches, A.; Mehdaoui, A.; Tapfer, L.

    1996-02-01

    We present experimental results obtained for high quality epitaxial thin films (film thicknesses around 5000 Å; rocking curve FWHM down to 0.1°). These films are obtained by laser ablation of REBa 2Cu 3O 7-δ (RE = Y, Er) deposited on SrTio 3 and YSZ substrates. The superconducting properties have been studied by complex susceptibility in an extended AC field range ( hac ≤ 300 Oe) and show sharp magnetic transition width and high critical currents (10 7A cm -2 < jc(77K) < 10 8A cm -2). The loss peak is only weakly depressed by an increasing AC field and the observed shifts are up to an order of magnitude lower than those observed for intragranular contributions in bulk samples. The agreement with the behaviour expected from a critical state model is also discussed.

  17. Laser Ablation of Gallium Arsenide in Different Solutions

    SciTech Connect

    Ganeev, R.A.; Kuroda, H.; Ryasnyanskii, A.I.

    2005-12-15

    The optical, structural, and nonlinear optical characteristics of GaAs nanoparticles obtained by laser ablation in different liquids were investigated. Thermally induced self-defocusing in GaAs solutions was observed using both a high pulse repetition rate and nanosecond pulses. In studying the nonlinear optical characteristics of GaAs solutions using picosecond and femtosecond pulses, two-photon absorption was observed. The nonlinear absorption coefficient of an aqueous GaAs solution measured by the Z-scan technique and the nonlinear susceptibility of GaAs nanoparticles were, respectively, 0.7 x 10{sup -9} cm W{sup -1} and 2 x 10{sup -9} esu at a wavelength of 795 nm.

  18. Ablation efficiency of α-Al2O3 in liquid phase and ambient air by nanosecond laser irradiation

    NASA Astrophysics Data System (ADS)

    Sajti, Csaba László; Sattari, Ramin; Chichkov, Boris; Barcikowski, Stephan

    2010-07-01

    Ablation efficiency and influences of laser parameters on a material removal rate by a nanosecond laser irradiation of α-Al2O3 are studied in gas and liquid phases. The laser ablation in the air yields maximum material removal rate of 12 ng/pulse using a 4.6-mJ pulse energy at 4-kHz repetition rate, compared to 88 ng/pulse in the water flow. Using a specific interpulse distance and a laser repetition rate further increase material removal rate by factor of 3 and 65, respectively, owing to an optimized lattice temperature and laser pulse interactions with the generated cavitation bubble. For the ablation in the air, these parameters do not significantly affect the ablation efficiency.

  19. Synthesis of gold nanoparticles by laser ablation of an Au foil inside and outside ionic liquids

    NASA Astrophysics Data System (ADS)

    Wender, Heberton; Andreazza, Marcos L.; Correia, Ricardo R. B.; Teixeira, Sérgio R.; Dupont, Jairton

    2011-03-01

    Stable gold nanoparticles (AuNPs) were prepared by simple laser ablation of an Au foil placed inside or outside four ionic liquids (ILs), without the addition of any external chemical reagent. Irregular spherical AuNPs with a diameter range of 5 to 20 nm were produced after laser ablation of an Au foil located inside or outside the ILs 1-n-butyl-3-methylimidazolium tetrafluoroborate (BMI.BF4), 1-n-butyl-3-methylimidazolium hexafluorophosphate (BMI.PF6) and 1-(3-cyanopropyl)-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ((BCN)MI.NTf2). Additionally, whereas laser ablation inside the IL 1-n-butyl-3-methylimidazolium dicyanamide BMI.N(CN)2 produced flower-like shaped nanoparticles of about 50 nm in size, ablation outside this IL presented similar results to the others ILs studied, as determined by TEM and UV-Vis. The size and shape of the prepared NPs were related to where NP nucleation and growth occurred, i.e., at the IL surface or within the IL. Indeed, the chemical composition of the IL/air interface and surface ion orientation played important roles in the stabilization of the AuNPs formed by laser ablation outside the ILs.

  20. Pilot-scale synthesis of metal nanoparticles by high-speed pulsed laser ablation in liquids.

    PubMed

    Streubel, René; Bendt, Georg; Gökce, Bilal

    2016-05-20

    The synthesis of catalysis-relevant nanoparticles such as platinum and gold is demonstrated with productivities of 4 g h(-1) for pulsed laser ablation in liquids (PLAL). The major drawback of low productivity of PLAL is overcome by utilizing a novel ultrafast high-repetition rate laser system combined with a polygon scanner that reaches scanning speeds up to 500 m s(-1). This high scanning speed is exploited to spatially bypass the laser-induced cavitation bubbles at MHz-repetition rates resulting in an increase of the applicable, ablation-effective, repetition rate for PLAL by two orders of magnitude. The particle size, morphology and oxidation state of fully automated synthesized colloids are analyzed while the ablation mechanisms are studied for different laser fluences, repetition rates, interpulse distances, ablation times, volumetric flow rates and focus positions. It is found that at high scanning speeds and high repetition rate PLAL the ablation process is stable in crystallite size and decoupled from shielding and liquid effects that conventionally occur during low-speed PLAL. PMID:27053598

  1. Pilot-scale synthesis of metal nanoparticles by high-speed pulsed laser ablation in liquids

    NASA Astrophysics Data System (ADS)

    Streubel, René; Bendt, Georg; Gökce, Bilal

    2016-05-01

    The synthesis of catalysis-relevant nanoparticles such as platinum and gold is demonstrated with productivities of 4 g h‑1 for pulsed laser ablation in liquids (PLAL). The major drawback of low productivity of PLAL is overcome by utilizing a novel ultrafast high-repetition rate laser system combined with a polygon scanner that reaches scanning speeds up to 500 m s‑1. This high scanning speed is exploited to spatially bypass the laser-induced cavitation bubbles at MHz-repetition rates resulting in an increase of the applicable, ablation-effective, repetition rate for PLAL by two orders of magnitude. The particle size, morphology and oxidation state of fully automated synthesized colloids are analyzed while the ablation mechanisms are studied for different laser fluences, repetition rates, interpulse distances, ablation times, volumetric flow rates and focus positions. It is found that at high scanning speeds and high repetition rate PLAL the ablation process is stable in crystallite size and decoupled from shielding and liquid effects that conventionally occur during low-speed PLAL.

  2. Laser ablation at 337 nm of nitrocellulose and nylon sensitized with organic dopants

    NASA Astrophysics Data System (ADS)

    Skordoulis, Constantine D.; Kosmidis, Constantine E.

    1993-05-01

    The laser induced ablative decomposition of nitrocellulose and nylon sensitized with organic dopants (Stilbene 420, Coumarin 120, and Rhodamine 6G) has been studied. Ablation with a low power nitrogen laser is hereby reported for the first time. With the addition of dyes strongly absorbing at 337 nm the photoetching rate of the pure materials can be significantly increased. A two step photochemical mechanism considering the decomposition of the polymers from excited electronic states and the energy transfer process from the dye to the polymer are discussed.

  3. Orbit Modification of Earth-Crossing Asteroids/Comets Using Rendezvous Spacecraft and Laser Ablation

    NASA Technical Reports Server (NTRS)

    Park, Sang-Young; Mazanek, Daniel D.

    2005-01-01

    This report describes the approach and results of an end-to-end simulation to deflect a long-period comet (LPC) by using a rapid rendezvous spacecraft and laser ablation system. The laser energy required for providing sufficient deflection DELTA V and an analysis of possible intercept/rendezvous spacecraft trajectories are studied in this analysis. These problems minimize a weighted sum of the flight time and required propellant by using an advanced propulsion system. The optimal thrust-vector history and propellant mass to use are found in order to transfer a spacecraft from the Earth to a targeted celestial object. One goal of this analysis is to formulate an optimization problem for intercept/rendezvous spacecraft trajectories. One approach to alter the trajectory of the object in a highly controlled manner is to use pulsed laser ablative propulsion. A sufficiently intense laser pulse ablates the surface of a near-Earth object (NEO) by causing plasma blowoff. The momentum change from a single laser pulse is very small. However, the cumulative effect is very effective because the laser can interact with the object over long periods of time. The laser ablation technique can overcome the mass penalties associated with other nondisruptive approaches because no propellant is required to generate the DELTA V (the material of the celestial object is the propellant source). Additionally, laser ablation is effective against a wide range of surface materials and does not require any landing or physical attachment to the object. For diverting distant asteroids and comets, the power and optical requirements of a laser ablation system on or near the Earth may be too extreme to contemplate in the next few decades. A hybrid solution would be for a spacecraft to carry a laser as a payload to a particular celestial body. The spacecraft would require an advanced propulsion system capable of rapid rendezvous with the object and an extremely powerful electrical generator, which is

  4. Effect of nozzle geometry on the performance of laser ablative propulsion thruster

    NASA Astrophysics Data System (ADS)

    Li, Long; Jiao, Long; Tang, Zhiping; Hu, Xiaojun; Peng, Jie

    2016-05-01

    The performance of "ablation mode" laser propulsion thrusters can be improved obviously by nozzle constraint. The nozzle geometry of "ablation mode" laser propulsion thrusters has been studied experimentally with CO2 lasers. Experimental results indicate that the propulsion performance of cylindrical nozzle thrusters is better than expansionary nozzle thrusters at the same lengths. The cylindrical nozzle thrusters were optimized by different laser energies. The results show that two important factors, the length-to-diameter ratio α and the thruster diameter to laser-spot diameter ratio β, affect the propulsion performance of the thruster obviously. The momentum coupling coefficient C m increases with the increase of α, while C m increases at first and then decreases with the increase of β.

  5. Investigations of the damage mechanisms during ultrashort pulse laser ablation of dental tissue

    NASA Astrophysics Data System (ADS)

    Domke, Matthias; Wick, Sebastian; Laible, Maike; Rapp, Stephan; Kuznetsova, Julia; Homann, Christian; Huber, Heinz P.; Sroka, Ronald

    2015-07-01

    Several investigations of dental tissue ablation with ultrashort pulsed lasers suggest that these lasers enable precise and selective material removal and reduce the formation of micro cracks and thermal effects, when compared to ns-pulses. In this study, two damage mechanisms are presented occurring during ablation of dentin using a laser emitting pulses of a duration of 380 fs at a wavelength of 1040 nm. First, it was found that nano cracks appear around the craters after single fs-pulse ablation. These cracks are directed to the crater and cross the dentinal tubules. Transient investigation of the single fs-pulse ablation process by pump-probe microscopy suggest that the driving mechanism could be a pressure wave that is released after stress confinement. Second, squared ablation holes were created by moving the laser focus at scan speeds between 0.5 mm/s and 2.0 m/s and fluences up to 14 J/cm2. It was found that deep cracks appear at the edges of the squared holes, if the scan speed is about 0.5 m/s. The fluence has only a minor impact on the crack formation. The crack propagation was investigated in the depth using x-ray micro tomography and optical coherence tomography. It was found that these cracks appear in the depth down to the dental pulp. These findings suggest that fast scanning of the laser beam is the key for damage free processing using ultrashort pulse lasers. Then, ablation rates of about 2.5 - 3.5 mm3/min/W can be achieved in dentine with pulse durations of 380 fs.

