Study on elucidation of bactericidal effects induced by laser beam irradiation Measurement of dynamic stress on laser irradiated surface

NASA Astrophysics Data System (ADS)

Furumoto, Tatsuaki; Kasai, Atsushi; Tachiya, Hiroshi; Hosokawa, Akira; Ueda, Takashi

2010-09-01

In dental treatment, many types of laser beams have been used for various surgical treatments, and the influences of laser beam irradiation on bactericidal effect have been investigated. However, most of the work has been performed by irradiating to an agar plate with the colony of bacteria, and very few studies have been reported on the physical mechanism of bactericidal effects induced by laser beam irradiation. This paper deals with the measurement of dynamic stress induced in extracted human enamel by irradiation with Nd:YAG laser beams. Laser beams can be delivered to the enamel surface through a quartz optical fiber. Dynamic stress induced in the specimen using elastic wave propagation in a cylindrical long bar made of aluminum alloy is measured. Laser induced stress intensity is evaluated from dynamic strain measured by small semiconductor strain gauges. Carbon powder and titanium dioxide powder were applied to the human enamel surface as absorbents. Additionally, the phenomenon of laser beam irradiation to the human enamel surface was observed with an ultrahigh speed video camera. Results showed that a plasma was generated on the enamel surface during laser beam irradiation, and the melted tissues were scattered in the vertical direction against the enamel surface with a mushroom-like wave. Averaged scattering velocity of the melted tissues was 25.2 m/s. Induced dynamic stress on the enamel surface increased with increasing laser energy in each absorbent. Induced dynamic stresses with titanium dioxide powder were superior to those with carbon powder. Induced dynamic stress was related to volume of prepared cavity, and induced stress for the removal of unit volume of human enamel was 0.03 Pa/mm 3.

Biophysical principles of regulatory action of low-intensity laser irradiation

NASA Astrophysics Data System (ADS)

Mostovnikov, Vasili A.; Mostovnikova, Galina R.; Plavski, Vitali Y.; Plavskaja, Ljudmila G.

1996-01-01

The investigations carried out in our group on biological systems of various organization level (enzyme molecules in solution, human and animal cell cultures), allowed us to conclude, that the light-induced changes of spatial structure of cells components form the basis of biological activity (and as a consequence therapeutic effect) of various wavelength low-intensity laser emission. Photophysical mechanism of these changes lies in the reorientation of highregulated anisotropic parts (domains) with the liquid-crystalline type of ordering of the cell components due to the interaction between the electric field and the light induced integral electric dipole of the domain. The mechanism of such reorientation is well established in physics of liquid crystals of nematic type and is known as light induced analogue of Frederix's effect. The following results enable us to draw the conclusion about the determining role of the orientations effects on the biological activity mechanism of low-intensity laser radiation: (1) the possibility of reversible modification of spatial structure and enzyme molecules functional activity under the influence of laser radiation outside the band of their own or admixture absorption; (2) the dependence of biological effect of laser radiation on the functional activity of cells vs. polarization degree of the light with the maximum photobiological effects observed for linear-polarized radiation; (3) the equivalence of a static magnetic field and low-intensity laser radiation in action on functional activity of the cells and the lowering of the laser field intensity for the achieving the definite changes of the cell functional activity in the presence of static magnetic field.

Synthesis of polyynes by intense femtosecond laser irradiation of SWCNTs suspended in methanol

NASA Astrophysics Data System (ADS)

Zhao, Junwei; Zhang, Yifan; Fang, Yanghao; Fan, Zhengfu; Ma, Guohong; Liu, Yi; Zhao, Xinluo

2017-08-01

Polyyne samples C2nH2 (n = 4-6) were synthesized by irradiating single-wall carbon nanotubes in methanol with intense femtosecond laser pulses. For obtaining isolated polyynes (C8H2, C10H2, and C12H2), the original solution was separated by high performance liquid chromatography. The surface-enhanced Raman scattering spectra of isolated polyynes in Ag colloid have been investigated with naturally drying time, and clear peaks in the region of β band for the isolated C8H2 were observed at 1910 and 1958 cm-1 in the damp-dried Ag colloid samples for the first time.

Laser pulse heating of steel mixing with WC particles in a irradiated region

NASA Astrophysics Data System (ADS)

Shuja, S. Z.; Yilbas, B. S.; Ali, H.; Karatas, C.

2016-12-01

Laser pulse heating of steel mixing with tungsten carbide (WC) particles is carried out. Temperature field in the irradiated region is simulated in line with the experimental conditions. In the analysis, a laser pulse parameter is introduced, which defines the laser pulse intensity distribution at the irradiated surface. The influence of the laser parameter on the melt pool size and the maximum temperature increase in the irradiated region is examined. Surface temperature predictions are compared with the experimental data. In addition, the distribution of WC particles and their re-locations in the treated layer, due to combination of the natural convection and Marangoni currents, are predicted. The findings are compared to the experimental data. It is found that surface temperature predictions agree well with the experimental data. The dislocated WC particles form a streamlining in the near region of the melt pool wall, which agree with the experimental findings. The Gaussian distribution of the laser pulse intensity results in the maximum peak temperature and the maximum flow velocity inside the melt pool. In this case, the melt pool depth becomes the largest as compared to those corresponding to other laser pulse intensity distributions at the irradiated surface.

Coulomb explosion of hydrogen clusters irradiated by an ultrashort intense laser pulse

NASA Astrophysics Data System (ADS)

Li, Hongyu; Liu, Jiansheng; Wang, Cheng; Ni, Guoquan; Li, Ruxin; Xu, Zhizhan

2006-08-01

The explosion dynamics of hydrogen clusters driven by an ultrashort intense laser pulse has been analyzed analytically and numerically by employing a simplified Coulomb explosion model. The dependence of average and maximum proton kinetic energy on cluster size, pulse duration, and laser intensity has been investigated respectively. The existence of an optimum cluster size allows the proton energy to reach the maximum when the cluster size matches with the intensity and the duration of the laser pulse. In order to explain our experimental results such as the measured proton energy spectrum and the saturation effect of proton energy, the effects of cluster size distribution as well as the laser intensity distribution on the focus spot should be considered. A good agreement between them is obtained.

The dynamics of Al/Pt reactive multilayer ignition via pulsed-laser irradiation

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

Murphy, Ryan D.; Reeves, Robert V.; Yarrington, Cole D.

2015-12-07

Reactive multilayers consisting of alternating layers of Al and Pt were irradiated by single laser pulses ranging from 100 μs to 100 ms in duration, resulting in the initiation of rapid, self-propagating reactions. The threshold intensities for ignition vary with the focused laser beam diameter, bilayer thickness, and pulse length and are affected by solid state reactions and conduction of heat away from the irradiated regions. High-speed photography was used to observe ignition dynamics during irradiation and elucidate the effects of heat transfer into a multilayer foil. For an increasing laser pulse length, the ignition process transitioned from a more uniform tomore » a less uniform temperature profile within the laser-heated zone. A more uniform temperature profile is attributed to rapid heating rates and heat localization for shorter laser pulses, and a less uniform temperature profile is due to slower heating of reactants and conduction during irradiation by longer laser pulses. Finite element simulations of laser heating using measured threshold intensities indicate that micron-scale ignition of Al/Pt occurs at low temperatures, below the melting point of both reactants.« less

The dynamics of Al/Pt reactive multilayer ignition via pulsed-laser irradiation

DOE PAGES

Murphy, Ryan D.; Reeves, Robert V.; Yarrington, Cole D.; ...

2015-12-07

Reactive multilayers consisting of alternating layers of Al and Pt were irradiated by single laser pulses ranging from 100 μs to 100 ms in duration, resulting in the initiation of rapid, self-propagating reactions. The threshold intensities for ignition vary with the focused laser beam diameter, bilayer thickness, and pulse length and are affected by solid state reactions and conduction of heat away from the irradiated regions. We used high-speed photography to observe ignition dynamics during irradiation and elucidate the effects of heat transfer into a multilayer foil. For an increasing laser pulse length, the ignition process transitioned from a moremore » uniform to a less uniform temperature profile within the laser-heated zone. A more uniform temperature profile is attributed to rapid heating rates and heat localization for shorter laser pulses, and a less uniform temperature profile is due to slower heating of reactants and conduction during irradiation by longer laser pulses. Lastly, finite element simulations of laser heating using measured threshold intensities indicate that micron-scale ignition of Al/Pt occurs at low temperatures, below the melting point of both reactants.« less

Multi-keV X-ray area source intensity at SGII laser facility

NASA Astrophysics Data System (ADS)

Wang, Rui-rong; An, Hong-hai; Xie, Zhi-yong; Wang, Wei

2018-05-01

Experiments for investigating the feasibility of multi-keV backlighters for several different metallic foil targets were performed at the Shenguang II (SGII) laser facility in China. Emission spectra in the energy range of 1.65-7.0 keV were measured with an elliptically bent crystal spectrometer, and the X-ray source size was measured with a pinhole camera. The X-ray intensity near 4.75 keV and the X-ray source size for titanium targets at different laser intensity irradiances were studied. By adjusting the total laser energy at a fixed focal spot size, laser intensity in the range of 1.5-5.0 × 1015 W/cm2, was achieved. The results show that the line emission intensity near 4.75 keV and the X-ray source size are dependent on the laser intensity and increase as the laser intensity increases. However, an observed "peak" in the X-ray intensity near 4.75 keV occurs at an irradiance of 4.0 × 1015 W/cm2. For the employed experimental conditions, it was confirmed that the laser intensity could play a significant role in the development of an efficient multi-keV X-ray source. The experimental results for titanium indicate that the production of a large (˜350 μm in diameter) intense backlighter source of multi-keV X-rays is feasible at the SGII facility.

Spectral irradiance of singly and doubly ionized zinc in low-intensity laser-plasma ultraviolet light sources

NASA Astrophysics Data System (ADS)

Szilagyi, John; Parchamy, Homaira; Masnavi, Majid; Richardson, Martin

2017-01-01

The absolute spectral irradiances of laser-plasmas produced from planar zinc targets are determined over a wavelength region of 150 to 250 nm. Strong spectral radiation is generated using 60 ns full-width-at-half-maximum, 1.0 μm wavelength laser pulses with incident laser intensities as low as ˜5 × 108 W cm-2. A typical radiation conversion efficiency of ˜2%/2πsr is measured. Numerical calculations using a comprehensive radiation-hydrodynamics model reveal the strong experimental spectra to originate mainly from 3d94s4p-3d94s2, 3d94s4d-3d94s4p, and 3d94p-3d94s, 3d94d-3d94p unresolved-transition arrays in singly and doubly ionized zinc, respectively.

Backscattering measuring system for optimization of intravenous laser irradiation dose

NASA Astrophysics Data System (ADS)

Rusina, Tatyana V.; Popov, V. D.; Melnik, Ivan S.; Dets, Sergiy M.

1996-11-01

Intravenous laser blood irradiation as an effective method of biostimulation and physiotherapy becomes a more popular procedure. Optimal irradiation conditions for each patient are needed to be established individually. A fiber optics feedback system combined with conventional intravenous laser irradiation system was developed to control of irradiation process. The system consists of He-Ne laser, fiber optics probe and signal analyzer. Intravenous blood irradiation was performed in 7 healthy volunteers and 19 patients with different diseases. Measurements in vivo were related to in vitro blood irradiation which was performed in the same conditions with force-circulated venous blood. Comparison of temporal variations of backscattered light during all irradiation procedures has shown a strong discrepancy on optical properties of blood in patients with various health disorders since second procedure. The best cure effect was achieved when intensity of backscattered light was constant during at least five minutes. As a result, the optical irradiation does was considered to be equal 20 minutes' exposure of 3 mW He-Ne laser light at the end of fourth procedure.

Ablation Behavior of Plasma-Sprayed La1-xSrxTiO3+δ Coating Irradiated by High-Intensity Continuous Laser.

PubMed

Zhu, Jinpeng; Ma, Zhuang; Gao, Yinjun; Gao, Lihong; Pervak, Vladimir; Wang, Lijun; Wei, Chenghua; Wang, Fuchi

2017-10-11

Laser protection for optical components, particularly those in high-power laser systems, has been a major concern. La 1-x Sr x TiO 3+δ with its good optical and thermal properties can be potentially applied as a high-temperature optical protective coating or high-reflectivity material for optical components. However, the high-power laser ablation behavior of plasma-sprayed La 1-x Sr x TiO 3+δ (x = 0.1) coatings has rarely been investigated. Thus, in this study, laser irradiation experiments were performed to study the effect of high-intensity continuous laser on the ablation behavior of the La 1-x Sr x TiO 3+δ coating. The results show that the La 1-x Sr x TiO 3+δ coating undergoes three ablation stages during laser irradiation: coating oxidation, formation and growth of new structures (columnar and dendritic crystals), and mechanical failure. A finite-element simulation was also conducted to explore the mechanism of the ablation damage to the La 1-x Sr x TiO 3+δ coating and provided a good understanding of the ablation behavior. The apparent ablation characteristics are attributed to the different temperature gradients determined by the reflectivity and thermal diffusivity of the La 1-x Sr x TiO 3+δ coating material, which are critical factors for improving the antilaser ablation property. Now, the stainless steel substrate deposited by it can effectively work as a protective shield layer against ablation by laser irradiation.

Coulomb explosion of hydrogen clusters irradiated by an ultrashort intense laser pulse

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

Li Hongyu; Liu Jiansheng; Wang Cheng

The explosion dynamics of hydrogen clusters driven by an ultrashort intense laser pulse has been analyzed analytically and numerically by employing a simplified Coulomb explosion model. The dependence of average and maximum proton kinetic energy on cluster size, pulse duration, and laser intensity has been investigated respectively. The existence of an optimum cluster size allows the proton energy to reach the maximum when the cluster size matches with the intensity and the duration of the laser pulse. In order to explain our experimental results such as the measured proton energy spectrum and the saturation effect of proton energy, the effectsmore » of cluster size distribution as well as the laser intensity distribution on the focus spot should be considered. A good agreement between them is obtained.« less

Central nervous system transplantation benefited by low-level laser irradiation

NASA Astrophysics Data System (ADS)

Rochkind, S.; Lubart, Rachel; Wollman, Yoram; Simantov, Rabi; Nissan, Moshe; Barr-Nea, Lilian

1990-06-01

Effect of low-level laser irradiation on the central nervous system transplantation is reported. Ernbryonal brain allografts were transplanted into the brain of 20 adult rats and peripheral nerve graft transplanted into the severely injured spinal cord of 16 dogs. The operated wound of 10 rats and 8 dogs were exposed daily for 21 days to lowpower laser irradiation CW HeNe laser (35 mW, 632.8 run, energy density of 30 J/cm2 at each point for rats and 70 J/cm2 at each point for dogs). This study shows that (i) the low-level laser irradiation prevents extensive glial scar formation (a limiting factor in CNS regeneration) between embryonal transplants and host brain; (ii) Dogs made paraplegic by spinal cord injury were able to walk 3-6 months later. Recovery of these dogs was effected by the implantation of a fragment of autologous sciatic nerve at the site of injury and subsequently exposing the dogs to low-level laser irradiation. The effect of laser irradiation on the embryonal nerve cells grown in tissue culture was also observed. We found that low-level laser irradiation induced intensive migration of neurites outward of the aggregates 15-22 The results of the present study and our previous investigations suggest that low-level laser irradiation is a novel tool for treatment of peripheral and central nervous system injuries.

Ultra-Intense Short-Pulse Pair Creation Using the Texas Petawatt Laser

NASA Astrophysics Data System (ADS)

Liang, Edison; Henderson, Alexander; Clarke, Taylor; Taylor, Devin; Chaguine, Petr; Serratto, Kristina; Riley, Nathan; Dyer, Gilliss; Donovan, Michael; Ditmire, Todd

2013-10-01

We report results from the 2012 pair creation experiment using the Texas Petawatt Laser. Up to 1011 positrons per steradian were detected using 100 Joule pulses from the Texas Petawatt Laser to irradiate gold targets, with peak laser intensities up to 1.9 × 1021W/cm2 and pulse durations as short as 130 fs. Positron-to-electron ratios exceeding 20% were measured on some shots. The positron energy, positron yield per unit laser energy, and inferred positron density are significantly higher than those reported in previous experiments. This confirms that, for a given laser energy, higher intensity and shorter pulses irradiating thicker targets are more favorable for pair creation. Narrow-band high-energy positrons up to 23 MeV were observed from thin targets. Supported by DOE Grant DE-SC-0001481 and Rice FIF.

Low-intensity laser irradiation at 660 nm stimulates cytochrome c oxidase in stressed fibroblast cells.

PubMed

Houreld, Nicolette N; Masha, Roland T; Abrahamse, Heidi

2012-07-01

Low-intensity laser irradiation (LILI) has been used to modulate a variety of biological processes, including diabetic wound healing. The mechanism of action is thought to exist primarily with the mitochondria. This study aimed to determine the effect of irradiation on normal, diabetic, and ischemic mitochondrial electron transport chain (ETC) complexes. Normal, diabetic and ischemic human skin fibroblast mitochondria were irradiated in vitro at a wavelength of 660 nm and a fluence of either 5 or 15 J/cm(2). Non-irradiated mitochondria served as controls. Enzyme activities of mitochondrial complexes I, II, III, and IV were determined immediately post-irradiation. Normal, diabetic, and ischemic cells were irradiated and adenosine triphosphate (ATP) and active mitochondria were determined by luminescence and fluorescent microscopy, respectively. Irradiated diabetic mitochondria at a fluence of 15 J/cm(2) showed a significant decrease in complex III activity (P < 0.05). Normal (P < 0.01) and diabetic (P < 0.05) mitochondria irradiated at either 5 or 15 J/cm(2) showed a significant increase in complex IV activity. ATP results showed a significant increase in irradiated normal cells (5 J/cm(2); P < 0.05) and diabetic cells (15 J/cm(2); P < 0.01). There was a higher accumulation of active mitochondria in irradiated cells than non-irradiated cells. Irradiation at 660 nm has the ability to influence mitochondrial enzyme activity, in particular cytochrome c oxidase. This leads to increased mitochondrial activity and ATP synthesis. Copyright © 2012 Wiley Periodicals, Inc.

[Effects of low intensity infra-red laser irradiation on ultrastructure and proliferation of liver cells in experimental hepatitis and cirrhosis].

PubMed

Baĭbekov, I M; Vorozheĭkin, V M; Artykov, Sh N

1992-04-01

With the aid of light, electron transmission and scanning electron microscopy and radioautography and stereometry, the influence of low-intensive laser irradiation (LILI) (infrared) was studied in normal rat liver and in experimental cirrhosis and hepatitis. It was revealed that arsenide-gallium laser irradiation causes the change of intracellular structure. These changes show the intensification on their specific function manifest in an increase of relative volume of intracellular structures. The changes of microvessels show the activation of microcirculation. The elevation of the index of the labelled nuclei testify to increased proliferation. The similar influences of LILI on the liver ultrastructure and proliferation in hepatitis and cirrhosis are accompanied by the reduction of the pathological changes of the liver--the hepatocytes oedema, granular, vacuolar and fatty dystrophy.

Proton-induced Nuclear Reactions Using Compact High-Contrast High-Intensity Laser

NASA Astrophysics Data System (ADS)

Ogura, Koichi; Shizuma, Toshiyuki; Hayakawa, Takehito; Yogo, Akifumi; Nishiuchi, Mamiko; Orimo, Satoshi; Sagisaka, Akito; Pirozhkov, Alexander; Mori, Michiaki; Kiriyama, Hiromitsu; Kanazawa, Shuhei; Kondo, Shunji; Nakai, Yoshiki; Shimoura, Takuya; Tanoue, Manabu; Akutsu, Atsushi; Motomura, Tomohiro; Okada, Hajime; Kimura, Toyoaki; Oishi, Yuji; Nayuki, Takuya; Fujii, Takashi; Nemoto, Koshichi; Daido, Hiroyuki

2009-06-01

A multi-MeV proton beam driven by a compact laser with an intensity of ˜1020 W/cm2 is used to induce the nuclear reaction 11B(p,n)11C. The total activity of 11C produced after 60 shots of laser irradiation is found to be 11.1+/-0.4 Bq. The possibility of thin layer activation (TLA) analysis using a high-intensity ultrashort-pulse laser is discussed.

Laser-enhanced thermal effect of moderate intensity focused ultrasound on bio-tissues

NASA Astrophysics Data System (ADS)

Zhao, JinYu; Zhang, ShuYi; Shui, XiuJi; Fan, Li

2017-09-01

For avoiding extra-damage to healthy tissues surrounding the focal point during high intensity focused ultrasound (HIFU) treatment in medical therapy, to reduce the ultrasonic intensity outside the focal point is expected. Thus, the heating processes induced by moderate intensity focused ultrasound (MIFU) and enhanced by combined irradiation of laser pulses for bio-tissues are studied in details. For fresh bio-tissues, the enhanced thermal effects by pulsed laser combined with MIFU irradiation are observed experimentally. To explore the mechanisms of these effects, several tissue-mimicking materials composed of agar mixed with graphite powders are prepared and studied for comparison, but the laser-enhanced thermal effects in these mimicking materials are much less than that in the fresh bio-tissues. Therefore, it is suggested that the laser-enhanced thermal effects may be mainly attributed to bio-activities and related photo-bio-chemical effects of fresh tissues.

Effect of Er:YAG laser irradiation on bonding property of zirconia ceramics to resin cement.

PubMed

Lin, Yihua; Song, Xiaomeng; Chen, Yaming; Zhu, Qingping; Zhang, Wei

2013-12-01

This study aimed to investigate whether or not an erbium: yttrium-aluminum-garnet (Er:YAG) laser could improve the bonding property of zirconia ceramics to resin cement. Surface treatments can improve the bonding properties of dental ceramics. However, little is known about the effect of Er:YAG laser irradiated on zirconia ceramics. Specimens of zirconia ceramic pieces were made, and randomly divided into 11 groups according to surface treatments, including one control group (no treatment), one air abrasion group, and nine Er:YAG laser groups. The laser groups were subdivided by applying different energy intensities (100, 200, or 300 mJ) and irradiation times (5, 10, or 15 sec). After surface treatments, ceramic pieces had their surface morphology observed, and their surface roughness was measured. All specimens were bonded to resin cement. Shear bond strength was measured after the bonded specimens were stored in water for 24 h, and additionally aged by thermocycling. Statistical analyses were performed using one way analysis of variance (ANOVA) and Tukey's test for shear bond strength, and Dunnett's t test for surface roughness, with α=0.05. Er:YAG laser irradiation changed the morphological characteristics of zirconia ceramics. Higher energy intensities (200, 300 mJ) could roughen the ceramics, but also caused surface cracks. There were no significant differences in the bond strength between the control group and the laser groups treated with different energy intensities or irradiation times. Air abrasion with alumina particles induced highest surface roughness and shear bond strength. Er:YAG laser irradiation cannot improve the bonding property of zirconia ceramics to resin cement. Enhancing irradiation intensities and extending irradiation time have no benefit on the bond of the ceramics, and might cause material defect.

Condensation of ablation plumes in the irradiation of metals by high-intensity nanosecond laser pulses at atmospheric pressure

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

Kozadaev, K V

2016-01-31

The Anisimov–Luk'yanchuk model is adapted for describing the condensation of vapour-plasma plumes produced in the irradiation of metal targets by high-intensity (10{sup 8} – 10{sup 10} W cm{sup -2}) nanosecond (10 – 100 ns) pulses at atmospheric pressure. The resultant data suggest that the initial stages of the development of metal ablation plumes correspond with a high degree of accuracy to the Zel'dovich–Raizer theory of dynamic condensation; however, at the stage of the ablation plume decay, the liquid-droplet phase is formed primarily by coalescence of 'nuclei'. (interaction of laser radiation with matter. laser plasma)

Low-intensity laser irradiation at 660 nm stimulates transcription of genes involved in the electron transport chain.

PubMed

Masha, Roland T; Houreld, Nicolette N; Abrahamse, Heidi

2013-02-01

Low-intensity laser irradiation (LILI) has been shown to stimulate cellular functions leading to increased adenosine triphosphate (ATP) synthesis. This study was undertaken to evaluate the effect of LILI on genes involved in the mitochondrial electron transport chain (ETC, complexes I-IV) and oxidative phosphorylation (ATP synthase). Four human skin fibroblast cell models were used in this study: normal non-irradiated cells were used as controls while wounded, diabetic wounded, and ischemic cells were irradiated. Cells were irradiated with a 660 nm diode laser with a fluence of 5 J/cm(2) and gene expression determined by quantitative real-time reverse transcription (RT) polymerase chain reaction (PCR). LILI upregulated cytochrome c oxidase subunit VIb polypeptide 2 (COX6B2), cytochrome c oxidase subunit VIc (COX6C), and pyrophosphatase (inorganic) 1 (PPA1) in diabetic wounded cells; COX6C, ATP synthase, H+transporting, mitochondrial Fo complex, subunit B1 (ATP5F1), nicotinamide adenine dinucleotide (NADH) dehydrogenase (ubiquinone) 1 alpha subcomplex, 11 (NDUFA11), and NADH dehydrogenase (ubiquinone) Fe-S protein 7 (NDUFS7) in wounded cells; and ATPase, H+/K+ exchanging, beta polypeptide (ATP4B), and ATP synthase, H+ transporting, mitochondrial Fo complex, subunit C2 (subunit 9) (ATP5G2) in ischemic cells. LILI at 660 nm stimulates the upregulation of genes coding for subunits of enzymes involved in complexes I and IV and ATP synthase.

Disassembly time of deuterium-cluster-fusion plasma irradiated by an intense laser pulse.

PubMed

Bang, W

2015-07-01

Energetic deuterium ions from large deuterium clusters (>10nm diameter) irradiated by an intense laser pulse (>10(16)W/cm(2)) produce DD fusion neutrons for a time interval determined by the geometry of the resulting fusion plasma. We present an analytical solution of this time interval, the plasma disassembly time, for deuterium plasmas that are cylindrical in shape. Assuming a symmetrically expanding deuterium plasma, we calculate the expected fusion neutron yield and compare with an independent calculation of the yield using the concept of a finite confinement time at a fixed plasma density. The calculated neutron yields agree quantitatively with the available experimental data. Our one-dimensional simulations indicate that one could expect a tenfold increase in total neutron yield by magnetically confining a 10-keV deuterium fusion plasma for 10ns.

Dissociation of β-Sheet Stacking of Amyloid β Fibrils by Irradiation of Intense, Short-Pulsed Mid-infrared Laser.

PubMed

Kawasaki, Takayasu; Yaji, Toyonari; Ohta, Toshiaki; Tsukiyama, Koichi; Nakamura, Kazuhiro

2018-02-05

Structure of amyloid β (Aβ) fibrils is rigidly stacked by β-sheet conformation, and the fibril state of Aβ is profoundly related to pathogenesis of Alzheimer's disease (AD). Although mid-infrared light has been used for various biological researches, it has not yet been known whether the infrared light changes the fibril structure of Aβ. In this study, we tested the effect of irradiation of intense mid-infrared light from a free-electron laser (FEL) targeting the amide bond on the reduction of β-sheet content in Aβ fibrils. The FEL reduced entire contents of proteins exhibiting β-sheet structure in brain sections from AD model mice, as shown by synchrotron-radiation infrared microscopy analysis. Since Aβ 1-42 fibril absorbed a considerable FEL energy at amide I band (6.17 μm), we irradiated the FEL at 6.17 μm and found that β-sheet content of naked Aβ 1-42 fibril was decreased using infrared microscopic analysis. Consistent with the decrease in the β-sheet content, Congo-red signal is decreased after the irradiation to Aβ 1-42 fibril. Furthermore, electron microscopy analysis revealed that morphologies of the fibril and proto-fibril were largely changed after the irradiation. Thus, mid-infrared light dissociates β-sheet structure of Aβ fibrils, which justifies exploration of possible laser-based therapy for AD.

Adaptation and penetration of resin-based root canal sealers in root canals irradiated with high-intensity lasers.

PubMed

Moura-Netto, Cacio; Mello-Moura, Anna Carolina Volpi; Palo, Renato Miotto; Prokopowitsch, Igor; Pameijer, Cornelis H; Marques, Marcia Martins

2015-03-01

This research analyzed the quality of resin-based sealer adaptation after intracanal laser irradiation. Extracted teeth (n = 168) were root canal treated and divided into four groups, according to dentin surface treatment: no laser; Nd:YAG laser (1.5 W, 100 mJ, 15 Hz); diode laser (2.5 W in CW), and Er:YAG laser (1 W, 100 mJ, 10 Hz). The teeth were divided into four subgroups according to the sealer used: AH Plus, EndoREZ, Epiphany, and EpiphanySE. For testing the sealing after root canal obturation, the penetration of silver nitrate solution was measured, whereas to evaluate the adaptation and penetration of the sealer into the dentin, environmental scanning electron microscopy (ESEM) was used. The ESEM images were analyzed using a four-grade criteria score by three evaluators. The inter-examiner agreement was confirmed by Kappa test and the scores statistically compared by the Kruskal-Wallis' test (p < 0.05). Both adaptation and sealer penetration in root canals were not affected by the laser irradiation. Nd:YAG and diode laser decreased the tracer penetration for AH Plus, whereas EndoREZ and EpiphanySE performances were affected by Nd:YAG irradiation (p < 0.05). It can be concluded that intracanal laser irradiation can be used as an adjunct in endodontic treatment; however, the use of hydrophilic resin sealers should be avoided when root canals were irradiated with Nd:YAG laser.

Adaptation and penetration of resin-based root canal sealers in root canals irradiated with high-intensity lasers

NASA Astrophysics Data System (ADS)

Moura-Netto, Cacio; Mello-Moura, Anna Carolina Volpi; Palo, Renato Miotto; Prokopowitsch, Igor; Pameijer, Cornelis H.; Marques, Marcia Martins

2015-03-01

This research analyzed the quality of resin-based sealer adaptation after intracanal laser irradiation. Extracted teeth (n=168) were root canal treated and divided into four groups, according to dentin surface treatment: no laser; Nd:YAG laser (1.5 W, 100 mJ, 15 Hz) diode laser (2.5 W in CW), and Er:YAG laser (1 W, 100 mJ, 10 Hz). The teeth were divided into four subgroups according to the sealer used: AH Plus, EndoREZ, Epiphany, and EpiphanySE. For testing the sealing after root canal obturation, the penetration of silver nitrate solution was measured, whereas to evaluate the adaptation and penetration of the sealer into the dentin, environmental scanning electron microscopy (ESEM) was used. The ESEM images were analyzed using a four-grade criteria score by three evaluators. The inter-examiner agreement was confirmed by Kappa test and the scores statistically compared by the Kruskal-Wallis' test (p<0.05). Both adaptation and sealer penetration in root canals were not affected by the laser irradiation. Nd:YAG and diode laser decreased the tracer penetration for AH Plus, whereas EndoREZ and EpiphanySE performances were affected by Nd:YAG irradiation (p<0.05). It can be concluded that intracanal laser irradiation can be used as an adjunct in endodontic treatment; however, the use of hydrophilic resin sealers should be avoided when root canals were irradiated with Nd:YAG laser.

Intense Femtosecond Laser-Mediated Electrical Discharge Enables Preparation of Amorphous Nickel Phosphide Nanoparticles.

PubMed

Ma, Zhuo-Chen; Chen, Qi-Dai; Han, Bing; Li, He-Long; Wang, Lei; Zhang, Yong-Lai; Sun, Hong-Bo

2018-05-09

Reported here is a high-efficiency preparation method of amorphous nickel phosphide (Ni-P) nanoparticles by intense femtosecond laser irradiation of nickel sulfate and sodium hypophosphite aqueous solution. The underlying mechanism of the laser-assisted preparation was discussed in terms of the breaking of chemical bond in reactants via highly intense electric field discharge generated by the intense femtosecond laser. The morphology and size of the nanoparticles can be tuned by varying the reaction parameters such as ion concentration, ion molar ratio, laser power, and irradiation time. X-ray diffraction and transmission electron microscopy results demonstrated that the nanoparticles were amorphous. Finally, the thermogravimetric-differential thermal analysis experiment verified that the as-synthesized noncrystalline Ni-P nanoparticles had an excellent catalytic capability toward thermal decomposition of ammonium perchlorate. This strategy of laser-mediated electrical discharge under such an extremely intense field may create new opportunities for the decomposition of molecules or chemical bonds that could further facilitate the recombination of new atoms or chemical groups, thus bringing about new possibilities for chemical reaction initiation and nanomaterial synthesis that may not be realized under normal conditions.

Stopping and Coulomb explosion of energetic carbon clusters in a plasma irradiated by an intense laser field

NASA Astrophysics Data System (ADS)

Wang, Guiqiu; Wang, Younian

2015-09-01

The interaction of a charged particle beam with a plasma is a very important subject of relevance for many fields of physics, such as inertial confinement fusion (ICF) driven by ion or electron beams, high energy density physics, and related astrophysical problems. Recently, a promising ICF scheme has been proposed, in which the plasma target is irradiated simultaneously by intense laser and ion beams. For molecular ion or cluster, slowing down process will company the Coulomb explosion phenomenon. In this paper, we present a study of the effects of intense radiation field (RF) on the interaction of energetic carbon clusters in a plasma. The emphasis is laid on the dynamic polarization and correlation effects of the constituent ions within the cluster in order to disclose the role of the vicinage effects on the Coulomb explosion and energy deposition of the clusters in plasma. On the other hand, affecting of a strong laser field on the cluster propagating in plasma is considered, the influence of a large range of laser parameters and plasma parameters on the Coulomb explosion and stopping power are discussed. This work is supported by the National Natural Science Foundation of China (11375034), and the Fundamental Research Funds for the Central Universities of China (3132015144, 3132014337).

Molecular mechanism of biological and therapeutical effect of low-intensity laser irradiation

NASA Astrophysics Data System (ADS)

Mostovnikov, Vasili A.; Mostovnikova, Galina R.; Plavski, Vitali Y.; Plavskaja, Ljudmila G.; Morozova, Raisa P.

1995-05-01

The investigations carried out in our group on biological systems of various organization level (enzyme molecules in solution, human and animal cell cultures), allowed us to conclude, that the light-induced changes of spatial structure of cells components form the basis of biological activity (and as a consequence therapeutic effect) of various wavelength low-intensity laser emission. Photophysical mechanism of these changes lies in the reorientation of highregulated anisotropic parts (domains) with the liquid-crystalline type of ordering of the cell components due to the interaction between the electric field and the light induced integral electric dipole of the domain. The mechanism of such reorientation is well established in physics of liquid crystals of nematic type and is known as light induced analogue of Frederix's effect. The following results enable us to draw the conclusion about the determining role of the orientations effects on the biological activity mechanism of low-intensity laser radiation: (i) the possibility of reversible modification of spatial structure and enzyme molecules functional activity under the influence of laser radiation outside the band of their own or admixture absorption; (ii) the dependence of biological effect of laser radiation on the functional activity of cells vs. polarization degree of the light with the maximum photobiological effects observed for linear-polarized radiation; (iii) the equivalence of a static magnetic field and low-intensity laser radiation in action on functional activity of the cells and the lowering of the laser field intensity for the achieving the difinite changes of the cell functional activity in the presence of static magnetic field.