  6. Study of the efficacy of prosthetic laryngoplasty followed by Nd:YAG laser ventricular ablation for treatment of left laryngeal hemiplegia in the horse

    NASA Astrophysics Data System (ADS)

    Lam, Brenda; Tate, Lloyd P.; Correa, Maria T.

    1992-06-01

    A telephone survey was conducted to assess the efficacy of laryngoplasty surgery followed by Nd:YAG laser laryngeal ventricular ablation. Forty-three horses were included in the study that were treated at North Carolina State University, College of Veterinary Medicine (NCSU- CVM) January 1987 and September 1990. Questions asked of the owners or trainers of the horses related to complications that the horses may have had since leaving the hospital, ability to perform after treatment relative to before treatment, how respiratory noise after treatment related to before treatment, results of follow-up endoscopic exams, additional surgery that may have been performed, and owner satisfaction with the procedure. Wilcoxon signed rank test was used to determine the success of the procedure. Success was defined as a reduction of noise or improvement in performance ability. Results of the test indicated that the two procedures had an effect in reducing respiratory noise (p equals 0.0001) and increasing performance (p equals 0.0017).

  7. Ion extraction from positively biased laser-ablation plasma

    NASA Astrophysics Data System (ADS)

    Isono, Fumika; Nakajima, Mitsuo; Hasegawa, Jun; Horioka, Kazuhiko

    2016-07-01

    Ions were extracted through a grounded grid from a positively biased laser-ablation plasma and the behaviors were investigated. Since the plasma was positively biased against the grounded wall, we could extract the ions without insulated gap. We confirmed formation of a virtual anode when we increased the distance between the grid and the ion collector. Results also indicated that when the ion flux from the ablation plasma exceeded a critical value, the current was strongly suppressed to the space charge limited level due to the formation of virtual anode.

  8. Surface Modification of ICF Target Capsules by Pulsed Laser Ablation

    DOE PAGESBeta

    Carlson, Lane C.; Johnson, Michael A.; Bunn, Thomas L.

    2016-06-30

    Topographical modifications of spherical surfaces are imprinted on National Ignition Facility (NIF) target capsules by extending the capabilities of a recently developed full surface (4π) laser ablation and mapping apparatus. The laser ablation method combines the precision, energy density and long reach of a focused laser beam to pre-impose sinusoidal modulations on the outside surface of High Density Carbon (HDC) capsules and the inside surface of Glow Discharge Polymer (GDP) capsules. Sinusoidal modulations described in this paper have sub-micron to 10’s of microns vertical scale and wavelengths as small as 30 μm and as large as 200 μm. The modulatedmore » patterns are created by rastering a focused laser fired at discrete capsule surface locations for a specified number of pulses. The computer program developed to create these raster patterns uses inputs such as laser beam intensity profile, the material removal function, the starting surface figure and the desired surface figure. The patterns are optimized to minimize surface roughness. Lastly, in this paper, simulated surfaces are compared with actual ablated surfaces measured using confocal microscopy.« less

  9. Ultraviolet laser ablation of polycarbonate and glass in air

    SciTech Connect

    Bormotova, T. A.; Blumenthal, R.

    2009-02-01

    The fundamental physical processes that follow ultraviolet laser ablation of polycarbonate and borosilicate glass in air have been investigated using photodeflection as a function of the distance from the surface to probe laser. Four features were observed in the data sets for each material. Two of these features correlate well with gas dynamical predictions for the expansion of the shock wave and gas plume. The third feature is consistent with the propagation of the popping sound of the laser ablation event. The final feature, which occurs at very early times and does not shift significantly in time as the surface to probe distance is increased from 0 to greater than 6 mm, has been tentatively ascribed to the ejection of fast electrons. The final significant observation is complete blocking of the probe laser, only observed during borosilicate ablation, which is attributed to scattering of the probe laser light by macroscopic SiO{sub x} particles that grow in the final stages of plume expansion and cooling.

  10. Low electron temperature in ablating materials formed by picosecond soft x-ray laser pulses

    NASA Astrophysics Data System (ADS)

    Ishino, Masahiko; Hasegawa, Noboru; Nishikino, Masaharu; Pikuz, Tatiana; Skobelev, Igor; Faenov, Anatoly; Inogamov, Nail; Kawachi, Tetsuya; Yamagiwa, Mitsuru

    2015-09-01

    To study the ablation process induced by the soft x-ray laser pulse, we investigated the electron temperature of the ablating material. Focused soft x-ray laser pulses having a wavelength of 13.9 nm and duration of 7 ps were irradiated onto the LiF, Al, and Cu surfaces, and we observed the optical emission from the surfaces by use of an optical camera. On sample surfaces, we could confirm damage structures, but no emission signal in the visible spectral range during ablation could be observed. Then, we estimated the electron temperature in the ablating matter. To consider the radiation from a heated layer, we supposed a black-body radiator as an object. The calculation result was that the electron temperature was estimated to be lower than 1 eV and the process duration was shorter than 1000 ps. The theoretical model calculation suggests the spallative ablation for the interaction between the soft x-ray laser and materials. The driving force for the spallation is an increasing pressure appearing in the heated layer, and the change of the surface is considered to be due to a splash of a molten layer. The model calculation predicts that the soft x-ray laser with the fluence around the ablation threshold can create an electron temperature around 1 eV in a material. The experimental result is in good accordance with the theoretical prediction. Our investigation implies that the spallative ablation occurs in the low electron temperature region of a non-equilibrium state of warm dense matter.

  11. Solid material evaporation into an ECR source by laser ablation

    SciTech Connect

    Harkewicz, R.; Stacy, J.; Greene, J.; Pardo, R.C.

    1993-09-01

    In an effort to explore new methods of producing ion beams from solid materials, we are attempting to develop a laser-ablation technique for evaporating materials directly into an ECR ion source plasma. A pulsed NdYaG laser with approximately 25 watts average power and peak power density on the order of 10{sup 7} W/cm{sup 2} has been used off-line to measure ablation rates of various materials as a function of peak laser power. The benefits anticipated from the successful demonstration of this technique include the ability to use very small quantities of materials efficiently, improved material efficiency of incorporation into the ECR plasma, and decoupling of the material evaporation process from the ECR source tuning operation. Here we report on the results of these tests and describe the design for incorporating such a system directly with the ATLAS PII-ECR ion source.

  12. Preliminary characterization of hard dental tissue ablation with femtosecond lasers

    NASA Astrophysics Data System (ADS)

    Neev, Joseph; Squier, Jeffrey A.

    1998-05-01

    Because of low operating speed and excessive collateral damage, lasers have not succeeded in replacing conventional tools in many surgical and dental applications. Recent developments now allow the new generation of amplified ultrashort pulse lasers to operate at high repetition rates and high single pulse energies. A Titanium:sapphire Chirped Pulse Regenerative Amplifier system operating at 1 KHz and 50 fs pulse duration, was used to demonstrate ultrashort pulse ablation of hard and soft tissue. Maximum ablation rates for enamel and dentin were approximately 0.650 micrometers /pulse and 1.2 micrometers /pulse respectively. Temperature measurements at both front and rear surface of a 1 mm dentin and enamel slices showed minimal increases. Scanning electron micrographs clearly show that little thermal damage is generate by the laser system. If an effective delivery system is developed, ultrashort pulse system may offer a viable alternative as a safe, low noise dental tool.

  13. Generic incubation law for laser damage and ablation thresholds

    NASA Astrophysics Data System (ADS)

    Sun, Zhanliang; Lenzner, Matthias; Rudolph, Wolfgang

    2015-02-01

    In multi-pulse laser damage and ablation experiments, the laser-induced damage threshold (LIDT) usually changes with the number of pulses in the train, a phenomenon known as incubation. We introduce a general incubation model based on two physical mechanisms—pulse induced change of (i) absorption and (ii) critical energy that must be deposited to cause ablation. The model is applicable to a broad class of materials and we apply it to fit data for dielectrics and metals. It also explains observed changes of the LIDT as a function of the laser repetition rate. We discuss under which conditions the crater-size method to determine LIDTs can be applied in multi-pulse experiments.

  14. Thrust Measurements in Ballistic Pendulum Ablative Laser Propulsion Experiments

    SciTech Connect

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

    2008-04-28

    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 and 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.

  15. Acoustical measurements during Erbium:YAG laser ablation of porcine calcified tissues

    NASA Astrophysics Data System (ADS)

    Saaf, Randall R.; Wong, Brian J.; Milner, Thomas E.; Peavy, George M.; Anvari, Bahman

    1998-07-01

    The Erbium:YAG laser ((lambda) equals 2.94 micrometer) has been suggested for use in dental, orthopedic, and middle ear surgery due to decreased thermal trauma, precise ablation characteristics, and potential fiber optic delivery. While there has been much focus on the thermal and photoacoustic events that occur during pulsed laser ablation of hard tissue, there are few studies that examine the acoustic energy generated by these devices during ablation from an audiologic standpoint. In this study, the porcine otic capsule, nasal bone, and teeth were irradiated with an Erbium:YAG laser. Frequencies of 5 and 10 Hz shot repetition rate were used with .5 to 4 W average power. Additionally, a burst mode consisting of three pulses was used with .2 to 1.4 J total energy. During ablation, acoustic measurements were made using a sound level meter held 20 mm away from the target site. A constant spot size of 500 micrometer was maintained for each laser blast. With each set of laser parameters, the sound intensity (dB SPL) exceeded 70 dB. Peak intensity measurements of 95 dB were measured. The clinical significance of these findings is discussed and the acoustical aspects of middle ear function and noise trauma are reviewed.

  16. Liquid-assisted laser ablation of advanced ceramics and glass-ceramic materials

    NASA Astrophysics Data System (ADS)

    Garcia-Giron, A.; Sola, D.; Peña, J. I.

    2016-02-01

    In this work, results obtained by laser ablation of advanced ceramics and glass-ceramic materials assisted by liquids are reported. A Q-switched Nd:YAG laser at its fundamental wavelength of 1064 nm with pulse-width in the nanosecond range was used to machine the materials, which were immersed in water and ethylene glycol. Variation in geometrical parameters, morphology, and ablation yields were studied by using the same laser working conditions. It was observed that machined depth and removed volume depended on the thermal, optical, and mechanical features of the processed materials as well as on the properties of the surrounding medium in which the laser processing was carried out. Variation in ablation yields was studied in function of the liquid used to assist the laser process and related to refractive index and viscosity. Material features and working conditions were also related to the obtained results in order to correlate ablation parameters with respect to the hardness of the processed materials.

  17. Compact And Robust Laser Impulse Measurement Device, With Ultrashort Pulse Laser Ablation Results

    NASA Astrophysics Data System (ADS)

    Kremeyer, Kevin; Lapeyre, John; Hamann, Steven

    2008-04-01

    An impulse measurement device and analysis package was conceived, designed, constructed, tested, and demonstrated to be capable of: measuring nanoNewton-seconds to milliNewton-seconds of impulse due to laser-ablation; being transported as carry-on baggage; set-up and tear-down times of less than an hour; target exchange times of less than two minutes (targets can be ablated at multiple positions for thousands of shots); measurements in air and in vacuum; error of just a few percent; repeatability over a wide range of potential systematic error sources; and time between measurements, including ring-down and analysis, of less than 30 seconds. The instrument consists of a cantilever (i.e. leaf spring), whose time-dependent displacement/oscillation is measured and analyzed to determine the impulse imparted by a laser pulse to a target. These shapes are readily/commercially available, and any target material can be used, provided it can be fashioned in the form of a cantilever, or as a coating/film/tape, suitable for mounting on a cantilever of known geometry. The instrument was calibrated both statically and dynamically, and measurements were performed on brass, steel, and Aluminum, using laser pulses of ˜7 ns, ˜500 ps, and ˜500 fs. The results agree well with those published in the literature, with surface effects, atmosphere, and pre-/post-pulses demonstrating interesting effects and indicating areas for further study. These parameters should be carefully controlled and held constant during a series of measurements. The impulse imparted by ablation due to laser filaments in air was also explored.

  18. Modeling of dynamical processes in laser ablation

    SciTech Connect

    Leboeuf, J.N.; Chen, K.R.; Donato, J.M.; Geohegan, D.B.; Liu, C.L.; Puretzky, A.A.; Wood, R.F.

    1995-12-31

    Various physics and computational approaches have been developed to globally characterize phenomena important for film growth by pulsed-laser deposition of materials. These include thermal models of laser-solid target interactions that initiate the vapor plume, plume ionization and heating through laser absorption beyond local thermodynamic equilibrium mechanisms, hydrodynamic and collisional descriptions of plume transport, and molecular dynamics models of the interaction of plume particles with the deposition substrate.

  19. Next generation Er:YAG fractional ablative laser

    NASA Astrophysics Data System (ADS)

    Heinrich, A.; Vizhanyo, A.; Krammer, P.; Summer, S.; Gross, S.; Bragagna, T.; Böhler, C.

    2011-03-01

    Pantec Biosolutions AG presents a portable fractional ablative laser system based on a miniaturized diode pumped Er:YAG laser. The system can operate at repetition rates up to 500 Hz and has an incorporated beam deflection unit. It is smaller, lighter and cost efficient compared to systems based on lamp pumped Er:YAG lasers and incorporates a skin layer detection to guarantee precise control of the microporation process. The pulse parameters enable a variety of applications in dermatology and in general medicine, as demonstrated by first results on transdermal drug delivery of FSH (follicle stimulating hormone).

  20. Planar laser-driven ablation model for nonlocalized absorption

    SciTech Connect

    Dahmani, F.; Kerdja, T. )

    1991-05-01

    A model for planar laser-driven ablation is presented. Nonlocalized inverse bremsstrahlung absorption of laser energy at a density {ital n}{sub 1}{lt}{ital n}{sub {ital c}} is assumed. A steady-state solution in the conduction zone is joined to a rarefaction wave in the underdense plasma. The calculations relate all steady-state fluid quantities to only the material, absorbed intensity, and laser wavelength. The theory agrees well with results from a computer hydrodynamics code MEDUSA (Comput. Phys. Commun. {bold 7}, 271 (1974)) and experiments.

  1. Pulsed laser ablation of binary semiconductors: mechanisms of vaporisation and cluster formation

    SciTech Connect

    Bulgakov, A V; Evtushenko, A B; Shukhov, Yu G; Ozerov, I; Marin, W

    2010-12-29

    Formation of small clusters during pulsed ablation of two binary semiconductors, zinc oxide and indium phosphide, in vacuum by UV, visible, and IR laser radiation is comparatively studied. The irradiation conditions favourable for generation of neutral and charged Zn{sub n}O{sub m} and In{sub n}P{sub m} clusters of different stoichiometry in the ablation products are found. The size and composition of the clusters, their expansion dynamics and reactivity are analysed by time-of-flight mass spectrometry. A particular attention is paid to the mechanisms of ZnO and InP ablation as a function of laser fluence, with the use of different ablation models. It is established that ZnO evapourates congruently in a wide range of irradiation conditions, while InP ablation leads to enrichment of the target surface with indium. It is shown that this radically different character of semiconductor ablation determines the composition of the nanostructures formed: zinc oxide clusters are mainly stoichiometric, whereas In{sub n}P{sub m} particles are significantly enriched with indium. (photonics and nanotechnology)

  2. Thermal-mechanical modeling of laser ablation hybrid machining

    NASA Astrophysics Data System (ADS)

    Matin, Mohammad Kaiser

    2001-08-01

    Hard, brittle and wear-resistant materials like ceramics pose a problem when being machined using conventional machining processes. Machining ceramics even with a diamond cutting tool is very difficult and costly. Near net-shape processes, like laser evaporation, produce micro-cracks that require extra finishing. Thus it is anticipated that ceramic machining will have to continue to be explored with new-sprung techniques before ceramic materials become commonplace. This numerical investigation results from the numerical simulations of the thermal and mechanical modeling of simultaneous material removal from hard-to-machine materials using both laser ablation and conventional tool cutting utilizing the finite element method. The model is formulated using a two dimensional, planar, computational domain. The process simulation acronymed, LAHM (Laser Ablation Hybrid Machining), uses laser energy for two purposes. The first purpose is to remove the material by ablation. The second purpose is to heat the unremoved material that lies below the ablated material in order to ``soften'' it. The softened material is then simultaneously removed by conventional machining processes. The complete solution determines the temperature distribution and stress contours within the material and tracks the moving boundary that occurs due to material ablation. The temperature distribution is used to determine the distance below the phase change surface where sufficient ``softening'' has occurred, so that a cutting tool may be used to remove additional material. The model incorporated for tracking the ablative surface does not assume an isothermal melt phase (e.g. Stefan problem) for laser ablation. Both surface absorption and volume absorption of laser energy as function of depth have been considered in the models. LAHM, from the thermal and mechanical point of view is a complex machining process involving large deformations at high strain rates, thermal effects of the laser, removal of

  3. Ablation performances in natural and synthetic quartz using an Infra Red femtosecond laser system

    NASA Astrophysics Data System (ADS)

    Courtieu, C.; D'Abzac, F.; Seydoux-Guillaume, A.; Guillaume, D.

    2009-12-01

    Performances of laser ablation have been widely explored, especially for industrial purposes. Nevertheless, some study fields remain unknown, notably the use of Infra-Red femtosecond pulses for the ablation of hard transparent materials. Thus, we present analytical results on quartz, which is the most widespread mineral in earth sciences, especially for fluid inclusions studies[1]. We used a commercial Ti:Sapphire femtosecond pulsed laser operated at its fundamental wavelength (λ=800nm). Ablation thresholds have been determined for N=1 and 10 consecutive shots (τ=60fs, E(pulse)=0.1-1mJ/pulse)[2]. Sequences from N=10 to 8000 shots (τ=60fs, E(pulse)=1mJ/pulse and f=5Hz) have been carried out with two different focusing optics: a convergent 50mm focusing lens and a 25mm focusing Cassegrain objective (wavefront corrected). Experiments have been realized on polished and unpolished single synthetic and natural (Campério, Swiss Alps) crystals, with a laser beam parallel and perpendicular to the quartz C-axis. Series of craters have then been observed with an optical microscope. Threshold fluence for a single shot is variable from Fth=1.1J.cm-2 (unpolished surface) to Fth=2.9J.cm-2 (polished surface). For N=10, threshold decreases to Fth=0.1J.cm-2 (unpolished surface) and Fth=1.76J.cm-2 (polished surface) respectively. When using lens, a constant ablation rate of ~0.5µm/pulse can be calculated until N=2000 shots. Crater stops developing after N=3000 shots. The maximum depth measured is 1342µm. Ablation pattern is different when using the Cassegrain objective. An initial ablation rate of ~0.5µm/pulse decreases following a logarithmic trend until a maximum crater depth of ~350µm (N=3000 shots). Orientation of the crystal lattice has shown no influence on ablation performances. Data bring evidences of capabilities of Infra Red femtosecond laser ablation, even in high IR-transmitting materials. High fluence regime is not required. Matter removal is not dependant on the

  4. 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.

  5. Controlled Contamination of Epoxy Composites with PDMS and Removal by Laser Ablation

    NASA Technical Reports Server (NTRS)

    Palmieri, Frank; Ledesma, Rodolfo; Cataldo, Daniel; Lin, Yi; Wohl, Christopher; Gupta, Mool; Connell, John

    2016-01-01

    Surface preparation is critical to the performance of adhesively bonded composites. During manufacturing, minute quantities of mold release compounds are inevitably deposited on faying surfaces and may compromise bond performance. To ensure safety, mechanical fasteners and other crack arrest features must be installed in the bondlines of primary structures, which negates some advantages of adhesively bonded construction. Laser ablation is an automated, repeatable, and scalable process with high potential for the surface preparation of metals and composites in critical applications such as primary airframe structures. In this study, laser ablation is evaluated on composite surfaces for the removal of polydimethylsiloxane (PDMS), a common mold release material. Composite panels were contaminated uniformly with PDMS film thicknesses as low as 6.0 nm as measured by variable angle spectroscopic ellipsometry. Bond performance was assessed by mechanical testing using a 250 F cure, epoxy adhesive and compared with pre-bond surface inspection results. Water contact angle, optically stimulated electron emission, and laser induced breakdown spectroscopy were used to characterize contaminated and laser ablated surfaces. The failure mode obtained from double cantilever beam tests correlated well with surface characterization data. The test results indicated that even low levels of PDMS were not completely removed by laser ablation.

  6. New Combined Laser Ablation Platform Determines Cell Wall Chemistry (Fact Sheet)

    SciTech Connect

    Not Available

    2011-09-01

    NREL has designed and developed a combined laser ablation/pulsed sample introduction/mass spectrometry platform that integrates pyrolysis and/or laser ablation with resonance-enhanced multiphoton ionization (REMPI) time-of-flight mass spectrometry. Using this apparatus, we can measure the cell wall chemical composition of untreated biomass materials. Understanding the chemical composition of untreated biomass is key to both the biochemical and thermochemical conversion of lignocellulosic biomass to biofuels. In the biochemical conversion process, the new technique provides a better understanding of the chemistry of lignin and will improve accessibility to plant sugars. In thermochemical conversion, the information provided by the new technique may help to reduce the formation of unwanted byproducts during gasification. NREL validated the ability of the system to detect pyrolysis products from plant materials using poplar, a potentially high-impact bioenergy feedstock. In the technique, biomass vapors are produced by laser ablation using the 3rd harmonic of an Nd:YAG laser (355 nm). The resulting vapors are entrained in a free jet expansion of helium, then skimmed and introduced into an ionization region. REMPI is used to ionize the vapors because it is highly sensitive for detecting lignin and aromatic metabolites. The laser ablation method was used to selectively volatilize specific plant tissues and detect lignin-based products from the vapors with enhanced sensitivity. This will allow the determination of lignin distribution in future biomass studies.

  7. Preparation of GaN Nanostructures by Laser Ablation of ga Metal

    NASA Astrophysics Data System (ADS)

    El Nadi, Lotfia; Omar, Magdy M.; Mehena, Galila A.; Moniem, Hussien M. A.