Nuclear Fusion In Gases Of Deuterium Clusters And Hot Electron Generation In Droplet Sprays Under Irradiation With An Intense Femtosecond Laser

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

T. Ditmire; Zweiback, J; Cowan, T E

In conclusion, we have observed the production of 2.45 MeV deuterium fusion neutrons when a gas of deuterium clusters is irradiated with a 120 mJ, 35 fs laser pulse. When the focal position is optimized, we have observed as many as 10{sup 4} neutrons per laser shot. This yield is consistent with some simple estimates for the fusion yield. We also find that the fusion yield is a sensitive function of the deuterium cluster size in the target jet, a consequence of the Coulomb explosion origin of the fast deuterons. We also find that the neutron pulse duration is fast,more » with a characteristic burn time of well under 1 ns. This experiment may represent a means for producing a compact, table-top source of short pulse fusion neutrons for applications. Furthermore, we have measured hard x-ray yield from femtosecond laser interactions with both solid and micron scale droplet targets. Strong hard x-ray production is observed from both targets. However, the inferred electron temperature is somewhat higher in the case of irradiation of the droplets. These data are consistent with PIC simulations. This finding indicates that quite unique hot electron dynamics occur during the irradiation of wavelength scale particles by an intense laser field and likely warrants further study.« less

Disassembly time of deuterium-cluster-fusion plasma irradiated by an intense laser pulse

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

Bang, W.

Energetic deuterium ions from large deuterium clusters (>10 nm diameter) irradiated by an intense laser pulse (>10¹⁶ W/cm²) produce DD fusion neutrons for a time interval determined by the geometry of the resulting fusion plasma. We show an analytical solution of this time interval, the plasma disassembly time, for deuterium plasmas that are cylindrical in shape. Assuming a symmetrically expanding deuterium plasma, we calculate the expected fusion neutron yield and compare with an independent calculation of the yield using the concept of a finite confinement time at a fixed plasma density. The calculated neutron yields agree quantitatively with the availablemore » experimental data. Our one-dimensional simulations indicate that one could expect a tenfold increase in total neutron yield by magnetically confining a 10 - keV deuterium fusion plasma for 10 ns.« less

Disassembly time of deuterium-cluster-fusion plasma irradiated by an intense laser pulse

DOE PAGES

Bang, W.

2015-07-02

Energetic deuterium ions from large deuterium clusters (>10 nm diameter) irradiated by an intense laser pulse (>10¹⁶ W/cm²) produce DD fusion neutrons for a time interval determined by the geometry of the resulting fusion plasma. We show an analytical solution of this time interval, the plasma disassembly time, for deuterium plasmas that are cylindrical in shape. Assuming a symmetrically expanding deuterium plasma, we calculate the expected fusion neutron yield and compare with an independent calculation of the yield using the concept of a finite confinement time at a fixed plasma density. The calculated neutron yields agree quantitatively with the availablemore » experimental data. Our one-dimensional simulations indicate that one could expect a tenfold increase in total neutron yield by magnetically confining a 10 - keV deuterium fusion plasma for 10 ns.« less

Propagation in compressed matter of hot electrons created by short intense lasers

NASA Astrophysics Data System (ADS)

Batani, D.; Bernardinello, A.; Masella, V.; Pisani, F.; Koenig, M.; Krishnan, J.; Benuzzi, A.; Ellwi, S.; Hall, T.; Norreys, P.; Djaoui, A.; Neely, D.; Rose, S.; Fews, P.; Key, M.

1998-02-01

We performed the first experimental study of propagation in compressed matter of hot electrons created by a short pulse intense laser. The experiment has been carried out with the VULCAN laser at Rutherford compressing plastic targets with two ns laser beams at an intensity ⩾1014W/cm2. A CPA beam with an intensity ⩾1016W/cm2 irradiated the rear side of the target and created hot electrons propagating through the compressed matter. K-α emission was used as diagnostics of hot electron penetration by putting a chloride plastic layer inside the target.

Excimer laser irradiation of metal surfaces

NASA Astrophysics Data System (ADS)

Kinsman, Grant

In this work a new method of enhancing CO2 laser processing by modifying the radiative properties of a metal surface is studied. In this procedure, an excimer laser (XeCl) or KrF) exposes the metal surface to overlapping pulses of high intensity, 10(exp 8) - 10(exp 9) W cm(exp -2), and short pulse duration, 30 nsec FWHM (Full Width Half Maximum), to promote structural and chemical change. The major processing effect at these intensities is the production of a surface plasma which can lead to the formation of a laser supported detonation wave (LSD wave). This shock wave can interact with the thin molten layer on the metal surface influencing to a varying degree surface oxidation and roughness features. The possibility of the expulsion, oxidation and redeposition of molten droplets, leading to the formation of micron thick oxide layers, is related to bulk metal properties and the incident laser intensity. A correlation is found between the expulsion of molten droplets and a Reynolds number, showing the interaction is turbulent. The permanent effects of these interactions on metal surfaces are observed through scanning electron microscopy (SEM), transient calorimetric measurements and Fourier transform infrared (FTIR) spectroscopy. Observed surface textures are related to the scanning procedures used to irradiate the metal surface. Fundamental radiative properties of a metal surface, the total hemispherical emissivity, the near-normal spectral absorptivity, and others are examined in this study as they are affected by excimer laser radiation. It is determined that for heavily exposed Al surface, alpha' (10.6 microns) can be increased to values close to unity. Data relating to material removal rates and chemical surface modification for excimer laser radiation is also discussed. The resultant reduction in the near-normal reflectivity solves the fundamental problem of coupling laser radiation into highly reflective and conductive metals such as copper and aluminum. The

Low intensity 635 nm diode laser irradiation inhibits fibroblast-myofibroblast transition reducing TRPC1 channel expression/activity: New perspectives for tissue fibrosis treatment.

PubMed

Sassoli, Chiara; Chellini, Flaminia; Squecco, Roberta; Tani, Alessia; Idrizaj, Eglantina; Nosi, Daniele; Giannelli, Marco; Zecchi-Orlandini, Sandra

2016-03-01

Low-level laser therapy (LLLT) or photobiomodulation therapy is emerging as a promising new therapeutic option for fibrosis in different damaged and/or diseased organs. However, the anti-fibrotic potential of this treatment needs to be elucidated and the cellular and molecular targets of the laser clarified. Here, we investigated the effects of a low intensity 635 ± 5 nm diode laser irradiation on fibroblast-myofibroblast transition, a key event in the onset of fibrosis, and elucidated some of the underlying molecular mechanisms. NIH/3T3 fibroblasts were cultured in a low serum medium in the presence of transforming growth factor (TGF)-β1 and irradiated with a 635 ± 5 nm diode laser (continuous wave, 89 mW, 0.3 J/cm(2) ). Fibroblast-myofibroblast differentiation was assayed by morphological, biochemical, and electrophysiological approaches. Expression of matrix metalloproteinase (MMP)-2 and MMP-9 and of Tissue inhibitor of MMPs, namely TIMP-1 and TIMP-2, after laser exposure was also evaluated by confocal immunofluorescence analyses. Moreover, the effect of the diode laser on transient receptor potential canonical channel (TRPC) 1/stretch-activated channel (SAC) expression and activity and on TGF-β1/Smad3 signaling was investigated. Diode laser treatment inhibited TGF-β1-induced fibroblast-myofibroblast transition as judged by reduction of stress fibers formation, α-smooth muscle actin (sma) and type-1 collagen expression and by changes in electrophysiological properties such as resting membrane potential, cell capacitance and inwardly rectifying K(+) currents. In addition, the irradiation up-regulated the expression of MMP-2 and MMP-9 and downregulated that of TIMP-1 and TIMP-2 in TGF-β1-treated cells. This laser effect was shown to involve TRPC1/SAC channel functionality. Finally, diode laser stimulation and TRPC1 functionality negatively affected fibroblast-myofibroblast transition by interfering with TGF-β1 signaling, namely reducing the

Laser-enhanced high-intensity focused ultrasound heating in an in vivo small animal model

NASA Astrophysics Data System (ADS)

Jo, Janggun; Yang, Xinmai

2016-11-01

The enhanced heating effect during the combination of high-intensity focused ultrasound (HIFU) and low-optical-fluence laser illumination was investigated by using an in vivo murine animal model. The thighs of murine animals were synergistically irradiated by HIFU and pulsed nano-second laser light. The temperature increases in the target region were measured by a thermocouple under different HIFU pressures, which were 6.2, 7.9, and 9.8 MPa, in combination with 20 mJ/cm2 laser exposures at 532 nm wavelength. In comparison with conventional laser therapies, the laser fluence used here is at least one order of magnitude lower. The results showed that laser illumination could enhance temperature during HIFU applications. Additionally, cavitation activity was enhanced when laser and HIFU irradiation were concurrently used. Further, a theoretical simulation showed that the inertial cavitation threshold was indeed decreased when laser and HIFU irradiation were utilized concurrently.

Shield gas induced cracks during nanosecond-pulsed laser irradiation of Zr-based metallic glass

NASA Astrophysics Data System (ADS)

Huang, Hu; Noguchi, Jun; Yan, Jiwang

2016-10-01

Laser processing techniques have been given increasing attentions in the field of metallic glasses (MGs). In this work, effects of two kinds of shield gases, nitrogen and argon, on nanosecond-pulsed laser irradiation of Zr-based MG were comparatively investigated. Results showed that compared to argon gas, nitrogen gas remarkably promoted the formation of cracks during laser irradiation. Furthermore, crack formation in nitrogen gas was enhanced by increasing the peak laser power intensity or decreasing the laser scanning speed. X-ray diffraction and micro-Raman spectroscopy indicated that the reason for enhanced cracks in nitrogen gas was the formation of ZrN.

Enhanced water window x-ray emission from in situ formed carbon clusters irradiated by intense ultra-short laser pulses

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

Chakravarty, U.; Rao, B. S.; Arora, V.

Enhanced water window x-ray emission (23–44 Å) from carbon clusters, formed in situ using a pre-pulse, irradiated by intense (I > 10{sup 17} W/cm{sup 2}) ultra-short laser pulse, is demonstrated. An order of magnitude x-ray enhancement over planar graphite target is observed in carbon clusters, formed by a sub-ns pre-pulse, interacting with intense main pulse after a delay. The effect of the delay and the duration of the main pulse is studied for optimizing the x-ray emission in the water window region. This x-ray source has added advantages of being an efficient, high repetition rate, and low debris x-ray source.

Temperature modeling of laser-irradiated azo-polymer thin films.

PubMed

Yager, Kevin G; Barrett, Christopher J

2004-01-08

Azobenzene polymer thin films exhibit reversible surface mass transport when irradiated with a light intensity and/or polarization gradient, although the exact mechanism remains unknown. In order to address the role of thermal effects in the surface relief grating formation process peculiar to azo polymers, a cellular automaton simulation was developed to model heat flow in thin films undergoing laser irradiation. Typical irradiation intensities of 50 mW/cm2 resulted in film temperature rises on the order of 5 K, confirmed experimentally. The temperature gradient between the light maxima and minima was found, however, to stabilize at only 10(-4) K within 2 micros. These results indicate that thermal effects play a negligible role during inscription, for films of any thickness. Experiments monitoring surface relief grating formation on substrates of different thermal conductivity confirm that inscription is insensitive to film temperature. Further simulations suggest that high-intensity pulsed irradiation leads to destructive temperatures and sample ablation, not to reversible optical mass transport. (c) 2004 American Institute of Physics

Quasi-monoenergetic proton beam from a proton-layer embedded metal foil irradiated by an intense laser pulse

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

Kim, Kyung Nam; Lee, Kitae, E-mail: klee@kaeri.re.kr; Kumar, Manoj

A target structure, ion-layer embedded foil (ILEF) is proposed for producing a quasi-monoenergetic proton beam by utilizing a bulk electrostatic field, which is generated by irradiating the target with an ultra-intense laser pulse, inside the plasma. Compared with the case of a single metal foil in which the proton layer is initially present on the surface, in the ILEF target, the proton layer is initially located inside a metal foil. A two-dimensional particle-in-cell (PIC) simulation shows that the target generates a proton beam with a narrow energy spread. With a laser intensity of 2 × 10{sup 19 }W/cm{sup 2}, a 22-MeV proton beammore » with an energy spread of 8% at the full-width-half-maximum (FWHM) is obtained when the proton layer is located at 0.4 μm inside the rear surface of a 2.4 μm-thick copper foil. When the proton layer moves toward the front side, a proton beam with a flat-top energy distribution ranging from 15 MeV to 35 MeV is obtained. Further, with a higher laser intensity of 10{sup 21 }W/cm{sup 2}, a proton beam with the maximum energy of 345 MeV and FWHM energy spread of 7.2% is obtained. The analysis of the PIC simulation with an aid of a fluid analysis shows that the spectrum is affected by the initial position of the proton layer, its initial spread during the formation of the sheath field, and the space charge effect.« less

Effect of metal surfaces on matrix-assisted laser desorption/ionization analyte peak intensities.

PubMed

Kancharla, Vidhyullatha; Bashir, Sajid; Liu, Jingbo L; Ramirez, Oscar M; Derrick, Peter J; Beran, Kyle A

2017-10-01

Different metal surfaces in the form of transmission electron microscope grids were examined as support surfaces in matrix-assisted laser desorption/ionization time-of-flight mass spectrometry with a view towards enhancement of peptide signal intensity. The observed enhancement between 5-fold and 20-fold relative to the normal stainless steel slide was investigated by applying the thermal desorption model for matrix-assisted laser desorption/ionization. A simple model evaluates the impact that the thermal properties of the metals have on the ion yield of the analyte. It was observed that there was not a direct, or strong, correlation between the thermal properties of the metals and the corresponding ion yield of the peptides. The effects of both fixed and variable laser irradiances versus ion yield were also examined for the respective metals studied. In all cases the use of transmission electron microscope grids required much lower laser irradiances in order to generate similar peak intensities as those observed with a stainless steel surface.

Thermal Changes of Maize Seed by Laser Irradiation

NASA Astrophysics Data System (ADS)

Hernandez-Aguilar, C.; Dominguez-Pacheco, A.; Cruz-Orea, A.

2015-09-01

In this research, the thermal evolution in maize seeds ( Zea mays L.) was studied when low-intensity laser irradiation was applied during 60 s. The seeds were irradiated in three different conditions: suspended in air, placed on an aluminum surface, and finally placed on a cardboard; the evolution of the seed temperature was measured by an infrared camera. Photoacoustic spectroscopy and the Rosencwaig and Gersho model were used to determine the optical absorption coefficient (β ) of the seeds. The results indicate that using 650 nm laser light and 27.4 mW, it is possible to produce temperature changes (up to 9.06°C after 1 min) on the seeds. Comparing the mean temperature of the seeds, during and after the incidence of light from a laser, it was found that there were statistically significant differences (P≤ 0.05) from time t1 to time t_{16} (t1 to t_{16}) and t3 to t_{16}, for the laser turned on and off, respectively. The seed condition that had the highest temperature variation, relative to the initial temperature (during the irradiation laser exposure), involved the seeds suspended in air. With regard to the stage of decay of the temperature, it was found that the seed condition that decays more slowly was the seed placed on the cardboard. It was also found that black-dyed maize seeds are optically opaque in the 300 nm to 700 nm range Also, the thermal diffusion length is smaller than the optical penetration length. In the present investigation, it was shown that there is a thermal component associated with the mechanisms of laser biostimulation, which is also a function of the container materials of the seed. In this way, the effects of laser treatment on maize seeds involve at least a temperature effect. It is important to know the temperature changes in the seeds that have been irradiated with a laser beam since they could have substantial practical and theoretical importance.

Collisionless absorption of intense laser radiation in nanoplasma

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

Zaretsky, D F; Korneev, Philipp A; Popruzhenko, Sergei V

The rate of linear collisionless absorption of an electromagnetic radiation in a nanoplasma - classical electron gas localised in a heated ionised nanosystem (thin film or cluster) irradiated by an intense femtosecond laser pulse - is calculated. The absorption is caused by the inelastic electron scattering from the self-consistent potential of the system in the presence of a laser field. The effect proves to be appreciable because of a small size of the systems. General expressions are obtained for the absorption rate as a function of the parameters of the single-particle self-consistent potential and electron distribution function in the regimemore » linear in field. For the simplest cases, where the self-consistent field is created by an infinitely deep well or an infinite charged plane, closed analytic expressions are obtained for the absorption rate. Estimates presented in the paper demonstrate that, over a wide range of the parameters of laser pulses and nanostructures, the collisionless mechanism of heating electron subsystem can be dominant. The possibility of experimental observation of the collisionless absorption of intense laser radiation in nanoplasma is also discussed. (interaction of laser radiation with matter)« less

Design of refractive laser beam shapers to generate complex irradiance profiles

NASA Astrophysics Data System (ADS)

Li, Meijie; Meuret, Youri; Duerr, Fabian; Vervaeke, Michael; Thienpont, Hugo

2014-05-01

A Gaussian laser beam is reshaped to have specific irradiance distributions in many applications in order to ensure optimal system performance. Refractive optics are commonly used for laser beam shaping. A refractive laser beam shaper is typically formed by either two plano-aspheric lenses or by one thick lens with two aspherical surfaces. Ray mapping is a general optical design technique to design refractive beam shapers based on geometric optics. This design technique in principle allows to generate any rotational-symmetric irradiance profile, yet in literature ray mapping is mainly developed to transform a Gaussian irradiance profile to a uniform profile. For more complex profiles especially with low intensity in the inner region, like a Dark Hollow Gaussian (DHG) irradiance profile, ray mapping technique is not directly applicable in practice. In order to these complex profiles, the numerical effort of calculating the aspherical surface points and fitting a surface with sufficient accuracy increases considerably. In this work we evaluate different sampling approaches and surface fitting methods. This allows us to propose and demonstrate a comprehensive numerical approach to efficiently design refractive laser beam shapers to generate rotational-symmetric collimated beams with a complex irradiance profile. Ray tracing analysis for several complex irradiance profiles demonstrates excellent performance of the designed lenses and the versatility of our design procedure.

System for obtaining smooth laser beams where intensity variations are reduced by spectral dispersion of the laser light (SSD)

DOEpatents

Skupsky, S.; Kessler, T.J.; Short, R.W.; Craxton, S.; Letzring, S.A.; Soures, J.

1991-09-10

In an SSD (smoothing by spectral dispersion) system which reduces the time-averaged spatial variations in intensity of the laser light to provide uniform illumination of a laser fusion target, an electro-optic phase modulator through which a laser beam passes produces a broadband output beam by imposing a frequency modulated bandwidth on the laser beam. A grating provides spatial and angular spectral dispersion of the beam. Due to the phase modulation, the frequencies (''colors'') cycle across the beam. The dispersed beam may be amplified and frequency converted (e.g., tripled) in a plurality of beam lines. A distributed phase plate (DPP) in each line is irradiated by the spectrally dispersed beam and the beam is focused on the target where a smooth (uniform intensity) pattern is produced. The color cycling enhances smoothing and the use of a frequency modulated laser pulse prevents the formation of high intensity spikes which could damage the laser medium in the power amplifiers. 8 figures.

System for obtaining smooth laser beams where intensity variations are reduced by spectral dispersion of the laser light (SSD)

DOEpatents

Skupsky, Stanley; Kessler, Terrance J.; Short, Robert W.; Craxton, Stephen; Letzring, Samuel A.; Soures, John

1991-01-01

In an SSD (smoothing by spectral dispersion) system which reduces the time-averaged spatial variations in intensity of the laser light to provide uniform illumination of a laser fusion target, an electro-optic phase modulator through which a laser beam passes produces a broadband output beam by imposing a frequency modulated bandwidth on the laser beam. A grating provides spatial and angular spectral dispersion of the beam. Due to the phase modulation, the frequencies ("colors") cycle across the beam. The dispersed beam may be amplified and frequency converted (e.g., tripled) in a plurality of beam lines. A distributed phase plate (DPP) in each line is irradiated by the spectrally dispersed beam and the beam is focused on the target where a smooth (uniform intensity) pattern is produced. The color cycling enhances smoothing and the use of a frequency modulated laser pulse prevents the formation of high intensity spikes which could damage the laser medium in the power amplifiers.

Comparison of high-intensity pulsed and continuous-wave irradiation on benzoporphyrin derivative-induced photosensitization of bladder cancer cells

NASA Astrophysics Data System (ADS)

Diddens, Heyke C.; Gillies, Robert; Hasan, Tayyaba

1994-08-01

Benzoporphyrin derivative, monoacid ring A (BPD-MA) is a second generation porphyrin photosensitizer, with a significant absorption at 692 nm. The ability of two different lasers (a high-intensity pulsed ruby laser, and a continuous wave (cw) argon-ion laser pumped dye laser) in producing photodynamic damage to human bladder carcinoma cells in vitro under similar conditions was compared. Cells incubated in 0.14 (mu) M BPD-MA for 3 hours were irradiated with 1 or 3 J/cm2 with either pulsed or cw irradiation at 694 nm. Cell survival was determined using an MTT assay. With the ruby laser essentially no phototoxicity was observed at the high intensity pulsed irradiances used, whereas 38% and 6% survival rates were observed for 1 and 3 J/cm2, respectively, using cw irradiation. Possible explanations for the lack of BPD-MA phototoxicity using the ruby laser are: rapid photodegradation, saturation and excitation into higher excited states of the sensitizer. No BPD-MA photodegradation was observed in 1.4 (mu) M BPD-MA in 10% fetal calf serum solutions using the ruby laser. However, an oxygen-dependent photodegradation with the formation of a chlorin-type photoproduct was observed in these solutions using cw irradiation. A simple calculation indicated that the high pulse irradiances used in this study (4.4 X 107 W/cm2) were approximately 3 orders of magnitude greater than required for the onset of saturation. If higher excited states (Sn or Tn) are populated, they do not undergo any photochemistry resulting in phototoxicity or in photoproduct formation. These results show that with the low saturation threshold of BPD-MA, the choice of source and irradiance are important considerations in planning a therapeutic regime.

Colour changes by laser irradiation of reddish building limestones

NASA Astrophysics Data System (ADS)

Grossi, C. M.; Benavente, D.

2016-10-01

We have used X-ray photoelectron spectroscopy (XPS) as a novel method to investigate the causes of colour changes in a reddish limestone under irradiation by a Q-switched Nd:YAG 1064 nm laser. We irradiated clean dry and wet surfaces of Pidramuelle Roja, a building stone frequently used in the Asturian heritage, at fluences ranging from 0.12 to 1.47 J cm-2. We measured the colour coordinates and undertook XPS analysis of the state of oxidation of iron both before and after irradiation. Visible colour changes and potential aesthetic damage occurred on dry surfaces from a fluence of 0.31 J cm-2, with the stone showing a greening effect and very intense darkening. The colour change on dry surfaces was considerably higher than on wet surfaces, which at the highest fluence (1.47 J cm-2) was also above the human visual detection threshold. The use of XPS demonstrated that the change in colour (chroma and hue) is associated with a reduction in the iron oxidation state on dry surfaces during laser irradiation. This points out to a potential routinary use of XPS to analyse causes of colour changes during laser cleaning in other types of coloured building stones.

The effect of low-level laser irradiation on dog spermatozoa motility is dependent on laser output power.

PubMed

Corral-Baqués, M I; Rivera, M M; Rigau, T; Rodríguez-Gil, J E; Rigau, J

2009-09-01

Biological tissues respond to low-level laser irradiation and so do dog spermatozoa. Among the main parameters to be considered when a biological tissue is irradiated is the output power. We have studied the effects on sperm motility of 655 nm continuous wave diode laser irradiation at different output powers with 3.34 J (5.97 J/cm(2)). The second fraction of fresh dog sperm was divided into five groups: control, and four to be irradiated with an average output power of 6.8 mW, 15.4 mW, 33.1 mW and 49.7 mW, respectively. At 0 min and 45 min after irradiation, pictures were taken and a computer aided sperm analysis (CASA) performed to analyse different motility parameters. The results showed that different output powers affected dog semen motility parameters differently. The highest output power showed the most intense effects. Significant changes in the structure of the motile sperm subpopulation were linked to the different output powers used.

Laser irradiation of carbon nanotube films: Effects and heat dissipation probed by Raman spectroscopy

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

Mialichi, J. R.; Brasil, M. J. S. P.; Iikawa, F.

We investigate the thermal properties of thin films formed by single- and multi-walled carbon nanotubes submitted to laser irradiation using Raman scattering as a probe of both the tube morphology and the local temperature. The nanotubes were submitted to heating/cooling cycles attaining high laser intensities ({approx}1.4 MW/cm{sup 2}) under vacuum and in the presence of an atmosphere, with and without oxygen. We investigate the heat diffusion of the irradiated nanotubes to their surroundings and the effect of laser annealing on their properties. The presence of oxygen during laser irradiation gives rise to an irreversible increase of the Raman efficiency ofmore » the carbon nanotubes and to a remarkable increase of the thermal conductivity of multi-walled films. The second effect can be applied to design thermal conductive channels in devices based on carbon nanotube films using laser beams.« less

Antibacterial effects of Nd:YAG laser irradiation within root canal dentin.

PubMed

Klinke, T; Klimm, W; Gutknecht, N

1997-02-01

The microbial flora of the root canal dentin can cause failures in the conventional treatment of infected root canals if it cannot be sufficiently removed by preparation and chemical disinfection of the root canal. The aim of this study is to examine the bactericidal effects of neodymium:yttriumaluminum garnet (Nd:YAG) laser irradiation in the depth of the root canal dentin. Following sterilization, longitudinal section dentin slices of different thicknesses (100-1000 microns) were inoculated on one side with 4 microliters of a Streptococcus mutans suspension. The opposite sides of the dentin slices were then irradiated four times for 10-20 sec (according to the sample area) using the Nd:YAG laser at a setting of 1.5 W, 15 pps with a 200 microns glass fiber from an angle of about 5 degrees. The bacteria were then removed from the dentin using vibration and plated out on culture dishes that were selective for Streptococcus mutans. When compared with untreated control slices, counting of the colonies revealed a highly significant elimination of bacteria for all thicknesses following laser irradiation. Although the intensity of the laser irradiation decreased after penetration of a 1000-micron dentin slice, the bactericidal mode of action was still effective.

Laser irradiation effects on the surface, structural and mechanical properties of Al-Cu alloy 2024

NASA Astrophysics Data System (ADS)

Yousaf, Daniel; Bashir, Shazia; Akram, Mahreen; kalsoom, Umm-i.-; Ali, Nisar

2014-02-01

Laser irradiation effects on surface, structural and mechanical properties of Al-Cu-Mg alloy (Al-Cu alloy 2024) have been investigated. The specimens were irradiated for various fluences ranging from 3.8 to 5.5 J/cm2 using an Excimer (KrF) laser (248 nm, 18 ns, 30 Hz) under vacuum environment. The surface and structural modifications of the irradiated targets have been investigated by scanning electron microscope (SEM) and X-ray diffractometer (XRD), respectively. SEM analysis reveals the formation of micro-sized craters along the growth of periodic surface structures (ripples) at their peripheries. The size of the craters initially increases and then decreases by increasing the laser fluence. XRD analysis shows an anomalous trend in the peak intensity and crystallite size of the specimen irradiated for various fluences. A universal tensile testing machine and Vickers microhardness tester were employed in order to investigate the mechanical properties of the irradiated targets. The changes in yield strength, ultimate tensile strength and microhardness were found to be anomalous with increasing laser fluences. The changes in the surface and structural properties of Al-Cu alloy 2024 after laser irradiation have been associated with the changes in mechanical properties.

Influence of the fractioned irradiation energy in the phototherapy with low intensity laser on the growth of human dental pulp fibroblasts

NASA Astrophysics Data System (ADS)

Meneguzzo, D. T.; Eduardo, C. P.; Ribeiro, M. S.; Marques, M. M.

2008-03-01

Laser phototherapy has proven to improve treatment of several pathologies in dentistry. The aim of the present study was to analyze the low power laser phototherapy effects comparing multiple irradiations with the same total energy at once. This in vitro study focuses on the biostimulation of cellular growth of pulp fibroblasts (FP5 cell lineage). The cells were grown in Dulbecco's Modified Eagle's (DME) medium with either 5% (nutritional deficit) or 10% fetal bovine serum (FBS). Laser irradiation was carried out with diode lasers with the following parameters: 685 nm, 40 mW, spot size 0.019 cm2. The groups were: G1(6.3J/cm2, 3 s, 0.12J), G2 (12.6J/cm2, 6 s, 0.24J), G3 (18.9J/cm2, 9 s, 0.36J), G4 (2 irradiations of 6.3J/cm2, 0.24J), G5 (3 irradiations of 6.3J/cm2, 0.36J), G6 (5% SFB, negative control, without irradiation), and G7 (10% SFB, positive control, without irradiation). On groups G4 and G5 the irradiation was performed with 6h-intervals. For growth analysis, the MTT test was used 24 hours after the last irradiation. The data from spectrophotometer were analyzed by ANOVA followed by the Tukey's test. The groups submitted to multiple irradiations presented significantly higher cell growth than the groups with single irradiation. This cell growth was similar to that of positive control group. The laser phototherapy with multiple irradiations is more effective on cellular growth.

Laser etching of groove structures with micro-optical fiber-enhanced irradiation

PubMed Central

2012-01-01

A microfiber is used as a laser-focusing unit to fabricate a groove structure on TiAlSiN surfaces. After one laser pulse etching, a groove with the minimum width of 265 nm is manufactured at the area. This technique of microfabricating the groove in microscale is studied. Based on the near-field intensity enhancement at the contact area between the fiber and the surface during the laser irradiation, simulation results are also presented, which agree well with the experimental results. PMID:22713521

Treatment of acute pancreatitis with mexidol and low-intensity laser radiation

NASA Astrophysics Data System (ADS)

Parzyan, G. R.; Geinits, A. V.

2001-04-01

This article presents the results of treatment of 54 patients with acute pancreatitis. The patients were divided into two groups according to the method of treatment. The control group (26 patients) received a conventional therapy, whereas the experimental group (28 patients) received mexidol in combination with the intravenous laser irradiation of blood. Clinical and laboratory tests confirmed a high efficiency of the combined therapy based on the administration of mexidol antioxidant and low-intensity (lambda) equals 0.63 micrometers diode laser irradiation of blood. This therapeutic technique produced an influence on the basic pathogenetic mechanisms of acute pancreatitis. The application of this method of treatment improved the course and prognosis of acute pancreatitis.

Intra-pulse transition between ion acceleration mechanisms in intense laser-foil interactions

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

Padda, H.; King, M.; Gray, R. J.

Multiple ion acceleration mechanisms can occur when an ultrathin foil is irradiated with an intense laser pulse, with the dominant mechanism changing over the course of the interaction. Measurement of the spatial-intensity distribution of the beam of energetic protons is used to investigate the transition from radiation pressure acceleration to transparency-driven processes. It is shown numerically that radiation pressure drives an increased expansion of the target ions within the spatial extent of the laser focal spot, which induces a radial deflection of relatively low energy sheath-accelerated protons to form an annular distribution. Through variation of the target foil thickness, themore » opening angle of the ring is shown to be correlated to the point in time transparency occurs during the interaction and is maximized when it occurs at the peak of the laser intensity profile. Corresponding experimental measurements of the ring size variation with target thickness exhibit the same trends and provide insight into the intra-pulse laser-plasma evolution.« less

Influence of irradiation conditions on plasma evolution in laser-surface interaction

NASA Astrophysics Data System (ADS)

Hermann, J.; Boulmer-Leborgne, C.; Dubreuil, B.; Mihailescu, I. N.

1993-09-01

The plasma plume induced by pulsed CO2 laser irradiation of a Ti target at power densities up to 4×108 W cm-2 was studied by emission spectroscopy. Time- and space-resolved measurements were performed by varying laser intensity, laser temporal pulse shape, ambient gas pressure, and the nature of the ambient gas. Experimental results are discussed by comparison with usual models. We show that shock wave and plasma propagation depend critically on the ratio Ivap/Ii, Ivap being the intensity threshold for surface vaporization and Ii the plasma ignition threshold of the ambient gas. Spectroscopic diagnostics of the helium breakdown plasma show maximum values of electron temperature and electron density in the order of kTe˜10 eV and ne=1018 cm-3, respectively. The plasma cannot be described by local thermodynamic equilibrium modeling. Nevertheless, excited metal atoms appear to be in equilibrium with electrons, hence, they can be used like a probe to measure the electron temperature. In order to get information on the role of the plasma in the laser-surface interaction, Ti surfaces were investigated by microscopy after irradiation. Thus an enhanced momentum transfer from the plasma to the target due to the recoil pressure of the breakdown plasma could be evidenced.

LPI studies with grazing incidence irradiation at the Nike laser

NASA Astrophysics Data System (ADS)

Weaver, J.; Kehne, D.; Schmitt, A.; Obenschain, S.; Serlin, V.; Oh, J.; Lehmberg, R.; Seely, J.

2013-10-01

Studies of laser plasma instabilities (LPI) at the Nike laser facility at NRL have previously concentrated on planar targets irradiated with their surface normal aligned to the central axis of the laser. Shots with planar targets rotated up 60° to the laser have shown changes in thresholds for the two-plasmon decay instability and stimulated Raman scattering near the quarter critical region. In the case of rotated low-Z targets, spectra were observed to shift to lower wavelength and were substantially stronger in the visible and ultraviolet spectral ranges. The low-Z target data show growth at an incident intensity slightly below (~30%) the threshold values observed at normal incidence. A rapid rise in signal level over the same laser intensities was also observed in the hard x-ray data which serve as an overall indicator of LPI activity. Shots with rotated planar high-Z targets showed that the visible and ultraviolet emissions dropped significantly when compared to low-Z targets in the same geometry. This presentation will include results from upcoming experiments to determine the LPI signal for low-Z, high-Z, and high-Z coated targets at lower laser intensities for several angles of target rotation. Shots with widely separated laser beams are also planned to explore cross beam energy transport at Nike. Work supported by DoE/NNSA.

First-principles simulation of the optical response of bulk and thin-film α-quartz irradiated with an ultrashort intense laser pulse

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

Lee, Kyung-Min; Min Kim, Chul; Moon Jeong, Tae, E-mail: jeongtm@gist.ac.kr

A computational method based on a first-principles multiscale simulation has been used for calculating the optical response and the ablation threshold of an optical material irradiated with an ultrashort intense laser pulse. The method employs Maxwell's equations to describe laser pulse propagation and time-dependent density functional theory to describe the generation of conduction band electrons in an optical medium. Optical properties, such as reflectance and absorption, were investigated for laser intensities in the range 10{sup 10} W/cm{sup 2} to 2 × 10{sup 15} W/cm{sup 2} based on the theory of generation and spatial distribution of the conduction band electrons. The method was applied tomore » investigate the changes in the optical reflectance of α-quartz bulk, half-wavelength thin-film, and quarter-wavelength thin-film and to estimate their ablation thresholds. Despite the adiabatic local density approximation used in calculating the exchange–correlation potential, the reflectance and the ablation threshold obtained from our method agree well with the previous theoretical and experimental results. The method can be applied to estimate the ablation thresholds for optical materials, in general. The ablation threshold data can be used to design ultra-broadband high-damage-threshold coating structures.« less

The study towards high intensity high charge state laser ion sources.