    2011-06-01

    In the present study, GaN nanodots (0D) and nanowires (1D) nanostructures were prepared on stainless steal substrates applying laser ablation technique. The target of Ga metal mixed with NaNO2 was introduced in a central bore of a graphite rod of a confined geometry set up. The laser beam was normally focused onto the central bore and the ablated plume of Ga metal was deposited on stainless steal substrate lying below the graphite rod in an atmosphere of slow flow of nitrogen gas with or without ammonia vapor. The pulsed N2 laser beam having a wavelength of 337± 2 nm, pulse duration 15±1 ns and energy per pulse of 15±1 m J, could be focused on the central bore by a cylindrical quartz lens to a spot of dimensions 500 × 700 μm2 t providing target irradiance of 0.2-0.3 GW/cm2 per pulse. The ablated plum was collected after several thousand laser shots. The morphology and structure of the formed nanostructures were investigated by Scanning electron microscope and Energy Dispersive X-Ray Spectroscopy. The growth mechanism is most likely by Solid-Liquid-Vapor phase during the laser ablation processes. The role of the carbon, the NaNO2 and the flowing gas on the growth of Nanostructures of GaN are discussed.

  8. Photodynamic Therapy with Ablative Carbon Dioxide Fractional Laser in Treatment of Actinic Keratosis

    PubMed Central

    Jang, Yong Hyun; Lee, Dong Jun; Shin, Jaeyoung; Kang, Hee Young; Lee, Eun-So

    2013-01-01

    Background Recently, photodynamic therapy (PDT) has been shown to be an effective first-line treatment for actinic keratosis (AK). However, a major limitation of PDT is the long incubation time required to allow penetration of the photosensitizer. Objective The aim of this study was to assess if pretreatment with an ablative carbon dioxide (CO2) fractional laser can reduce the incubation time of the photosensitizer. Methods Initially, 29 patients with a total of 34 AK lesions were treated with an ablative CO2 fractional laser at Ajou University Hospital between January and December 2010. Immediately after the laser treatment, topical 20% 5-aminolevulinic acid or methyl-aminolevulinate was applied to the AK lesions and incubated for 70 to 90 minutes. Then, the treated areas were illuminated with a red light source. Improvement was clinically or histologically assessed eight weeks after the treatment. Results In spite of the short incubation time, 24 lesions (70.6%) showed a complete response (CR) within three sessions of PDT (10 lesions a clinical CR and 14 lesions a clinical/histological CR). There were no significant side effects associated with the combination of ablative CO2 fractional laser and PDT. Conclusion Ablative CO2 fractional laser may be considered an additional treatment option for reducing the incubation time of the photosensitizer in PDT. PMID:24371387

  9. Focal Laser Ablation of Prostate Cancer: Definition, Needs, and Future

    PubMed Central

    Colin, Pierre; Mordon, Serge; Nevoux, Pierre; Marqa, Mohammed Feras; Ouzzane, Adil; Puech, Philippe; Bozzini, Gregory; Leroux, Bertrand; Villers, Arnauld; Betrouni, Nacim

    2012-01-01

    Current challenges and innovations in prostate cancer management concern the development of focal therapies that allow the treatment of only the cancer areas sparing the rest of the gland to minimize the potential morbidity. Among these techniques, focal laser ablation (FLA) appears as a potential candidate to reach the goal of focusing energy delivery on the identified targets. The aim of this study is to perform an up-to-date review of this new therapeutic modality. Relevant literature was identified using MEDLINE database with no language restrictions (entries: focal therapy, laser interstitial thermotherapy, prostate cancer, FLA) and by cross-referencing from previously identified studies. Precision, real-time monitoring, MRI compatibility, and low cost of integrated system are principal advantages of FLA. Feasibility and safety of this technique have been reported in phase I assays. FLA might eventually prove to be a middle ground between active surveillance and radical treatment. In conclusion, FLA may have found a role in the management of prostate cancer. However, further trials are required to demonstrate the oncologic effectiveness in the long term. PMID:22666240

  10. Laser ablation synthesis of lanthanide oxide clusters: Mechanisms and chemistry

    SciTech Connect

    Gibson, J.K.

    1995-07-15

    Excimer laser ablation into vacuum of hydrated lanthanide oxalates has produced new lanthanide (Ln) oxide cluster ions which were identified by time-of-flight mass spectrometry. In addition to binary oxide clusters (Ln{sub {ital m}}O{sup +}{sub {ital n}}), mixed lanthanide oxide clusters [Ln{sub {ital m}1}Ln{sub {ital m}2}{sup {prime}}O{sup +}{sub {ital n}} with ({ital m}1+{ital m}2){le}9] were discerned for the following Ln-Ln{prime}: La-Tb, La-Ho, La-Lu, and Ho-Lu. The observed cluster ion stoichiometries, abundance distributions, and hydration systematics provide insights into cluster formation mechanisms and chemistries. Time-variable ion sampling revealed cluster enhancement in the tail of the ablation plume. The body of experimental results support cluster formation by aggregation of small ablated species. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

  11. An Electron Emission Effect on Dynamics of Laser Ablation

    SciTech Connect

    Nastoyashchii, A. F.

    2004-03-30

    The paper deals with the effect of electron emission on a heat transfer in the area of a plasma critical density (near plasma-solid surface boundary). As is known, experimental data show the limitation of electron thermal conductivity in the mentioned area. In the laser fusion research just the limitation of the heat transfer at target irradiation with long-wave lasers has made application of CO2-lasers unreasonable in spite of their high efficiency. On other hand, as to the applied tasks of laser ablation (e.g. in launching small-scale satellites) the aspect of the CO2-lasers application is being widely discussed. In the paper the mentioned limitation is explained on the basis of classical representations. It is marked, that the heat transfer limitations arise from the conditions of preserving plasma quasi-neutrality at the absorption area boundary where the electron density is close to critical one for the given laser wavelength. Possible mechanisms of the electron emission in the mode of the laser ablation are discussed.

  12. LASER ABLATION-INDUCTIVELY COUPLED PLASMA-ATOMIC EMISSION SPECTROSCOPY STUDY AT THE 222-S LABORATORY USING HOT-CELL GLOVE BOX PROTOTYPE SYSTEM

    SciTech Connect

    LOCKREM LL; OWENS JW; SEIDEL CM

    2009-03-26

    This report describes the installation, testing and acceptance of the Waste Treatment and Immobilization Plant procured laser ablation-inductively coupled plasma-atomic emission spectroscopy (LA-ICP-AES) system for remotely analyzing high-level waste samples in a hot cell environment. The 2005-003; ATS MP 1027, Management Plan for Waste Treatment Plant Project Work Performed by Analytical Technical Services. The APD group at the 222-S laboratory demonstrated acceptable turnaround time (TAT) and provide sufficient data to assess sensitivity, accuracy, and precision of the LA-ICP-AES method.

  13. LASER ABLATION-INDUCTIVELY COUPLED PLASMA-ATOMIC EMISSION SPECTROSCOPY STUDY AT THE 222-S LABORATORY USING HOT-CELL GLOVE BOX PROTOTYPE SYSTEM

    SciTech Connect

    SEIDEL CM; JAIN J; OWENS JW

    2009-02-23

    This report describes the installation, testing, and acceptance of the Waste Treatment and Immobilization Plant (WTP) procured laser ablation-inductively coupled plasma-atomic emission spectroscopy (LA-ICP-AES) system for remotely analyzing high-level waste (HLW) samples in a hot cell environment. The work was completed by the Analytical Process Development (APD) group in accordance with Task Order 2005-003; ATS MP 1027, Management Plan for Waste Treatment Plant Project Work Performed by Analytical Technical Services. The APD group at the 222-S Laboratory demonstrated acceptable turnaround time (TAT) and provide sufficient data to assess sensitivity, accuracy, and precision of the LA-ICP-AES method.

  14. Laser-driven ablation through fast electrons in PALS experiment

    NASA Astrophysics Data System (ADS)

    Gus'kov, S. Yu.; Chodukowski, T.; Demchenko, N.; Kalinowska, Z.; Kasperczuk, A.; Krousky, E.; Pfeifer, M.; Pisarczyk, P.; Pisarczyk, T.; Renner, O.; Skala, J.; Smid, M.; Ullschmied, J.

    2016-03-01

    Energy transfer to shock wave in Al and Cu targets irradiated by a laser pulse with intensity of I≈1-50 PW/cm2 and duration of 250 ps was investigated at Prague Asterix Laser System (PALS). The iodine laser provided energy in the range of 100-600 J at the first and third harmonic frequencies. The focal spot radius of laser beam on the target was varied from 160 to 40 μm. The dominant contribution of fast electron energy transfer into the ablation process was found when using the first harmonic radiation, the focal spot radius of 40-100 μm, and the energy of 300-600 J. The fast electron heating results in the growth of ablation pressure from 60 Mbar at the intensity of 10 PW/cm2 to 180 Mbar at the intensity of 50 PW/cm2 and in the growth of the efficiency of the energy conversion into the shock wave from 2 to 7% under the conditions of 2D ablation.

  15. Analytical model for CO(2) laser ablation of fused quartz.

    PubMed

    Nowak, Krzysztof M; Baker, Howard J; Hall, Denis R

    2015-10-10

    This paper reports the development of an analytical model, with supporting experimental data, which quite accurately describes the key features of CO2 laser ablation of fused silica glass. The quantitative model of nonexplosive, evaporative material removal is shown to match the experimental data very well, to the extent that it can be used as a tool for ablative measurements of absorption coefficient and vaporization energy. The experimental results indicated that a minimum of 12  MJ kg-1 is required to fully vaporize fused quartz initially held at room temperature, which is in good agreement with the prediction of the model supplied with input data available in the literature. An optimal window for the machining of fused quartz was revealed in terms of pulse duration 20-80 μs and CO2 laser wavelength optimized for maximum absorption coefficient. Material removal rates of 0.33 μm per J cm-2 allow for a high-precision depth control with modest laser stability. The model may also be used as a parameter selection guide for CO2 laser ablation of fused silica or other materials of similar thermophysical properties. PMID:26479800

  16. Gas Effect On Plasma Dynamics Of Laser Ablation Zinc Oxide

    NASA Astrophysics Data System (ADS)

    Abdelli-Messaci, S.; Kerdja, T.; Lafane, S.; Malek, S.

    2008-09-01

    In order to synthesis zinc oxide thin films and nanostructures, laser ablation of ZnO target into both vacuum and oxygen atmosphere was performed. The gas effect on the plume dynamics was studied for O2 pressures varied between 10-2 to 70 mbar. Plasma plume evolution was investigated by ICCD camera fast imaging. The plasma was created by a KrF excimer laser (λ = 248 nm, τ = 25 ns) at a fluence of 2 J/cm2. The light emitted by the plume was observed along the perpendicular to the ejection direction through a fast intensified charge-coupled device (ICCD). We have found that the plasma dynamics is very affected by the gas pressures. The photographs reveal the stratification of plasma into slow and fast components for 0.5 mbar O2 pressures and beyond. The photographs also show the apparition of hydrodynamic instabilities which are related to chemical reactions between the plasma and the surrounding gas for a certain range of pressures.

  17. Gas Effect On Plasma Dynamics Of Laser Ablation Zinc Oxide

    SciTech Connect

    Abdelli-Messaci, S.; Kerdja, T.; Lafane, S.; Malek, S.

    2008-09-23

    In order to synthesis zinc oxide thin films and nanostructures, laser ablation of ZnO target into both vacuum and oxygen atmosphere was performed. The gas effect on the plume dynamics was studied for O{sub 2} pressures varied between 10{sup -2} to 70 mbar. Plasma plume evolution was investigated by ICCD camera fast imaging. The plasma was created by a KrF excimer laser ({lambda} = 248 nm, {tau} = 25 ns) at a fluence of 2 J/cm{sup 2}. The light emitted by the plume was observed along the perpendicular to the ejection direction through a fast intensified charge-coupled device (ICCD). We have found that the plasma dynamics is very affected by the gas pressures. The photographs reveal the stratification of plasma into slow and fast components for 0.5 mbar O{sub 2} pressures and beyond. The photographs also show the apparition of hydrodynamic instabilities which are related to chemical reactions between the plasma and the surrounding gas for a certain range of pressures.

  18. Femtosecond laser ablation properties of transparent materials: impact of the laser process parameters on the machining throughput

    NASA Astrophysics Data System (ADS)

    Matylitsky, V. V.; Hendricks, F.; Aus der Au, J.

    2013-03-01

    High average power, high repetition rate femtosecond lasers with μJ pulse energies are increasingly used for bio-medical and material processing applications. With the introduction of femtosecond laser systems such as the SpiritTM platform developed by High Q Lasers and Spectra-Physics, micro-processing of solid targets with femtosecond laser pulses have obtained new perspectives for industrial applications [1]. The unique advantage of material processing with subpicosecond lasers is efficient, fast and localized energy deposition, which leads to high ablation efficiency and accuracy in nearly all kinds of solid materials. The study on the impact of the laser processing parameters on the removal rate for transparent substrate using femtosecond laser pulses will be presented. In particular, examples of micro-processing of poly-L-lactic acid (PLLA) - bio-degradable polyester and XensationTM glass (Schott) machined with SpiritTM ultrafast laser will be shown.

  19. Microjet-assisted dye-enhanced diode laser ablation of cartilaginous tissue

    NASA Astrophysics Data System (ADS)

    Pohl, John; Bell, Brent A.; Motamedi, Massoud; Frederickson, Chris J.; Wallace, David B.; Hayes, Donald J.; Cowan, Daniel

    1994-08-01

    Recent studies have established clinical application of laser ablation of cartilaginous tissue. The goal of this study was to investigate removal of cartilaginous tissue using diode laser. To enhance the interaction of laser light with tissue, improve the ablation efficiency and localize the extent of laser-induced thermal damage in surrounding tissue, we studied the use of a novel delivery system developed by MicroFab Technologies to dispense a known amount of Indocyanine Green (ICG) with a high spatial resolution to alter the optical properties of the tissue in a controlled fashion. Canine intervertebral disks were harvested and used within eight hours after collection. One hundred forty nL of ICG was topically applied to both annulus and nucleus at the desired location with the MicroJet prior to each irradiation. Fiber catheters (600 micrometers ) were used and positioned to irradiate the tissue with a 0.8 mm spot size. Laser powers of 3 - 10 W (Diomed, 810 nm) were used to irradiate the tissue with ten pulses (200 - 500 msec). Discs not stained with ICG were irradiated as control samples. Efficient tissue ablation (80 - 300 micrometers /pulse) was observed using ICG to enhance light absorption and confine thermal damage while there was no observable ablation in control studied. The extent of tissue damage observed microscopically was limited to 50 - 100 micrometers . The diode laser/Microjet combination showed promise for applications involving removal of cartilaginous tissue. This procedure can be performed using a low power compact diode laser, is efficient, and potentially more economical compared to procedures using conventional lasers.

  20. Synthesis of Nickel Nanomaterial by Pulsed Laser Ablation in Liquid Medium and its Characterization

    SciTech Connect

    Gopal, R.; Singh, S. C.; Swarnkar, R. K.; Singh, M. K.; Agarwal, A.

    2009-06-29

    Laser ablation of nickel nanoparticles suspended in double deionized water has been studied using Nd:YAG laser (355 nm) with energy 30 mJ/pulse. Produced nanoparticles are analyzed by UV-visible absorption spectroscopy at certain interval (0, 20, 40, 60 minute). The particles are characterized by Transmission Electron Microscopy (TEM), and X-ray Diffraction (XRD). TEM image shows that particles have crystal like structure and these particles are in the range of 20 nm to 50 nm.

  1. Synthesis of Nickel Nanomaterial by Pulsed Laser Ablation in Liquid Medium and its Characterization

    NASA Astrophysics Data System (ADS)

    Gopal, R.; Singh, M. K.; Agarwal, A.; Singh, S. C.; Swarnkar, R. K.

    2009-06-01

    Laser ablation of nickel nanoparticles suspended in double deionized water has been studied using Nd:YAG laser (355 nm) with energy 30 mJ/pulse. Produced nanoparticles are analyzed by UV-visible absorption spectroscopy at certain interval (0, 20, 40, 60 minute). The particles are characterized by Transmission Electron Microscopy (TEM), and X-ray Diffraction (XRD). TEM image shows that particles have crystal like structure and these particles are in the range of 20 nm to 50 nm.

  2. Characterization of UV laser ablation for microprocessing of a-Si:H thin films

    NASA Astrophysics Data System (ADS)

    Molpeceres, C.; Lauzurica, S.; Ocaña, J. L.; Gandía, J. J.; Urbina, L.; Cárabe, J.; Villar, F.; Escarré, J.; Bertomeu, J.; Andreu, J.

    2006-04-01

    Hydrogenated amorphous silicon has been widely studied last years, both from the basic research and industrial points of view, due to the important set of potential applications that this material offers, ranging from Thin Films Transistors (TFTs) to solar cells technologies. In different fabrication steps of a-Si:H based devices, laser sources have been used as appropriate tools for cutting, crystallising, contacting, patterning, etc., and more recent research lines are undertaking the problem of a-Si:H selective laser ablation for different applications. The controlled ablation of photovoltaic materials with minimum debris and small heat affected zone with low processing costs, is one of the main difficulties for the successful implementation of laser micromachining as competitive technology in this field. This work presents a detailed study of a-Si:H laser ablation in the ns regime. Ablation curves are measured and fluence thresholds are determined. Additionally, and due to the improved performance in optolectronic properties associated to the nanocrystalline silicon (nc-Si:H), some samples of this material have been also studied.

  3. A u.v. fiber-coupled resonant laser-ablation chamber

    NASA Astrophysics Data System (ADS)

    Campbell, M.; Zheng, R.; Ledingham, K. W. D.; Clark, A.; Marshall, A.; Singhal, R. P.

    1993-10-01

    This paper describes the characterization of a u.v. transmitting fibre which forms the basis of a novel type of resonant ablation vacuum chamber. Resonant Laser Ablation (RLA) is a relatively new surface analysis technique which has been used to study impurity concentrations at relatively low laser fluences. These results have indicated that if a moderately focused laser resonant wavelength laser beam is directed at a grazing angle of incidence to the target surface, the resulting ion yield may be enhanced by two orders of magnitude or more. RLA is therefore ideally suited to surface analysis. However, it is known that any movement of the beam relative to the surface of the target results in poor reproducibility and it is for this reason that a large core all-silica u.v. transmitting fibre has been chosen to couple the laser beam to the vacuum chamber. An additional advantage of the fibre is that the laser beam is confined within it thereby rendering the system intrinsically safe. Because of its underlying importance to the success of the ablation system, the method of measuring beam attenuation in the fibre, as a function of laser wavelength and fluence, is discussed in detail.

  4. Plasma effects during ablation and drilling using pulsed solid-state lasers

    NASA Astrophysics Data System (ADS)

    Breitling, Detlef; Ruf, Andreas; Berger, Peter W.; Dausinger, Friedrich H.; Klimentov, Sergei M.; Pivovarov, Paval A.; Kononenko, Taras V.; Konov, Vitali I.

    2003-09-01

    Plasma and vapor plumes generated by ultrashort laser pulses have been studied by various optical methods for both single pulse ablation as well as high-repetition rate drilling. Time-resolved shadow and resonance absorption photographs enable to determine the plume and vapor expansion behavior and, by means of an analytical shock wave model, allow to estimate an energy balance that can be refined by plasma transmission measurements. The results furthermore suggest that several types of laser-induced plasmas can be distinguished according to their origin: the material vapor plasma originating at the ablated surface even at moderate intensities, a breakdown plasma at increased power densities occurring in cold vapor or dust particles left from previous ablations during repetitively-pulsed processing and, finally, the optical breakdown in the pure atmosphere at high intensities. The latter also gives rise to nonlinear scattering phenomena resulting in a strong redistribution of the energy density in the beam profile.

  5. Multi-level diffractive optical elements produced by excimer laser ablation of sol-gel.

    PubMed

    Neiss, Estelle; Flury, Manuel; Mager, Loïc; Rehspringer, Jean-Luc; Fort, Alain; Montgomery, Paul; Gérard, Philippe; Fontaine, Joël; Robert, Stéphane

    2008-09-01

    Material ablation by excimer laser micromachining is a promising approach for structuring sol-gel materials as we demonstrate in the present study. Using the well-known direct etching technique, the behaviour of different hybrid organic/inorganic self-made sol-gel materials is examined with a KrF* laser. Ablated depths ranging from 0.1 to 1.5 microm are obtained with a few laser pulses at low fluence (< 1 J/cm(2)). The aim is to rapidly transfer surface relief multi-level diffractive patterns in such a substrate, without intermediate steps. The combination with the 3D profilometry technique of coherence probe microscopy permits to analyse the etching process with the aim of producing multi-level Diffractive Optical Elements (DOE). Examples of four-level DOEs with 10 microm square elementary cells are presented, as well as their laser reconstructions in the infrared. PMID:18773015

  6. Optical transmission and laser ablation of pathologically changed eye lens capsule

    NASA Astrophysics Data System (ADS)

    Gamidov, A. A.; Bolshunov, A. V.; Yuzhakov, A. V.; Shcherbakov, E. M.; Baum, O. I.; Sobol, E. N.

    2015-02-01

    Optical transmission and ablation mechanisms in the secondary cataract films under the impact of 1.06-mm laser radiation are studied. The comparison of incident and transmitted (paraxial) radiation power at different values of the power density is carried out for two types of the eye lens capsule tissue (hard and soft) possessing different optical and mechanical properties. It is found that the effective attenuation coefficient for soft films is almost five times as large as that for the hard ones. The obtained measurement data on the transparency variation in the process of laser action allow the temperature evaluation and the determination of dominant mechanism of laser ablation, as well as the development of recommendations, providing the prevention or reduction of possible side effects. The obtained results can be used to optimise the regimes of laser impact in the process of the opacified lens capsule removal.