PubMed

Zhao, H Y; Jin, Q Y; Sha, S; Zhang, J J; Li, Z M; Liu, W; Sun, L T; Zhang, X Z; Zhao, H W

2014-02-01

As one of the candidate ion sources for a planned project, the High Intensity heavy-ion Accelerator Facility, a laser ion source has been being intensively studied at the Institute of Modern Physics in the past two years. The charge state distributions of ions produced by irradiating a pulsed 3 J/8 ns Nd:YAG laser on solid targets of a wide range of elements (C, Al, Ti, Ni, Ag, Ta, and Pb) were measured with an electrostatic ion analyzer spectrometer, which indicates that highly charged ions could be generated from low-to-medium mass elements with the present laser system, while the charge state distributions for high mass elements were relatively low. The shot-to-shot stability of ion pulses was monitored with a Faraday cup for carbon target. The fluctuations within ±2.5% for the peak current and total charge and ±6% for pulse duration were demonstrated with the present setup of the laser ion source, the suppression of which is still possible.

Temperature changes on the root surfaces of mandibular incisors after an 810-nm high-intensity intracanal diode laser irradiation

NASA Astrophysics Data System (ADS)

da Fonseca Alvarez, Andrea; Moura-Netto, Cacio; Daliberto Frugoli, Alexandre; Fernando, Casemiro; Correa Aranha, Ana Cecilia; Davidowicz, Harry

2012-01-01

Temperature changes caused by laser irradiation can promote damage to the surrounding dental tissues. In this study, we evaluated the temperature changes of recently extracted human mandibular incisors during intracanal irradiation with an 810-nm diode laser at different settings. Fifty mandibular incisors were enlarged up to an apical size of ISO No. 40 file. After the final rinse with 17% ethylenediaminetetraacetic acid, 0.2% lauryl sodium sulfate biologic detergent, and sterile water, samples were irradiated with circular movements from apex to crown through five different settings of output power (1.5, 2.0, 2.5, 3.0, and 3.5 W) in continuous mode. The temperature changes were measured on both sides of the apical and middle root thirds using two thermopar devices. A temperature increase of 7 °C was considered acceptable as a safe threshold when applying the diode laser. Results: The results showed that only 3.5-W output power increased the outer surface temperature above the critical value. Conclusion: The recommended output power can be stipulated as equal to or less than 3 W to avoid overheating during diode laser irradiation on thin dentin walls.

Cytosolic Irradiation of Femtosecond Laser Induces Mitochondria-dependent Apoptosis-like Cell Death via Intrinsic Reactive Oxygen Cascades

PubMed Central

Yoon, Jonghee; Ryu, Seung-wook; Lee, Seunghee; Choi, Chulhee

2015-01-01

High-intensity femtosecond lasers have recently been used to irreversibly disrupt nanoscale structures, such as intracellular organelles, and to modify biological functions in a reversible manner: so-called nanosurgery and biophotomodulation. Femtosecond laser pulses above the threshold intensity sufficient for reversible biophotomodulation can cause irreversible changes in the irradiated cell, eventually leading to cell death. Here, we demonstrated that cytosolic irradiation with a femtosecond laser produced intrinsic cascades of reactive oxygen species (ROS), which led to rapid apoptosis-like cell death via a caspase and poly (ADP-ribose) polymerase 1 (PARP-1) signaling pathway. We further showed that cells with enhanced mitochondrial fusion activity are more resilient to laser-induced stress compared to those with enforced mitochondrial fission. Taken together, these findings provide fundamental insight into how optical stimulation intervenes in intrinsic cellular signaling pathways and functions. PMID:25648455

Cytosolic irradiation of femtosecond laser induces mitochondria-dependent apoptosis-like cell death via intrinsic reactive oxygen cascades.

PubMed

Yoon, Jonghee; Ryu, Seung-Wook; Lee, Seunghee; Choi, Chulhee

2015-02-04

High-intensity femtosecond lasers have recently been used to irreversibly disrupt nanoscale structures, such as intracellular organelles, and to modify biological functions in a reversible manner: so-called nanosurgery and biophotomodulation. Femtosecond laser pulses above the threshold intensity sufficient for reversible biophotomodulation can cause irreversible changes in the irradiated cell, eventually leading to cell death. Here, we demonstrated that cytosolic irradiation with a femtosecond laser produced intrinsic cascades of reactive oxygen species (ROS), which led to rapid apoptosis-like cell death via a caspase and poly (ADP-ribose) polymerase 1 (PARP-1) signaling pathway. We further showed that cells with enhanced mitochondrial fusion activity are more resilient to laser-induced stress compared to those with enforced mitochondrial fission. Taken together, these findings provide fundamental insight into how optical stimulation intervenes in intrinsic cellular signaling pathways and functions.

Nanoparticles alloying in liquids: Laser-ablation-generated Ag or Pd nanoparticles and laser irradiation-induced AgPd nanoparticle alloying

NASA Astrophysics Data System (ADS)

Semaltianos, N. G.; Chassagnon, R.; Moutarlier, V.; Blondeau-Patissier, V.; Assoul, M.; Monteil, G.

2017-04-01

Laser irradiation of a mixture of single-element micro/nanomaterials may lead to their alloying and fabrication of multi-element structures. In addition to the laser induced alloying of particulates in the form of micro/nanopowders in ambient atmosphere (which forms the basis of the field of additive manufacturing technology), another interesting problem is the laser-induced alloying of a mixture of single-element nanoparticles in liquids since this process may lead to the direct fabrication of alloyed-nanoparticle colloidal solutions. In this work, bare-surface ligand-free Ag and Pd nanoparticles in solution were prepared by laser ablation of the corresponding bulk target materials, separately in water. The two solutions were mixed and the mixed solution was laser irradiated for different time durations in order to investigate the laser-induced nanoparticles alloying in liquid. Nanoparticles alloying and the formation of AgPd alloyed nanoparticles takes place with a decrease of the intensity of the surface-plasmon resonance peak of the Ag nanoparticles (at ∼405 nm) with the irradiation time while the low wavelength interband absorption peaks of either Ag or Pd nanoparticles remain unaffected by the irradiation for a time duration even as long as 30 min. The nanoalloys have lattice constants with values between those of the pure metals, which indicates that they consist of Ag and Pd in an approximately 1:1 ratio similar to the atomic composition of the starting mixed-nanoparticle solution. Formation of nanoparticle networks consisting of bimetallic alloyed nanoparticles and nanoparticles that remain as single elements (even after the end of the irradiation), joining together, are also formed. The binding energies of the 3d core electrons of both Ag and Pd nanoparticles shift to lower energies with the irradiation time, which is also a typical characteristic of AgPd alloyed nanoparticles. The mechanisms of nanoparticles alloying and network formation are also

Nanoparticles alloying in liquids: Laser-ablation-generated Ag or Pd nanoparticles and laser irradiation-induced AgPd nanoparticle alloying.

PubMed

Semaltianos, N G; Chassagnon, R; Moutarlier, V; Blondeau-Patissier, V; Assoul, M; Monteil, G

2017-04-18

Laser irradiation of a mixture of single-element micro/nanomaterials may lead to their alloying and fabrication of multi-element structures. In addition to the laser induced alloying of particulates in the form of micro/nanopowders in ambient atmosphere (which forms the basis of the field of additive manufacturing technology), another interesting problem is the laser-induced alloying of a mixture of single-element nanoparticles in liquids since this process may lead to the direct fabrication of alloyed-nanoparticle colloidal solutions. In this work, bare-surface ligand-free Ag and Pd nanoparticles in solution were prepared by laser ablation of the corresponding bulk target materials, separately in water. The two solutions were mixed and the mixed solution was laser irradiated for different time durations in order to investigate the laser-induced nanoparticles alloying in liquid. Nanoparticles alloying and the formation of AgPd alloyed nanoparticles takes place with a decrease of the intensity of the surface-plasmon resonance peak of the Ag nanoparticles (at ∼405 nm) with the irradiation time while the low wavelength interband absorption peaks of either Ag or Pd nanoparticles remain unaffected by the irradiation for a time duration even as long as 30 min. The nanoalloys have lattice constants with values between those of the pure metals, which indicates that they consist of Ag and Pd in an approximately 1:1 ratio similar to the atomic composition of the starting mixed-nanoparticle solution. Formation of nanoparticle networks consisting of bimetallic alloyed nanoparticles and nanoparticles that remain as single elements (even after the end of the irradiation), joining together, are also formed. The binding energies of the 3d core electrons of both Ag and Pd nanoparticles shift to lower energies with the irradiation time, which is also a typical characteristic of AgPd alloyed nanoparticles. The mechanisms of nanoparticles alloying and network formation are also

Optimized two- and three-colour laser pulses for the intense terahertz wave generation

NASA Astrophysics Data System (ADS)

Zhang, Lei; Wang, Guo-Li; Zhou, Xiao-Xin

2016-11-01

Based on the photocurrent model, we perform a theoretical study on the optimization of terahertz (THz) wave emission from argon gas irradiated by the two- and three-colour laser fields. To obtain stronger THz radiation for the given conditions, a genetic algorithm method is applied to search for the optimum laser parameters. For the two-colour field, our optimizations reveal two types of optimal scheme, and each one dominates the THz generation in different regions of intensity ratio for a given total laser intensity. One scheme is the combination of a fundamental laser pulse and its second harmonic, while the other is the fundamental pulse with its fourth harmonic. For each scheme, the optimal intensity ratio and phase delay are obtained. For the three-colour case, our optimization shows that the excellent waveform for the strongest THz radiation is composed of a fundamental laser pulse, and its second, third harmonics, with appropriate intensity ratio and carrier-envelope phase. Such a 3-colour field can generate strong THz radiation comparable with a 10-colour sawtooth wave [Martínez et al., Phys. Rev. Lett. 114, 183901 (2015)]. The physical mechanisms for the enhancement of THz wave emission in gases are also discussed in detail. Our results give helpful guidance for intense THz generation with tabletop femtosecond laser device in experiment.

The Effect of Laser Irradiation on Adipose Derived Stem Cell Proliferation and Differentiation

NASA Astrophysics Data System (ADS)

Abrahamse, H.; de Villiers, J.; Mvula, B.

2009-06-01

There are two fundamental types of stem cells: Embryonic Stem cells and Adult Stem cells. Adult Stem cells have a more restricted potential and can usually differentiate into a few different cell types. In the body these cells facilitate the replacement or repair of damaged or diseased cells in organs. Low intensity laser irradiation was shown to increase stem cell migration and stimulate proliferation and it is thought that treatment of these cells with laser irradiation may increase the stem cell harvest and have a positive effect on the viability and proliferation. Our research is aimed at determining the effect of laser irradiation on differentiation of Adipose Derived Stem Cells (ADSCs) into different cell types using a diode laser with a wavelength of 636 nm and at 5 J/cm2. Confirmation of stem cell characteristics and well as subsequent differentiation were assessed using Western blot analysis and cellular morphology supported by fluorescent live cell imaging. Functionality of subsequent differentiated cells was confirmed by measuring adenosine triphosphate (ATP) production and cell viability.

Au-C allotrope nano-composite films at extreme conditions generated by intense ultra-short laser

NASA Astrophysics Data System (ADS)

Khan, Saif A.; Saravanan, K.; Tayyab, M.; Bagchi, S.; Avasthi, D. K.

2016-07-01

Structural evolution of gold-carbon allotrope nano-composite films under relativistically intense, ultra-short laser pulse irradiation is studied in this work. Au-C nano-composite films, having 4 and 10 at.% of Au, were deposited by co-sputtering technique on silicon substrates. Au-C60 NC films with 2.5 at.% Au were deposited on 12 μm thick Al foil using co-evaporation technique. These samples were radiated with single pulse from 45 fs, 10 TW Ti:Sapphire Laser at RRCAT at an intensity of 3 × 1018 W cm-2. The morphological and compositional changes were investigated using scanning electron microscopy (SEM) and Rutherford back-scattering spectrometry (RBS) techniques. Laser pulse created three morphologically distinct zones around the point of impact on samples with silicon substrates. The gold content in 600 μm circular region around a point of impact is found to reduce by a factor of five. Annular rings of ∼70 nm in diameter were observed in case of Au-C NC film after irradiation. Laser pulse created a hole of about 400 μm in the sample with Al foil as substrate and wavy structures of 6 μm wavelength are found to be created around this hole. The study shows radial variation in nano-structure formation with varying local intensity of laser pulse.

Directional enhancement of selected high-order-harmonics from intense laser irradiated blazed grating targets.

PubMed

Zhang, Guobo; Chen, Min; Liu, Feng; Yuan, Xiaohui; Weng, Suming; Zheng, Jun; Ma, Yanyun; Shao, Fuqiu; Sheng, Zhengming; Zhang, Jie

2017-10-02

Relativistically intense laser solid target interaction has been proved to be a promising way to generate high-order harmonics, which can be used to diagnose ultrafast phenomena. However, their emission direction and spectra still lack tunability. Based upon two-dimensional particle-in-cell simulations, we show that directional enhancement of selected high-order-harmonics can be realized using blazed grating targets. Such targets can select harmonics with frequencies being integer times of the grating frequency. Meanwhile, the radiation intensity and emission area of the harmonics are increased. The emission direction is controlled by tailoring the local blazed structure. Theoretical and electron dynamics analysis for harmonics generation, selection and directional enhancement from the interaction between multi-cycle laser and grating target are carried out. These studies will benefit the generation and application of laser plasma-based high order harmonics.

Preferential destruction of metallic single-walled carbon nanotubes by laser irradiation.

PubMed

Huang, Houjin; Maruyama, Ryuichiro; Noda, Kazuhiro; Kajiura, Hisashi; Kadono, Koji

2006-04-13

Upon laser irradiation in air, metallic single-walled carbon nanotubes (SWNTs) in carbon nanotube thin film can be destroyed in preference to their semiconducting counterparts when the wavelength and power intensity of the irradiation are appropriate and the carbon nanotubes are not heavily bundled. Our method takes advantage of these two species' different rates of photolysis-assisted oxidation, creating the possibility of defining the semiconducting portions of carbon nanotube (CNT) networks using optical lithography, particularly when constructing all-CNT FETs (without metal electrodes) in the future.

Emission intensity modulation of radio-frequency helium glow-discharge emission source by laser ablation.

PubMed

Matsuta, Hideyuki; Naeem, Tariq M; Wagatsuma, Kazuaki

2003-06-01

A novel emission excitation source comprising a high repetition rate diode-pumped Q-switched Nd:YAG laser and a Grimm-style glow-discharge lamp is described. Laser-ablated atoms are introduced into the He glow discharge plasma, which then give emission signals. By using phase-sensitive detection with a lock-in amplifier, the emission signal modulated by the pulsed laser can be detected selectively. It is possible to estimate only the emission intensity of sample atoms ablated by laser irradiation with little interference from the other species in the plasma.

Interaction of intense ultrashort pulse lasers with clusters.

NASA Astrophysics Data System (ADS)

Petrov, George

2007-11-01

The last ten years have witnessed an explosion of activity involving the interaction of clusters with intense ultrashort pulse lasers. Atomic or molecular clusters are targets with unique properties, as they are halfway between solid and gases. The intense laser radiation creates hot dense plasma, which can provide a compact source of x-rays and energetic particles. The focus of this investigation is to understand the salient features of energy absorption and Coulomb explosion by clusters. The evolution of clusters is modeled with a relativistic time-dependent 3D Molecular Dynamics (MD) model [1]. The Coulomb interaction between particles is handled by a fast tree algorithm, which allows large number of particles to be used in simulations [2]. The time histories of all particles in a cluster are followed in time and space. The model accounts for ionization-ignition effects (enhancement of the laser field in the vicinity of ions) and a variety of elementary processes for free electrons and charged ions, such as optical field and collisional ionization, outer ionization and electron recapture. The MD model was applied to study small clusters (1-20 nm) irradiated by a high-intensity (10^16-10^20 W/cm^2) sub-picosecond laser pulse. We studied fundamental cluster features such as energy absorption, x-ray emission, particle distribution, average charge per atom, and cluster explosion as a function of initial cluster radius, laser peak intensity and wavelength. Simulations of novel applications, such as table-top nuclear fusion from exploding deuterium clusters [3] and high power synchrotron radiation for biological applications and imaging [4] have been performed. The application for nuclear fusion was motivated by the efficient absorption of laser energy (˜100%) and its high conversion efficiency into ion kinetic energy (˜50%), resulting in neutron yield of 10^6 neutrons/Joule laser energy. Contributors: J. Davis and A. L. Velikovich. [1] G. M. Petrov, et al Phys

Effects of laser-magnetic blood irradiation in vivo

NASA Astrophysics Data System (ADS)

Zalesskaya, Galina; Ulaschik, Vladimir; Kuchinsky, Andrej; Galay, Olga

2007-06-01

Laser-magnetic field action on blood in vivo was studied within a range 440-650 nm. The primary mechanisms of laser-magnetic blood irradiation in vivo were studied at (1) laser and non-laser irradiation with light of various wavelengths, (2) autohemo-magnetic-therapy, (3) multicolored over-vein irradiation of the blood, (4) the laser-magnetic field actions. Hemoglobin is considered as primary photoacceptor of radiation. The dependence of effectiveness of laser action on light wavelength was compared with known action spectra for blood photostimulation. Magnetic field enhancement of the laser- induced reactions was discussed as result of magnetic field influence on ferromagnetic hem inclusions and on a structure of hemoglobin peptide chains. Hemoglobin oxygenation or deoxygenation processes were analyzed as a first stage of the therapeutic effects depending on a preceding hemoglobin oxygenation degree at pathological state. The laser- magnetic irradiation causes tendency to the normalization of these process. It is proposed that the secondary reactions are initiated by reversible structural changes of erythrocytes membrane caused the strong hemoglobin absorption.

Sapphire capillary interstitial irradiators for laser medicine

NASA Astrophysics Data System (ADS)

Shikunova, I. A.; Dolganova, I. N.; Dubyanskaya, E. N.; Mukhina, E. E.; Zaytsev, K. I.; Kurlov, V. N.

2018-04-01

In this paper, we demonstrate instruments for laser radiation delivery based on sapphire capillary needles. Such sapphire irradiators (introducers) can be used for various medical applications, such as photodynamic therapy, laser hyperthermia, laser interstitial thermal therapy, and ablation of tumors of various organs. Unique properties of sapphire allow for effective redistribution of the heat, generated in biological tissues during their exposure to laser radiation. This leads to homogeneous distribution of the laser irradiation around the needle, and lower possibility of formation of the overheating focuses, as well as the following non-transparent thrombi.

Investigation of room temperature UV emission of ZnO films with different defect densities induced by laser irradiation.

PubMed

Zhao, Yan; Jiang, Yijian

2010-08-01

We studied the room temperature UV emission of ZnO films with different defect densities which is fabricated by KrF laser irradiation process. It is shown room temperature UV photoluminescence of ZnO film is composed of contribution from free-exciton (FX) recombination and its longitudinal-optical phonon replica (FX-LO) (1LO, 2LO). With increase of the defect density, the FX emission decreased and FX-LO emission increased dramatically; and the relative strengths of FX to FX-LO emission intensities determine the peak position and intensity of UV emission. What is more, laser irradiation with moderate energy density could induce the crystalline ZnO film with very flat and smooth surface. This investigation indicates that KrF laser irradiation could effectively modulate the exciton emission and surface morphology, which is important for the application of high performance of UV emitting optoelectronic devices. Copyright 2010 Elsevier B.V. All rights reserved.

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

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

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

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

Effects of laser acupoint irradiation on energy metabolism of brain tissue of rats with cerebral ischemia-reperfusion

NASA Astrophysics Data System (ADS)

Xiong, Guoxin; Li, Xinzhong

2017-12-01

The protective effect and mechanism of low-intensity laser acupoint irradiation on focal cerebral ischemia-reperfusion (CIR) injury in rats were investigated. Male Sprague-Dawley rats were randomly divided into a sham group, a CIR model (model) group, and a model plus laser irradiation (laser) group. The focal CIR model was induced by middle cerebral artery occlusion in all except the rats in the sham group. After modeling, the Baihui, Mingmen, and left Zusanli points of the rats in the laser group were irradiated with 15 mW using a semiconductor laser, and each point was irradiated for 15 min once a day for 7 d. The treatments used in the sham and model groups were the same as in the laser group except that the laser output power was zero. After treatment, the expressions of serum superoxide dismutase (SOD) activity and serum malonaldehyde (MDA) content, the expression of growth-associated protein (GAP-43), the activities of succinic dehydrogenase and lactic dehydrogenase in brain tissue, were measured. The results showed that acupoint irradiation with a semiconductor laser can improve energy metabolism, enhance the expression of GAP-43, increase the levels of expression of serum SOD, and decrease the serum MDA content in a rat model of focal CIR, suggesting the mechanism for reduction of CIR injury.

Reduction of time-averaged irradiation speckle nonuniformity in laser-driven plasmas due to target ablation

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

Epstein, R.

1997-09-01

In inertial confinement fusion (ICF) experiments, irradiation uniformity is improved by passing laser beams through distributed phase plates (DPPs), which produce focused intensity profiles with well-controlled, reproducible envelopes modulated by fine random speckle. [C. B. Burckhardt, Appl. Opt. {bold 9}, 695 (1970); Y. Kato and K. Mima, Appl. Phys. B {bold 29}, 186 (1982); Y. Kato {ital et al.}, Phys. Rev. Lett. {bold 53}, 1057 (1984); Laboratory for Laser Energetics LLE Review 33, NTIS Document No. DOE/DP/40200-65, 1987 (unpublished), p. 1; Laboratory for Laser Energetics LLE Review 63, NTIS Document No. DOE/SF/19460-91, 1995 (unpublished), p. 1.] A uniformly ablating plasmamore » atmosphere acts to reduce the contribution of the speckle to the time-averaged irradiation nonuniformity by causing the intensity distribution to move relative to the absorption layer of the plasma. This occurs most directly as the absorption layer in the plasma moves with the ablation-driven flow, but it is shown that the effect of the accumulating ablated plasma on the phase of the laser light also makes a quantitatively significant contribution. Analytical results are obtained using the paraxial approximation applied to the beam propagation, and a simple statistical model is assumed for the properties of DPPs. The reduction in the time-averaged spatial spectrum of the speckle due to these effects is shown to be quantitatively significant within time intervals characteristic of atmospheric hydrodynamics under typical ICF irradiation intensities. {copyright} {ital 1997 American Institute of Physics.}« less

Is there a stimulation of blood microcirculation at low level laser irradiation

NASA Astrophysics Data System (ADS)

Rogatkin, Dmitry; Dunaev, Andrey

2014-05-01

In 1980-2000 besides the laser surgery an intensive evolution of Low Level Laser Therapy (LLLT) had started in medicine, especially in Russia as well as in several other East-European countries. At the same time the biophysical mechanisms of LLLT are still the subject of disputes. One of the most popular clinical effects at Low Level Laser Irradiation (LLLI) being mentioned in medical publications for justification of the LLLT healing outcome is a stimulation of blood microcirculation in irradiated area. It was declared a priori at a dawn of LLLT and is now a basis of medical interpretation of healing mechanisms of LLLT at least in Russia. But in past 20 years a lot of investigation was carried out on optical registration of microhaemodynamic parameters in vivo as well as a number of noninvasive diagnostic tools was created for that. So, today it is possible to experimentally check the blood microcirculation stimulation hypothesis. Our study was aimed on that during the past 10 years. The most precision and accurate experiments we have carried out recently using simultaneously three different noninvasive diagnostic techniques: Laser Doppler Flowmetry, Tissue Reflectance Oximetry and Infrared Thermography. All these methods didn't confirm the effect on the blood microcirculation stimulation in skin or mucosa at irradiation with the power density below 50 mW/cm2 and irradiation time up to 5-6 minutes. Above this threshold the heating on 0,8…1 °C of tissue in the field of irradiation and the corresponding synchronous increase of all parameters of microhemodynamics were observed.

Melting in Superheated Silicon Films Under Pulsed-Laser Irradiation

NASA Astrophysics Data System (ADS)

Wang, Jin Jimmy

This thesis examines melting in superheated silicon films in contact with SiO2 under pulsed laser irradiation. An excimer-laser pulse was employed to induce heating of the film by irradiating the film through the transparent fused-quartz substrate such that most of the beam energy was deposited near the bottom Si-SiO2 interface. Melting dynamics were probed via in situ transient reflectance measurements. The temperature profile was estimated computationally by incorporating temperature- and phase-dependent physical parameters and the time-dependent intensity profile of the incident excimer-laser beam obtained from the experiments. The results indicate that a significant degree of superheating occurred in the subsurface region of the film. Surface-initiated melting was observed in spite of the internal heating scheme, which resulted in the film being substantially hotter at and near the bottom Si-SiO2 interface. By considering that the surface melts at the equilibrium melting point, the solid-phase-only heat-flow analysis estimates that the bottom Si-SiO2 interface can be superheated by at least 220 K during excimer-laser irradiation. It was found that at higher laser fluences (i.e., at higher temperatures), melting can be triggered internally. At heating rates of 1010 K/s, melting was observed to initiate at or near the (100)-oriented Si-SiO2 interface at temperatures estimated to be over 300 K above the equilibrium melting point. Based on theoretical considerations, it was deduced that melting in the superheated solid initiated via a nucleation and growth process. Nucleation rates were estimated from the experimental data using Johnson-Mehl-Avrami-Kolmogorov (JMAK) analysis. Interpretation of the results using classical nucleation theory suggests that nucleation of the liquid phase occurred via the heterogeneous mechanism along the Si-SiO2 interface.

Effect of laser irradiation for healing of the skin-muscle wounds of animals

NASA Astrophysics Data System (ADS)

Lapina, Victoria A.; Veremei, Eduard I.; Pancovets, Evgeniy A.

2000-05-01

The purpose of our investigation was to study the medical effect of low-intensity laser influence on healing of skin- muscle wounds of agricultural animals. We used the laser radiation of low intensity for cub's therapy: to sucking-pigs after herniotomy and castration, to cattle cubs after skin- muscle wounds. The animals were kept under clinical observation up to their recovery. The recuperation dynamic was observed by changing of blood quotients, leukograms, sizes of inflammatory edema, general behavior of animals. The positive dynamic of blood quotients of the experimental animal groups was really higher than that in control. The analysis of wound healing after laser influence shows that wound surface of experimental group was to a great extent smaller in comparison with control group of animals. So, these facts testify about anti-inflammatory action of laser radiation, which hastens regenerative and rehabilitative processes. Analysis of the obtained experimental data has revealed the positive influence of laser irradiation on the dynamics of wound adhesion of agricultural animals.

Effect of different laser irradiation on the dysentery bacilli

NASA Astrophysics Data System (ADS)

Ou, Lin; Chen, Rong; Chen, Yanjiao; Li, Depin; Wen, Caixia

1998-08-01

The S. flexnesi, which have high drug-resistance especially in Cm, Sm, Tc, SD, were irradiated by Ar+ laser at 488 nm and semiconductor laser at 808 nm. The experiment results have shown that both Ar+ laser and semiconductor laser with power density of 1.7 w/cm2 and irradiation dose of 2000 J/cm2 can conduce to the bacterial lethality and increase the mutation rates of the bacterial drug-sensitivity, and 'Colony Count' method have the superiority over the 'Inhibacteria Ring' method. At the mean time it further indicate that the high power semiconductor laser would play an important role in the sciences of laser biological medicine. But the effect of the near infrared semiconductor laser is far lower than that of Ar+ laser of shorter wavelength at the same irradiation dose. It is clear that the output and irradiation dose of near infrared semiconductor laser shall be increased in order to get the same rates of the bacterial lethality and the drug-sensitivity mutation as Ar+ laser's.

Energy Penetration into Arrays of Aligned Nanowires Irradiated with Relativistic Intensities: Scaling to Terabar Pressures

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

Bargsten, Clayton; Hollinger, Reed; Capeluto, Maria Gabriela

Ultra-high-energy-density (UHED) matter, characterized by energy densities > 1 x 10 8 J cm -3 and pressures greater than a gigabar, is encountered in the center of stars and in inertial confinement fusion capsules driven by the world’s largest lasers. Similar conditions can be obtained with compact, ultra-high contrast, femtosecond lasers focused to relativistic intensities onto targets composed of aligned nanowire arrays. Here we report the measurement of the key physical process in determining the energy density deposited in high aspect ratio nanowire array plasmas: the energy penetration. By monitoring the x-ray emission from buried Co tracer segments in Nimore » nanowire arrays irradiated at an intensity of 4 x 10 19 W cm -2, we demonstrate energy penetration depths of several μm, leading to UHED plasmas of that size. Relativistic 3D particle-in-cell-simulations, validated by these measurements, predict that irradiation of nanostructures at intensities of > 1 x 10 22 W cm -2 will lead to a virtually unexplored extreme UHED plasma regime characterized by energy densities in excess of 8 x 10 10 J cm -3, equivalent to a pressure of 0.35 Tbar.« less

Energy penetration into arrays of aligned nanowires irradiated with relativistic intensities: Scaling to terabar pressures.

PubMed

Bargsten, Clayton; Hollinger, Reed; Capeluto, Maria Gabriela; Kaymak, Vural; Pukhov, Alexander; Wang, Shoujun; Rockwood, Alex; Wang, Yong; Keiss, David; Tommasini, Riccardo; London, Richard; Park, Jaebum; Busquet, Michel; Klapisch, Marcel; Shlyaptsev, Vyacheslav N; Rocca, Jorge J

2017-01-01

Ultrahigh-energy density (UHED) matter, characterized by energy densities >1 × 10 8 J cm -3 and pressures greater than a gigabar, is encountered in the center of stars and inertial confinement fusion capsules driven by the world's largest lasers. Similar conditions can be obtained with compact, ultrahigh contrast, femtosecond lasers focused to relativistic intensities onto targets composed of aligned nanowire arrays. We report the measurement of the key physical process in determining the energy density deposited in high-aspect-ratio nanowire array plasmas: the energy penetration. By monitoring the x-ray emission from buried Co tracer segments in Ni nanowire arrays irradiated at an intensity of 4 × 10 19 W cm -2 , we demonstrate energy penetration depths of several micrometers, leading to UHED plasmas of that size. Relativistic three-dimensional particle-in-cell simulations, validated by these measurements, predict that irradiation of nanostructures at intensities of >1 × 10 22 W cm -2 will lead to a virtually unexplored extreme UHED plasma regime characterized by energy densities in excess of 8 × 10 10 J cm -3 , equivalent to a pressure of 0.35 Tbar.

Energy penetration into arrays of aligned nanowires irradiated with relativistic intensities: Scaling to terabar pressures

PubMed Central

Bargsten, Clayton; Hollinger, Reed; Capeluto, Maria Gabriela; Kaymak, Vural; Pukhov, Alexander; Wang, Shoujun; Rockwood, Alex; Wang, Yong; Keiss, David; Tommasini, Riccardo; London, Richard; Park, Jaebum; Busquet, Michel; Klapisch, Marcel; Shlyaptsev, Vyacheslav N.; Rocca, Jorge J.

2017-01-01

Ultrahigh-energy density (UHED) matter, characterized by energy densities >1 × 108 J cm−3 and pressures greater than a gigabar, is encountered in the center of stars and inertial confinement fusion capsules driven by the world’s largest lasers. Similar conditions can be obtained with compact, ultrahigh contrast, femtosecond lasers focused to relativistic intensities onto targets composed of aligned nanowire arrays. We report the measurement of the key physical process in determining the energy density deposited in high-aspect-ratio nanowire array plasmas: the energy penetration. By monitoring the x-ray emission from buried Co tracer segments in Ni nanowire arrays irradiated at an intensity of 4 × 1019 W cm−2, we demonstrate energy penetration depths of several micrometers, leading to UHED plasmas of that size. Relativistic three-dimensional particle-in-cell simulations, validated by these measurements, predict that irradiation of nanostructures at intensities of >1 × 1022 W cm−2 will lead to a virtually unexplored extreme UHED plasma regime characterized by energy densities in excess of 8 × 1010 J cm−3, equivalent to a pressure of 0.35 Tbar. PMID:28097218

Low-intensity infrared laser effects on zymosan-induced articular inflammatory response

NASA Astrophysics Data System (ADS)

Januária dos Anjos, Lúcia Mara; da Fonseca, Adenilson d. S.; Gameiro, Jacy; de Paoli, Flávia

2015-03-01

Low-level therapy laser is a phototherapy treatment that involves the application of low power light in the red or infrared wavelengths in various diseases such as arthritis. In this work, we investigated whether low-intensity infrared laser therapy could cause death by caspase-6 apoptosis or DNA damage pathways in cartilage cells after zymosaninduced articular inflammatory process. Inflammatory process was induced in C57BL/6 mouse by intra-articular injection of zymosan into rear tibio-tarsal joints. Thirty animals were divided in five groups: (I) control, (II) laser, (III) zymosan-induced, (IV) zymosan-induced + laser and (V). Laser exposure was performed after zymosan administration with low-intensity infrared laser (830 nm), power 10 mW, fluence 3.0 J/cm2 at continuous mode emission, in five doses. Twenty-four hours after last irradiation, the animals were sacrificed and the right joints fixed and demineralized. Morphological analysis was observed by hematoxylin and eosin stain, pro-apoptotic (caspase-6) was analyzed by immunocytochemistry and DNA fragmentation was performed by TUNEL assay in articular cartilage cells. Inflammatory process was observed in connective tissue near to articular cartilage, in IV and V groups, indicating zymosan effect. This process was decreased in both groups after laser treatment and dexamethasone. Although groups III and IV presented higher caspase-6 and DNA fragmentation percentages, statistical differences were not observed when compared to groups I and II. Our results suggest that therapies based on low-intensity infrared lasers could reduce inflammatory process and could not cause death by caspase-6 apoptosis or DNA damage pathways in cartilage cells after zymosan-induced articular inflammatory process.

Influence of low-intensity laser radiation on the dynamics of some phytohormone content in the callus tissues of wheat Triticum aestivum L.

NASA Astrophysics Data System (ADS)

Dudareva, L. V.; Rudikovskaya, E. G.; Shmakov, V. N.; Rudikovskii, A. V.; Salyaev, R. K.

2017-05-01

We carried out an analysis of the influence of low-intensity He-Ne laser radiation on the dynamics of changes observed in the content of the phytohormones abscisic, jasmonic, salicylic, and indoleacetic acids in wheat calluses of Triticum aestivum L. using chromatography-mass spectrometry. He-Ne laser irradiation (λ  =  632.8 nm) in its stimulant dose (3.5 J cm-2) was proved to cause a decrease in jasmonic and indoleacetic acid content and, simultaneously, a significant (2.5-3 times) increase in ‘stress’ abscisic and salicylic acids. The response of jasmonic acid to He-Cd laser irradiation (λ  =  441 nm) was specific, which is probably due to the blue-light-induced biosynthesis of the acid. This article discusses a possible connection between substantial changes in growth regulator content within the plant tissue under the influence of low-intensity laser irradiation and the stress character of this type of radiation.