  7. A comparison of the characteristics of excimer and femtosecond laser ablation of acrylonitrile butadiene styrene (ABS)

    NASA Astrophysics Data System (ADS)

    See, Tian Long; Liu, Zhu; Li, Lin; Zhong, Xiang Li

    2016-02-01

    This paper presents an investigation on the ablation characteristics of excimer laser (λ = 248 nm, τ = 15 ns) and femtosecond laser (λ = 800 nm, τ = 100 fs) on ABS polymer sheets. The laser-material interaction parameters (ablation threshold, optical penetration depth and incubation factor) and the changes in material chemical properties were evaluated and compared between the two lasers. The work shows that the ablation threshold and effective optical penetration depth values are dependent on the wavelength of laser beam (photon energy) and the pulse width. The ablation threshold value is lower for the excimer laser ablation of ABS (Fth = 0.087 J/cm2) than that for the femtosecond laser ablation of ABS (Fth = 1.576 J/cm2), demonstrating a more dominating role of laser wavelength than the pulse width in influencing the ablation threshold. The ablation depth versus the logarithmic scale of laser fluence shows two linear regions for the fs laser ablation, not previously known for polymers. The effective optical penetration depth value is lower for excimer laser ablation (α-1 = 223 nm) than that for femtosecond laser ablation (α-1 = 2917 nm). The ablation threshold decreases with increasing number of pulses (NOP) due to the chain scission process that shortens the polymeric chains, resulting in a weaker polymeric configuration and the dependency is governed by the incubation factor. Excimer laser treatment of ABS eliminates the Cdbnd C bond completely through the chain scission process whereas Cdbnd C bond is partially eliminated through the femtosecond laser treatment due to the difference in photon energy of the two laser beams. A reduction in the Cdbnd C bond through the chain scission process creates free radical carbons which then form crosslinks with each other or react with oxygen, nitrogen and water in air producing oxygen-rich (Csbnd O and Cdbnd O bond) and nitrogen-rich (Csbnd N) functional groups.

  8. The laser ablation model development of glass substrate cutting assisted with the thermal fracture and ultrasonic mechanisms

    NASA Astrophysics Data System (ADS)

    Huang, Kuo-Cheng; Hsiao, Wen-Tse; Hwang, Chi-Hung; Lin, Ru-Li; Andrew Yeh, Jer-Liang

    2015-04-01

    This study presents three hybrid processing models for cutting a glass substrate, and compares their cutting speeds. The three models are (I) thermal fracture cutting technology (TFCT)-assisted laser ablation, (II) ultrasonic-assisted laser ablation, and (III) ultrasonic and TFCT-assisted laser ablation. In the experiment, a 12 W 355 nm Nd:YVO4 laser system, a 40 W CO2 laser and an ultrasonic transducer were used to cut 3 mm thick soda-lime glasses. Lasers and ultrasonic transducers were used as heat sources and vibration sources, respectively. Results show that the surface morphology of the soda-lime glass sheet depends on the processing models. After cutting, the surface and cross-sectional morphology of glass substrate were observed using a portable digital microscope and residual stresses were also evaluated thanks to a photoelasticity instrument.

  9. Utilizing confocal laser endomicroscopy for evaluating the adequacy of laparoscopic liver ablation

    PubMed Central

    Johnson, Sean P.; Walker‐Samuel, Simon; Gurusamy, Kurinchi; Clarkson, Matthew J.; Thompson, Stephen; Song, Yi; Totz, Johannes; Cook, Richard J.; Desjardins, Adrien E.; Hawkes, David J.; Davidson, Brian R.

    2015-01-01

    Background Laparoscopic liver ablation therapy can be used for the treatment of primary and secondary liver malignancy. The increased incidence of cancer recurrence associated with this approach, has been attributed to the inability of monitoring the extent of ablated liver tissue. Methods The feasibility of assessing liver ablation with probe‐based confocal laser endomicroscopy (CLE) was studied in a porcine model of laparoscopic microwave liver ablation. Following the intravenous injection of the fluorophores fluorescein and indocyanine green, CLE images were recorded at 488 nm and 660 nm wavelength and compared to liver histology. Statistical analysis was performed to assess if fluorescence intensity change can predict the presence of ablated liver tissue. Results CLE imaging of fluorescein at 488 nm provided good visualization of the hepatic microvasculature; whereas, CLE imaging of indocyanine green at 660 nm enabled detailed visualization of hepatic sinusoid architecture and interlobular septations. Fluorescence intensity as measured in relative fluorescence units was found to be 75–100% lower in ablated compared to healthy liver regions. General linear mixed modeling and ROC analysis found the decrease in fluorescence to be statistically significant. Conclusion Laparoscopic, dual wavelength CLE imaging using two different fluorophores enables clinically useful visualization of multiple liver tissue compartments, in greater detail than is possible at a single wavelength. CLE imaging may provide valuable intraoperative information on the extent of laparoscopic liver ablation. Lasers Surg. Med. 48:299–310, 2016. © 2015 The Authors. Lasers in Surgery and Medicine Published by Wiley Periodicals, Inc. PMID:26718623

  10. The mesoscopic modeling of laser ablation

    NASA Astrophysics Data System (ADS)

    Stoneham, A. M.; Ramos, M. M. D.; Ribeiro, R. M.

    It is common to look at the atomic processes of removal of atoms or ions from surfaces. At this microscopic scale, one has to understand which surface ions are involved, which excited states are created, how electrons are transferred and scattered, and how the excitation leads to ion removal. It is even more common to look at continuum models of energy deposition in solids, and at the subsequent heat transfer. In these macroscopic analyses, thermal conduction is combined with empirical assumptions about surface binding. Both these pictures are useful, and both pictures have weaknesses. The atomistic pictures concentrate on relatively few atoms, and do not recognize structural features or the energy and carrier fluxes on larger scales. The continuum macroscopic models leave out crystallographic information and the interplay of the processes with high nonequilibrium at smaller scales. Fortunately, there is a middle way: mesoscopic modeling, which both models the key microstructural features and provides a link between microscopic and macroscopic. In a mesoscopic model, the length scale is determined by the system; often this scale is similar to the grain size. Microstructural features like grain boundaries or dislocations are considered explicitly. The time scale in a mesoscopic model is determined by the ablation process (such as the pulse length) rather than the short time limitations of molecular dynamics, yet the highly nonequilibrium behavior is adequately represented. Mesoscopic models are especially important when key process rates vary on a short length scale. Some microstructural feature (like those in dentine or dental enamel) may absorb light much more than others; other features (like grain boundaries) may capture carriers readily, or allow easier evaporation, or capture and retain charge (like grain boundaries); it is these processes which need a mesoscopic analysis. The results described will be taken largely from the work on MgO of Ribeiro, Ramos, and

  11. Ablation and nanostructuring of metals by femtosecond laser pulses

    SciTech Connect

    Ashitkov, S I; Komarov, P S; Ovchinnikov, A V; Struleva, E V; Agranat, M B; Zhakhovskii, V V; Inogamov, N A

    2014-06-30

    Using an interferometric continuous monitoring technique, we have investigated the motion of the surface of an aluminium target in the case of femtosecond laser ablation at picosecond time delays relative to the instant of laser exposure. Measurements of the temporal target dispersion dynamics, molecular dynamics simulation results and the morphology of the ablation crater have demonstrated a thermomechanical (spall) nature of the disruption of the condensed phase due to the cavitation-driven formation and growth of vapour phase nuclei upon melt expansion, followed by the formation of surface nanostructures upon melt solidification. The tensile strength of heated aluminium in a condensed state has been determined experimentally at an expansion rate of ∼10{sup 9} s{sup -1}. (extreme light fields and their applications)

  12. Targets on superhydrophobic surfaces for laser ablation ion sources

    NASA Astrophysics Data System (ADS)

    Renisch, D.; Beyer, T.; Blaum, K.; Block, M.; Düllmann, Ch. E.; Eberhardt, K.; Eibach, M.; Nagy, Sz.; Neidherr, D.; Nörtershäuser, W.; Smorra, C.

    2012-06-01

    Target preparation techniques for a laser ablation ion source at the Penning-trap mass spectrometer TRIGA-TRAP have been investigated with regard to future experiments with actinides. To be able to perform mass measurements on these nuclides considering their limited availability, an efficient target preparation technique is mandatory. Here, we report on a new approach for target production using backings, which are pretreated in a way that a superhydrophobic surface is formed. This resulted in improved targets with a more homogeneous distribution of the target material compared to standard techniques with unmodified backings. It was demonstrated that the use of these new targets in a laser ablation ion source improved the ion production significantly.

  13. CdTe nanoparticles synthesized by laser ablation

    SciTech Connect

    Semaltianos, N. G.; Logothetidis, S.; Perrie, W.; Romani, S.; Potter, R. J.; Dearden, G.; Watkins, K. G.; Sharp, M.

    2009-07-20

    Nanoparticle generation by laser ablation of a solid target in a liquid environment is an easy, fast, and 'green' method for a large scale production of nanomaterials with tailored properties. In this letter we report the synthesis of CdTe nanoparticles by femtosecond laser [387 nm, 180 fs, 1 kHz, pulse energy=6 {mu}J (fluence=1.7 J/cm{sup 2})] ablation of the target material. Nanoparticles with diameters from {approx}2 up to {approx}25 nm were observed to be formed in the colloidal solution. Their size distribution follows the log-normal function with a statistical median diameter of {approx_equal}7.1 nm. Their crystal structure is the same as that of the bulk material (cubic zincblende) and they are slightly Cd-rich (Cd:Te percentage ratio {approx}1:0.9). Photoluminescence emission from the produced nanoparticles was detected in the deep red ({approx}652 nm)

  14. Hydrodynamic simulation of ultrashort pulse laser ablation of gold film

    NASA Astrophysics Data System (ADS)

    Yu, Dong; Jiang, Lan; Wang, Feng; Shi, Xuesong; Qu, Liangti; Lu, Yongfeng

    2015-06-01

    The electron collision frequency in a hydrodynamic model was improved to match the laser energy absorbed with experimental data. The model calculation was used to investigate the ablation depth and the dependence of the threshold fluence of gold film on pulse width and wavelength. Two methods for estimating the ablation depth are introduced here with their respective scope of application. The dependence of the threshold fluence of gold film on the pulse width of the laser with a 1053 nm center wavelength agreed well with the experimental data. It was also observed that for pulses shorter than ~200 ps, the threshold fluence showed linear dependence on the logarithm of pulse width and increased with the wavelength, which was different from previous results.

  15. Laser-ablation-assisted microparticle acceleration for drug delivery

    NASA Astrophysics Data System (ADS)

    Menezes, V.; Takayama, K.; Ohki, T.; Gopalan, J.

    2005-10-01

    Localized drug delivery with minimal tissue damage is desired in some of the clinical procedures such as gene therapy, treatment of cancer cells, treatment of thrombosis, etc. We present an effective method for delivering drug-coated microparticles using laser ablation on a thin metal foil containing particles. A thin metal foil, with a deposition of a layer of microparticles is subjected to laser ablation on its backface such that a shock wave propagates through the foil. Due to shock wave loading, the surface of the foil containing microparticles is accelerated to very high speeds, ejecting the deposited particles at hypersonic speeds. The ejected particles have sufficient momentum to penetrate soft body tissues, and the penetration depth observed is sufficient for most of the pharmacological treatments. We have tried delivering 1μm tungsten particles into gelatin models that represent soft tissues, and liver tissues of an experimental rat. Sufficient penetration depths have been observed in these experiments with minimum target damage.

  16. Growth of epitaxial thin films by pulsed laser ablation

    SciTech Connect

    Lowndes, D.H.