Intravascular low-intensity He-Ne laser irradiation therapy on idiopathic edema

NASA Astrophysics Data System (ADS)

Gao, Yunqing; Liu, T. C.; Tang, Xiang-Jun

1998-11-01

194 patients with psoriasis were treated by intravascular low level laser irradiation combined with Vit C 2.0g iv and O2 inhale to the nose. An hour once a day, for 5-40 times, and 13.06 times in average, ten times with 4-7 days intervals. The results: cured 23 cases, good effected 61 cases, improved 110 cases, relapsed 10 cases. Curative effect was related to treatment times, cured and good effected 5 times 12.5 percent, 10 times 31 percent, 15 times 94 percent. A matched control group in 17 patients was treated by drug. The results: good effected 1 case, improved 13 cases, not effected 3 cases.

[Histopathological study of wound healing process of rat tongue and femur by excimer laser irradiation--possibility of cutting of vital tissue by laser irradiation].

PubMed

Ochiai, S

1990-12-01

The possibilities of bone and soft tissue ablation without thermal damage by 248 nm KrF excimer laser irradiation were examined. A defect was made on the rat tongue by laser at pulse width: 15 nsec, power density: 12 W/cm2, pulse repetition rate: 20 Hz and irradiated time: 60 seconds. The same size defect was made by stainless steel surgical knife for control. The tongues were examined histopathologically at timed sequence from 1 hour to 7 days after operation. The rat femur was cut by laser at pulse width: 15 nsec, power density: 2.6 kW/cm2, pulse repetition rate: 30 Hz and irradiated time: 3 minutes. The femur was amputated by dental diamond disc for control. The femurs were examined histopathologically at timed sequence from 1 hour to 16 weeks after operation. The rat tongue was easily excised with little thermal injury by laser irradiation, and its healing process is almost the same as that of the control. The laser irradiation had no hemostatic effect. The femur could be amputated by laser irradiation but its wound healing was prolonged. The laser ablation stump showed massive necrosis probably due to the thermal injury and these necrotic bones likely disturbed the wound repair. The degree of the thermal injury by the excimer laser irradiation might depend on the irradiation condition because the condition of bone amputation was stronger than that of tongue excision.

TDDFT investigation of excitation of water tetramer under femtosecond laser pulse irradiation

NASA Astrophysics Data System (ADS)

Wang, Zhiping; Xu, Xuefen; Zhang, Fengshou; Qian, Chaoyi

2018-04-01

We study the static properties of water tetramer in ground state, the optical absorption spectra and ultrafast nonadiabatic dynamical response of water tetramer to short and intense laser pulses with different intensities by a real-space, real-time implementation of time-dependent density functional theory coupled to molecular dynamics (TDDFT-MD) nonadiabatically. The calculated results are in good agreement with available values in literature. Four typical irradiated scenarios of water tetramer in laser field, which are “normal vibration,” “break and reorganization,” “fragmentation and new formation” and “pure fragmentation”, are explored by discussing the ionization, the bond lengths of OH bonds and hydrogen bonds and the kinetic energy of ions. The dynamic simulation shows that the reaction channel of water tetramer can really be controlled by choosing appropriate laser parameters referring to the optical absorption spectra and hydrogen ions play an important role in the reaction channel. Furthermore, it is found that the laser intensity affects the kinetic energy of ejected protons more than that of the remaining fragments and all dynamic processes are somehow directly related to the velocity of departing protons.

High-intensity laser-accelerated ion beam produced from cryogenic micro-jet target

DOE PAGES

Gauthier, M.; Kim, J. B.; Curry, C. B.; ...

2016-08-24

Here, we report on the successful operation of a newly developed cryogenic jet target at high intensity laser-irradiation. Using the frequency-doubled Titan short pulse laser system at Jupiter Laser Facility, Lawrence Livermore National Laboratory, we demonstrate the generation of a pure proton beam a with maximum energy of 2 MeV. Furthermore, we record a quasi-monoenergetic peak at 1.1 MeV in the proton spectrum emitted in the laser forward direction suggesting an alternative acceleration mechanism. Using a solid-density mixed hydrogen-deuterium target, we are also able to produce pure proton-deuteron ion beams. With its high purity, limited size, near-critical density, and high-repetitionmore » rate capability, this target is promising for future applications.« less

High-intensity laser-accelerated ion beam produced from cryogenic micro-jet target

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

Gauthier, M., E-mail: maxence.gauthier@stanford.edu; Kim, J. B.; Curry, C. B.

2016-11-15

We report on the successful operation of a newly developed cryogenic jet target at high intensity laser-irradiation. Using the frequency-doubled Titan short pulse laser system at Jupiter Laser Facility, Lawrence Livermore National Laboratory, we demonstrate the generation of a pure proton beam a with maximum energy of 2 MeV. Furthermore, we record a quasi-monoenergetic peak at 1.1 MeV in the proton spectrum emitted in the laser forward direction suggesting an alternative acceleration mechanism. Using a solid-density mixed hydrogen-deuterium target, we are also able to produce pure proton-deuteron ion beams. With its high purity, limited size, near-critical density, and high-repetition ratemore » capability, this target is promising for future applications.« less

Experimental and theoretical basis of agricultural plant immunostimulation with regard to pathogenic fungi by magnetic field and He-Ne laser irradiation

NASA Astrophysics Data System (ADS)

Belski, Alexey I.; Chivanov, Vadym D.

1996-09-01

Spring barley, winter wheat and maize seeds were subjected to the action of He-Ne laser irradiation having a low intensity in the visible region of the spectrum (628-640 nm) in conjunction with magnetic fields. The following results were obtained: laser irradiation with magnetic fields induced activation of the natural plant defence/immune systems gave the harvest crop level increased to about 50- 300 percent; a correlation was established between the rate of the fungal pathogens growth and the stimulation of plant immunity after the seeds had been treated with laser irradiation and magnetic field.

In vitro laser nerve repair: protein solder strip irradiation or irradiation alone?

PubMed

Trickett, I; Dawes, J M; Knowles, D S; Lanzetta, M; Owen, E R

1997-01-01

This study investigated the potential of sutureless nerve repair using two promising laser fusion methods: direct 2 microns irradiation of the epineurium, and protein solder assisted epineurial fusion using a 800 nm laser. Laser anastomosis of the rat sciatic nerve was performed in vitro without stay sutures in two groups of six animals. In the first group, direct laser fusion used a pulsed Cr, Tm: YAG laser. In the second group an albumin-based fluid solder containing the dye indocyanine green was applied to the epineurium, then irradiated with a diode laser. These two techniques were compared with regards to coaptation success and axonal damage. Direct laser welding produced weak bonds despite microscopic investigation of the irradiated nerves showing fusion of the epineurium. The unsatisfactory bonding can be attributed to poor tissue overlap and insufficient protein in the thin epineurium denaturation of underlying axons was also observed. In contrast, the laser solder method produced successful welds with greatly reduced axonal damage, and significantly improved the tensile strength. This study confirmed the technical possibilities of sutureless nerve anastomosis. Laser activated solders enable stronger bonds, by the addition of protein to the anastomosis site, and less thermal damage to underlying tissue through selective absorption of laser energy by dye in the solder. Further in vivo studies are required before drawing final conclusions.

Volumetric Heating of Ultra-High Energy Density Relativistic Plasmas by Ultrafast Laser Irradiation of Aligned Nanowire Arrays

NASA Astrophysics Data System (ADS)

Bargsten, Clayton; Hollinger, Reed; Shlyaptsev, Vyacheslav; Pukhov, Alexander; Keiss, David; Townsend, Amanda; Wang, Yong; Wang, Shoujun; Prieto, Amy; Rocca, Jorge

2014-10-01

We have demonstrated the volumetric heating of near-solid density plasmas to keV temperatures by ultra-high contrast femtosecond laser irradiation of arrays of vertically aligned nanowires with an average density up to 30% solid density. X-ray spectra show that irradiation of Ni and Au nanowire arrays with laser pulses of relativistic intensities ionizes plasma volumes several micrometers in depth to the He-like and Co-like (Au 52 +) stages respectively. The penetration depth of the heat into the nanowire array was measured monitoring He-like Co lines from irradiated arrays in which the nanowires are composed of a Co segment buried under a selected length of Ni. The measurement shows the ionization reaches He-like Co for depth of up to 5 μm within the target. This volumetric plasma heating approach creates a new laboratory plasma regime in which extreme plasma parameters can be accessed with table-top lasers. Scaling to higher laser intensities promises to create plasmas with temperatures and pressures approaching those in the center of the sun. Work supported by the U.S Department of Energy, Fusion Energy Sciences and the Defense Threat Reduction Agency grant HDTRA-1-10-1-0079. A.P was supported by of DFG-funded project TR18.

Low resistance nonalloyed Ni/Au Ohmic contacts to p-GaN irradiated by KrF excimer laser

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

Oh, Min-Suk; Hwang, Dae-Kue; Lim, Jae-Hong

2006-07-24

A specific contact resistance of 8.9x10{sup -5} {omega} cm{sup 2} was obtained for a Ni/Au Ohmic layer on the KrF laser-irradiated p-GaN. It was found that laser irradiation increases the hole concentration from 4.1x10{sup 17} to 9.7x10{sup 17} cm{sup -3} by removing hydrogen atoms from p-GaN layer. The native oxide was also removed as evidenced by the Ga 2p peak shift and the decrease in the intensity of O 1s peak in the x-ray photoelectron spectra. The formation of a low resistance is attributed to the increase in the hole concentration and the removal of native oxide from p-GaN bymore » laser irradiation.« less

Biochemical responses of isolated lung CSCs after application of low intensity laser irradiation

NASA Astrophysics Data System (ADS)

Abrahamse, Heidi; Crous, Anine

2016-03-01

Studies have shown that using high fluences of Low Intensity Laser Irradiation (HF-LILI) produce apoptotic effects on normal and neoplastic cells. This study aimed to determine whether HF-LILI induce cell death in lung CSCs. Lung CSCs were isolated using the stem cell marker CD 133, characterized using flow cytometry, and applied in experiments which included treatment with LILI at wavelengths of 636, 825 and 1060 nm with fluences ranging from 5 J/cm2 to 40 J/cm2. Viability and proliferation studies, using Alamar blue assay and adenosine triphosphate luminescence (ATP), indicated an increase when treating lung CSCs with low fluences of 5 - 20 J/cm2 and a decrease in viability and proliferation as well as an increase in apoptosis when applying a fluence of 40 J/cm2 indicated by flow cytometry using Annexin V and propidium iodide (PI) dyes. Results indicate that LILI, when treating lung CSCs, can induce either a bio-stimulatory or bio-inhibitory effect depending on the wavelength and fluence used. This study indicated successful apoptotic induction of lung CSCs. Future experiments should be able to conclude the exact mechanism behind HF-LILI, which can be used in the targeted treatments of CSC elimination, implementing HF-LILI in the same manner as PDT in the absence of a photosensitizer.

The effect of low-intensity laser therapy on wound healing in Streptozotocin-induced diabetic rats

NASA Astrophysics Data System (ADS)

Rabelo, Sylvia B.; Villaverde, Antonio G. J. B.; Salgado, Miguel A. C.; Melo, Milene d. S.; Nicolau, Renata A.; Pacheco, Marcos T. T.

2004-10-01

Diabetes Mellitus is a condition that results in a delay of the wound healing process, that is associated with an insufficient production of collagen, a decrease of the amount of collagen fibrils and deficient blood flow in the wound area. It is sugested that Low Intensity Laser Therapy acts by improving wound healing in normal organisms, accelerating tissue regeneration. The aim of this work was to investigate the biostimulatory effect of the HeNe laser irradiation, at 632.8 nm, on wound healing in 15 male rats suffering from diabetes induced by Streptozotocin, compared to 15 control diabetic animals. Irradiation parameters were: laser power of 15mW, exposition time of 17 s., irradiated area of 0.025 cm2 and laser energy density of 10 J/cm2. Full-thickness skin squared samples, with 5 mm of non-injured tissue around the wound, were obtained at 4, 7 and 15 days after wounding procedure (5 treated and 5 control animals each time). The histopathologic analysis performed by haematoxylin-cosin staining. Results suggested that the irradiation of diabetic rats was efficient for wound healing. Treated group presented better quality of the wound tissues by the macroscopic observation than control group and the microscopic analysis demonstrated that treated animals had better histopathologic evaluation than non treated.

Decomposition of cyclohexane ion induced by intense femtosecond laser fields by ion-trap time-of-flight mass spectrometry

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

Yamazaki, Takao; Watanabe, Yusuke; Kanya, Reika

2016-01-14

Decomposition of cyclohexane cations induced by intense femtosecond laser fields at the wavelength of 800 nm is investigated by ion-trap time-of-flight mass spectrometry in which cyclohexane cations C{sub 6}H{sub 12}{sup +} stored in an ion trap are irradiated with intense femtosecond laser pulses and the generated fragment ions are recorded by time-of-flight mass spectrometry. The various fragment ion species, C{sub 5}H{sub n}{sup +} (n = 7, 9), C{sub 4}H{sub n}{sup +} (n = 5–8), C{sub 3}H{sub n}{sup +} (n = 3–7), C{sub 2}H{sub n}{sup +} (n = 2–6), and CH{sub 3}{sup +}, identified in the mass spectra show that decompositionmore » of C{sub 6}H{sub 12}{sup +} proceeds efficiently by the photo-irradiation. From the laser intensity dependences of the yields of the fragment ion species, the numbers of photons required for producing the respective fragment ions are estimated.« less

Photobiomodulation in laser surgery

NASA Astrophysics Data System (ADS)

Liu, Timon Cheng-Yi; Rong, Dong-Liang; Huang, Jin; Deng, Xiao-Yuan; Liu, Song-Hao

2006-01-01

Laser surgery provides good exposure with clear operating fields and satisfactory preliminary functional results. In contrast to conventional excision, it was found that matrix metalloproteinases and the tissue inhibitors of metalloproteinases -1 mRNA expression is higher, myofibroblasts appeared and disappeared slower in laser excision wounds. It has been suggested that the better anatomical and functional results achieved following laser cordectomy may be explained by the fact that such procedures result in better, more rapid healing processes to recover vocal cord for early glottic tumors and better. In this paper, the role of photobiomodulation in laser surgery will be discussed by the cultured monolayer normal human skin fibroblast model of the photobiomodulation of marginal irradiation of high intensity laser beam, the photobiomodulation related to the irradiated tissue, the biological information model of photobiomodulation and the animal models of laser surgery. Although high intensity laser beam is so intense that it destroys the irradiated cells or tissue, its marginal irradiation intensity is so low that there is photobiomodulation on non-damage cells to modulate the regeneration of partly damaged tissue so that the surgery of laser of different parameters results in different post-surgical recovery. It was concluded that photobiomodulation might play an important role in the long-term effects of laser surgery, which might be used to design laser surgery.

GaAlAs laser irradiation induces active tertiary dentin formation after pulpal apoptosis and cell proliferation in rat molars.

PubMed

Shigetani, Yoshimi; Sasa, Natsuki; Suzuki, Hironobu; Okiji, Takashi; Ohshima, Hayato

2011-08-01

This study aimed to clarify pulpal responses to gallium-aluminum-arsenide (GaAlAs) laser irradiation. Maxillary first molars of 8-week-old rats were irradiated at an output power of 0.5 or 1.5 W for 180 seconds, and the samples were collected at intervals of 0 to 14 days. The demineralized paraffin sections were processed for immunohistochemistry for heat-shock protein (HSP)-25 and nestin in addition to cell proliferation assay using bromodeoxyuridine (BrdU) labeling and apoptosis assay using deoxynucleotidyl transferase deoxyuridine triphosphate nick end labeling (TUNEL). Intense HSP-25 and nestin immunoreactivities in the odontoblast layer were weakened immediately after 0.5-W irradiation and recovered on day 1, resulting in slight tertiary dentin formation by day 14. On the contrary, 1.5-W irradiation immediately induced the loss of HSP-25 and nestin-immunoreactivities in the odontoblast layer. On day 1, numerous TUNEL-positive cells appeared in a degenerative zone that was surrounded by intense HSP-25 immunoreactivity. BrdU-positive cells occurred within the intensely HSP-25-immunopositive areas during days 2 through 5, whereas TUNEL-positive cells gradually decreased in number by day 5. HSP-25- and nestin-positive odontoblast-like cells were arranged along the pulp-dentin border by day 7, resulting in remarkable tertiary dentin formation on day 14. The output energy determined pulpal healing patterns after GaAlAs laser irradiation; the higher energy induced the apoptosis in the affected dental pulp including odontoblasts followed by active cell proliferation in the intense HSP-25-immunoreactive areas surrounding the degenerative tissue, resulting in abundant tertiary dentin formation. Thus, the optimal GaAlAs laser irradiation elicited intentional tertiary dentin formation in the dental pulp. Copyright © 2011 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

Effects of γ-ray irradiation on optical absorption and laser damage performance of KDP crystals containing arsenic impurities.

PubMed

Guo, D C; Jiang, X D; Huang, J; Wang, F R; Liu, H J; Xiang, X; Yang, G X; Zheng, W G; Zu, X T

2014-11-17

The effects of γ-irradiation on potassium dihydrogen phosphate crystals containing arsenic impurities are investigated with different optical diagnostics, including UV-VIS absorption spectroscopy, photo-thermal common-path interferometer and photoluminescence spectroscopy. The optical absorption spectra indicate that a new broad absorption band near 260 nm appears after γ-irradiation. It is found that the intensity of absorption band increases with the increasing irradiation dose and arsenic impurity concentration. The simulation of radiation defects show that this absorption is assigned to the formation of AsO₄⁴⁻ centers due to arsenic ions substituting for phosphorus ions. Laser-induced damage threshold test is conducted by using 355 nm nanosecond laser pulses. The correlations between arsenic impurity concentration and laser induced damage threshold are presented. The results indicate that the damage performance of the material decreases with the increasing arsenic impurity concentration. Possible mechanisms of the irradiation-induced defects formation under γ-irradiation of KDP crystals are discussed.

Numerical studies of acceleration of thorium ions by a laser pulse of ultra-relativistic intensity

NASA Astrophysics Data System (ADS)

Domanski, Jaroslaw; Badziak, Jan

2018-01-01

One of the key scientific projects of ELI-Nuclear Physics is to study the production of extremely neutron-rich nuclides by a new reaction mechanism called fission-fusion using laser-accelerated thorium (232Th) ions. This research is of crucial importance for understanding the nature of the creation of heavy elements in the Universe; however, they require Th ion beams of very high beam fluencies and intensities which are inaccessible in conventional accelerators. This contribution is a first attempt to investigate the possibility of the generation of intense Th ion beams by a fs laser pulse of ultra-relativistic intensity. The investigation was performed with the use of fully electromagnetic relativistic particle-in-cell code. A sub-μm thorium target was irradiated by a circularly polarized 20-fs laser pulse of intensity up to 1023 W/cm2, predicted to be attainable at ELI-NP. At the laser intensity 1023 W/cm2 and an optimum target thickness, the maximum energies of Th ions approach 9.3 GeV, the ion beam intensity is > 1020 W/cm2 and the total ion fluence reaches values 1019 ions/cm2. The last two values are much higher than attainable in conventional accelerators and are fairly promising for the planned ELI-NP experiment.

Effect of laser irradiance and wavelength on the analysis of gold- and silver-bearing minerals with laser-induced breakdown spectroscopy

NASA Astrophysics Data System (ADS)

Díaz, Daniel; Molina, Alejandro; Hahn, David

2018-07-01

The influence of laser irradiance and wavelength on the analysis of gold and silver in ore and surrogate samples with laser-induced breakdown spectroscopy (LIBS) was evaluated. Gold-doped mineral samples (surrogates) and ore samples containing naturally-occurring gold and silver were analyzed with LIBS using 1064 and 355 nm laser wavelengths at irradiances from 0.36 × 109 to 19.9 × 109 W/cm2 and 0.97 × 109 to 4.3 × 109 W/cm2, respectively. The LIBS net, background and signal-to-background signals were analyzed. For all irradiances, wavelengths, samples and analytes the calibration curves behaved linearly for concentrations from 1 to 9 μg/g gold (surrogate samples) and 0.7 to 47.0 μg/g silver (ore samples). However, it was not possible to prepare calibration curves for gold-bearing ore samples (at any concentration) nor for gold-doped surrogate samples with gold concentrations below 1 μg/g. Calibration curve parameters for gold-doped surrogate samples were statistically invariant at 1064 and 355 nm. Contrary, the Ag-ore analyte showed higher emission intensity at 1064 nm, but the signal-to-background normalization reduced the effect of laser wavelength of silver calibration plots. The gold-doped calibration curve metrics improved at higher laser irradiance, but that did not translate into lower limits of detection. While coefficients of determination (R2) and limits of detection did not vary significantly with laser wavelength, the LIBS repeatability at 355 nm improved up to a 50% with respect to that at 1064 nm. Plasma diagnostics by the Boltzmann and Stark broadening methods showed that the plasma temperature and electron density did not follow a specific trend as the wavelength changed for the delay and gate times used. This research presents supporting evidence that the LIBS discrete sampling features combined with the discrete and random distribution of gold in minerals hinder gold analysis by LIBS in ore samples; however, the use of higher laser

Acute effects of pulsed-laser irradiation on the arterial wall

NASA Astrophysics Data System (ADS)

Nakamura, Fumitaka; Kvasnicka, Jan; Lu, Hanjiang; Geschwind, Herbert J.; Levame, Micheline; Bousbaa, Hassan; Lange, Francoise

1992-08-01

Pulsed laser coronary angioplasty with an excimer or a holmium-yttrium-aluminum-garnet (Ho:YAG) laser may become an alternative treatment for patients with coronary artery disease. However, little is known about its acute consequences on the normal arterial wall. This study was designed to examine the acute histologic consequences of these two pulsed lasers on the arterial wall of normal iliac arteries in rabbits. Irradiation with each laser was performed in 15 normal iliac sites on eight male New Zealand white rabbits. The excimer laser was operated at 308 nm, 25 Hz, 50 mJ/mm2/pulse, and 135 nsec/pulse and the Ho:YAG laser was operated at 2.1 micrometers , 3/5 Hz, 400 mJ/pulse, and 250 microsecond(s) ec/pulse. The excimer and Ho:YAG laser were coupled into a multifiber wire-guided catheter of 1.4 and 1.5 mm diameter, respectively. The sites irradiated with excimer or Ho:YAG laser had the same kinds of histologic features, consisting of exfoliation of the endothelium, disorganization of internal elastic lamina, localized necrosis of vascular smooth muscle cells, and fissures in the medial layer. However, the sites irradiated with excimer laser had lower grading scores than those irradiated with Ho:YAG laser (p < 0.05). Laser irradiation with excimer or Ho:YAG laser of normal arteries results in localized mechanical vascular injury.

Influence of plasmon coupling on the photoluminescence of ZnS/Ag nanoparticles obtained by laser irradiation in liquid

NASA Astrophysics Data System (ADS)

Moos, Rafaela; Graff, Ismael L.; de Oliveira, Vinicius S.; Schreiner, Wido H.; Bezerra, Arandi G.

2017-10-01

We investigate the photoluminescence, optical absorption and structural properties of ZnS submitted to laser irradiation in water and isopropyl alcohol. Nanoparticles were produced by irradiating micro-sized ZnS particles dispersed in both liquids, with and without the addition of Ag nanoparticles, taking advantage of the laser-assisted fragmentation effect. When ZnS microparticles are irradiated either in pure water or isopropyl alcohol a considerable size reduction is achieved (from micra to few nanometers). The photoluminescence of these nanoparticles mainly occurs in the UV, centered at 350 nm, and with smaller intensity in the visible, centered at 600 nm. Irradiation of ZnS microparticles dispersed in colloidal silver triggers a reaction between both materials, modifying its optical absorption and photoluminescent properties. After irradiation of ZnS in alcohol containing Ag nanoparticles, a giant increase of the UV photoluminescence is observed. Interestingly, when the irradiation is performed in aqueous Ag nanoparticles colloids, the photoluminescence suffers a red-shift towards the violet-blue. The data show that core-shell (Ag-ZnO) nanostructures are formed after irradiation and the visible emission likely originates from the ZnO shell grown around silver nanoparticles. The presence of Ag nanoparticles in the liquid medium promotes a stronger absorption of the laser beam during irradiation due to the coupling with the surface plasmon resonance, fostering intense reactions among ZnS, Ag nanoparticles, and the liquid medium. Our study shows that with a simple change of the liquid medium wherein the irradiation is conducted the photoluminescence can be tuned from UV to visible and core-shell nanostructures can be obtained.

Phase transformation pathways of ultrafast-laser-irradiated Ln2O3 (Ln =Er -Lu )

NASA Astrophysics Data System (ADS)

Rittman, Dylan R.; Tracy, Cameron L.; Chen, Chien-Hung; Solomon, Jonathan M.; Asta, Mark; Mao, Wendy L.; Yalisove, Steven M.; Ewing, Rodney C.

2018-01-01

Ultrafast laser irradiation causes intense electronic excitations in materials, leading to transient high temperatures and pressures. Here, we show that ultrafast laser irradiation drives an irreversible cubic-to-monoclinic phase transformation in Ln2O3 (Ln =Er -Lu ), and explore the mechanism by which the phase transformation occurs. A combination of grazing incidence x-ray diffraction and transmission electron microscopy are used to determine the magnitude and depth-dependence of the phase transformation, respectively. Although all compositions undergo the same transformation, their transformation mechanisms differ. The transformation is pressure-driven for Ln =Tm -Lu , consistent with the material's phase behavior under equilibrium conditions. However, the transformation is thermally driven for Ln =Er , revealing that the nonequilibrium conditions of ultrafast laser irradiation can lead to novel transformation pathways. Ab initio molecular-dynamics simulations are used to examine the atomic-scale effects of electronic excitation, showing the production of oxygen Frenkel pairs and the migration of interstitial oxygen to tetrahedrally coordinated constitutional vacancy sites, the first step in a defect-driven phase transformation.

Induction of subterahertz surface waves on a metal wire by intense laser interaction with a foil

NASA Astrophysics Data System (ADS)

Teramoto, Kensuke; Inoue, Shunsuke; Tokita, Shigeki; Yasuhara, Ryo; Nakamiya, Yoshihide; Nagashima, Takeshi; Mori, Kazuaki; Hashida, Masaki; Sakabe, Shuji

2018-02-01

We have demonstrated that a pulsed electromagnetic wave (Sommerfeld wave) of subterahertz frequency and 11-MV/m field strength can be induced on a metal wire by the interaction of an intense femtosecond laser pule with an adjacent metal foil at a laser intensity of 8.5 × 1018W /c m2 . The polarity of the electric field of this surface wave is opposite to that obtained by the direct interaction of the laser with the wire. Numerical simulations suggest that an electromagnetic wave associated with electron emission from the foil induces the surface wave. A tungsten wire is placed normal to an aluminum foil with a gap so that the wire is not irradiated and damaged by the laser pulse, thus making it possible to generate surface waves on the wire repeatedly.

All optical electron injector using an intense ultrashort pulse laser and a solid wire target

NASA Astrophysics Data System (ADS)

Palchan, T.; Eisenmann, S.; Zigler, A.; Kaganovich, D.; Hubbard, R. F.; Fraenkel, M.; Fisher, D.; Henis, Z.

2006-05-01

Energetic electron bunches were generated by irradiating a solid tungsten wire 13 μm wide with 50 femtosecond pulses at an intensity of ˜3×1018 W/cm2. The electron yield, energy spectrum and angular distribution were measured. These energetic electron bunches are suitable for injection into a laser driven plasma accelerator. An all-optical electron injector based on this approach could simplify timing and alignment in future laser-plasma accelerator experiments.

Ultrastructural properties of laser-irradiated and heat-treated dentin.

PubMed

Rohanizadeh, R; LeGeros, R Z; Fan, D; Jean, A; Daculsi, G

1999-12-01

Previous studies using scanning electron microscopy and infrared absorption spectroscopy reported that laser irradiation causes compositional changes in enamel. The purpose of this study was to evaluate the ultrastructural and compositional changes in dentin caused by irradiation with a short-pulse laser (Q-switched Nd:YAG). The irradiated and non-irradiated areas of the lased dentin samples were investigated by scanning (SEM) and transmission electron microscopy (TEM), micro-micro electron diffraction, and electron microprobe analysis of dispersive energy (EDX). Heat-treated dentin was similarly investigated. This study demonstrated that laser irradiation resulted in the recrystallization of dentin apatite and in the formation of additional calcium phosphate phases consisting of magnesium-substituted beta-tricalcium phosphate, beta-TCMP, beta-(Ca,Mg)3(PO4)2, and tetracalcium phosphate, TetCP, Ca4(PO4)O. TEM analyses of the modified and unmodified zones of the irradiated areas showed two types of crystal populations: much larger crystals from the modified zone and crystals with size and morphology similar to those of dentin apatite in the unmodified zone. The morphology of crystals in the modified zones in the irradiated dentin resembled those of dentin sintered at 800 or 950 degrees C. In the irradiated areas (modified and unmodified zones), the Ca/P ratio was lower compared with that in the non-irradiated dentin. The Mg/Ca ratio in the modified zones was higher than that in the unmodified zones and in the non-irradiated dentin. In sintered dentin, the Mg/Ca ratio increased as a function of sintering temperature. The ultrastructural and compositional changes observed in laser-irradiated dentin may be attributed to high temperature and high pressure induced by microplasma during laser irradiation. These changes may alter the solubility of the irradiated dentin, making it less susceptible to acid dissolution or to the caries process.

Correlated electronic decay in expanding clusters triggered by intense XUV pulses from a Free-Electron-Laser

PubMed Central

Oelze, Tim; Schütte, Bernd; Müller, Maria; Müller, Jan P.; Wieland, Marek; Frühling, Ulrike; Drescher, Markus; Al-Shemmary, Alaa; Golz, Torsten; Stojanovic, Nikola; Krikunova, Maria

2017-01-01

Irradiation of nanoscale clusters and large molecules with intense laser pulses transforms them into highly-excited non- equilibrium states. The dynamics of intense laser-cluster interaction is encoded in electron kinetic energy spectra, which contain signatures of direct photoelectron emission as well as emission of thermalized nanoplasma electrons. In this work we report on a so far not observed spectrally narrow bound state signature in the electron kinetic energy spectra from mixed Xe core - Ar shell clusters ionized by intense extreme-ultraviolet (XUV) pulses from a free-electron-laser. This signature is attributed to the correlated electronic decay (CED) process, in which an excited atom relaxes and the excess energy is used to ionize the same or another excited atom or a nanoplasma electron. By applying the terahertz field streaking principle we demonstrate that CED-electrons are emitted at least a few picoseconds after the ionizing XUV pulse has ended. Following the recent finding of CED in clusters ionized by intense near-infrared laser pulses, our observation of CED in the XUV range suggests that this process is of general relevance for the relaxation dynamics in laser produced nanoplasmas. PMID:28098175

Quantum-electrodynamic cascades in intense laser fields

NASA Astrophysics Data System (ADS)

Narozhny, N. B.; Fedotov, A. M.

2015-01-01

It is shown that in an intense laser field, along with cascades similar to extensive air showers, self-sustaining field-energized cascades can develop. For intensities of 1024~ \\text {W cm}-2 or higher, such cascades can even be initiated by a particle at rest in the focal area of a tightly focused laser pulse. The cascade appearance effect can considerably alter the progression of any process occurring in a high-intensity laser field. At very high intensities, the evolvement of such cascades can lead to the depletion of the laser field. This paper presents a design of an experiment to observe these two cascade types simultaneously already in next-generation laser facilities.

Kinetics of laser irradiated nanoparticles cloud

NASA Astrophysics Data System (ADS)

Mishra, S. K.; Upadhyay Kahaly, M.; Misra, Shikha

2018-02-01

A comprehensive kinetic model describing the complex kinetics of a laser irradiated nanoparticle ensemble has been developed. The absorbed laser radiation here serves dual purpose, viz., photoenhanced thermionic emission via rise in its temperature and direct photoemission of electrons. On the basis of mean charge theory along with the equations for particle (electron) and energy flux balance over the nanoparticles, the transient processes of charge/temperature evolution over its surface and mass diminution on account of the sublimation (phase change) process have been elucidated. Using this formulation phenomenon of nanoparticle charging, its temperature rise to the sublimation point, mass ablation, and cloud disintegration have been investigated; afterwards, typical timescales of disintegration, sublimation and complete evaporation in reference to a graphite nanoparticle cloud (as an illustrative case) have been parametrically investigated. Based on a numerical analysis, an adequate parameter space describing the nanoparticle operation below the sublimation temperature, in terms of laser intensity, wavelength and nanoparticle material work function, has been identified. The cloud disintegration is found to be sensitive to the nanoparticle charging through photoemission; as a consequence, it illustrates that radiation operating below the photoemission threshold causes disintegration in the phase change state, while above the threshold, it occurs with the onset of surface heating.

Energy penetration into arrays of aligned nanowires irradiated with relativistic intensities: Scaling to terabar pressures

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

Bargsten, Clayton; Hollinger, Reed; Capeluto, Maria Gabriela

Ultrahigh-energy density (UHED) matter, characterized by energy densities >1 × 10 8 J cm –3 and pressures greater than a gigabar, is encountered in the center of stars and inertial confinement fusion capsules driven by the world’s largest lasers. Similar conditions can be obtained with compact, ultrahigh contrast, femtosecond lasers focused to relativistic intensities onto targets composed of aligned nanowire arrays. We report the measurement of the key physical process in determining the energy density deposited in high-aspect-ratio nanowire array plasmas: the energy penetration. By monitoring the x-ray emission from buried Co tracer segments in Ni nanowire arrays irradiated atmore » an intensity of 4 × 10 19 W cm –2, we demonstrate energy penetration depths of several micrometers, leading to UHED plasmas of that size. As a result, relativistic three-dimensional particle-in-cell simulations, validated by these measurements, predict that irradiation of nanostructures at intensities of >1 × 10 22 W cm –2 will lead to a virtually unexplored extreme UHED plasma regime characterized by energy densities in excess of 8 × 10 10 J cm –3, equivalent to a pressure of 0.35 Tbar.« less

Energy penetration into arrays of aligned nanowires irradiated with relativistic intensities: Scaling to terabar pressures

DOE PAGES

Bargsten, Clayton; Hollinger, Reed; Capeluto, Maria Gabriela; ...

2017-01-11

Ultrahigh-energy density (UHED) matter, characterized by energy densities >1 × 10 8 J cm –3 and pressures greater than a gigabar, is encountered in the center of stars and inertial confinement fusion capsules driven by the world’s largest lasers. Similar conditions can be obtained with compact, ultrahigh contrast, femtosecond lasers focused to relativistic intensities onto targets composed of aligned nanowire arrays. We report the measurement of the key physical process in determining the energy density deposited in high-aspect-ratio nanowire array plasmas: the energy penetration. By monitoring the x-ray emission from buried Co tracer segments in Ni nanowire arrays irradiated atmore » an intensity of 4 × 10 19 W cm –2, we demonstrate energy penetration depths of several micrometers, leading to UHED plasmas of that size. As a result, relativistic three-dimensional particle-in-cell simulations, validated by these measurements, predict that irradiation of nanostructures at intensities of >1 × 10 22 W cm –2 will lead to a virtually unexplored extreme UHED plasma regime characterized by energy densities in excess of 8 × 10 10 J cm –3, equivalent to a pressure of 0.35 Tbar.« less

Energy Density in Aligned Nanowire Arrays Irradiated with Relativistic Intensities: Path to Terabar Pressure Plasmas

NASA Astrophysics Data System (ADS)

Rocca, J.; Bargsten, C.; Hollinger, R.; Shylaptsev, V.; Wang, S.; Rockwood, A.; Wang, Y.; Keiss, D.; Capeluto, M.; Kaymak, V.; Pukhov, A.; Tommasini, R.; London, R.; Park, J.