    1992-01-01

    High-quality, high-temperature superconductor (HTSc) films can be grown by the pulsed laser ablation (PLA) process. This article provides a detailed introduction to the advantages and curent limitations of PLA for epitaxial film growth. Emphasis is placed on experimental methods and on exploitation of PLA to control epitaxial growth at either the unit cell or the atomic-layer level. Examples are taken from recent HTSc film growth. 33 figs, 127 refs. (DLC)

  17. Growth of epitaxial thin films by pulsed laser ablation

    SciTech Connect

    Lowndes, D.H.

    1992-10-01

    High-quality, high-temperature superconductor (HTSc) films can be grown by the pulsed laser ablation (PLA) process. This article provides a detailed introduction to the advantages and curent limitations of PLA for epitaxial film growth. Emphasis is placed on experimental methods and on exploitation of PLA to control epitaxial growth at either the unit cell or the atomic-layer level. Examples are taken from recent HTSc film growth. 33 figs, 127 refs. (DLC)

  18. Particle size dependent chemistry from laser ablation of brass.

    PubMed

    Liu, Chunyi; Mao, Xianglei; Mao, Sam S; Greif, Ralph; Russo, Richard E

    2005-10-15

    The proportion of zinc and copper in particles formed by laser ablation of brass was found to vary with the particle diameter. Energy-dispersive X-ray analysis showed that smaller particles were zinc enhanced while larger particles were composed mostly of copper. A model based on condensation of vapor onto large droplets ejected from a melted liquid layer is proposed to describe the change in particle composition versus size. PMID:16223257

  19. Fabrication of Sapphire Micro Optics by F 2-Laser Ablation

    NASA Astrophysics Data System (ADS)

    Wiesner, Markus; Ihlemann, Jürgen

    F2-laser irradiation enables high precision ablation of sapphire. A mask projection system with high numerical aperture, equipped with an optical coherence tomography module for focus control, delivers submicron resolution. High fluences of up to 10 J/cm2 lead to smooth, crack free surfaces. Various micro-optical elements like fiber tip lenses, gratings, and diffractive optical elements can be manufactured this way.

  20. Optical feedback signal for ultrashort laser pulse ablation of tissue

    SciTech Connect

    Kim, B.-M.; Feit, M.D.; Rubenchik, A.M.; Mammini, B.M.; Da Silva, L.B.

    1997-07-01

    An optical feedback system for controlled precise tissue ablation is discussed. Our setup includes an ultrashort pulse laser (USPL), and a diagnostic system using analysis of either tissue fluorescence or plasma emission luminescence. Current research is focused on discriminating hard and soft tissues such as bone and spinal cord during surgery using either technique. Our experimental observations exhibit considerable spectroscopic contrast between hard and soft tissue, and both techniques offer promise for a practical diagnostic system.

  1. Spin-offs from laser ablation in art conservation

    NASA Astrophysics Data System (ADS)

    Asmus, J.; Elford, J.; Parfenov, V.

    2013-05-01

    In 1973 The Center for Art Conservation Studies (CASS) was established at the University of California, San Diego (UCSD). This was in response to demonstrations that were conducted during January-March 1972 in Venice for UNESCO, Venice in Peril, International Fund for Monuments, and the Italian Petroleum Institute (ENI). The feasibility investigation explored in-situ pulsed holography, holographic interferometry, and laser ablation divestment for applications in art conservation practice. During subsequent decades scores of UCSD graduate and undergraduate students as well as conservators, conservation scientists, academics, and engineers who resided in CASS as "Visiting Scholars" contributed to advancing the understanding and performance of radiation technologies in the arts. Several technologies in addition to those involving optical wavelengths were also investigated to aid in art conservation and conservation science. Magnetic Resonance Imaging (MRI) and Nuclear Magnetic Resonance (NMR) were employed to detect and map moisture within masonry. Lead isotopic analyses revealed authenticity and provenance of Benin bronzes. Inside-out x-ray radiography facilitated the detection of defects in stone. Ultrasonic imaging was introduced for the mapping of fresco strata. Photoacoustic Spectroscopy (PAS) was used to characterize varnish layers on paintings. Digital image processing was introduced in order to detect and visualize pentimenti within paintings as well as to perform virtual restoration and provide interactive museum displays. Holographic images were employed as imaginary theater sets. In the years that followed the graduation of students and the visits of professional collaborators, numerous other applications of radiation ablation began appearing in a wide variety of other fields such as aircraft maintenance, ship maintenance, toxic chemical remediation, biological sterilization, food processing, industrial fabrication, industrial maintenance, nuclear

  2. Effects of Yb:KYW thin-disk femtosecond laser ablation on enamel surface roughness

    NASA Astrophysics Data System (ADS)

    Liu, Jing; Sun, Yuchun; Wang, Yong; Lü, Peijun

    2014-07-01

    This study aimed to quantitatively evaluate the surface roughness of enamel following ablation with a Yb:KYW thin-disk femtosecond pulsed laser at different fluences (F), scanning speeds and scanning line spacings. Thirty human extracted teeth were sectioned into crowns and roots along the cementum-enamel junction, and then the crowns were cut longitudinally into sheets about 1.5 mm thick. The samples were randomly divided into ten groups (n=3). Samples of groups 1-8 were irradiated with a femtosecond pulsed laser. These enamel samples were fixed on a stage at focus plane, and a laser beam irradiated onto the samples through a galvanometric scanning system, with which rectangular movement could be achieved. Samples of groups 9 and 10 were prepared with grinding instruments. Following ablation and preparation, the samples were examined for surface roughness with a three-dimensional laser profile measurement microscope. The results showed that scanning speed and scanning line spacing had little influence on the surface roughness of femtosecond pulsed laser-ablated enamel, except when F=4 J/cm2. When a lower fluence was used, the enamel surface roughness was higher, and vice versa. This study showed that various laser fluences, scanning speeds and scanning line spacings can affect and alter enamel surface roughness. Therefore, adequate parameters should be chosen to achieve the proper therapeutic benefits.

  3. Evolution and imaging of nanoparticles observed in laser ablated carbon plume

    SciTech Connect

    Yadav, Dheerendra; Gupta, Varun; Thareja, Raj K.

    2009-09-15

    We report evidence of nanoparticles formation in laser ablated carbon plasma created by irradiating a graphite target with nanosecond neodymium doped yttrium aluminum garnet laser. The temporal evolution and spatial distribution of C{sub 2} molecules in the plasma is studied using optical emission spectroscopy, dynamic imaging and laser induced fluorescence techniques. The laser induced fluorescence spectrum and imaging of C{sub 2} fluorescence corresponding to transition d {sup 3}PI{sub g}-a {sup 3}PI{sub u} (0, 1) (lambda=563.5 nm) is investigated by probing the expanding plume using a dye laser. The temporal evolution of ground state number density of C{sub 2} shows density varying from 2.6x10{sup 20}/m{sup 3} to 1.2x10{sup 22}/m{sup 3} on varying delay between the ablating and probe pulse from 200 to 600 ns. A peculiar bifurcation of carbon plume into two parts at approx270 ns after the formation of plasma is attributed to recombination of carbon species and formation of nanoparticles. This study may help in quantitatively understanding of formation of carbon molecular species and the nanoparticles produced in laser ablated carbon plume.

  4. 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

  5. Study of cluster anions generated by laser ablation of titanium oxides: a high resolution approach based on Fourier transform ion cyclotron resonance mass spectrometry.

    PubMed

    Barthen, Nicolas; Millon, Eric; Aubriet, Frédéric

    2011-03-01

    Laser ablation of titanium oxides at 355 nm and ion-molecule reactions between [(TiO(2))(x)](-•) cluster anions and H(2)O or O(2) were investigated by Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS) with an external ion source. The detected anions correspond to [(TiO(2))(x)(H(2)O)(y)OH](-) and [(TiO(2))(x)(H(2)O)(y)O(2)](-•) oxy-hydroxide species with x=1 to 25 and y=1, 2, or 3 and were formed by a two step process: (1) laser ablation, which leads to the formation of [(TiO(2))(x)](-•) cluster anions as was previously reported, and (2) ion-molecule reactions during ion storage. Reactions of some [(TiO(2))(x)](-•) cluster anions with water and dioxygen conducted in the FTICR cell confirm this assessment. Tandem mass spectrometry experiments were also performed in sustained off-resonance irradiation collision-induced dissociation (SORI-CID) mode. Three fragmentation pathways were observed: (1) elimination of water molecules, (2) O(2) loss for radical anions, and (3) fission of the cluster. Density functional theory (DFT) calculations were performed to explain the experimental data. PMID:21472569

  6. Laser ablation loading of a radiofrequency ion trap

    NASA Astrophysics Data System (ADS)

    Zimmermann, K.; Okhapkin, M. V.; Herrera-Sancho, O. A.; Peik, E.

    2012-06-01

    The production of ions via laser ablation for the loading of radiofrequency (RF) ion traps is investigated using a nitrogen laser with a maximum pulse energy of 0.17 mJ and a peak intensity of about 250 MW/cm2. A time-of-flight mass spectrometer is used to measure the ion yield and the distribution of the charge states. Singly charged ions of elements that are presently considered for the use in optical clocks or quantum logic applications could be produced from metallic samples at a rate of the order of magnitude 105 ions per pulse. A linear Paul trap was loaded with Th+ ions produced by laser ablation. An overall ion production and trapping efficiency of 10-7 to 10-6 was attained. For ions injected individually, a dependence of the capture probability on the phase of the RF field has been predicted. In the experiment this was not observed, presumably because of collective effects within the ablation plume.

  7. Microscopic and macroscopic modeling of femtosecond laser ablation of metals

    NASA Astrophysics Data System (ADS)

    Povarnitsyn, Mikhail E.; Fokin, Vladimir B.; Levashov, Pavel R.

    2015-12-01

    Simulation of femtosecond laser ablation of a bulk aluminum target is performed using two complementary approaches. The first method is single-fluid two-temperature hydrodynamics (HD) completed with a two-temperature equation of state (EOS). The second approach is a combination of classical molecular dynamics (MD) and a continuum model of a free electron subsystem. In both methods, an identical and accurate description of optical and transport properties of the electron subsystem is based on wide-range models reproducing effects of electron heat wave propagation, electron-phonon/ion coupling and laser energy absorption on a time-dependent profile of the dielectric function. For simulation of homogeneous nucleation in a metastable liquid phase, a kinetic model of nucleation is implemented in the HD approach. The phase diagrams of the EOS and MD potential are in good agreement that gives opportunity to compare the dynamics of laser ablation obtained by both methods directly. Results of simulation are presented in the range of incident fluences 0.1-20 J/cm2 and match well with experimental findings for an ablation crater depth. The MD accurately reproduces nonequilibrium phase transitions and takes into account surface effects on nanoscale. The HD approach demonstrates good qualitative agreement with the MD method in the dynamics of phase explosion and spallation. Other advantages and disadvantages of both approaches are examined and discussed.

  8. 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

  9. 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.

  10. Reduction of spectral interferences and noise effects in laser ablation molecular isotopic spectrometry with partial least square regression - a computer simulation study

    NASA Astrophysics Data System (ADS)

    Mao, Xianglei; Chan, George C.-Y.; Zorba, Vassilia; Russo, Richard E.