2016-10-01

Ultra-high-energy-density (UHED) plasmas, characterized by energy densities >1 x 108 J cm-3 and pressures greater than a gigabar are encountered in the center of stars and in inertial confinement fusion capsules driven by the world's largest lasers. Similar conditions can be obtained with compact, ultra-high contrast, femtosecond lasers focused to relativistic intensities onto aligned nanowire array targets. Here we report the measurement of the key physical process in determining the energy density deposited in high aspect ratio nanowire array plasmas: the energy penetration. By monitoring the x-ray emission from buried Co tracer segments in Ni nanowire arrays irradiated at an intensity of 4 x 1019 W cm-2, we demonstrate energy penetration depths of several μm, leading to UHED plasmas of that size. Relativistic 3D particle-in-cell-simulations validated by these measurements predict that irradiation of nanostructures at increased intensity will lead to a virtually unexplored extreme UHED plasma regime characterized by energy densities in excess of 8 x 1010 J cm-3, equivalent to a pressure of 0.35 Tbar. This work was supported by the Fusion Energy Program, Office of Science of the U.S Department of Energy, and by the Defense Threat Reduction Agency.

Generation of shock waves and formation of craters in a solid material irradiated by a short laser pulse

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

Gus'kov, Sergei Yu; Borodziuk, S; Kasperczuk, A

2004-11-30

The results of investigations are presented which are concerned with laser radiation absorption in a target, the plasma state of its ablated material, the energy transfer to the solid target material, the characteristics of the shock wave and craters on the target surface. The investigation involved irradiation of a planar target by a subnanosecond plasma-producing laser pulse. The experiments were carried out with massive aluminium targets using the PALS iodine laser, whose pulse duration (0.4 ns) was much shorter than the shock wave attenuation and on-target crater formation times (50-200 ns). The investigations were conducted for a laser radiation energymore » of 100 J at two wavelengths of 0.438 and 1.315 {mu}m. For a given pulse energy, the irradiation intensity was varied in a broad range (10{sup 13}-10{sup 16} W cm{sup -2}) by varying the radius of the laser beam. The efficiency of laser radiation-to-shock energy transfer was determined as a function of the intensity and wavelength of laser radiation; also determined were the characteristics of the plasma plume and the shock wave propagating in the solid target, including the experimental conditions under which two-dimensional effects are highly significant. (invited paper)« less

Effect of laser soldering irradiation on covalent bonds of pure collagen.

PubMed

Constantinescu, Mihai A; Alfieri, Alex; Mihalache, George; Stuker, Florian; Ducray, Angélique; Seiler, Rolf W; Frenz, Martin; Reinert, Michael

2007-03-01

Laser tissue welding and soldering is being increasingly used in the clinical setting for defined surgical procedures. The exact induced changes responsible for tensile strength are not yet fully investigated. To further improve the strength of the bonding, a better understanding of the laser impact at the subcellular level is necessary. The goal of this study was to analyze whether the effect of laser irradiation on covalent bonding in pure collagen using irradiances typically applied for tissue soldering. Pure rabbit and equine type I collagen were subjected to laser irradiation. In the first part of the study, rabbit and equine collagen were compared using identical laser and irradiation settings. In the second part of the study, equine collagen was irradiated at increasing laser powers. Changes in covalent bonding were studied indirectly using the sodium dodecylsulfate polyacrylamide gel electrophoresis (SDS-PAGE) technique. Tensile strengths of soldered membranes were measured with a calibrated tensile force gauge. In the first experiment, no differences between the species-specific collagen bands were noted, and no changes in banding were found on SDS-PAGE after laser irradiation. In the second experiment, increasing laser irradiation power showed no effect on collagen banding in SDS-PAGE. Finally, the laser tissue soldering of pure collagen membranes showed virtually no determinable tensile strength. Laser irradiation of pure collagen at typical power settings and exposure times generally used in laser tissue soldering does not induce covalent bonding between collagen molecules. This is true for both rabbit and equine collagen proveniences. Furthermore, soldering of pure collagen membranes without additional cellular components does not achieve the typical tensile strength reported in native, cell-rich tissues. This study is a first step in a better understanding of laser impact at the molecular level and might prove useful in engineering of combined

Laser Induced Damage in Optical Materials: 1981. Symposium on Optical Materials for High Power Lasers (13th). Held in Boulder, Colorado on 17-18 November 1981

DTIC Science & Technology

1983-09-01

pulses Ncr) of polymer materials in the multiple irradiation regime at a fixed laser intensity corresponding to Ncr = 20 for PMMA...KCl to repetitively pulsed 10.6 ~m laser irradiation . The technique of pulsed laser calorimetry [1] was used and at low intensity (~2s0 Mw/cm 2 ) a...power pulsed lasers . Under irradiation by high in­ tensity pUlsed monochromatic sources intensity dependent absorption mechanisms can be

Spatiotemporal control of laser intensity

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

Froula, Dustin H.; Turnbull, David; Davies, Andrew S.

The controlled coupling of a laser to a plasma has the potential to address grand scientific challenges including reaching the Schwinger limit, developing compact free electron lasers, extending linear colliders to TeV energies, and generating novel light sources for probing electron dynamics within molecules. Currently, many such applications have limited flexibility and poor control over the laser focal volume. Here we present an advanced focusing scheme called a “flying focus” where a chromatic focusing system combined with chirped laser pulses enables a small–diameter laser focus to propagate nearly 100 times its Rayleigh length, while decoupling the speed at which themore » peak intensity moves from its group velocity. This unprecedented spatiotemporal control over the laser focal volume allows the laser focus to co- or counter–propagate along its axis at any velocity. Experiments validating the concept measured subluminal (-0.09c) to superluminal (39c) focal spot velocities generating a nearly constant peak intensity over 4.5 mm.« less

Spatiotemporal control of laser intensity

DOE PAGES

Froula, Dustin H.; Turnbull, David; Davies, Andrew S.; ...

2018-03-12

The controlled coupling of a laser to a plasma has the potential to address grand scientific challenges including reaching the Schwinger limit, developing compact free electron lasers, extending linear colliders to TeV energies, and generating novel light sources for probing electron dynamics within molecules. Currently, many such applications have limited flexibility and poor control over the laser focal volume. Here we present an advanced focusing scheme called a “flying focus” where a chromatic focusing system combined with chirped laser pulses enables a small–diameter laser focus to propagate nearly 100 times its Rayleigh length, while decoupling the speed at which themore » peak intensity moves from its group velocity. This unprecedented spatiotemporal control over the laser focal volume allows the laser focus to co- or counter–propagate along its axis at any velocity. Experiments validating the concept measured subluminal (-0.09c) to superluminal (39c) focal spot velocities generating a nearly constant peak intensity over 4.5 mm.« less

Photobiomodulation of wound healing via visible and infrared laser irradiation.

PubMed

Solmaz, Hakan; Ulgen, Yekta; Gulsoy, Murat

2017-05-01

Fibroblast cells are known to be one of the key elements in wound healing process, which has been under the scope of research for decades. However, the exact mechanism of photobiomodulation on wound healing is not fully understood yet. Photobiomodulation of 635 and 809 nm laser irradiation at two different energy densities were investigated with two independent experiments; first, in vitro cell proliferation and then in vivo wound healing. L929 mouse fibroblast cell suspensions were exposed with 635 and 809 nm laser irradiations of 1 and 3 J/cm 2 energy densities at 50 mW output power separately for the investigation of photobiomodulation in vitro. Viabilities of cells were examined by means of MTT assays performed at the 24th, 48th, and 72nd hours following the laser irradiations. Following the in vitro experiments, 1 cm long cutaneous incisional skin wounds on Wistar albino rats (n = 24) were exposed with the same laser sources and doses in vivo. Wound samples were examined on 3rd, 5th, and 7th days of healing by means of mechanical tensile strength tests and histological examinations. MTT assay results showed that 635 nm laser irradiation of both energy densities after 24 h were found to be proliferative. One joule per square centimeter laser irradiation results also had positive effect on cell proliferation after 72 h. However, 809 nm laser irradiation at both energy densities had neither positive nor negative affects on cell viability. In vivo experiment results showed that, 635 nm laser irradiation of both energy densities stimulated wound healing in terms of tensile strength, whereas 809 nm laser stimulation did not cause any stimulative effect. The results of mechanical tests were compatible with the histological evaluations. In this study, it is observed that 635 nm laser irradiations of low energy densities had stimulative effects in terms of cell proliferation in vitro and mechanical strength of incisions in vivo. However, 809 nm laser

Electron spectra of xenon clusters irradiated with a laser-driven plasma soft-x-ray laser pulse

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

Namba, S.; Takiyama, K.; Hasegawa, N.

Xenon clusters were irradiated with plasma soft-x-ray laser pulses (having a wavelength of 13.9 nm, time duration of 7 ps, and intensities of up to 10 GW/cm{sup 2}). The laser photon energy was high enough to photoionize 4d core electrons. The cross section is large due to a giant resonance. The interaction was investigated by measuring the electron energy spectra. The photoelectron spectra for small clusters indicate that the spectral width due to the 4d hole significantly broadens with increasing cluster size. For larger clusters, the electron energy spectra evolve into a Maxwell-Boltzmann distribution, as a strongly coupled cluster nanoplasmamore » is generated.« less

Histological observation on dental hard tissue irradiated by ultrashort-pulsed laser

NASA Astrophysics Data System (ADS)

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

2006-04-01

In the field of dentistry, effectiveness of USPL irradiation is researched because USPL has less thermal side effect to dental hard tissue. In this paper, we observed morphological change and optical change of dental hard tissue irradiated by USPL for discussing the safety and effectiveness of USPL irradiation to dental hard tissues. Irradiated samples were crown enamel and root dentin of bovine teeth. Lasers were Ti:sapphire laser, which had pulse duration (P d)of 130 fsec and pulse repetition rate (f) of 1kHz and wavelength (l) of 800nm, free electron laser (FEL), which had P d of 15 μsec and f of 10Hz and wavelength of 9.6μm, and Er:YAG laser, which had P d of 250 μsec and f of 10Hz and wavelength of 2.94μm. After laser irradiation, the sample surfaces and cross sections were examined with SEM and EDX. The optical change of samples was observed using FTIR. In SEM, the samples irradiated by USPL had sharp and accurate ablation with no crack and no carbonization. But, in FEL and Er:YAG laser, the samples has rough ablation with crack and carbonization. It was cleared that the P/Ca ratio of samples irradiated by USPL had same value as non-irradiated samples. There was no change in the IR absorption spectrum between samples irradiated by USPL and non-irradiated sample. But, they of samples irradiated by FEL and Er:YAG laser, however, had difference value as non-irradiated samples. These results showed that USPL might be effective to ablate dental hard tissue without thermal damage.

Phase transformation pathways of ultrafast-laser-irradiated Ln 2 O 3 ( Ln = Er – Lu )

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

Rittman, Dylan R.; Tracy, Cameron L.; Chen, Chien-Hung

Ultrafast laser irradiation causes intense electronic excitations in materials, leading to transient high temperatures and pressures. Here, we show that ultrafast laser irradiation drives an irreversible cubic-to-monoclinic phase transformation in Ln 2O 3 ( Ln = Er – Lu ) , and explore the mechanism by which the phase transformation occurs. A combination of grazing incidence x-ray diffraction and transmission electron microscopy are used to determine the magnitude and depth-dependence of the phase transformation, respectively. Although all compositions undergo the same transformation, their transformation mechanisms differ. The transformation is pressure-driven for Ln = Tm – Lu , consistent with themore » material's phase behavior under equilibrium conditions. However, the transformation is thermally driven for Ln = Er , revealing that the nonequilibrium conditions of ultrafast laser irradiation can lead to novel transformation pathways. Ab initio molecular-dynamics simulations are used to examine the atomic-scale effects of electronic excitation, showing the production of oxygen Frenkel pairs and the migration of interstitial oxygen to tetrahedrally coordinated constitutional vacancy sites, the first step in a defect-driven phase transformation.« less

Phase transformation pathways of ultrafast-laser-irradiated Ln 2 O 3 ( Ln = Er – Lu )

DOE PAGES

Rittman, Dylan R.; Tracy, Cameron L.; Chen, Chien-Hung; ...

2018-01-10

Ultrafast laser irradiation causes intense electronic excitations in materials, leading to transient high temperatures and pressures. Here, we show that ultrafast laser irradiation drives an irreversible cubic-to-monoclinic phase transformation in Ln 2O 3 ( Ln = Er – Lu ) , and explore the mechanism by which the phase transformation occurs. A combination of grazing incidence x-ray diffraction and transmission electron microscopy are used to determine the magnitude and depth-dependence of the phase transformation, respectively. Although all compositions undergo the same transformation, their transformation mechanisms differ. The transformation is pressure-driven for Ln = Tm – Lu , consistent with themore » material's phase behavior under equilibrium conditions. However, the transformation is thermally driven for Ln = Er , revealing that the nonequilibrium conditions of ultrafast laser irradiation can lead to novel transformation pathways. Ab initio molecular-dynamics simulations are used to examine the atomic-scale effects of electronic excitation, showing the production of oxygen Frenkel pairs and the migration of interstitial oxygen to tetrahedrally coordinated constitutional vacancy sites, the first step in a defect-driven phase transformation.« less

Platelet derived growth factor secretion and bone healing after Er:YAG laser bone irradiation.

PubMed

Kesler, Gavriel; Shvero, Dana Kesler; Tov, Yariv Siman; Romanos, George

2011-03-01

Er:YAG laser irradiation has been reported to enhance wound healing. However, no studies have evaluated the synthesis of growth factors after laser irradiation. The present study investigated the effects of laser irradiation on the amount of secretion of platelet derived growth factor (PDGF) in the wound, clarifying the effects of the Er:YAG laser on the bone healing. Osteotomies were prepared in the tibiae of 28 rats using an Er:YAG laser (test group). Maximum power of 8 watts, energy per pulse of 700 mJ, and frequency up to 50 Hz were used. The laser was used with external water irrigation, a spot size of 2 mm, energy per pulse of 500 to 1000 mJ/pulse, and energy density of 32 J/cm(2). Twenty eight additional rats served as a control group and their osteotomies were prepared with a drill 1.3 mm in diameter at 1000 rpm, with simultaneous saline irrigation. Two rats from the tested group and 2 from the control group were sacrificed on each day following surgery (1-14 days), and the tissue specimens were prepared for histologic evaluation. Immunohistochemical staining with anti-PDGF was performed after histologic examination. The difference between the PDGF staining intensities of the 2 treatment groups was analyzed using a multivariate logistic regression test. A significant rise in PDGF staining occurred in both groups 2-3 days following surgery. However, while high PDGF counts remained for the 2-week experimental period in the laser group, PDGF levels in the control group returned to baseline levels 8 days post surgery. The 2 groups (laser and control) were found to be different throughout the experiment, and the rat type was found to be a significant predictor (P  =  .000011). The present study demonstrated that Er:YAG laser irradiation seems to stimulate the secretion of PDGF in osteotomy sites in a rat model. It is possible that the high levels of PDGF are part of the mechanism that Er:YAG irradiation enhances and improves the healing of

Spatiotemporal control of laser intensity

NASA Astrophysics Data System (ADS)

Froula, Dustin H.; Turnbull, David; Davies, Andrew S.; Kessler, Terrance J.; Haberberger, Dan; Palastro, John P.; Bahk, Seung-Whan; Begishev, Ildar A.; Boni, Robert; Bucht, Sara; Katz, Joseph; Shaw, Jessica L.

2018-05-01

The controlled coupling of a laser to plasma has the potential to address grand scientific challenges1-6, but many applications have limited flexibility and poor control over the laser focal volume. Here, we present an advanced focusing scheme called a `flying focus', where a chromatic focusing system combined with chirped laser pulses enables a small-diameter laser focus to propagate nearly 100 times its Rayleigh length. Furthermore, the speed at which the focus moves (and hence the peak intensity) is decoupled from the group velocity of the laser. It can co- or counter-propagate along the laser axis at any velocity. Experiments validating the concept measured subluminal (-0.09c) to superluminal (39c) focal-spot velocities, generating a nearly constant peak intensity over 4.5 mm. Among possible applications, the flying focus could be applied to a photon accelerator7 to mitigate dephasing, facilitating the production of tunable XUV sources.

Properties of Au/Copper oxide nanocomposite prepared by green laser irradiation of the mixture of individual suspensions

NASA Astrophysics Data System (ADS)

Aazadfar, Parvaneh; Solati, Elmira; Dorranian, Davoud

2018-04-01

The fundamental wavelength of a Q-switched pulsed Nd:YAG laser was employed to produce Au and copper oxide nanoparticles via pulsed laser ablation method in water. Different volumetric ratio of nanoparticles were mixed and irradiated by the second harmonic pulses of the Nd:YAG laser to prepare Au/Copper oxide nanocomposite. The experimental investigation was dedicated to study the properties of Au/Copper oxide nanocomposite as a function of volumetric ratio of Au nanoparticles and copper oxide nanoparticles. Nanocomposites of Au and copper oxide were found almost spherical in shape. Adhesion of spherical nanostructure in Au/Copper oxide nanocomposites was decreased with increasing the concentration of Au nanoparticles. Crystalline phase of the Au/Copper oxide nanocomposites differs with the change in the volumetric ratio of Au and copper oxide nanoparticles. The intensity of surface plasmon resonance of Au nanoparticles was decreased after irradiation. Au/Copper oxide nanocomposites suspensions have emissions in the visible range. Results reveal that green laser irradiation of nanoparticle suspensions is an appropriate method to synthesize Au based nanocomposites with controlled composition and size.

Proton acceleration measurements using fs laser irradiation of foils in the target normal sheath acceleration regime

NASA Astrophysics Data System (ADS)

Batani, D.; Boutoux, G.; Burgy, F.; Jakubowska, K.; Ducret, J. E.

2018-05-01

We present experimental results obtained at the CELIA laboratory using the laser ECLIPSE to study proton acceleration from ultra-intense laser pulses. Several types of targets were irradiated with different laser conditions (focusing and prepulse level). Proton emission was characterized using time-of-flight detectors (SiC and diamond) and a Thomson parabola spectrometer. In all cases, the maximum energy of observed protons was of the order of 260 keV with a large energy spectrum. Such characteristics are typical of protons emitted following the target normal sheath acceleration mechanism for low-energy short-pulse lasers like ECLIPSE.

Pulsed-Laser Irradiation Space Weathering Of A Carbonaceous Chondrite

NASA Technical Reports Server (NTRS)

Thompson, M. S.; Keller, L. P.; Christoffersen, R.; Loeffler, M. J.; Morris, R. V.; Graff, T. G.; Rahman, Z.

2017-01-01

Grains on the surfaces of airless bodies experience irradiation from solar energetic particles and melting, vaporization and recondensation processes associated with micrometeorite impacts. Collectively, these processes are known as space weathering and they affect the spectral properties, composition, and microstructure of material on the surfaces of airless bodies, e.g. Recent efforts have focused on space weathering of carbonaceous materials which will be critical for interpreting results from the OSIRIS-REx and Hayabusa2 missions targeting primitive, organic-rich asteroids. In addition to returned sample analyses, space weathering processes are quantified through laboratory experiments. For example, the short-duration thermal pulse from hypervelocity micrometeorite impacts have been simulated using pulsed-laser irradiation of target material e.g. Recent work however, has shown that pulsed-laser irradiation has variable effects on the spectral properties and microstructure of carbonaceous chondrite samples. Here we investigate the spectral characteristics of pulsed-laser irradiated CM2 carbonaceous chondrite, Murchison, including the vaporized component. We also report the chemical and structural characteristics of specific mineral phases within the meteorite as a result of pulsed-laser irradiation.

Surface micro-structuring of silicon by excimer-laser irradiation in reactive atmospheres

NASA Astrophysics Data System (ADS)

Pedraza, A. J.; Fowlkes, J. D.; Jesse, S.; Mao, C.; Lowndes, D. H.

2000-12-01

The formation mechanisms of cones and columns by pulsed-laser irradiation in reactive atmospheres were studied using scanning electron microscopy and profilometry. Deep etching takes place in SF6- and O2- rich atmospheres and consequently, silicon-containing molecules and clusters are released. Transport of silicon from the etched/ablated regions to the tip of columns and cones and to the side of the cones is required because both structures, columns and cones, protrude above the initial surface. The laser-induced micro-structure is influenced not only by the nature but also by the partial pressure of the reactive gas in the atmosphere. Irradiation in Ar following cone formation in SF6 produced no additional growth but rather melting and resolidification. Subsequent irradiation using again a SF6 atmosphere lead to cone restructuring and growth resumption. Thus the effects of etching plus re-deposition that produce column/cone formation and growth are clearly separated from the effects of just melting. On the other hand, irradiation continued in air after first performed in SF6 resulted in: (a) an intense etching of the cones and a tendency to transform them into columns; (b) growth of new columns on top of the existing cones and (c) filamentary nano-structures coating the sides of the columns and cones.

Assessing infrared intensity using the evaporation rate of liquid hydrogen inside a cryogenic integrating sphere for laser fusion targets

NASA Astrophysics Data System (ADS)

Iwano, K.; Iwamoto, A.; Asahina, T.; Yamanoi, K.; Arikawa, Y.; Nagatomo, H.; Nakai, M.; Norimatsu, T.; Azechi, H.

2017-07-01

Infrared (IR) heating processes have been studied to form a deuterium layer in an inertial confinement fusion target. To understand the relationship between the IR intensity and the fuel layering time constant, we have developed a new method to assess the IR intensity during irradiation. In our method, a glass flask acting as a dummy target is filled with liquid hydrogen (LH2) and is then irradiated with 2-μm light. The IR intensity is subsequently calculated from the time constant of the LH2 evaporation rate. Although LH2 evaporation is also caused by the heat inflow from the surroundings and by the background heat, the evaporation rate due to IR heating can be accurately determined by acquiring the time constant with and without irradiation. The experimentally measured IR intensity is 0.66 mW/cm2, which agrees well with a value estimated by considering the IR photon energy balance. Our results suggest that the present method can be used to measure the IR intensity inside a cryogenic system during IR irradiation of laser fusion targets.

Assessing infrared intensity using the evaporation rate of liquid hydrogen inside a cryogenic integrating sphere for laser fusion targets.

PubMed

Iwano, K; Iwamoto, A; Asahina, T; Yamanoi, K; Arikawa, Y; Nagatomo, H; Nakai, M; Norimatsu, T; Azechi, H

2017-07-01

Infrared (IR) heating processes have been studied to form a deuterium layer in an inertial confinement fusion target. To understand the relationship between the IR intensity and the fuel layering time constant, we have developed a new method to assess the IR intensity during irradiation. In our method, a glass flask acting as a dummy target is filled with liquid hydrogen (LH 2 ) and is then irradiated with 2-μm light. The IR intensity is subsequently calculated from the time constant of the LH 2 evaporation rate. Although LH 2 evaporation is also caused by the heat inflow from the surroundings and by the background heat, the evaporation rate due to IR heating can be accurately determined by acquiring the time constant with and without irradiation. The experimentally measured IR intensity is 0.66 mW/cm 2 , which agrees well with a value estimated by considering the IR photon energy balance. Our results suggest that the present method can be used to measure the IR intensity inside a cryogenic system during IR irradiation of laser fusion targets.

Ion acceleration in shell cylinders irradiated by a short intense laser pulse

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

Andreev, A.; ELI-ALPS, Szeged; Platonov, K.

The interaction of a short high intensity laser pulse with homo and heterogeneous shell cylinders has been analyzed using particle-in-cell simulations and analytical modeling. We show that the shell cylinder is proficient of accelerating and focusing ions in a narrow region. In the case of shell cylinder, the ion energy exceeds the ion energy for a flat target of the same thickness. The constructed model enables the evaluation of the ion energy and the number of ions in the focusing region.

Effect of three different intensities of infrared laser energy on the levels of amino acid neurotransmitters in the cortex and hippocampus of rat brain.

PubMed

Ahmed, Nawal Abd El Hay; Radwan, Nasr Mahmoud; Ibrahim, Khayria Mansour; Khedr, Mona Emam; El Aziz, Mona A; Khadrawy, Yasser Ashry

2008-10-01

The aim of this study is to investigate the effects of three different intensities of infrared diode laser radiation on amino acid neurotransmitters in the cortex and hippocampus of rat brain. Lasers are known to induce different neurological effects such as pain relief, anesthesia, and neurosuppressive effects; however, the precise mechanisms of these effects are not clearly elucidated. Amino acid neurotransmitters (glutamate, aspartate, glutamine, gamma-aminobutyric acid [GABA], glycine, and taurine) play vital roles in the central nervous system (CNS). The shaved scalp of each rat was exposed to different intensities of infrared laser energy (500, 190, and 90 mW) and then the rats were sacrificed after 1 h, 7 d, and 14 d of daily laser irradiation. The control groups were exposed to the same conditions but without exposure to laser. The concentrations of amino acid neurotransmitters were measured by high-performance liquid chromatography (HPLC). The rats subjected to 500 mW of laser irradiation had a significant decrease in glutamate, aspartate, and taurine in the cortex, and a significant decrease in hippocampal GABA. In the cortices of rats exposed to 190 mW of laser irradiation, an increase in aspartate accompanied by a decrease in glutamine were observed. In the hippocampus, other changes were seen. The rats irradiated with 90 mW showed a decrease in cortical glutamate, aspartate, and glutamine, and an increase in glycine, while in the hippocampus an increase in glutamate, aspartate, and GABA were recorded. We conclude that daily laser irradiation at 90 mW produced the most pronounced inhibitory effect in the cortex after 7 d. This finding may explain the reported neurosuppressive effect of infrared laser energy on axonal conduction of hippocampal and cortical tissues of rat brain.

Thermal imaging of high power diode lasers subject to back-irradiance

NASA Astrophysics Data System (ADS)

Li, C.; Pipe, K. P.; Cao, C.; Thiagarajan, P.; Deri, R. J.; Leisher, P. O.

2018-03-01

CCD-based thermoreflectance imaging and finite element modeling are used to study the two-dimensional (2D) temperature profile of a junction-down broad-area diode laser facet subject to back-irradiance. By determining the temperature rise in the active region (ΔΤAR) at different diode laser optical powers, back-irradiance reflectance levels, and back-irradiance spot locations, we find that ΔΤAR increases by nearly a factor of three when the back-irradiance spot is centered in the absorbing substrate approximately 5 μm away from the active region, a distance roughly equal to half of the back-irradiance spot FWHM (9 μm). This corroborates prior work studying the relationship between the back-irradiance spot location and catastrophic optical damage, suggesting a strong thermal basis for reduced laser lifetime in the presence of back-irradiance for diode lasers fabricated on absorbing substrates.

Ultrastructure observation of middle ear mucosa with laser irradiation

NASA Astrophysics Data System (ADS)

Kang, Mengkui; Yang, Shulan; Fang, Yaoyun; Sun, Jianhe

1998-08-01

In order to study the effects of He-Ne laser on the mucosa of middle ear mucosa from 9 patients with chronic otitis media, all of who had slight damp eardrum, were irradiated by low power He-Ne laser ten minutes per day for ten days. Specimen was taken before and after irradiation and observed under scanning electron microscope. It was found that the surface structure of the mucosa was more integral, the arrangement of the epithelial cell was closer together and microvilli arose among the noncilliated cells after irradiation. The inflammatory cell disappeared arid the morphologic structure appeared normal. These data provided the therapeutic evidence for the lower power He-Ne laser irradiation on patients with chronic purulent otitis midia.

Wavelength Dependence of Excimer Laser Irradiation Effects on Ethylene-Tetrafluoroethylene Copolymer

NASA Astrophysics Data System (ADS)

Hamada, Yuji; Kawanishi, Shunichi; Nishii, Masanobu; Sugimoto, Shun'ichi; Yamamoto, Tadashi

1994-08-01

Irradiation with an ArF laser at wavelength of 193 nm formed diene in a whole ethylene-tetrafluoroethylene copolymer (ETFE) film and irradiation with a KrF and a XeCl laser at 248 and 308 nm induced the carbonization of ETFE. ArF-laser radiation at 193 nm formed diene in the bulk of ETFE via the process of single-photon absorption, and in case of KrF and XeCl-laser irradiation multiphoton absorption brought about the carbonization of ETFE. The surface analysis by X-ray photoelectron spectroscopy showed that excimer laser-induced elimination of fluorine atoms depended on the laser wavelength.

Applications of Ultra-Intense, Short Laser Pulses

NASA Astrophysics Data System (ADS)

Ledingham, Ken W. D.

The high intensity laser production of electron, proton, ion and photon beams is reviewed particularly with respect to the laser-plasma interaction which drives the acceleration process. A number of applications for these intense short pulse beams is discussed e.g. ion therapy, PET isotope production and laser driven transmutation studies. The future for laser driven nuclear physics at the huge new, multi-petawatt proposed laser installation ELI in Bucharest is described. Many people believe this will take European nuclear research to the next level.

Hyper-Ramsey spectroscopy with probe-laser-intensity fluctuations

NASA Astrophysics Data System (ADS)

Beloy, K.

2018-03-01

We examine the influence of probe-laser-intensity fluctuations on hyper-Ramsey spectroscopy. We assume, as is appropriate for relevant cases of interest, that the probe-laser intensity I determines both the Rabi frequency (∝√{I } ) and the frequency shift to the atomic transition (∝I ) during probe-laser interactions with the atom. The spectroscopic signal depends on these two quantities that covary with fluctuations in the probe-laser intensity. Introducing a simple model for the fluctuations, we find that the signature robustness of the hyper-Ramsey method can be compromised. Taking the Yb+ electric octupole clock transition as an example, we quantify the clock error under different levels of probe-laser-intensity fluctuations.

Thermal imaging of high power diode lasers subject to back-irradiance

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

Li, C.; Pipe, K. P.; Cao, C.

In this study, CCD-based thermoreflectance imaging and finite element modeling are used to study the two-dimensional (2D) temperature profile of a junction-down broad-area diode laser facet subject to back-irradiance. By determining the temperature rise in the active region (ΔΤAR) at different diode laser optical powers, back-irradiance reflectance levels, and back-irradiance spot locations, we find that ΔΤAR increases by nearly a factor of three when the back-irradiance spot is centered in the absorbing substrate approximately 5 μm away from the active region, a distance roughly equal to half of the back-irradiance spot FWHM (9 μm). This corroborates prior work studying themore » relationship between the back-irradiance spot location and catastrophic optical damage, suggesting a strong thermal basis for reduced laser lifetime in the presence of back-irradiance for diode lasers fabricated on absorbing substrates.« less

Thermal imaging of high power diode lasers subject to back-irradiance

DOE PAGES

Li, C.; Pipe, K. P.; Cao, C.; ...

2018-03-07

In this study, CCD-based thermoreflectance imaging and finite element modeling are used to study the two-dimensional (2D) temperature profile of a junction-down broad-area diode laser facet subject to back-irradiance. By determining the temperature rise in the active region (ΔΤAR) at different diode laser optical powers, back-irradiance reflectance levels, and back-irradiance spot locations, we find that ΔΤAR increases by nearly a factor of three when the back-irradiance spot is centered in the absorbing substrate approximately 5 μm away from the active region, a distance roughly equal to half of the back-irradiance spot FWHM (9 μm). This corroborates prior work studying themore » relationship between the back-irradiance spot location and catastrophic optical damage, suggesting a strong thermal basis for reduced laser lifetime in the presence of back-irradiance for diode lasers fabricated on absorbing substrates.« less

Protective Effect of 940 nm Laser on Gamma-Irradiated Mice

PubMed Central

Efremova, Yulia; Navratil, Leos

2015-01-01

Abstract Objective: The purpose of this study was to investigate the radioprotective features of 940 nm laser on the life span of mice, and absolute counts of blood cells and their proportions in gamma-irradiated mice. Background data: An important feature of laser light is activation of mitotic division and differentiation of cells, which may be useful in activation of hematopoiesis in gamma-irradiated organisms. Materials and methods: Mice were randomly assigned to 11 groups according to the type(s) of influence. Generally, mice were irradiated in three different ways: with laser at different fluences, with gamma irradiation, or by combination of laser at different fluences and gamma irradiation in a different order. Mice were treated with 940 nm laser at 3, 12, or 18 J/cm2 and/or a lethal dose of gamma irradiation (8.7 Gy). Each group was randomly subdivided into two subgroups, in which the life span of the mice and blood cell counts (on 12th and 45th day after gamma irradiation) were analyzed. Results: Laser (940 nm) at a fluence of 3 J/cm2 significantly prolonged the life span of gamma-irradiated mice (p<0.05). In the same group, counts of white blood cells, lymphocytes, and neutrophils were higher on day 12 than in the gamma group. On day 45 after gamma irradiation, some signs of hematopoiesis repair were found in blood. There were no significant differences in counts of erythrocytes, monocytes, neutrophils, or the proportion of neutrophils between this group and the control group. Conclusions: In summary, 940 nm laser at a fluence of 3 J/cm2 demonstrates radioprotective features in an experiment with lethally irradiated mice. Mechanisms responsible for this effect will be investigated in further studies. PMID:25654740

Phase transformation pathways of Ln2O3 irradiated by ultrafast laser

NASA Astrophysics Data System (ADS)

Rittman, Dylan; Solomon, Jonathan; Chen, Curtis; Tracy, Cameron; Yalisove, Steven; Asta, Mark; Mao, Wendy; Ewing, Rodney

Ultrafast laser irradiation induces highly non-equilibrium conditions in materials through intense electronic excitation over very short timescales. Here, we show that ultrafast laser irradiation drives an irreversible cubic-to-monoclinic phase transformation in Ln2O3 (Ln = Er-Lu). A combination of grazing incidence X-ray diffraction and transmission electron microscopy is used to characterize the amount and depth-dependence of the phase transformation. Results indicate that-although all materials experience the same transformation-it is achieved through different damage mechanisms (pressure vs. thermal), and the short timescales associated with damage provides non-equilibrium routes of material modification. Ab initio molecular dynamics are used to isolate the effects of electronic excitations, and results are shown to be consistent with the trend in radiation resistance observed experimentally. Overall, this study provides a path to gain insight into the relationship between a material's equilibrium phase diagram and its behavior under highly non-equilibrium conditions. DOE/BES.

Optical spectroscopic characterizations of laser irradiated olivine grains

NASA Astrophysics Data System (ADS)

Yang, Yazhou; Zhang, Hao; Wang, Ziwei; Yuan, Ye; Li, Shaolin; Hsu, Weibiao; Liu, Chujian

2017-01-01

Context. Visible and near-infrared spectra of asteroids are known to be susceptible to nanophase irons produced by space weathering processes, thus making mineral identifications difficult. Mid-infrared spectroscopy may retain more mineral features owing to its lattice vibrational nature. Aims: We investigate the structure and reflectance spectral feature changes of olivine grains before and after simulated space weathering. Methods: We irradiate olivine grains by using pulsed laser to simulate varying degrees of micrometeorite bombardments. Reflectance measurements from 0.5 to 25 μm and radiative transfer calculations were carried out in order to compare them with each other. Results: Both the experimental simulations and modeling results indicate that the mid-infrared spectral features of olivine grains can survive the intense irradiations. Although the Christansen Feature is slightly shifted to longer wavelength, major vibrational bands remain essentially unchanged, because the lattice structure is quite immune to even the strongest irradiations, as revealed by both the X-ray diffraction and Raman scattering measurements. Conclusions: Mid-infrared spectroscopy is much more immune to productions of nanophase irons and amorphous materials and thus may be used more reliably in remote detections of minerals on asteroid surfaces.

Effect of low level laser therapy and high intensity laser therapy on endothelial cell proliferation in vitro: preliminary communication

NASA Astrophysics Data System (ADS)

Lukowicz, Malgorzata; Szymanska, Justyna; Goralczyk, Krzysztof; Zajac, Andrzej; Rość, Danuta

2013-01-01

Background: The main purpose of this study was to analyze the influence of power intensity and wavelength of Low Level Laser Therapy (LLLT) and HILT (High Intensity Laser Therapy) on endothelial cell proliferation. Material and methods: The tests were done on human umbilical vein endothelial cells (HUVEC). Cultures were exposed to laser irradiation of 660 nm and 670 nm at different dosages, power output was 10 - 40 mW as well as 820 nm with power 100 mW and 808 nm with power 1500 mW. Energy density was from 0.28 to 11,43 J/cm2. Cell proliferation of a control and tested culture was evaluated with a colorimetric device to detect live cells. The tests were repeated 8 times. Results: We observed good effects of LLLT on live isolated ECs and no effects in experiments on previous deep-frozen cultures. Also HILT stimulated the proliferation of HUVEC. Conclusion: Endothelial cells play a key role in vascular homeostasis in humans. We observed the stimulatory effect of LLLT and HILT on proliferation of HUVEC. Many factors influence the proliferation of EC, so is it necessary to continue the experiment with different doses, intensity and cell concentration.

Effect of low power laser irradiation on macrophage phagocytic capacity

NASA Astrophysics Data System (ADS)

Lu, Cuixia; Song, Sheng; Tang, Yu; Zhou, Feifan

2011-03-01

Phagocytosis and subsequent degradation of pathogens by macrophages play a pivotal role in host innate immunity in mammals. Laser irradiation has been found to produce photobiological effects with evidence of interference with immunological functions. However, the effects of laser on the immune response have not been extensively characterized. In this study, we focused our attention on the effects of He-Ne laser on the phagocytic activity of macrophages by using flow cytometry (FCM). After irradiating at fluence of 0, 1, 2 J/cm2 with He-Ne laser (632.8 nm, 3mw), the cells were incubated with microsphere and then subjected to FACS analysis. The results showed that Low-power laser irradiation (LPLI) leads to an increase in phagocytosis on both mouse peritoneal macrophages and the murine macrophage-like cell line RAW264.7. In addition, we demonstrated that LPLI increased phagocytosis of microsphere in a dose-dependent manner, reaching a maximum at fluence of 2 J/cm2. Taken together, our results indicated that Low-power laser irradiation with appropriate dosage can enhance the phagocytosis of macrophage, and provided a theoretical base for the clinical use of the He-Ne laser.

Heat profiles of laser-irradiated nails

NASA Astrophysics Data System (ADS)

Paasch, Uwe; Nenoff, Pietro; Seitz, Anna-Theresa; Wagner, Justinus A.; Kendler, Michael; Simon, Jan C.; Grunewald, Sonja

2014-01-01

Onychomycosis is a worldwide problem with no tendency for self-healing, and existing systemic treatments achieve disease-free nails in only 35 to 76% of cases. Recently, treatment of nail fungus with a near-infrared laser has been introduced. It is assumed that fungal eradication is mediated by local heat. To investigate if laser treatment has the potential to eradicate fungal hyphae and arthrospores, laser heat application and propagation needs to be studied in detail. This study aimed to measure nail temperatures using real-time videothermography during laser irradiation. Treatment was performed using 808- and 980-nm linear scanning diode lasers developed for hair removal, enabling contact-free homogeneous irradiation of a human nail plate in one pass. Average and peak temperatures increased pass by pass, while the laser beam moved along the nail plates. The achieved mean peak temperatures (808 nm: 74.1 to 112.4°C, 980 nm: 45.8 to 53.5°C), as well as the elevation of average temperatures (808 nm: 29.5 to 38.2°C, 980 nm: 27.1 to 32.6°C) were associated with pain that was equivalent to that of hair removal procedures and was not significantly different for various wavelengths. The linear scanning laser devices provide the benefits of contact-free homogeneous heating of the human nail while ensuring adequate temperature rises.

Heat profiles of laser-irradiated nails.

PubMed

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

2014-01-01

Onychomycosis is a worldwide problem with no tendency for self-healing, and existing systemic treatments achieve disease-free nails in only 35 to 76% of cases. Recently, treatment of nail fungus with a near-infrared laser has been introduced. It is assumed that fungal eradication is mediated by local heat. To investigate if laser treatment has the potential to eradicate fungal hyphae and arthrospores, laser heat application and propagation needs to be studied in detail. This study aimed to measure nail temperatures using real-time videothermography during laser irradiation. Treatment was performed using 808- and 980-nm linear scanning diode lasers developed for hair removal, enabling contact-free homogeneous irradiation of a human nail plate in one pass. Average and peak temperatures increased pass by pass, while the laser beam moved along the nail plates. The achieved mean peak temperatures (808 nm: 74.1 to 112.4°C, 980 nm: 45.8 to 53.5°C), as well as the elevation of average temperatures (808 nm: 29.5 to 38.2°C, 980 nm: 27.1 to 32.6°C) were associated with pain that was equivalent to that of hair removal procedures and was not significantly different for various wavelengths. The linear scanning laser devices provide the benefits of contact-free homogeneous heating of the human nail while ensuring adequate temperature rises.

Cracking and Exfoliation of TiO2 Film Irradiated with Excimer Laser

NASA Astrophysics Data System (ADS)

Qian, H. X.; Zhou, W.; Zheng, H. Y.

TiO2 film deposited on glass was irradiated in air with single-shot KrF excimer laser pulse. The surface roughened as the result of the laser ablation. It is further noted that single-pulse irradiation with fluence ranging from 400 to 1200 mJ/cm2 gave rise to protrusion of the irradiated surface above the original surface, which is in contrast to usual expectation that irradiated surface is below the unirradiated surface. The surface protrusion is mainly attributed to the effect of surface tension. At the laser fluence of 1000 mJ/cm2, cracks were formed in the irradiated area and severe film exfoliation was observed at the periphery of the irradiated area due to the release of internal stress. With higher laser fluence above 1000 mJ/cm2, patches of film were observed to peel off within the irradiated areas. Hydrodynamic ablation is proposed to account for film exfoliation. The observed phenomenon is useful for further understanding how TiO2 film reacts to strong UV laser irradiation.

Role of laser fluence in protein synthesis of cultured DRG neurons following low-level laser irradiation

NASA Astrophysics Data System (ADS)

Zheng, Liqin; Qiu, Caimin; Wang, Yuhua; Zeng, Yixiu; Yang, Hongqin; Zhang, Yanding; Xie, Shusen

2014-11-01

Low-level lasers have been used to relieve pain in clinical for many years. But the mechanism is not fully clear. In animal models, nitric oxide (NO) has been reported involving in the transmission and modulation of nociceptive signals. So the objective of this study was to establish whether low-level laser with different fluence could stimulate the production of nitric oxide synthese (NOS), which produces NO in cultured primary dorsal root ganglion neurons (DRG neurons). The primary DRG neurons were isolated from healthy Sprague Dawley rats (8-12 weeks of age) and spread on 35 mm culture dishes specially used for confocal microscopy. 24 hours after spreading, cells were irradiated with 658 nm laser for two consecutive days at the energy density of 20, 40, 60 and 80 mJ·cm-2 respectively. Control groups were not exposed to the laser, but were kept under the same conditions as the irradiated ones. The synthesis of NOS after laser irradiation was detected by immunofluorescence assay, and the changes of NOS were evaluated using confocal microscopy and Image J software. The results showed that all the laser fluence could promote the production of NOS in DRG neurons, especially the 60 mJ·cm-2 . These results demonstrated that low-level laser irradiation could modify protein synthesis in a dose- or fluence- dependent manner, and indicated that low-level laser irradiation might achieve the analgesic effect through modulation of NO production.

Laser methods of caries prophylaxis

NASA Astrophysics Data System (ADS)

Kunin, Anatoly A.; Dergunova, Elvira I.; Kazmina, Svetlana G.

1996-01-01

Low intensive laser irradiation is widely used for the treatment of many stomatological diseases. The caries static activity of HNL light and infrared lasers, its influence on the activation of microcirculation of the pulp enzyme system and on the increase of enamel permeability became clear. These data allow us to suppose that the low intensive laser irradiation may potent the activity of the initial caries by the increase of teeth stability to the factors provoking the caries.

Modelling periodic structure formation on 100Cr6 steel after irradiation with femtosecond-pulsed laser beams

NASA Astrophysics Data System (ADS)

Tsibidis, George D.; Mimidis, Alexandros; Skoulas, Evangelos; Kirner, Sabrina V.; Krüger, Jörg; Bonse, Jörn; Stratakis, Emmanuel

2018-01-01

We investigate the periodic structure formation upon intense femtosecond pulsed irradiation of chrome steel (100Cr6) for linearly polarised laser beams. The underlying physical mechanism of the laser-induced periodic structures is explored, their spatial frequency is calculated and theoretical results are compared with experimental observations. The proposed theoretical model comprises estimations of electron excitation, heat transfer, relaxation processes, and hydrodynamics-related mass transport. Simulations describe the sequential formation of sub-wavelength ripples and supra-wavelength grooves. In addition, the influence of the laser wavelength on the periodicity of the structures is discussed. The proposed theoretical investigation offers a systematic methodology towards laser processing of steel surfaces with important applications.

Venous Lake of the Lips Treated Using Photocoagulation with High-Intensity Diode Laser

PubMed Central

Galletta, Vivian C.; de Paula Eduardo, Carlos; Migliari, Dante A.

2010-01-01

Abstract Objective: To evaluate the effectiveness of photocoagulation with high-intensity diode laser in the treatment of venous lake (VL) lesions. Background Data: VL is a common vascular lesion characterized by elevated, usually dome-shaped papules, ranging in color from dark blue to dark purple, seen more frequently in elderly patients. They often occur as single lesions on the ears, face, lips, or neck. Once formed, lesions persist throughout life. Although these lesions are usually asymptomatic, they can bleed if injured. Methods: Seventeen patients (7 men and 10 women) with VL on the lip were treated using a noncontact diode laser (wavelength 808 nm, power output 2–3 W in continuous wave). Results: After only one irradiation exposure, all lesions were successfully treated. Healing was completed in approximately 2 to 3 weeks, and none of the patients experienced complications. Postoperative discomfort and scarring were not present or were minimal. Conclusion: Photocoagulation with high-intensity diode laser is an effective, bloodless procedure for the treatment of VL. PMID:19811083

Enhanced dense attosecond electron bunch generation by irradiating an intense laser on a cone target

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

Hu, Li-Xiang; Yu, Tong-Pu, E-mail: tongpu@nudt.edu.cn; Shao, Fu-Qiu

By using two-dimensional particle-in-cell simulations, we demonstrate enhanced spatially periodic attosecond electron bunches generation with an average density of about 10n{sub c} and cut-off energy up to 380 MeV. These bunches are acquired from the interaction of an ultra-short ultra-intense laser pulse with a cone target. The laser oscillating field pulls out the cone surface electrons periodically and accelerates them forward via laser pondermotive force. The inner cone wall can effectively guide these bunches and lead to their stable propagation in the cone, resulting in overdense energetic attosecond electron generation. We also consider the influence of laser and cone target parametersmore » on the bunch properties. It indicates that the attosecond electron bunch acceleration and propagation could be significantly enhanced without evident divergency by attaching a plasma capillary to the original cone tip.« less

Small-scale heat detection using catalytic microengines irradiated by laser

NASA Astrophysics Data System (ADS)

Liu, Zhaoqian; Li, Jinxing; Wang, Jiao; Huang, Gaoshan; Liu, Ran; Mei, Yongfeng

2013-01-01

We demonstrate a novel approach to modulating the motion speed of catalytic microtubular engines via laser irradiation/heating with regard to small-scale heat detection. Laser irradiation on the engines leads to a thermal heating effect and thus enhances the engine speed. During a laser on/off period, the motion behaviour of a microengine can be repeatable and reversible, demonstrating a regulation of motion speeds triggered by laser illumination. Also, the engine velocity exhibits a linear dependence on laser power in various fuel concentrations, which implies an application potential as local heat sensors. Our work may hold great promise in applications such as lab on a chip, micro/nano factories, and environmental detection.We demonstrate a novel approach to modulating the motion speed of catalytic microtubular engines via laser irradiation/heating with regard to small-scale heat detection. Laser irradiation on the engines leads to a thermal heating effect and thus enhances the engine speed. During a laser on/off period, the motion behaviour of a microengine can be repeatable and reversible, demonstrating a regulation of motion speeds triggered by laser illumination. Also, the engine velocity exhibits a linear dependence on laser power in various fuel concentrations, which implies an application potential as local heat sensors. Our work may hold great promise in applications such as lab on a chip, micro/nano factories, and environmental detection. Electronic supplementary information (ESI) available. See DOI: 10.1039/c2nr32494f

Effects of laser irradiation on immature olfactory neuroepithelial explants from the rat

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

Mester, A.F.; Snow, J.B. Jr.

1988-07-01

The photobiological effect of low-output laser irradiation on the maturation and regeneration of immature olfactory bipolar receptor cells of the rat was studied. The maturation and regeneration of the receptor cells of rat fetuses were quantified in neuroepithelial explants with morphometric analysis. The number of explants with outgrowth and the number and length of neuritic outgrowths were determined on a regular basis for 12 days. Explants in the experimental group were irradiated with a helium-neon laser using different incident energy densities (IED). Explants in the fluorescent light control group were exposed to fluorescent light for the same periods of timemore » as those in the experimental group were exposed to laser irradiation. Explants in another control group were not exposed to laser or fluorescent light irradiation. The IED of 0.5 J/cm2 laser irradiation has been found to increase significantly the number of explants with outgrowth and the number and length of the outgrowths. Other laser IEDs or fluorescent light irradiation did not influence maturation or regeneration.« less

Formation of periodic surface structures on dielectrics after irradiation with laser beams of spatially variant polarisation: a comparative study

NASA Astrophysics Data System (ADS)

Papadopoulos, Antonis; Skoulas, Evangelos; Tsibidis, George D.; Stratakis, Emmanuel

2018-02-01

A comparative study is performed to explore the periodic structure formation upon intense femtosecond-pulsed irradiation of dielectrics with radially and azimuthally polarised beams. Laser conditions have been selected appropriately to produce excited carriers with densities below the optical breakdown threshold in order to highlight the role of phase transitions in surface modification mechanisms. The frequency of the laser-induced structures is calculated based on a theoretical model that comprises estimation of electron density excitation, heat transfer, relaxation processes, and hydrodynamics-related mass transport. The influence of the laser wavelength in the periodicity of the structures is also unveiled. The decreased energy absorption for azimuthally polarised beams yields periodic structures with smaller frequencies which are more pronounced as the number of laser pulses applied to the irradiation spot increases. Similar results are obtained for laser pulses of larger photon energy and higher fluences. All induced periodic structures are oriented parallel to the laser beam polarisation.

Reduction of thermal damage in photodynamic therapy by laser irradiation techniques.

PubMed

Lim, Hyun Soo

2012-12-01

General application of continuous-wave (CW) laser irradiation modes in photodynamic therapy can cause thermal damage to normal tissues in addition to tumors. A new photodynamic laser therapy system using a pulse irradiation mode was optimized to reduce nonspecific thermal damage. In in vitro tissue specimens, tissue energy deposition rates were measured in three irradiation modes, CW, pulse, and burst-pulse. In addition, methods were tested for reducing variations in laser output and specific wavelength shifts using a thermoelectric cooler and thermistor. The average temperature elevation per 10 J/cm2 was 0.27°C, 0.09°C, and 0.08°C using the three methods, respectively, in pig muscle tissue. Variations in laser output were controlled within ± 0.2%, and specific wavelength shift was limited to ± 3 nm. Thus, optimization of a photodynamic laser system was achieved using a new pulse irradiation mode and controlled laser output to reduce potential thermal damage during conventional CW-based photodynamic therapy.

Plasma optical modulators for intense lasers

PubMed Central

Yu, Lu-Le; Zhao, Yao; Qian, Lie-Jia; Chen, Min; Weng, Su-Ming; Sheng, Zheng-Ming; Jaroszynski, D. A.; Mori, W. B.; Zhang, Jie

2016-01-01

Optical modulators can have high modulation speed and broad bandwidth, while being compact. However, these optical modulators usually work for low-intensity light beams. Here we present an ultrafast, plasma-based optical modulator, which can directly modulate high-power lasers with intensity up to 1016 W cm−2 to produce an extremely broad spectrum with a fractional bandwidth over 100%, extending to the mid-infrared regime in the low-frequency side. This concept relies on two co-propagating laser pulses in a sub-millimetre-scale underdense plasma, where a drive laser pulse first excites an electron plasma wave in its wake while a following carrier laser pulse is modulated by the plasma wave. The laser and plasma parameters suitable for the modulator to work are based on numerical simulations. PMID:27283369

A digital intensity stabilization system for HeNe laser

NASA Astrophysics Data System (ADS)

Wei, Zhimeng; Lu, Guangfeng; Yang, Kaiyong; Long, Xingwu; Huang, Yun

2012-02-01

A digital intensity stabilization system for HeNe laser is developed. Based on a switching power IC to design laser power supply and a general purpose microcontroller to realize digital PID control, the system constructs a closed loop to stabilize the laser intensity by regulating its discharge current. The laser tube is made of glass ceramics and its integrated structure is steady enough to eliminate intensity fluctuations at high frequency and attenuates all intensity fluctuations, and this makes it easy to tune the control loop. The control loop between discharge current and photodiode voltage eliminates the long-term drifts. The intensity stability of the HeNe laser with this system is 0.014% over 12 h.

Light-Irradiation Wavelength and Intensity Changes Influence Aflatoxin Synthesis in Fungi

PubMed Central

Suzuki, Tadahiro

2018-01-01

Fungi respond to light irradiation by forming conidia and occasionally synthesizing mycotoxins. Several light wavelengths, such as blue and red, affect the latter. However, the relationship between light irradiation and mycotoxin synthesis varies depending on the fungal species or strain. This study focused on aflatoxin (AF), which is a mycotoxin, and the types of light irradiation that increase AF synthesis. Light-irradiation tests using the visible region indicated that blue wavelengths in the lower 500 nm region promoted AF synthesis. In contrast, red wavelengths of 660 nm resulted in limited significant changes compared with dark conditions. Irradiation tests with different intensity levels indicated that a low light intensity increased AF synthesis. For one fungal strain, light irradiation decreased the AF synthesis under all wavelength conditions. However, the decrease was mitigated by 525 nm low intensity irradiation. Thus, blue-green low intensity irradiation may increase AF synthesis in fungi. PMID:29304012

Magnetic resonance thermometry for monitoring photothermal effects of interstitial laser irradiation

NASA Astrophysics Data System (ADS)

Goddard, Jessica; Jose, Jessnie; Figueroa, Daniel; Le, Kelvin; Liu, Hong; Nordquist, Robert E.; Hode, Tomas; Chen, Wei R.

2012-03-01

Selective photothermal interaction using dye-assisted non-invasive laser irradiation has limitations when treating deeper tumors or when the overlying skin is heavily pigmented. We developed an interstitial laser irradiation method to induce the desired photothermal effects. An 805-nm near-infrared laser with a cylindrical diffuser was used to treat rat mammary tumors by placing the active tip of the fiber inside the target tumors. Three different power settings (1.0 to 1.5 watts) were applied to treat animal tumors with an irradiation duration of 10 minutes. The temperature distributions of the treated tumors were measured by a 7.1-Tesla magnetic resonance imager using proton resonance frequency (PRF) method. Three-dimensional temperature profiles were reconstructed and assessed using PRF. This is the first time a 7.1-Tesla magnetic resonance imager has been used to monitor interstitial laser irradiation via PRF. This study provides a basic understanding of the photothermal interaction needed to control the thermal damage inside tumor using interstitial laser irradiation. It also shows that PRF can be used effectively in monitoring photothermal interaction. Our long-term goal is to develop a PRF-guided laser therapy for cancer treatment.

Membrane Protein Crystallization Using Laser Irradiation

NASA Astrophysics Data System (ADS)

Adachi, Hiroaki; Murakami, Satoshi; Niino, Ai; Matsumura, Hiroyoshi; Takano, Kazufumi; Inoue, Tsuyoshi; Mori, Yusuke; Yamaguchi, Akihito; Sasaki, Takatomo

2004-10-01

We demonstrate the crystallization of a membrane protein using femtosecond laser irradiation. This method, which we call the laser irradiated growth technique (LIGHT), is useful for producing AcrB crystals in a solution of low supersaturation range. LIGHT is characterized by reduced nucleation times. This feature is important for crystallizing membrane proteins because of their labile properties when solubilized as protein-detergent micelles. Using LIGHT, high-quality crystals of a membrane transporter protein, AcrB, were obtained. The resulting crystals were found to be of sufficiently high resolution for X-ray diffraction. The results reported here indicate that LIGHT is a powerful tool for membrane protein crystallization, as well as for the growth of soluble proteins.

Experimental study on rat NK cell activity improvement by laser acupoint irradiation

NASA Astrophysics Data System (ADS)

Yang, Dongxiao; Chen, Xiufeng; Ruan, Buqing; Yang, Feng

1998-08-01

To study the improvement of the natural killer (NK) cell activity by semiconductor laser acupoint irradiation, rats were used in this experiment and were injected immunosuppressant in their abdomen. The immunoassay was made after the surface irradiation and inner irradiation at Baihui point by semiconductor laser. The NK cell activity is an important index of immunologic function. The results showed that the NK cell activity after laser acupoint irradiation was enhanced. This enhancement is relatively important in the clinical therapy of tumor.

Laser Ablation of Poly(methylmethacrylate) Doped with Aromatic Compounds: Laser Intensity Dependence of Absorption Coefficient

NASA Astrophysics Data System (ADS)

Wang, Jun; Niino, Hiroyuki; Yabe, Akira

1999-02-01

We developed a novel method of obtaining an absorption coefficient which depends on the laser intensity, since a single-photon absorption coefficient of a polymer could not be applied to laser ablation. The relationship between the nonlinear absorption coefficient and the laser intensity was derived from experimental data of transmission and incident laser intensities. Using the nonlinear absorption coefficient of poly(methylmethacrylate) doped with benzil and pyrene, we succeeded in fitting the relationship of etch depth and laser intensity, obtained experimentally, and discussed the energy absorbed by the polymer at the threshold fluence.

Investigation of irradiation by different nonablative lasers on primary cultured skin fibroblasts.

PubMed

Weng, Y; Dang, Y; Ye, X; Liu, N; Zhang, Z; Ren, Q

2011-08-01

A variety of lasers with different wavelengths and biological effects are widely used for nonablative skin rejuvenation, but the underlying mechanisms have not been fully investigated. To investigate the effects of irradiation by different nonablative lasers on collagen synthesis and the antioxidant status of cultured fibroblasts to identify a possible mechanism for laser photorejuvenation. Cultured skin fibroblasts were irradiated with three different lasers: 532 nm potassium-titanyl phosphate (KTP), 1064 nm Q-switched neodymium:yttrium-aluminium-garnet (Nd:Yag) and 1064 nm long-pulse Nd:YAG, and production of collagen and changes in lactate dehydrogenase (LDH), malondialdehyde (MDA), superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) were assayed. Irradiation by all three lasers led to a marked increase in collagen production. Two major antioxidant enzymes, SOD and GSH, were significantly increased, whereas MDA was markedly reduced after laser irradiation. No change in LDH activity was found between nonirradiated and irradiated fibroblasts. This study indicates that the increased collagen synthesis by fibroblasts after laser treatment may be partly due to improved antioxidant capacity, which reduces oxidative stress and thus stimulates new collagen production. © The Author(s). CED © 2011 British Association of Dermatologists.

CO2 laser nerve stimulator with flat-top irradiance profile for human pain research

NASA Astrophysics Data System (ADS)

McCaughey, Ryan Gerard

Human pain research aims to further the understanding of how pain is processed by the body. Studies require a reproducible, quantifiable, scalable, pain specific and safe stimulus. Using laser light to raise the temperature of the skin to painful levels is a good method of satisfying these conditions. The CO[2] laser is an ideal source because its infrared radiation is readily absorbed in the upper layers of the skin, where the free nerve endings of pain-conveying fibres are located, causing localised heating and evoking pain. A pain stimulator based on a CO[2] laser has been developed. It is computer controlled with a graphical interface so that non specialists can easily operate the laser. Safety features have been incorporated to protect the operator and the subject. These include activation of a shutter to block the beam and shut-down of the laser, when, for example, potentially harmful laser parameters are selected or abnormal signals are sent to the laser. The CO[2] laser normally operates in TEM[00] mode, i.e. the irradiance of the beam decreases roughly exponentially from the centre. This is not ideal for thermal stimulation, since it will generate a temperature that also has a peak in the centre of the beam. This will result in non-uniform activation of nerve fibres. Lenses have been developed to redistribute the energy of the beam to produce a flattened super Gaussian irradiance profile for uniform heating of the skin. The shape of the lenses was determined by geometrical optics. They work by refracting the more intense central part of the beam towards the periphery. Solution of the heat transfer equation by a finite differences method, confirmed that the super Gaussian profile generated by the bean shaper produces a more uniform temperature distribution in skin. The model was also used to predict how varying skin parameters, such as thickness and water content, affects the temperature generated by irradiation with a CO[2] laser beam. The predicted skin

Modification of the amorphous carbon films by the ns-laser irradiation

NASA Astrophysics Data System (ADS)

Grigonis, Alfonsas; Marcinauskas, Liutauras; Vinciunaite, Vinga; Raciukaitis, Gediminas

2011-10-01

The effect of a nanosecond laser irradiation of thin (60 and 145 nm) amorphous, diamond-like carbon films deposited on Si substrate by an ion beam deposition (IBD) from pure acetylene and acetylene/hydrogen (1:2) gas mixture was analyzed in this work. The films were irradiated with the infrared (IR) and ultraviolet (UV) radiation of the nanosecond Nd:YAG lasers working at the first (1.16 eV) and the third (3.48 eV) harmonics, using a multi-shot regime. The IR laser irradiation stimulated a minor increase in the fraction of sp2 bonds, causing a slight decrease in the hardness of the films and initiated SiC formation. Irradiation with the UV laser caused the formation of carbides and increased hydrogenization of the Si substrate and the fraction of sp2 sites. Spalliation and ablation were observed at a higher energy density and with a large number of laser pulses per spot.

Detection of chemical changes in bone after irradiation with Er,Cr:YSGG laser

NASA Astrophysics Data System (ADS)

Benetti, Carolina; Santos, Moises O.; Rabelo, Jose S.; Ana, Patrícia A.; Correa, Paulo R.; Zezell, Denise M.

2011-03-01

The use of laser for bone cutting can be more advantageous than the use of drill. However, for a safe clinical application, it is necessary to know the effects of laser irradiation on bone tissues. In this study, the Fourier Transform Infrared spectroscopy (FTIR) was used to verify the molecular and compositional changes promoted by laser irradiation on bone tissue. Bone slabs were obtained from rabbit's tibia and analyzed using ATR-FTIR. After the initial analysis, the samples were irradiated using a pulsed Er,Cr:YSGG laser (2780nm), and analyzed one more time. In order to verify changes due to laser irradiation, the area under phosphate (1300-900cm-1), amides (1680-1200cm-1), water (3600-2400cm-1), and carbonate (around 870cm-1 and between 1600-1300cm-1) bands were calculated, and normalized by phosphate band area (1300-900cm-1). It was observed that Er,Cr:YSGG irradiation promoted a significant decrease in the content of water and amides I and III at irradiated bone, evidencing that laser procedure caused an evaporation of the organic content and changed the collagen structure, suggesting that these changes may interfere with the healing process. In this way, these changes should be considered in a clinical application of laser irradiation in surgeries.

Method for mounting laser fusion targets for irradiation

DOEpatents

Fries, R. Jay; Farnum, Eugene H.; McCall, Gene H.

1977-07-26

Methods for preparing laser fusion targets of the ball-and-disk type are disclosed. Such targets are suitable for irradiation with one or two laser beams to produce the requisite uniform compression of the fuel material.

Intense laser pulse propagation in ionizing gases

NASA Astrophysics Data System (ADS)

Bian, Zhigang

2003-10-01

There have been considerable technological advances in the development of high intensity, short pulse lasers. However, high intensity laser pulses are subject to various laser-plasma instabilities. In this thesis, a theory is developed to study the scattering instability that occurs when a laser pulse propagates through and ionizes a gas. The instability is due to the intensity dependence of the ionization rate, which leads to a transversely structured free electron density. The instability is convective in the frame of laser pulse, but can have a relatively short growth length scaling as Lg˜k0/k2p where k0 is the laser wave number, k2p=w2p/c 2 and op is the plasma frequency. The most unstable perturbations correspond to a scattering angle for which the transverse wave number is around the plasma wave number, k p. The scattered light is frequency upshifted. The comparison between simple analytic theory and numerical simulation shows good agreement. Instabilities can drastically change the shape of the laser pulse and reduce the propagation distance of the laser pulse. Therefore, we change the propagation conditions and reduce the laser-plasma interaction possibilities in applications which require an interaction length well in excess of the Rayleigh length of the laser beam. One of the methods is to use a capillary to propagate the laser pulse. We studied the propagation of short pulses in a glass capillary. The propagation is simulated using the code WAKE, which has been modified to treat the case in which the simulation boundary is the wall of a capillary. Parameters that were examined include transmission efficiency of the waveguides as a function of gas pressure, laser intensity, and waveguide length, which is up to 40 Rayleigh lengths. The transmission efficiency decreases with waveguide length due to energy loss through the side-walls of the capillary. The loss increases with gas pressure due to ionization of the gas and scattering of the radiation. The

Tuning excitation laser wavelength for secondary resonance in low-intensity phase-selective laser-induced breakdown spectroscopy for in-situ analytical measurement of nanoaerosols

NASA Astrophysics Data System (ADS)

Xiong, Gang; Li, Shuiqing; Tse, Stephen D.

2018-02-01

In recent years, a novel low-intensity phase-selective laser-induced breakdown spectroscopy (PS-LIBS) technique has been developed for unique elemental-composition identification of aerosolized nanoparticles, where only the solid-phase nanoparticles break down, forming nanoplasmas, without any surrounding gas-phase breakdown. Additional work has demonstrated that PS-LIBS emissions can be greatly enhanced with secondary resonant excitation by matching the excitation laser wavelength with an atomic transition line in the formed nanoplasma, thereby achieving low limits of detection. In this work, a tunable dye laser is employed to investigate the effects of excitation wavelength and irradiance on in-situ PS-LIBS measurements of TiO2 nanoaerosols. The enhancement factor by resonant excitation can be 220 times greater than that for non-resonant cases under similar conditions. Moreover, the emitted spectra are unique for the selected resonant transition lines for a given element, suggesting the potential to make precise phase-selective and analyte-selective measurements of nanoparticles in a multicomponent multiphase system. The enhancement factor by resonant excitation is highly sensitive to excitation laser wavelength, with narrow excitation spectral windows, i.e., 0.012 to 0.023 nm (FWHM, full width at half maximum) for Ti (I) neutral atomic lines, and 0.051 to 0.139 nm (FWHM) for Ti (II) single-ionized atomic lines. Boltzmann analysis of the emission intensities, temporal response of emissions, and emission dependence on excitation irradiance are investigated to understand aspects of the generated nanoplasmas such as temperature, local thermodynamic equilibrium (LTE), and excitation mechanism.

Low- and high-dose laser irradiation effects on cell migration and destruction

NASA Astrophysics Data System (ADS)

Layton, Elivia; Gallagher, Kyra A.; Zukerman, Sara; Stevens, Brianna; Zhou, Feifan; Liu, Hong; Chen, Wei R.

2018-02-01

Metastases are the cause of more than 90 percent of cancer-related deaths. Current treatment methods, including chemotherapy, radiation, and surgery, fail to target the metastases effectively. One potential treatment for metastatic cancer is laser immunotherapy (LIT). LIT combines the use of a photothermal laser with an immunoadjuvant, Glycated Chitosan (GC). GC combined with single-walled carbon nanotubes (SWNTs) has proven to be a viable alternative to traditional cancer treatment methods, when under irradiation of laser with appropriate wavelength. In this study, the effects of low dose and high dose laser irradiation on metastatic pancreatic cancer cell migration were observed. It was found that low dose irradiation increased the migration rate, but the high dose irradiation significantly decreased the migration rate of the cancer cells. When using LIT, the goal is to kill tumor cells and to prompt the correct immune response. If the tumor were irradiated with a low dose, it would promote metastasis. If the dose of irradiation were too high, it would destroy the entire tumor and the immune response would not recognize the tumor. Therefore, the laser dose plays an important role in LIT, particularly when using SWNT as light absorbing agent. Our results from this study will delineate the optimal laser irradiation dose for destroying tumor cells and at the same time preserve and release tumor antigens as a precursor of antitumor immune response.

Simulation analysis of impulse characteristics of space debris irradiated by multi-pulse laser

NASA Astrophysics Data System (ADS)

Lin, Zhengguo; Jin, Xing; Chang, Hao; You, Xiangyu

2018-02-01

Cleaning space debris with laser is a hot topic in the field of space security research. Impulse characteristics are the basis of cleaning space debris with laser. In order to study the impulse characteristics of rotating irregular space debris irradiated by multi-pulse laser, the impulse calculation method of rotating space debris irradiated by multi-pulse laser is established based on the area matrix method. The calculation method of impulse and impulsive moment under multi-pulse irradiation is given. The calculation process of total impulse under multi-pulse irradiation is analyzed. With a typical non-planar space debris (cube) as example, the impulse characteristics of space debris irradiated by multi-pulse laser are simulated and analyzed. The effects of initial angular velocity, spot size and pulse frequency on impulse characteristics are investigated.