    2016-08-01

    The fundamental analytical accuracies and precisions attainable by laser ablation molecular isotopic spectrometry (LAMIS), with emphasis on the impacts from spectral interferences and measurement noise, were investigated by means of computer simulation. The study focused on the analysis of a minor isotope at sub- to single-percentage abundance level. With a natural abundance about 1.1% for 13C, the C2 Swan band (d3Πg-a3Πu) with Δν = + 1 was selected as a representative system. The characteristics (e.g., noise amplitude and distribution, signal strength, and signal-to-background ratio) of the simulated spectra were experimentally characterized. Partial least square (PLS) regression was used to extract isotopic information from the simulated molecular spectra. In the absence of any spectral interference and with the use of a calibration set consisting of eleven isotopic standards, the theoretical accuracies and precisions with signal accumulation from 100 laser shots are about 0.002% and 0.001%, respectively, in absolute percentage abundance of 13C. The theoretical analytical accuracies slightly degrade, but are adequate for many applications, to 0.004% and 0.008% respectively, for calibrations involving only three and two isotopic standards. It was found that PLS regression is not only immune to both source-flicker and photon-shot noise, but is also effective in differentiating the spectral patterns from the analyte against those from spectral interferences. The influences of spectral interference from single or multiple atomic emission lines were simulated, and new ways to minimize their impacts were formulated and demonstrated. It was found that the wavelength range selected for the computation of the normalization factor should not contain any spectral-interfering peak, and a properly chosen wavelength range increases the tolerance of spectral interference by at least one order of magnitude. With matrix-matched calibration standards, the precisions (expressed

  11. Trace contaminant determination in fish scale by laser-ablation technique

    NASA Astrophysics Data System (ADS)

    Lee, Ida; Coutant, C. C.; Arakawa, E. T.

    1993-10-01

    Laser ablation on rings of fish scale has been used to analyze the historical accumulation of polychlorinated biphenyls (PCB) in striped bass in the Watts Bar Reservoir. Rings on a fish scale grow in a pattern that forms a record of the fish's chemical intake. In conjunction with the migration patterns of fish monitored by ecologists, relative PCB concentrations in the seasonal rings of fish scale can be used to study the PCB distribution in the reservoir. In this study, a tightly-focused laser beam from a XeCl excimer laser was used to ablate and ionize a small portion of a fish scale placed in a vacuum chamber. The ions were identified and quantified by a time-of-flight mass spectrometer. Studies of this type can provide valuable information for the Department of Energy (DOE) off-site clean-up efforts as well as identifying the impacts of other sources to local aquatic populations.

  12. Performance Characteristics of Low-Power Laser Ablative Thrusters for Small Satellites

    SciTech Connect

    Maesato, Hikaru; Koizumi, Eiichiro; Tahara, Hirokazu

    2006-05-02

    In a laser ablative thruster, laser is irradiated to some solid propellant; it is ablated, and then produced small powders and/or gas particles with high energy are expanded resulting in thrust generation. In this study, a Q-switch Nd:YAG laser with a wavelength of 1064 nm and an output energy of 0.65 J was irradiated to polymer propellants to examine performance characteristics of laser ablative thrusters for small satellites. Impulse bit and mass loss were measured. As polymer propellants, PTFE, PTFE(carbon: 10mass%), PTFE(carbon: 15mass%), POM, POM(carbon: 20mass%), PE and PVC were selected. The performance characteristics mainly depended on specific weight and carbon concentration of polymer propellant. PTFE(carbon: 10mass%) and POM(carbon: 20mass%) were preferable propellants for high performance although with PTFE(carbon: 10mass%) laser should be irradiated to its new surface for every shot. In laser irradiation with PTFE divergent nozzles, there existed an optimum nozzle geometry for improvement of performance characteristics. In a case with a nozzle half angle of 15 deg and a length of 3 mm, the momentum coupling coefficient and the specific impulse reached 112 {mu}Ns/J and 300 sec, respectively.

  13. Evaluation of laser ablation of knee cartilage as an alternative to microfracture surgery: pilot investigations

    NASA Astrophysics Data System (ADS)

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

    2010-02-01

    An emerging clinical treatment option for articular cartilage injury includes bone marrow stimulation techniques, such as microfracture, which has grown increasingly popular among athletes. During the microfracture procedure, the surgeon penetrates the subchondral bone with an awl and creates "microholes" deep enough to ensure bleeding from the bone marrow. This procedure triggers a spontaneous repair response that results in the formation of fibrocartilaginous repair tissue. This preliminary study aimed to evaluate the potential use of femtosecond lasers and Erbium:YAG lasers as alternatives to microfracture surgery of the knee by assessing the effects of ablation on bovine femoral condyles. Bovine femoral condyles were obtained and 8mm cube blocks were extracted. The specimen were ablated with various laser dosimetry parameters and observed using a high power dissecting microscope to examine the effects of the lasers. Further imaging with conventional histology (hematoxylin and eosin staining) was done to provide more accurate information. Preliminary results show some carbonization but demonstrate little thermal damage to surrounding tissues. The femtosecond laser offers a more precise and efficient ablation than the Erbium:YAG laser, but both are demonstrated to be possible alternatives to the surgical-skill dependent microfracture procedure.

  14. Characteristics of optical emission intensities and bubblelike phenomena induced by laser ablation in supercritical fluids

    NASA Astrophysics Data System (ADS)

    Takada, Noriharu; Machmudah, Siti; Goto, Hiroshi; Wahyudiono; Goto, Motonobu; Sasaki, Koichi

    2014-01-01

    We investigated the characteristics of laser ablation phenomena in supercritical fluids by optical emission and shadowgraph imaging. In comparison with laser ablation in liquid H2O, the optical emission of a laser ablation plasma produced in supercritical H2O had a longer lifetime and a larger transport length. It was found in supercritical CO2 that laser ablation plasmas with bright optical emissions were produced at a mass density of approximately 300 kg/m3. A clear correlation between the optical emission intensity and the density fluctuation was not observed in our experimental results, which were obtained in a regime deviated from the critical point. Bubblelike hollows were observed by shadowgraph imaging in both supercritical H2O and CO2. The dynamics of the bubblelike hollows were different from the dynamics of a cavitation bubble induced by laser ablation in a liquid medium but relatively similar to the dynamics of ambient gas in gas-phase laser ablation.

  15. Metallic targets ablation by laser plasma production in a vacuum

    NASA Astrophysics Data System (ADS)

    Beilis, I. I.

    2016-03-01

    A model of metallic target ablation and metallic plasma production by laser irradiation is reported. The model considers laser energy absorption by the plasma, electron emission from hot targets and ion flux to the target from the plasma as well as an electric sheath produced at the target-plasma interface. The proposed approach takes into account that the plasma, partially shields the laser radiation from the target, and also converts absorbed laser energy to kinetic and potential energies of the charged plasma particles, which they transport not only through the ambient vacuum but also through the electrostatic sheath to the solid surface. Therefore additional plasma heating by the accelerated emitted electrons and target heating caused by bombardment of it by the accelerated ions are considered. A system of equations, including equations for solid heat conduction, plasma generation, and plasma expansion, is solved self-consistently. The results of calculations explain the measured dependencies of ablation yield (μ g/pulse) for Al, Ni, and Ti targets on laser fluence in range of (5-21)J/cm2 published previously by Torrisi et al.

  16. Laser ablation of single-crystalline silicon by radiation of pulsed frequency-selective fiber laser

    NASA Astrophysics Data System (ADS)

    Veiko, V. P.; Skvortsov, A. M.; Huynh, C. T.; Petrov, A. A.

    2015-07-01

    We have studied the process of destruction of the surface of a single-crystalline silicon wafer scanned by the beam of a pulsed ytterbium-doped fiber laser radiation with a wavelength of λ = 1062 nm. It is established that the laser ablation can proceed without melting of silicon and the formation of a plasma plume. Under certain parameters of the process (radiation power, beam scan velocity, and beam overlap density), pronounced oxidation of silicon microparticles with the formation of a characteristic loose layer of fine powdered silicon dioxide has been observed for the first time. The range of lasing and beam scanning regimes in which the growth of SiO2 layer takes place is determined.

  17. A study of angular dependence in the ablation rate of polymers by nanosecond pulses

    NASA Astrophysics Data System (ADS)

    Pedder, James E. A.; Holmes, Andrew S.

    2006-02-01

    Measurements of ablation rate have traditionally been carried out only at normal incidence. However, in real-world applications ablation is often carried out at oblique angles, and it is useful to have prior knowledge of the ablation rate in this case. Detailed information about the angular dependence is also important for the development of ablation simulation tools, and can provide additional insight into the ablation mechanism. Previously we have reported on the angular dependence of direct-write ablation at 266 nm wavelength in solgel and polymer materials. In this paper we present a systematic study of angular dependence for excimer laser ablation of two polymer materials of interest for microfabrication: polycarbonate and SU8 photoresist. The results are used to improve simulation models to aid in mask design.

  18. Ablation of biological tissues by radiation of strontium vapor laser

    SciTech Connect

    Soldatov, A. N. Vasilieva, A. V.

    2015-11-17

    A two-stage laser system consisting of a master oscillator and a power amplifier based on sources of self- contained transitions in pairs SrI and SrII has been developed. The radiation spectrum contains 8 laser lines generating in the range of 1 – 6.45 μm, with a generation pulse length of 50 – 150 ns, and pulse energy of ∼ 2.5 mJ. The divergence of the output beam was close to the diffraction and did not exceed 0.5 mrad. The control range of the laser pulse repetition rate varied from 10 to 15 000 Hz. The given laser system has allowed to perform ablation of bone tissue samples without visible thermal damage.

  19. Doping of silicon by carbon during laser ablation process

    NASA Astrophysics Data System (ADS)

    Raciukaitis, G.; Brikas, M.; Kazlauskiene, V.; Miskinis, J.

    2007-04-01

    Effect of laser ablation on properties of remaining material was investigated in silicon. It was established that laser cutting of wafers in air induced doping of silicon by carbon. The effect was found to be more distinct by the use of higher laser power or UV radiation. Carbon ions created bonds with silicon in the depth of silicon. Formation of the silicon carbide type bonds was confirmed by SIMS, XPS and AES measurements. Modeling of the carbon diffusion was performed to clarify its depth profile in silicon. Photo-chemical reactions of such type changed the structure of material and could be a reason for the reduced quality of machining. A controlled atmosphere was applied to prevent carbonization of silicon during laser cutting.

  20. Doping of silicon with carbon during laser ablation process

    NASA Astrophysics Data System (ADS)

    Račiukaitis, G.; Brikas, M.; Kazlauskienė, V.; Miškinis, J.

    2006-12-01

    The effect of laser ablation on properties of remaining material in silicon was investigated. It was found that laser cutting of wafers in the air induced the doping of silicon with carbon. The effect was more distinct when using higher laser power or UV radiation. Carbon ions created bonds with silicon atoms in the depth of the material. Formation of the silicon carbide type bonds was confirmed by SIMS, XPS and AES measurements. Modeling of the carbon diffusion to clarify its depth profile in silicon was performed. Photochemical reactions of such type changed the structure of material and could be the reason of the reduced machining quality. The controlled atmosphere was applied to prevent carbonization of silicon during laser cutting.