Controllable generation of reactive oxygen species by femtosecond-laser irradiation

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

Yan, Wei; He, Hao, E-mail: haohe@tju.edu.cn; Wang, Yintao

Femtosecond lasers have been advancing Biophotonics research in the past two decades with multiphoton microscopy, microsurgery, and photodynamic therapy. Nevertheless, laser irradiation is identified to bring photodamage to cells via reactive oxygen species (ROS) generation with unclear mechanism. Meanwhile, currently in biological researches, there is no effective method to provide controllable ROS production precisely, which originally is leaked from mitochondria during respiration and plays a key role in a lot of important cellular processes and cellular signaling pathways. In this study, we show the process of how the tightly focused femtosecond-laser induces ROS generation solely in mitochondria at the verymore » beginning and then release to cytosol if the stimulus is intense enough. At certain weak power levels, the laser pulses induce merely moderate Ca{sup 2+} release but this is necessary for the laser to generate ROS in mitochondria. Cellular original ROS are also involved with a small contribution. When the power is above a threshold, ROS are then released to cytosol, indicating photodamage overwhelming cellular repair ability. The mechanisms in those two cases are quite different. Those results clarify parts of the mechanism in laser-induced ROS generation. Hence, it is possible to further this optical scheme to provide controllable ROS generation for ROS-related biological researches including mitochondrial diseases and aging.« less

Simulations of Foils Irradiated by Finite Laser Spots

NASA Astrophysics Data System (ADS)

Phillips, Lee

2006-10-01

Recent proposed designs (Obenchain et al., Phys. Plasmas 13 056320 (2006)) for direct-drive ICF targets for energy applications involve high implosion velocities with lower laser energies combined with higher irradiances. The use of high irradiances increases the likelihood of deleterious laser plasma instabilities (LPI) that may lead, for example, to the generation of fast electrons. The proposed use of a 248 nm KrF laser is expected to minimize LPI, and this is being studied by experiments on NRL's NIKE laser. Here we report on simulations aimed at designing and interpreting these experiments. The 2d simulations employ a modification of the FAST code to ablate plasma from CH and DT foils using laser pulses with arbitrary spatial and temporal profiles. These include the customary hypergaussian NIKE profile, gaussian profiles, and combinations of these. The simulations model the structure of the ablating plasma and the absorption of the laser light, providing parameters for design of the experiment and indicating where the relevant LPI (two-plasmon, Raman) may be observed.

Effects of erbium,chromium:YSGG laser irradiation on canine mandibular bone.

PubMed

Kimura, Y; Yu, D G; Fujita, A; Yamashita, A; Murakami, Y; Matsumoto, K

2001-09-01

Only relatively few reports have described the morphological effects on bone produced by erbium,chromium: yttrium,scandium,gallium,garnet (Er,Cr:YSGG) laser irradiation, and none has investigated the atomic changes or estimated the temperature increases involved. The objectives of this study were to investigate the morphological, atomic, and temperature changes in irradiated areas during and after laser irradiation, and to evaluate the cutting effect on canine mandibular bone in vitro. Two canine mandibular bones were cut into 3 to 5 cm pieces and irradiated by an Er,Cr:YSGG laser utilizing a water-air spray at 5 W and 8 Hz for 10 or 30 seconds. During and after laser irradiation, temperature increases in the irradiated areas were measured by thermography. The samples were then observed by stereoscopy and scanning electron microscopy to determine morphological changes and by energy dispersive x-ray spectroscopy to evaluate atomic alterations. Regular holes or grooves having sharp edges and smooth walls were produced, but no melting or carbonization was observed. The maximum temperature increase was an average 12.6 degrees C for 30-second irradiation. The continuous time of a temperature increase of more than 10 degrees C was consistently less than 10 seconds. An atomic analytical examination revealed that the calcium:phosphorus ratio was not significantly changed between the lased and unlased areas (P>0.0 1). These results showed that the Er,Cr:YSGG laser cuts canine mandibular bone effectively without burning, melting, or altering the calcium:phosphorus ratio of the irradiated bone.

Lasers Induced Damage in Optical Materials: 1985. Proceedings of the Symposium on Optical Materials for High-Power Lasers (17th) Held in Boulder, Colorado on October 28-30, 1985

DTIC Science & Technology

1988-07-01

optical coatings.[lj In * single and multilayer anatase TiO 2 coatings, sufficiently intense pulsed laser irradiation at 532 nm led to observation of...temperatures of pulsed laser - irradiated anatase coatings have been computed from Stokes/anti-Stokes band intensity ratios at zero time delay as a function of...Adar Time-Resolved Temperature Determinations from Raman Scattering of TiO𔃼 Coatings During Pulsed Laser Irradiation

In Vitro UV-Visible Spectroscopy Study of Yellow Laser Irradiation on Human Blood

NASA Astrophysics Data System (ADS)

Fuad, Siti Sakinah Mohd; Suardi, N.; Mustafa, I. S.

2018-04-01

This experimental study was performed to investigate the effect of low level yellow laser of 589nm wavelength with various laser irradiation time. Human blood samples with random diseases are irradiated with yellow laser of power density of 450mW/cm2 from 10 minutes to 60 minutes at 10 minutes intervals. The morphology of the red blood cell were also observed for different irradiation time. The result shows that there is a significant different in the absorption of light with varying laser irradiation time (p<0.01). The maximum absorption recorded at 40 minutes of irradiation at 340nm peak. Blood smear of the samples reveals that there are observable changes in the morphology of the red blood cell at 40 minutes and 60 minutes of irradiation.

Bactericidal effect of Nd:YAG laser irradiation in endodontics

NASA Astrophysics Data System (ADS)

Aun, Carlos E.; Barberini, Alexandre F.; Camargo, Selma C. C.; Silva Kfouri, Luciana; Lorenzetti Simionato, Maria R.

1999-05-01

The success of endodontic therapy is based on the elimination of bacterial colonization from the endodontic system and periapical tissues. Recent studies have been showing the bactericidal effect of laser in root canal treatment. The propose of the study is to evaluate the effect of Nd:YAG laser irradiation in contaminated root canal treatment. The propose of the study is to evaluate the effect of Nd:YAG laser irradiation in contaminated root canals from upper central incisor. For the experiment 12 teeth were selected, respect at the apical third, sterilized, and 10 μm Streptococcus sanguis liquid culture were inoculated in the root canals. The laser test groups were irradiated with Nd:YAG laser at standard setting of 15Hz, 100mj and 1,5 W for 10, 20 and 30 seconds each in slow helicoidal movements from the apex to the top using a 300 micrometers fiber. After the procedure the specimens were placed in Tryptic Soy Agar, the number of colony forming units was evaluated. The experiment showed a significant reduction on viability of Streptococcus sanguis at the respective time of 20 and 30 seconds.

Effect of laser intensity on radio frequency emissions from laser induced breakdown of atmospheric air

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

Vinoth Kumar, L.; Manikanta, E.; Leela, Ch.

2016-06-07

The studies on the effect of input laser intensity, through the variation of laser focusing geometry, on radio frequency (RF) emissions, over 30–1000 MHz from nanosecond (ns) and picosecond (ps) laser induced breakdown (LIB) of atmospheric air are presented. The RF emissions from the ns and ps LIB were observed to be decreasing and increasing, respectively, when traversed from tight to loose focusing conditions. The angular and radial intensities of the RF emissions from the ns and ps LIB are found to be consistent with sin{sup 2}θ/r{sup 2} dependence of the electric dipole radiation. The normalized RF emissions were observed tomore » vary with incident laser intensity (Iλ{sup 2}), indicating the increase in the induced dipole moment at moderate input laser intensities and the damping of radiation due to higher recombination rate of plasma at higher input laser intensities.« less

Two-photon excitation laser scanning microscopy of rabbit nasal septal cartilage following Nd:YAG-laser-mediated stress relaxation

NASA Astrophysics Data System (ADS)

Kim, Charlton C.; Wallace, Vincent P.; Coleno, Mariah L.; Dao, Xavier; Tromberg, Bruce J.; Wong, Brian J.

2000-04-01

Laser irradiation of hyaline cartilage result in stable shape changes due to temperature dependent stress relaxation. In this study, we determined the structural changes in chondrocytes within rabbit nasal septal cartilage tissue over a 12-day period using a two-photon laser scanning microscope (TPM) following Nd:YAG laser irradiation. During laser irradiation surface temperature, stress relaxation, and diffuse reflectance, were measured dynamically. Each specimen received one or two sequential laser exposures. The cartilage reached a peak surface temperature of about 61 degrees C during irradiation. Cartilage denatured in 50 percent EtOH was used as a positive control. TPM was performed to detect the fluorescence emission from the chondrocytes. Images of chondrocytes were obtained at depths up to 150 microns, immediately following laser exposure, and also following 12 days in culture. Few differences in the pattern or intensity of fluorescence was observed between controls and irradiated specimens imaged immediately following exposure, regardless of the number of laser pulses. However, following twelve days in tissue culture, the irradiated specimens increase, whereas the native tissue diminishes, in intensity and distribution of fluorescence in the cytoplasm. In contrast, the positive control shows only extracellular matrices and empty lacuna, feature consistent with cell membrane lysis.

Pair production by high intensity picosecond laser interacting with thick solid target at XingGuangIII

NASA Astrophysics Data System (ADS)

Wu, Yuchi; Dong, Kegong; Yan, Yonghong; Zhu, Bin; Zhang, Tiankui; Chen, Jia; Yu, Minghai; Tan, Fang; Wang, Shaoyi; Han, Dan; Lu, Feng; Gu, Yuqiu

2017-06-01

An experiment for pair production by high intensity laser irradiating thick solid targets is present. The experiment used picosecond beam of the XingGuangIII laser facility, with intensities up to several 1019 W/cm2, pulse durations about 0.8 ps and laser energies around 120 J. Pairs were generated from 1 mm-thick tantalum disk targets with different diameters from 1 mm to 10 mm. Energy spectra of hot electron from targetrear surface represent a Maxwellian distribution and obey a scaling of ∼(Iλ2)0.5. Large quantity of positrons were observed at the target rear normal direction with a yield up to 2.8 × 109 e+/sr. Owing to the target rear surface sheath field, the positrons behave as a quasi-monoenergetic beam with peak energy of several MeV. Our experiment shows that the peak energy of positron beam is inversely proportional to the target diameter.

Experimental Study of Proton Acceleration from Ultra Intense Laser Matter Interactions

NASA Astrophysics Data System (ADS)

Paudel, Yadab Kumar

This dissertation describes proton and ion acceleration measurements from high intensity (˜ 1019 Wcm-2) laser interactions with thin foil targets. Protons and ions accelerated from the back surface of a target driven by a high intensity laser are detected using solid-state nuclear track detector CR39. A simple digital imaging technique, with an adjustable halogen light source shined on CR39 and use of a digital camera with suitable f-number and exposure time, is used to detect particles tracks. This new technique improves the quality 2D image with vivid track patterns in CR39. Our technique allows us to quickly record and sort CR39 pieces for further analysis. This is followed by detailed quantitative information on the protons and ions. Protons and multicharged ions generated from high-intensity laser interactions with thin foil targets have been studied with a 100 TW laser system. Protons/ions with energies up to 10 MeV are accelerated either from the front or the rear surface of the target material. We have observed for the first time a self-radiograph of the target with a glass stalk holding the target itself in the stacked radiochromic films (RCF) placed behind the target. The self-radiography indicates that the fast ions accelerated backward, in a direction opposite to the laser propagation, are turning around in strong magnetic fields. This unique result is a signature of long-living (ns time scale) magnetic fields in the expanding plasma, which are important in energy transport during the intense laser irradiation and have never been considered in the previous studies. The magnetic fields induced by the main pulse near the absorption point expand rapidly with the backward accelerated protons in the pre-formed plasma. The protons are rotated by these magnetic fields and they are recorded in the RCF, making the self-radiography. Angular profiles of protons and multicharged ions accelerated from the target rear surface have been studied with the subpicosecond

Intense laser-driven ion beams in the relativistic-transparency regime: acceleration, control and applications

NASA Astrophysics Data System (ADS)

Fernandez, Juan C.

2016-10-01

Laser-plasma interactions in the novel regime of relativistically-induced transparency have been harnessed to generate efficiently intense ion beams with average energies exceeding 10 MeV/nucleon (>100 MeV for protons) at ``table-top'' scales. We have discovered and utilized a self-organizing scheme that exploits persisting self-generated plasma electric ( 0.1 TV/m) and magnetic ( 104 Tesla) fields to reduce the ion-energy (Ei) spread after the laser exits the plasma, thus separating acceleration from spread reduction. In this way we routinely generate aluminum and carbon beams with narrow spectral peaks at Ei up to 310 MeV and 220 MeV, respectively, with high efficiency ( 5%). The experimental demonstration has been done at the LANL Trident laser with 0.12 PW, high-contrast, 0.65 ps Gaussian laser pulses irradiating planar foils up to 250 nm thick. In this regime, Ei scales empirically with laser intensity (I) as I 1 / 2. Our progress is enabled by high-fidelity, massive computer simulations of the experiments. This work advances next-generation compact accelerators suitable for new applications. E . g ., a carbon beam with Ei 400 MeV and 10% energy spread is suitable for fast ignition (FI) of compressed DT. The observed scaling suggests that is feasible with existing target fabrication and PW-laser technologies, using a sub-ps laser pulse with I 2.5 ×1021 W/cm2. These beams have been used on Trident to generate warm-dense matter at solid-densities, enabling us to investigate its equation of state and mixing of heterogeneous interfaces purely by plasma effects distinct from hydrodynamics. They also drive an intense neutron-beam source with great promise for important applications such as active interrogation of shielded nuclear materials. Considerations on controlling ion-beam divergence for their increased utility are discussed. Funded by the LANL LDRD program.

Efficacy of Conventional Laser Irradiation Versus a New Method for Gingival Depigmentation (Sieve Method): A Clinical Trial.

PubMed

Houshmand, Behzad; Janbakhsh, Noushin; Khalilian, Fatemeh; Talebi Ardakani, Mohammad Reza

2017-01-01

Introduction: Diode laser irradiation has recently shown promising results for treatment of gingival pigmentation. This study sought to compare the efficacy of 2 diode laser irradiation protocols for treatment of gingival pigmentations, namely the conventional method and the sieve method. Methods: In this split-mouth clinical trial, 15 patients with gingival pigmentation were selected and their pigmentation intensity was determined using Dummett's oral pigmentation index (DOPI) in different dental regions. Diode laser (980 nm wavelength and 2 W power) was irradiated through a stipple pattern (sieve method) and conventionally in the other side of the mouth. Level of pain and satisfaction with the outcome (both patient and periodontist) were measured using a 0-10 visual analog scale (VAS) for both methods. Patients were followed up at 2 weeks, one month and 3 months. Pigmentation levels were compared using repeated measures of analysis of variance (ANOVA). The difference in level of pain and satisfaction between the 2 groups was analyzed by sample t test and general estimate equation model. Results: No significant differences were found regarding the reduction of pigmentation scores and pain and scores between the 2 groups. The difference in satisfaction with the results at the three time points was significant in both conventional and sieve methods in patients ( P = 0.001) and periodontists ( P = 0.015). Conclusion: Diode laser irradiation in both methods successfully eliminated gingival pigmentations. The sieve method was comparable to conventional technique, offering no additional advantage.

LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Dynamics of splashing of molten metals during irradiation with single CO2 laser pulses

NASA Astrophysics Data System (ADS)

Arutyunyan, R. V.; Baranov, V. Yu; Bol'shov, Leonid A.; Dolgov, V. A.; Malyuta, D. D.; Mezhevov, V. S.; Semak, V. V.

1988-03-01

An experimental investigation was made of the dynamics of the loss of the melt as a result of interaction with single-mode CO2 laser radiation pulses of 5-35 μs duration. The dynamics of splashing of the melt during irradiation with short pulses characterized by a Gaussian intensity distribution differed from that predicted by models in which the distribution of the vapor pressure was assumed to be radially homogeneous.

Effect of laser irradiation on the early-stage seed formation of laser-induced submicrometer-scale silica spheres

NASA Astrophysics Data System (ADS)

Kim, H. J.; Ha, S. Y.; Hong, Y. J.; Nam, S.; Oh, S. Y.; Lim, C.

2014-04-01

We describe the effect of irradiation on the early-stage seed formation of submicrometer-scale (SS) SiO2 spheres by a laser-induced process. A quartz cell containing chemical reagents was exposed to a pulsed laser (Nd:YAG, 532 nm) tuned to various energy densities, while SiO2 SS spheres are synthesized in the quartz cell by the Stöber, Fink, and Bohn method. Higher laser energy densities typically produce wider size distributions. In particular, bidisperse SiO2 spheres were obtained when the laser energy density was 1.15 J/cm2. The size distributions were widest with 1.15 J/cm2 and narrowest with 0.33 J/cm2 laser energy density. However, the compositions of the SiO2 SS spheres were not affected by laser irradiation, and we observed by the energy-dispersive X-ray spectroscopy that the compositions of the irradiated and nonirradiated SiO2 SS spheres were the same.

Investigations of ultrafast charge dynamics in laser-irradiated targets by a self probing technique employing laser driven protons

NASA Astrophysics Data System (ADS)

Ahmed, H.; Kar, S.; Cantono, G.; Nersisyan, G.; Brauckmann, S.; Doria, D.; Gwynne, D.; Macchi, A.; Naughton, K.; Willi, O.; Lewis, C. L. S.; Borghesi, M.

2016-09-01

The divergent and broadband proton beams produced by the target normal sheath acceleration mechanism provide the unique opportunity to probe, in a point-projection imaging scheme, the dynamics of the transient electric and magnetic fields produced during laser-plasma interactions. Commonly such experimental setup entails two intense laser beams, where the interaction produced by one beam is probed with the protons produced by the second. We present here experimental studies of the ultra-fast charge dynamics along a wire connected to laser irradiated target carried out by employing a 'self' proton probing arrangement - i.e. by connecting the wire to the target generating the probe protons. The experimental data shows that an electromagnetic pulse carrying a significant amount of charge is launched along the wire, which travels as a unified pulse of 10s of ps duration with a velocity close to speed of light. The experimental capabilities and the analysis procedure of this specific type of proton probing technique are discussed.

Biodegradability of poly(lactic-co-glycolic acid) after femtosecond laser irradiation

PubMed Central

Shibata, Akimichi; Yada, Shuhei; Terakawa, Mitsuhiro

2016-01-01

Biodegradation is a key property for biodegradable polymer-based tissue scaffolds because it can provide suitable space for cell growth as well as tailored sustainability depending on their role. Ultrashort pulsed lasers have been widely used for the precise processing of optically transparent materials, including biodegradable polymers. Here, we demonstrated the change in the biodegradation of a poly(lactic-co-glycolic acid) (PLGA) following irradiation with femtosecond laser pulses at different wavelengths. Microscopic observation as well as water absorption and mass change measurement revealed that the biodegradation of the PLGA varied significantly depending on the laser wavelength. There was a significant acceleration of the degradation rate upon 400 nm-laser irradiation, whereas 800 nm-laser irradiation did not induce a comparable degree of change. The X-ray photoelectron spectroscopy analysis indicated that laser pulses at the shorter wavelength dissociated the chemical bonds effectively, resulting in a higher degradation rate at an early stage of degradation. PMID:27301578

Pulsed-Laser Irradiation Space Weathering of a Carbonaceous Chondrite

NASA Astrophysics Data System (ADS)

Thompson, M. S.; Keller, L. P.; Christoffersen, R.; Loeffler, M. J.; Morris, R. V.; Graff, T. G.; Rahman, Z.

2017-07-01

We used pulsed laser irradiation of the Murchison meteorite to simulate space weathering processes in the laboratory. We analyzed changes in the spectral, chemical, and microstructural characteristics of the material after irradiation.

Factors affecting color strength of printing on film-coated tablets by UV laser irradiation: TiO2 particle size, crystal structure, or concentration in the film, and the irradiated UV laser power.

PubMed

Hosokawa, Akihiro; Kato, Yoshiteru

2011-08-01

The purpose of this article is to study factors affecting color strength of printing on film-coated tablets by ultraviolet (UV) laser irradiation: particle size, crystal structure, or concentration of titanium dioxide (TiO2) in film, and irradiated UV laser power. Hydroxypropylmethylcellulose films containing 4.0% of TiO2, of which BET particle sizes were ranging from 126.1 to 219.8 nm, were irradiated 3.14W of UV laser at a wavelength 355 nm to study effects of TiO2 particle size and crystal structure on the printing. The films containing TiO2 concentration ranging from 1.0 to 7.7% were irradiated 3.14 or 5.39W of the UV laser to study effect of TiO2 concentration on the printing. The film containing 4.0% of TiO2, was irradiated the UV laser up to 6.42W to study effect of the UV laser power on the printing. The color strength of the printed films was estimated by a spectrophotometer as total color difference (dE). Particle size, crystal structure, and concentration of TiO2 in the films did not affect the printing. In the relationship between the irradiated UV laser power and dE, there found an inflection point (1.6W). When the UV laser power was below 1.6W, the films were not printed. When it was beyond the point, total color difference increased linearly in proportion with the irradiated laser power. The color strength of the printing on film was not changed by TiO2 particle size, crystal structure, and concentration, but could be controlled by regulating the irradiated UV laser power beyond the inflection point.

Multipulse nanosecond laser irradiation of silicon for the investigation of surface morphology and photoelectric properties

NASA Astrophysics Data System (ADS)

Sardar, Maryam; Chen, Jun; Ullah, Zaka; Jelani, Mohsan; Tabassum, Aasma; Cheng, Ju; Sun, Yuxiang; Lu, Jian

2017-12-01

We irradiate the single crystal boron-doped silicon (Si) with different number of laser pulses at constant fluence (7.5 J cm-2) in ambient air using Nd:YAG laser and examine its surface morphology and photoelectric properties in details. The results obtained from optical micrographs reveal the increase in heat affected zone (HAZ) and melted area of laser irradiated Si with increasing number of laser pulses. The SEM micrographs evidence the formation of various surface morphologies like laser induced periodic surface structures, crater, microcracks, clusters, cavities, pores, trapped bubbles, nucleation sites, micro-bumps, redeposited material and micro- and nano-particles on the surface of irradiated Si. The surface profilometry analysis informs that the depth of crater is increased with increase in number of incident laser pulses. The spectroscopic ellipsometry reveals that the multipulse irradiation of Si changes its optical properties (refractive index and extinction coefficient). The current-voltage (I-V) characteristic curves of laser irradiated Si show that although the multipulse laser irradiation produces considerable number of surface defects and damages, the electrical properties of Si are well sustained after the multipulse irradiation. The current findings suggest that the multipulse irradiation can be an effective way to tune the optical properties of Si for the fabrication of wide range of optoelectronic devices.

Ablation of gold irradiated by femtosecond laser pulse: Experiment and modeling

NASA Astrophysics Data System (ADS)

Ashitkov, S. I.; Komarov, P. S.; Zhakhovsky, V. V.; Petrov, Yu V.; Khokhlov, V. A.; Yurkevich, A. A.; Ilnitsky, D. K.; Inogamov, N. A.; Agranat, M. B.

2016-11-01

We report on the ablation phenomena in gold sample irradiated by femtosecond laser pulses of moderate intensity. Dynamics of optical constants and expansion of a heated surface layer was investigated in a range from picosecond up to subnanosecond using ultrafast interferometry. Also morphology of the ablation craters and value of an ablation threshold (for absorbed fluence) were measured. The experimental data are compared with simulations of mass flows obtained by two-temperature hydrodynamics and molecular dynamics methods. Simulation shows evolution of a thin surface layer pressurized by a laser pulse. Unloading of the pressurized layer proceeds together with electron-ion thermalization, melting, cavitation and spallation of a part of surface liquid layer. The experimental and simulation results on two-temperature physics and on a fracture, surface morphology and strength of liquid gold at a strain rate ∼ 109 s-1 are discussed.

The Interaction of Intense Laser Pulses with Preformed Plasmas for Fast Ignitor Studies

NASA Astrophysics Data System (ADS)

MacKinnon, A. J.

1998-11-01

The understanding of the interaction of intense picosecond laser pulses with preformed plasmas is essential for the fast ignitor concept. One of the major issues for this scheme concerns the propagation of ultra intense laser pulses through near critical density plasmas. Measurements of self-channelling of picosecond pulses due to relativistic and ponderomotive expulsion effects have recently been obtained in preformed plasmas at laser irradiances between 5-9x10^18 Wcm-2 footnote M. Borghesi et al, Phys. Rev Lett 78, 879 (1997).. The channel expansion after the laser pulse has been measured and an expansion velocity up to 1x10^9cms-1. was observed, implying ion energies around 1MeV. In addition, it was observed via Faraday rotation of an optical probe that the self focused channel is surrounded by a multi-megagauss magnetic field as predicted by 3D PIC simulations footnote A. Pukhov and J. Meyer-ter-Vehn, Phys. Rev Lett 76, 3975 (1996); M. Borghesi et al, Phys. Rev. Lett. 80, 5137 (1998).. The existence of this magnetic field is important for magnetic self-channelling of the relativistic electrons to high plasma densities. Good agreement was observed between the measurements and the 3D PIC simulations. The experimental results and PIC simulations will be presented and their relevance to the fast ignitor concept will be discussed.

Laser treatment of cutaneous lesions with image-guided fine spot-scanning irradiation

NASA Astrophysics Data System (ADS)

Nitta, Isami; Zhao, Xuefeng; Kanno, Akihiro; Kan, Yasushi; Yoshimasa, Takezawa; Maruyama, Tomohiro; Maeda, Yoshitaka

2007-11-01

We propose a new laser irradiation method for the treatment of cutaneous lesions in plastic surgery. In general, lasers with a spot size of 1 to 10 mm are used in irradiation on diseased skin. Although the target absorbs more light energy according to the theory of selective photothermolysis, the surrounding tissue, however, is still somewhat damaged. In proposed method, an f-theta lens, which is assembled by a shrink fitter, focuses the irradiation laser beam to a very fine spot with the size of 125 μm. Guided by the captured object-image, such laser beam is conducted by a pair of galvanometer-driven mirrors to irradiate only the desired tissue target without thermal damage to surrounding tissue. Moreover, an optical coherence tomography, whose probe is capable of wide field of view, can be used to provide the guidance information for the best treatment. The usefulness of the developed laser therapy apparatus was demonstrated by performing an experiment on the removal of tattoo pigment.

Manipulating the mitochondria activity in human hepatic cell line Huh7 by low-power laser irradiation

PubMed Central

Lynnyk, Anna; Lunova, Mariia; Jirsa, Milan; Egorova, Daria; Kulikov, Andrei; Kubinová, Šárka; Lunov, Oleg; Dejneka, Alexandr

2018-01-01

Low-power laser irradiation of red light has been recognized as a promising tool across a vast variety of biomedical applications. However, deep understanding of the molecular mechanisms behind laser-induced cellular effects remains a significant challenge. Here, we investigated mechanisms involved in the death process in human hepatic cell line Huh7 at a laser irradiation. We decoupled distinct cell death pathways targeted by laser irradiations of different powers. Our data demonstrate that high dose laser irradiation exhibited the highest levels of total reactive oxygen species production, leading to cyclophilin D-related necrosis via the mitochondrial permeability transition. On the contrary, low dose laser irradiation resulted in the nuclear accumulation of superoxide and apoptosis execution. Our findings offer a novel insight into laser-induced cellular responses, and reveal distinct cell death pathways triggered by laser irradiation. The observed link between mitochondria depolarization and triggering ROS could be a fundamental phenomenon in laser-induced cellular responses. PMID:29541521

Effect of 830 nm Diode Laser Irradiation of Root Canal on Bond Strength of Metal and Fiber Post.

PubMed

Strefezza, Claudia; Amaral, Marcello Magri; Quinto, José; Gouw-Soares, Sheila Cynthia; Zamataro, Claudia Bianchi; Zezell, Denise Maria

2018-05-16

The correct selections of the cementing agent, the endodontic post material and placement protocol are critical to provide an increased longevity of the teeth that went through endodontic treatment. The irradiation with diode laser before post cementation, can promote an antimicrobial effect. However, there is a lack of information about the effect of 830 nm diode laser on the post bond strength. This study analyzed the effect of dentin root canal irradiation with high-intensity diode laser, at 830 nm, operating in continuous or pulsed mode, on the retention of metal or fiber posts, cemented with self-etching resinous composite (Panavia F) and zinc phosphate cement (ZnPO 4 ). Human roots were irradiated with diode laser (continuous and pulsed mode). The fiber posts were luted with Panavia F and the metal posts with Panavia F or ZnPO 4 cement. Specimens were sectioned into three sections (cervical, middle, and apical). The bond strength was measured by a push-out mechanical analysis. For the statistical analysis, a three-way ANOVA test was applied following a Tukey's pairwise comparison with a significance level of p = 0.05. The irradiated groups presented higher bond strength compared with nonirradiated group (p < 0.05), and the cervical and middle thirds presented higher on bond strength than the apical. The association of metal post and Panavia F presented higher bond strength when irradiated on continuous mode (p < 0.05). Fiber post and Panavia F presented higher bond strength associated to pulsed mode. The mode seems not to make a significant difference. These results corroborate the importance of the post bond to dentin and root canal debris removal to increase the tooth longevity. It was shown that the dentin to post bond strength were enhanced by the diode laser irradiation either on continuous or pulsed modes.

Large-scale studies of ion acceleration in laser-generated plasma at intensities from 1010 W/cm2 to 1019 W/cm2

NASA Astrophysics Data System (ADS)

Torrisi, L.

2018-02-01

A large-scale study of ion acceleration in laser-generated plasma, extended to intensities from 1010 W/cm2 up to 1019 W/cm2, is presented. Aluminium thick and thin foils were irradiated in high vacuum using different infrared lasers and pulse durations from ns up to fs scale. Plasma was monitored mainly using SiC detectors employed in time-of-flight configuration. Protons and aluminium ions, at different energies and yields, were measured as a function of the laser intensity. The discontinuity region between particle acceleration from both the backward plasma (BPA) in thick targets and the forward plasma in thin foils in the target normal sheath acceleration (TNSA) regimes were investigated.

Pulsed UV laser-induced modifications in optical and structural characteristics of alpha-irradiated PM-355 SSNTD.

PubMed

Alghamdi, S S; Farooq, W A; Baig, M R; Algarawi, M S; Alrashidi, Talal Mohammed; Ali, Syed Mansoor; Alfaramawi, K

2017-10-01

Pre- and postalpha-exposed PM-355 detectors were irradiated using UV laser with different number of pulses (100, 150, 200, 300, and 400). UV laser beam energy of 20mJ per pulse with a pulse width of 9ns was incident on an area of 19.6mm 2 of the samples. XRD spectra indicated that for both reference and UV-irradiated samples, the structure is amorphous, but the crystallite size increases upon UV irradiation. The same results were obtained from SEM analysis. Optical properties of PM-355 polymeric solid-state nuclear track detectors were also investigated. Absorbance measurements for all PM-355 samples in the range of 200-400nm showed that the absorption edge had a blue shift up to a certain value, and then, it had an oscillating behavior. Photoluminescence spectra of PM-355 at 250nm revealed a decrease in the broadband peak intensity as a function of the number of UV pulses, while the wavelengths corresponding to the peaks had random shifts. Copyright © 2017 Elsevier Ltd. All rights reserved.

Control of intracellular ionic concentrations by mid-infrared laser irradiation

NASA Astrophysics Data System (ADS)

Takebe, G.; Yamauchi, T.; Shimizu, Y.; Dougakiuchi, T.

2018-02-01

We successfully induced intracellular ion concentration changes in live culture cells using mid-infrared laser irradiation. The laser used for irradiation was a quantum cascade laser with a wavelength of 6.1 micrometers. We tuned the power of the laser to be between 30 to 60 mW at the sample. Cell lines, namely HeLa and Chinese hamster ovary cell lines, were used. They were cultured on specially fabricated silicon-bottom dishes. Live cells were stained using ion-sensitive dyes such as Calcium Green-1. The mid-infrared light was incident on the cell samples from the bottom of the dish through the silicon plate, and fluorescence imaging of the ion concentrations was performed using an upright fluorescence microscope placed on top of the sample stage. The mid-infrared lasers were operated in the continuous wave mode and light irradiations onto the cells were temporally controlled using a mechanical shutter in a periodical on-and-off pattern in the second timescale. The cells showed oscillations in their ionic concentration, which was synchronized with the periodical mid-infrared irradiation, and the threshold power needed for evoking the ion concentration change was dependent on the cell types and ion species. These results demonstrated that mid-infrared light directly changed the ionic response within cells and had the ability to change cell functions.

Nonlinear increase of X-ray intensities from thin foils irradiated with a 200 TW femtosecond laser

PubMed Central

Faenov, A. Ya.; Colgan, J.; Hansen, S. B.; Zhidkov, A.; Pikuz, T. A.; Nishiuchi, M.; Pikuz, S. A.; Skobelev, I. Yu.; Abdallah, J.; Sakaki, H.; Sagisaka, A.; Pirozhkov, A. S.; Ogura, K.; Fukuda, Y.; Kanasaki, M.; Hasegawa, N.; Nishikino, M.; Kando, M.; Watanabe, Y.; Kawachi, T.; Masuda, S.; Hosokai, T.; Kodama, R.; Kondo, K.

2015-01-01

We report, for the first time, that the energy of femtosecond optical laser pulses, E, with relativistic intensities I > 1021  W/cm2 is efficiently converted to X-ray radiation, which is emitted by “hot” electron component in collision-less processes and heats the solid density plasma periphery. As shown by direct high-resolution spectroscopic measurements X-ray radiation from plasma periphery exhibits unusual non-linear growth ~E4–5 of its power. The non-linear power growth occurs far earlier than the known regime when the radiation reaction dominates particle motion (RDR). Nevertheless, the radiation is shown to dominate the kinetics of the plasma periphery, changing in this regime (now labeled RDKR) the physical picture of the laser plasma interaction. Although in the experiments reported here we demonstrated by observation of KK hollow ions that X-ray intensities in the keV range exceeds ~1017  W/cm2, there is no theoretical limit of the radiation power. Therefore, such powerful X-ray sources can produce and probe exotic material states with high densities and multiple inner-shell electron excitations even for higher Z elements. Femtosecond laser-produced plasmas may thus provide unique ultra-bright X-ray sources, for future studies of matter in extreme conditions, material science studies, and radiography of biological systems. PMID:26330230

Nonlinear increase of X-ray intensities from thin foils irradiated with a 200 TW femtosecond laser

DOE PAGES

Faenov, A. Ya.; Colgan, J.; Hansen, S. B.; ...

2015-09-02

We report, for the first time, that the energy of femtosecond optical laser pulses, E, with relativistic intensities I > 10 21 W/cm 2 is efficiently converted to X-ray radiation, which is emitted by “hot” electron component in collision-less processes and heats the solid density plasma periphery. As shown by direct high-resolution spectroscopic measurements X-ray radiation from plasma periphery exhibits unusual non-linear growth ~E 4–5 of its power. The non-linear power growth occurs far earlier than the known regime when the radiation reaction dominates particle motion (RDR). Nevertheless, the radiation is shown to dominate the kinetics of the plasma periphery,more » changing in this regime (now labeled RDKR) the physical picture of the laser plasma interaction. Although in the experiments reported here we demonstrated by observation of KK hollow ions that X-ray intensities in the keV range exceeds ~10 17 W/cm 2, there is no theoretical limit of the radiation power. Therefore, such powerful X-ray sources can produce and probe exotic material states with high densities and multiple inner-shell electron excitations even for higher Z elements. As a result, femtosecond laser-produced plasmas may thus provide unique ultra-bright X-ray sources, for future studies of matter in extreme conditions, material science studies, and radiography of biological systems.« less

Numerical simulation of temperature field in K9 glass irradiated by ultraviolet pulse laser

NASA Astrophysics Data System (ADS)

Wang, Xi; Fang, Xiaodong

2015-10-01

The optical component of photoelectric system was easy to be damaged by irradiation of high power pulse laser, so the effect of high power pulse laser irradiation on K9 glass was researched. A thermodynamic model of K9 glass irradiated by ultraviolet pulse laser was established using the finite element software ANSYS. The article analyzed some key problems in simulation process of ultraviolet pulse laser damage of K9 glass based on ANSYS from the finite element models foundation, meshing, loading of pulse laser, setting initial conditions and boundary conditions and setting the thermal physical parameters of material. The finite element method (FEM) model was established and a numerical analysis was performed to calculate temperature field in K9 glass irradiated by ultraviolet pulse laser. The simulation results showed that the temperature of irradiation area exceeded the melting point of K9 glass, while the incident laser energy was low. The thermal damage dominated in the damage mechanism of K9 glass, the melting phenomenon should be much more distinct.

Study of laser preheating dependence on laser wavelength and intensity for MagLIF

NASA Astrophysics Data System (ADS)

Wei, M. S.; Harvey-Thompson, A. J.; Glinsky, M.; Nagayama, T.; Weis, M.; Geissel, M.; Peterson, K.; Fooks, J.; Krauland, C.; Giraldez, E.; Davies, J.; Campbell, E. M.; Bahr, R.; Edgell, D.; Stoeckl, C.; Glebov, V.; Emig, J.; Heeter, R.; Strozzi, D.

2017-10-01

The magnetized liner inertial fusion (MagLIF) scheme requires preheating underdense fuel to 100's eV temperature by a TW-scale long pulse laser via collisional absorption. To better understand how laser preheat scales with laser wavelength and intensity as well as to provide data for code validation, we have conducted a well-characterized experiment on OMEGA to directly compare laser propagation, energy deposition and laser plasma instabilities (LPI) using 2 ω (527 nm) and 3 ω (351 nm) lasers with intensity in the range of (1-5)x1014 Wcm-2. The laser beam (1 - 1.5 ns square pulse) enters the gas-filled plastic liner though a 2-µm thick polyimide window to heat an underdense Ar-doped deuterium gas with electron density of 5.5% of critical density. Laser propagation and plasma temperature are diagnosed by time-resolved 2D x-ray images and Ar emission spectroscopy, respectively. LPI is monitored by backscattering and hard x-ray diagnostics. The 2 ω beam propagation shows a noticeable larger lateral spread than the 3 ω beam, indicating laser spray due to filamentation. LPI is observed to increase with laser intensity and the 2 ω beam produces more hot electrons compared with the 3 ω beam under similar conditions. Results will be compared with radiation hydrodynamic simulations. Work supported by the U.S. DOE ARPA-E and NNSA.

Microjet formation and hard x-ray production from a liquid metal target irradiated by intense femtosecond laser pulses

NASA Astrophysics Data System (ADS)

Lar'kin, A.; Uryupina, D.; Ivanov, K.; Savel'ev, A.; Bonnet, T.; Gobet, F.; Hannachi, F.; Tarisien, M.; Versteegen, M.; Spohr, K.; Breil, J.; Chimier, B.; Dorchies, F.; Fourment, C.; Leguay, P.-M.; Tikhonchuk, V. T.

2014-09-01

By using a liquid metal as a target one may significantly enhance the yield of hard x-rays with a sequence of two intense femtosecond laser pulses. The influence of the time delay between the two pulses is studied experimentally and interpreted with numerical simulations. It was suggested that the first arbitrary weak pulse produces microjets from the target surface, while the second intense pulse provides an efficient electron heating and acceleration along the jet surface. These energetic electrons are the source of x-ray emission while striking the target surface. The microjet formation is explained based on the results given by both optical diagnostics and hydrodynamic modeling by a collision of shocks originated from two distinct zones of laser energy deposition.

Near-infrared laser irradiation improves the development of mouse pre-implantation embryos

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

Yokoo, Masaki; Mori, Miho

The aim of the present study was to assess the effects of near-infrared laser irradiation on the in vitro development of mouse embryos. Female ICR mice were superovulated with pregnant mare serum gonadotropin and human chorionic gonadotropin (hCG), and mated with male mice. Two-cell stage embryos were collected 40 h after administering hCG and cultured in M16 medium. Two-cell embryos (0 h after culture), 8-cell embryos (approx. 30 h after culture), morula (approx. 48 h after culture), and blastocysts (approx. 73 h after culture) were irradiated at 904 nm for 60 s. These embryos were cultured in a time-lapse monitoring system and the timing ofmore » blastocyst hatching was evaluated. Some of the irradiated blastocysts were transferred to the uterine horns of pseudopregnant recipients immediately after irradiation. Pregnancy rates, and offspring growth and fertility, were evaluated. Near-infrared laser irradiation increased the speed of in vitro mouse embryo development. In irradiated blastocysts, hatching was faster than in control (non-irradiated) blastocysts (18.4 vs. 28.2 h, P < 0.05). When 195 irradiated blastocysts were transferred to 18 pseudopregnant mice, all became pregnant and 92 (47.2%) normal-looking pups were born alive. When 182 control blastocysts were transferred to 17 pseudopregnant mice, 14 (82.4%) became pregnant and 54 (29.7%) normal-looking pups were born alive. The growth trajectories (up to 5 weeks) of offspring from irradiated blastocysts were similar to those from control blastocysts. Second generation offspring from transplanted animals were all fertile. These results indicate that near-infrared laser irradiation improves the quality of mouse embryo development in vitro, and increases the live birth rate without affecting the normality of the offspring. Thus, the near-infrared laser method may enhance the quality of embryos and contribute to improvements in reproductive technologies in mammals. - Highlights: • Irradiation of

Measurement of laser absorptivity for operating parameters characteristic of laser drilling regime

NASA Astrophysics Data System (ADS)

Schneider, M.; Berthe, L.; Fabbro, R.; Muller, M.

2008-08-01

Laser drilling in the percussion regime is commonly used in the aircraft industry to drill sub-millimetre holes in metallic targets. Characteristic laser intensities in the range of 10 MW cm-2 are typically employed for drilling metallic targets. With these intensities the temperature of the irradiated matter is above the vaporization temperature and the drilling process is led by hydrodynamic effects. Although the main physical processes involved are identified, this process is not correctly understood or completely controlled. A major characteristic coefficient of laser-matter interaction for this regime, which is the absorptivity of the laser on the irradiated surface, is still unknown, because of the perturbing effects due to laser beam geometrical trapping inside the drilled hole. So, by using time resolved experiments, this study deals with the direct measurement of the variation of the intrinsic absorption of aluminium, nickel and steel materials, as a function of the incident laser intensity up to 20 MW cm-2. We observe that for this incident intensity, the absorptivity can reach up to 80%. This very high and unexpected value is discussed by considering the microscopic behaviour of the heated matter near the vapour-liquid interface that undergoes possible Rayleigh-Taylor instability or volume absorption.

Mid-Infrared Spectroscopy Analysis of the Effects of Erbium, Chromium:Yattrium-Scandium-Gallium-Garnet (Er,Cr:YSGG) Laser Irradiation on Bone Mineral and Organic Components.

PubMed

Benetti, Carolina; Ana, Patricia Aparecida; Bachmann, Luciano; Zezell, Denise Maria

2015-12-01

The effects of varying the energy density of a high-intensity erbium, chromium: yttrium-scandium-gallium-garnet (Er,Cr:YSGG) laser on the mineral and organic components of bone tissue were evaluated using Fourier transform infrared spectroscopy. Bone samples obtained from the tibias of rabbits were irradiated with five energy densities (3, 6, 8, 12, and 15 J/cm(2)), and the effects on the carbonate to phosphate ratio and in the organic components were compared with those of nonirradiated samples. The increased temperature during the laser irradiation was also measured using infrared thermography to relate the observed spectral changes to the laser thermal effects. The analyses of the infrared spectra suggests that the irradiation with Er,Cr:YSGG promoted changes in bone tissue in both the mineral and organic components that depend on the laser energy density, pointing to the importance of using the proper energy density in clinical procedures.

Progress In Developing Laser Based Post Irradiation Examination Infrastructure

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

Smith, James A.; Scott, Clark L.; Benefiel, Brad C.

To be able to understand the performance of reactor fuels and materials, irradiated materials must be characterized effectively and efficiently in a high rad environment. The characterization work must be performed remotely and in an environment hostile to instrumentation. Laser based characterization techniques provide the ability to be remote and robust in a hot-cell environment. Laser based instrumentation also can provide high spatial resolution suitable for scanning and imaging large areas. The INL is currently developing three laser based Post Irradiation Examination (PIE) stations for the Hot Fuel Examination Facility at the INL. These laser based systems will characterize irradiatedmore » materials and fuels. The characterization systems are the following: Laser Shock Laser based ultrasonic C-scan system Gas Assay, Sample, and Recharge system (GASR, up-grade to an existing system). The laser shock technique will characterize material properties and failure loads/mechanisms in various materials such as LWR fuel, plate fuel, and next generation fuel forms, for PIE in high radiation areas. The laser shock-technique induces large amplitude shock waves to mechanically characterize interfaces such as the fuel-clad bond. The shock wave travels as a compression wave through the material to the free (unconfined) back surface and reflects back through the material under test as a rarefaction (tensile) wave. This rarefaction wave is the physical mechanism that produces internal de-lamination failure. As part of the laser shock system, a laser-based ultrasonic C-scan system will be used to detect and characterize debonding caused by the laser shock technique. The laser ultrasonic system will be fully capable of performing classical non-destructive evaluation testing and imaging functions such as microstructure characterization, flaw detection and dimensional metrology in complex components. The purpose of the GASR is to measure the pressure/volume of the plenum of an

Changes in surface morphology of enamel after Er:YAG laser irradiation

NASA Astrophysics Data System (ADS)

Rechmann, Peter; Goldin, Dan S.; Hennig, Thomas

1998-04-01

Aim of the study was to investigate the surface and subsurface structure of enamel after irradiation with an Er:YAG laser (wavelength 2.94 micrometer, pulse duration 250 - 500 microseconds, free running, beam profile close to tophead, focus diameter 600 micrometer, focus distance 13 mm, different power settings, air-water spray 2 ml/min; KAVO Key Laser 1242, Kavo Biberach, Germany). The surface of more than 40 freshly extracted wisdom teeth were irradiated using a standardized application protocol (pulse repetition rate 4 and 6 Hz, moving speed of the irradiation table 2 mm/sec and 3 mm/sec, respectively). On each surface between 3 and 5 tracks were irradiated at different laser energies (60 - 500 mJ/pulse) while each track was irradiated between one and ten times respectively. For the scanning electron microscope investigation teeth were dried in alcohol and sputtered with gold. For light microscopic examinations following laser impact, samples were fixed in formaldehyde, dried in alcohol and embedded in acrylic resin. Investigations revealed that at subsurface level cracks can not be observed even at application of highest energies. Borders of the irradiated tracks seem to be sharp while melted areas of different sizes are observed on the bottom of the tracks depending on applied energy. Small microcracks can be seen on the surface of these melted areas.

Laser-induced retinal injury thresholds: variation with retinal irradiated area

NASA Astrophysics Data System (ADS)

Lund, David J.; Schulmeister, Karl; Seiser, Bernhard; Edthofer, Florian

2005-04-01

The retinal injury threshold for exposure to a laser source varies as a function of the irradiated area on the retina. Currently accepted guidelines for the safe use of lasers provide that the MPE will increase as the diameter of the irradiated area for retinal diameters between 25 mm and 1700 mm, based on the ED50 data available in the late 1970s. Recent studies by Zuclich and Lund produced data showing that the ED50 for ns-duration exposures at 532 nm and ms duration exposures at 590 nm varied as the square of the diameter of the irradiated area on the retina. This paper will discuss efforts to resolve the disagreement between the new data and the earlier data though an analysis of all accessible data relating the retinal injury threshold to the diameter of the incident beam on the retina and through simulations using computer models of laser-induced injury. The results show that the retinal radiant exposure required to produce retinal injury is a function of both exposure duration and retinal irradiance diameter and that the current guidelines for irradiance diameter dependence do not accurately reflect the variation of the threshold data.

An in-vacuo optical levitation trap for high-intensity laser interaction experiments with isolated microtargets

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

Price, C. J., E-mail: c.price10@imperial.ac.uk; Giltrap, S.; Stuart, N. H.

2015-03-15

We report on the design, construction, and characterisation of a new class of in-vacuo optical levitation trap optimised for use in high-intensity, high-energy laser interaction experiments. The system uses a focused, vertically propagating continuous wave laser beam to capture and manipulate micro-targets by photon momentum transfer at much longer working distances than commonly used by optical tweezer systems. A high speed (10 kHz) optical imaging and signal acquisition system was implemented for tracking the levitated droplets position and dynamic behaviour under atmospheric and vacuum conditions, with ±5 μm spatial resolution. Optical trapping of 10 ± 4 μm oil droplets inmore » vacuum was demonstrated, over timescales of >1 h at extended distances of ∼40 mm from the final focusing optic. The stability of the levitated droplet was such that it would stay in alignment with a ∼7 μm irradiating beam focal spot for up to 5 min without the need for re-adjustment. The performance of the trap was assessed in a series of high-intensity (10{sup 17} W cm{sup −2}) laser experiments that measured the X-ray source size and inferred free-electron temperature of a single isolated droplet target, along with a measurement of the emitted radio-frequency pulse. These initial tests demonstrated the use of optically levitated microdroplets as a robust target platform for further high-intensity laser interaction and point source studies.« less

An in-vacuo optical levitation trap for high-intensity laser interaction experiments with isolated microtargets

NASA Astrophysics Data System (ADS)

Price, C. J.; Donnelly, T. D.; Giltrap, S.; Stuart, N. H.; Parker, S.; Patankar, S.; Lowe, H. F.; Drew, D.; Gumbrell, E. T.; Smith, R. A.

2015-03-01

We report on the design, construction, and characterisation of a new class of in-vacuo optical levitation trap optimised for use in high-intensity, high-energy laser interaction experiments. The system uses a focused, vertically propagating continuous wave laser beam to capture and manipulate micro-targets by photon momentum transfer at much longer working distances than commonly used by optical tweezer systems. A high speed (10 kHz) optical imaging and signal acquisition system was implemented for tracking the levitated droplets position and dynamic behaviour under atmospheric and vacuum conditions, with ±5 μm spatial resolution. Optical trapping of 10 ± 4 μm oil droplets in vacuum was demonstrated, over timescales of >1 h at extended distances of ˜40 mm from the final focusing optic. The stability of the levitated droplet was such that it would stay in alignment with a ˜7 μm irradiating beam focal spot for up to 5 min without the need for re-adjustment. The performance of the trap was assessed in a series of high-intensity (1017 W cm-2) laser experiments that measured the X-ray source size and inferred free-electron temperature of a single isolated droplet target, along with a measurement of the emitted radio-frequency pulse. These initial tests demonstrated the use of optically levitated microdroplets as a robust target platform for further high-intensity laser interaction and point source studies.

Solar irradiance dictates settlement timing and intensity of marine mussels

PubMed Central

Fuentes-Santos, Isabel; Labarta, Uxío; Álvarez-Salgado, X. Antón; Fernández-Reiriz, Mª José

2016-01-01

Identifying the environmental factors driving larval settlement processes is crucial to understand the population dynamics of marine invertebrates. This work aims to go a step ahead and predict larval presence and intensity. For this purpose we consider the influence of solar irradiance, wind regime and continental runoff on the settlement processes. For the first time, we conducted a 5-years weekly monitoring of Mytilus galloprovincialis settlement on artificial suspended substrates, which allowed us to search for interannual variability in the settlement patterns. Comparison between the seasonal pattern of larval settlement and solar irradiance, as well as the well-known effect of solar irradiance on water temperature and food availability, suggest that solar irradiance indirectly influences the settlement process, and support the use of this meteorological variable to predict settlement occurrence. Our results show that solar irradiance allows predicting the beginning and end of the settlement cycle a month in advance: Particularly we have observed that solar irradiance during late winter indirectly drives the timing and intensity of the settlement onset, Finally, a functional generalise additive model, which considers the influence of solar irradiance and continental runoff on the settlement process, provides an accurate prediction of settlement intensity a fortnight in advance. PMID:27384527

Solar irradiance dictates settlement timing and intensity of marine mussels

NASA Astrophysics Data System (ADS)

Fuentes-Santos, Isabel; Labarta, Uxío; Álvarez-Salgado, X. Antón; Fernández-Reiriz, Mª José

2016-07-01

Identifying the environmental factors driving larval settlement processes is crucial to understand the population dynamics of marine invertebrates. This work aims to go a step ahead and predict larval presence and intensity. For this purpose we consider the influence of solar irradiance, wind regime and continental runoff on the settlement processes. For the first time, we conducted a 5-years weekly monitoring of Mytilus galloprovincialis settlement on artificial suspended substrates, which allowed us to search for interannual variability in the settlement patterns. Comparison between the seasonal pattern of larval settlement and solar irradiance, as well as the well-known effect of solar irradiance on water temperature and food availability, suggest that solar irradiance indirectly influences the settlement process, and support the use of this meteorological variable to predict settlement occurrence. Our results show that solar irradiance allows predicting the beginning and end of the settlement cycle a month in advance: Particularly we have observed that solar irradiance during late winter indirectly drives the timing and intensity of the settlement onset, Finally, a functional generalise additive model, which considers the influence of solar irradiance and continental runoff on the settlement process, provides an accurate prediction of settlement intensity a fortnight in advance.

Improving the intensity of a focused laser beam

NASA Astrophysics Data System (ADS)

Haddadi, Sofiane; Fromager, Michael; Louhibi, Djelloul; Hasnaoui, Abdelkrim; Harfouche, Ali; Cagniot, Emmanuel; ńit-Ameur, Kamel

2015-03-01

Let us consider the family of symmetrical Laguerre-Gaus modes of zero azimuthal order which will be denoted as LGp0 . The latter is made up of central lobe surrounded by p concentric rings of light. The fundamental mode LG00 is a Gaussian beam of width W. The focusing of a LGp0 beam of power P by a converging lens of focal length f produces a focal spot keeping the LGp0 -shape and having a central intensity I0= 2PW2/(λf)2 whatever the value of the radial order p. Many applications of lasers (laser marking, laser ablation, …) seek nowadays for a focal laser spot with the highest as possible intensity. For a given power P, increasing intensity I0 can be achieved by increasing W and reducing the focal length f. However, this way of doing is in fact limited because the ratio W/f cannot increase indefinitely at the risk of introducing a huge truncation upon the edge of the lens. In fact, it is possible to produce a single-lobed focal spot with a central intensity of about p times the intensity I0. This result has been obtained by reshaping (rectification) a LGp0 beam thanks to a proper Binary Diffractive Optical Element (BDOE). In addition, forcing a laser cavity to oscillate upon a LGp0 can improve the power extract due to a mode volume increasing with the mode order p. This could allow envisaging an economy of scale in term of laser pumping power for producing a given intensity I0. In addition, we have demonstrated that a rectified LGp0 beam better stand the lens spherical aberration than the usual Gaussian beam.

Plasma density limits for hole boring by intense laser pulses.

PubMed

Iwata, Natsumi; Kojima, Sadaoki; Sentoku, Yasuhiko; Hata, Masayasu; Mima, Kunioki

2018-02-12

High-power lasers in the relativistic intensity regime with multi-picosecond pulse durations are available in many laboratories around the world. Laser pulses at these intensities reach giga-bar level radiation pressures, which can push the plasma critical surface where laser light is reflected. This process is referred to as the laser hole boring (HB), which is critical for plasma heating, hence essential for laser-based applications. Here we derive the limit density for HB, which is the maximum plasma density the laser can reach, as a function of laser intensity. The time scale for when the laser pulse reaches the limit density is also derived. These theories are confirmed by a series of particle-in-cell simulations. After reaching the limit density, the plasma starts to blowout back toward the laser, and is accompanied by copious superthermal electrons; therefore, the electron energy can be determined by varying the laser pulse length.

Mechanical properties and molecular structure analysis of subsurface dentin after Er:YAG laser irradiation.

PubMed

He, Zhengdi; Chen, Lingling; Hu, Xuejuan; Shimada, Yasushi; Otsuki, Masayuki; Tagami, Junji; Ruan, Shuangchen

2017-10-01

The purpose of this study was to evaluate the chemical and mechanical modifications in subsurface dentin layer after Er: YAG (Erbium-Yttrium Aluminium Garnet) laser irradiation, as the guidance of new dental restorative materials specific for laser irradiated dentin. Dentin disks obtained from extracted human molars were prepared and exposed to a single pulse Er:YAG laser irradiation at 80mJ/pulse. After laser irradiation the mechanical and chemical characteristics of intertubular dentin in subsurface layer were studied using nanoindentation tester and micro-Raman spectromy (μ-RS). The dentin 5-50µm depth beneath the lased surface was determined as testing area. Two-way analysis of variance (ANOVA) were used to compare the mechanical values between lased and untreated subsurface dentin (P = 0.05). A laser affected subsurface dentin layer after Er:YAG laser treatment is present. The laser irradiation is considered to decrease the mechanical properties in the superficial subsurface layer (<15µm deep). There was no significant difference in nanohardness and Young's modulus between lased subsurface dentin and untreated dentin (p > 0.05) under the depth of 15µm. However, the dentin at 5µm and 10µm depth beneath the lased surface exhibited significantly lower (~ 47.8% and ~ 33.6% respectively) hardness (p < 0.05). Er:YAG laser irradiation affected both mineral and organic components in subsurface dentin layer, a higher degree of crystallinity and reduced organic compounds occurred in the lased subsurface dentin. Under the tested laser parameters, Er:YAG laser irradiation causes lower mechanical values and reduction of organic components in subsurface dentin, which has deleterious effects on resin adhesion to this area. Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.

Modeling of a VMJ PV array under Gaussian high intensity laser power beam condition

NASA Astrophysics Data System (ADS)

Eom, Jeongsook; Kim, Gunzung; Park, Yongwan

2018-02-01

The high intensity laser power beaming (HILPB) system is one of the most promising systems in the long-rang wireless power transfer field. The vertical multi-junction photovoltaic (VMJ PV) array converts the HILPB into electricity to power the load or charges a battery. The output power of a VMJ PV array depends mainly on irradiance values of each VMJ PV cells. For simulating an entire VMJ PV array, the irradiance profile of the Gaussian HILPB and the irradiance level of the VMJ PV cell are mathematically modeled first. The VMJ PV array is modeled as a network with dimension m*n, where m represents the number of VMJ PV cells in a column, and n represents the number of VMJ PV cells in a row. In order to validate the results obtained in modeling and simulation, a laboratory setup was developed using 55 VMJ PV array. By using the output power model of VMJ PV array, we can establish an optimal power transmission path by the receiver based on the received signal strength. When the laser beam from multiple transmitters aimed at a VMJ PV array at the same time, the received power is the sum of all energy at a VMJ PV array. The transmitter sends its power characteristics as optically coded laser pulses and powers as HILPB. Using the attenuated power model and output power model of VMJ PV array, the receiver can estimate the maximum receivable powers from the transmitters and select optimal transmitters.

Laser-based irradiation apparatus and method to measure the functional dose-rate response of semiconductor devices

DOEpatents

Horn, Kevin M [Albuquerque, NM

2008-05-20

A broad-beam laser irradiation apparatus can measure the parametric or functional response of a semiconductor device to exposure to dose-rate equivalent infrared laser light. Comparisons of dose-rate response from before, during, and after accelerated aging of a device, or from periodic sampling of devices from fielded operational systems can determine if aging has affected the device's overall functionality. The dependence of these changes on equivalent dose-rate pulse intensity and/or duration can be measured with the apparatus. The synchronized introduction of external electrical transients into the device under test can be used to simulate the electrical effects of the surrounding circuitry's response to a radiation exposure while exposing the device to dose-rate equivalent infrared laser light.

Measurements of ion energies from the explosion of large hydrogen iodide clusters irradiated by intense femtosecond laser pulses

NASA Astrophysics Data System (ADS)

Tisch, J. W. G.; Hay, N.; Springate, E.; Gumbrell, E. T.; Hutchinson, M. H. R.; Marangos, J. P.

1999-10-01

We present measurements of ion energies from the interaction of intense, femtosecond laser pulses with large mixed-species clusters. Multi-keV protons and ~100-keV iodine ions are observed from the explosion of HI clusters produced in a gas jet operated at room temperature. Clusters formed from molecular gases such as HI are thus seen to extend the advantages of the laser-cluster interaction to elements that do not readily form single-species clusters. In the light of recently reported nuclear fusion in laser-heated clusters, we also examine the possibility of boosting the explosion energies of low-Z ions through the use of mixed species clusters.

Effect of laser irradiation on the functional activity of enzymes with different structural complexity

NASA Astrophysics Data System (ADS)

Ostrovtsova, Svetlana A.; Volodenkov, Alexander P.; Maskevich, Alexander A.; Artsukevich, Irina M.; Anufrik, Slavomir S.; Makarchikov, Alexander F.; Chernikevich, Ivan P.; Stepuro, Vitali I.

1998-05-01

Three enzymes differing in their structural composition were irradiated by UV lasers to study the effect of temperature, protein concentration and addition of small molecules on their sensitivity to radiation exposure. The laser-induced effects were due to the structural complexity of the protein molecules and depended on the dose applied, the wavelength and the density of irradiation. The multi-enzyme 2- oxoglutarate dehydrogenase complex was subjected to pronounced irradiation-induced changes whereas the response of the two other enzymes was less significant. Reduction of the protein levels in irradiated samples was important under the XeCl laser coercion and the effects depended on the doses applied. The laser irradiation effects are suggested to be realized by means of conformational changes in the protein molecules and intermolecular association- dissociation processes.

Damage Threshold of In Vivo Rabbit Cornea by 2 micron Laser Irradiation

DTIC Science & Technology

2007-01-01

in laser injury experiments? Implications for human exposure limits. Health Phys 2002; 82(3):335-347. 11. Siegman AE, Sasnett MW, Johnston TF. Choice... Laser Irradiation DISTRIBUTION: Approved for public release, distribution unlimited This paper is part of the following report: TITLE: Conference on...part numbers comprise the compilation report: ADP023676 thru ADP023710 UNCLASSIFIED Damage Threshold of In Vivo Rabbit Cornea by 2 gm Laser Irradiation

SEM analysis of enamel surface treated by Er:YAG laser: influence of irradiation distance.

PubMed

Souza-Gabriel, A E; Chinelatti, M A; Borsatto, M C; Pécora, J D; Palma-Dibb, R G; Corona, S A M

2008-07-01

Depending on the distance of laser tip to dental surface a specific morphological pattern should be expected. However, there have been limited reports that correlate the Er:YAG irradiation distance with dental morphology. To assess the influence of Er:YAG laser irradiation distance on enamel morphology, by means of scanning electron microscopy (SEM). Sixty human third molars were employed to obtain discs (approximately =1 mm thick) that were randomly assigned to six groups (n=10). Five groups received Er:YAG laser irradiation (80 mJ/2 Hz) for 20 s, according to the irradiation distance: 11, 12, 14, 16, or 17 mm and the control group was treated with 37% phosphoric acid for 15 s. The laser-irradiated discs were bisected. One hemi-disc was separated for superficial analysis without subsequent acid etching, and the other one, received the phosphoric acid for 15 s. Samples were prepared for SEM. Laser irradiation at 11 and 12 mm provided an evident ablation of enamel, with evident fissures and some fused areas. At 14, 16 and 17 mm the superficial topography was flatter than in the other distances. The subsequent acid etching on the lased-surface partially removed the disorganized tissue. Er:YAG laser in defocused mode promoted slight morphological alterations and seems more suitable for enamel conditioning than focused irradiation. The application of phosphoric acid on lased-enamel surface, regardless of the irradiation distance, decreased the superficial irregularities.

High resolution laser beam induced current images under trichromatic laser radiation: approximation to the solar irradiation.

PubMed

Navas, F J; Alcántara, R; Fernández-Lorenzo, C; Martín-Calleja, J

2010-03-01

A laser beam induced current (LBIC) map of a photoactive surface is a very useful tool when it is necessary to study the spatial variability of properties such as photoconverter efficiency or factors connected with the recombination of carriers. Obtaining high spatial resolution LBIC maps involves irradiating the photoactive surface with a photonic beam with Gaussian power distribution and with a low dispersion coefficient. Laser emission fulfils these characteristics, but against it is the fact that it is highly monochromatic and therefore has a spectral distribution different to solar emissions. This work presents an instrumental system and procedure to obtain high spatial resolution LBIC maps in conditions approximating solar irradiation. The methodology developed consists of a trichromatic irradiation system based on three sources of laser excitation with emission in the red, green, and blue zones of the electromagnetic spectrum. The relative irradiation powers are determined by either solar spectrum distribution or Planck's emission formula which provides information approximate to the behavior of the system if it were under solar irradiation. In turn, an algorithm and a procedure have been developed to be able to form images based on the scans performed by the three lasers, providing information about the photoconverter efficiency of photovoltaic devices under the irradiation conditions used. This system has been checked with three photosensitive devices based on three different technologies: a commercial silicon photodiode, a commercial photoresistor, and a dye-sensitized solar cell. These devices make it possible to check how the superficial quantum efficiency has areas dependent upon the excitation wavelength while it has been possible to measure global incident photon-to-current efficiency values approximating those that would be obtained under irradiation conditions with sunlight.

Time-resolved SFG study of formate on a Ni( 1 1 1 ) surface under irradiation of picosecond laser pulses

NASA Astrophysics Data System (ADS)

Noguchi, H.; Okada, T.; Onda, K.; Kano, S. S.; Wada, A.; Domen, K.

2003-03-01

Time-resolved sum-frequency generation spectroscopy was carried out on a deuterated formate (DCOO) adsorbed on Ni(1 1 1) surface to investigate the surface reaction dynamics under instantaneous surface temperature jump induced by the irradiation by picosecond laser pulses. The irradiation of pump pulse (800 nm) caused the rapid intensity decrease of both CD and OCO stretching modes of bridged formate on Ni(1 1 1). Different temporal behaviors of intensity recovery between these two vibrational modes were observed, i.e., CD stretching mode recovered faster than OCO. This is the first result to show that the dynamics of adsorbates on metals strongly depends on the observed vibrational mode. From the results of temperature and pump fluence dependence, we concluded that the observed intensity change was not due to the decomposition or desorption, but was induced by a non-thermal process.

Simulations of controlled spectral emission of Al plasmas generated by temporally tailored laser irradiation

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

Colombier, J. P.; Guillermin, M.; Garrelie, F.

2010-10-08

Hydrodynamics simulations and irradiation experiments were performed to correlate ul-trashort intensity envelopes of the laser fields and thermodynamical states reached by the emerging plasma phase in ablation regimes. We discuss the efficiency of energy coupling as a function of different intensity envelopes and the resulting temperature, density and ionization states since the energy delivery rate is an essential factor that predetermines the material thermodynamic evolution. Subsequently, we examine the plasma composition in calculating the proportion of neutral/ion species typical of LIBS signals and comparing it with neutral/ion ratios given by experimental results. Moreover, the calculations allow to investigate the efficiencymore » of nanoparticles generation from materials subjected to different heating rates. These can be related to hydrodynamic ejection of nanosized liquid layers upon the action of mechanic waves. With support from numerical simulations of the hydrodynamic advance of the excited matter, experiments revealed that mastering intensity envelopes of ultrashort laser pulse leads to further control on the ablation products. Emerging plasma phase in a hot state generates specific spectral emission patterns that can serve as indicators for its controlled formation and kinetic evolution.« less

In Vitro Evaluation of Dentin Hydraulic Conductance After 980 nm Diode Laser Irradiation.

PubMed

Rizzante, Fabio A P; Maenosono, Rafael M; Duarte, Marco A H; Furuse, Adilson Y; Palma-Dibb, Regina G; Ishikiriama, Sérgio K

2016-03-01

Dentin hypersensitivity treatments are based on the physical obliteration of the dentinal tubules to reduce hydraulic conductance. The aim of the present study is to evaluate the hydraulic conductance of bovine root dentin after irradiation with a 980-nm diode laser, with or without associated fluoride varnish. Sixty bovine root dentin specimens were divided into six groups (n = 10 in each group): G1, G3, and G5 (0.5 W, 0.7 W, and 1 W diode laser, respectively); G2, G4, and G6 (fluoride varnish application + 0.5 W, 0.7 W, and 1 W diode laser, respectively). The dentin hydraulic conductance was evaluated at four time periods with a fluxmeter: 1) with smear layer, 2) after 37% phosphoric acid etching, 3) after the treatments, and 4) after 6% citric acid challenge. After the dentinal fluid flow measurements, specimens were also evaluated for mineral composition using energy dispersive X-ray spectroscopy (EDS). Analysis demonstrated a better result with increased irradiation power (P < 0.001), especially if the diode laser irradiation was associated with the application of fluoride varnish (P < 0.001), ensuring a greater reduction in permeability. Considering the groups treated only with laser irradiation, the 1 W group was superior when compared with the 0.5 W and 0.7 W irradiated groups immediately after treatment (P < 0.001). After citric acid testing, all groups showed similar results, except when comparing the 1 W groups with the 0.5 W groups (P = 0.04). EDS results of the irradiated groups showed an increase in the proportion of calcium and phosphorus ions, which demonstrates a superficial composition modification after laser treatments. Laser irradiation of exposed dentin promoted significant reduction in the dentin hydraulic conductance, mainly with higher energy densities and association with fluoride varnish.

FT-Raman spectroscopic analysis of Nd:YAG and Er,Cr:YSGG laser irradiated enamel for preventive purposes

NASA Astrophysics Data System (ADS)

Ana, P. A.; Kauffmann, C. M. F.; Bachmann, L.; Soares, L. E. S.; Martin, A. A.; Gomes, A. S. L.; Zezell, D. M.

2014-03-01

This study evaluated the effect of combining laser irradiation with fluoride on an enamel microstructure and demineralization by FT-Raman spectroscopy (FTRS). Eighty human enamel slabs were divided into eight groups: (G1) untreated; (G2) acidulated phosphate fluoride application (APF—1.23% F- for 4 min) (G3) Nd:YAG irradiation (84.9 J cm-2, 60 mJ/pulse) (G4) Nd:YAG + APF; (G5) APF + Nd:YAG; (G6) Er,Cr:YSGG irradiation (2.8 J cm-2, 12.5 mJ/pulse) (G7) Er,Cr:YSGG + APF; and (G8) APF + Er,Cr:YSGG. After treatment, the samples were submitted to a ten-day pH-cycling model. Chemical changes were determined on the slabs before and after treatment, and also after pH-cycling, by FTRS in the range 400-4000 cm-1. The inorganic bands at 440, 590, 870, 960, 1100 cm-1, and the organic bands at 1270, 1450, 1670, 2945 cm-1 were considered. Demineralization promoted reduction in organic contents; Nd:YAG laser irradiation promoted loss of carbonate and organic content, while Er,Cr:YSGG did not produce significant changes in the relative band intensities of organic and inorganic contents of the enamel. In lased samples, no effects caused by pH-cycling on enamel were observed. In conclusion, laser treatment and its association with fluoride can somehow interfere with the demineralization dynamics, reducing its effects over the enamel.

Intense laser pulse propagation in capillary discharge plasma channels

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

Hubbard, R.F.; Moore, C.I.; Sprangle, P.

Optical guiding of intense laser pulses is required for plasma-based accelerator concepts such as the laser wakefield accelerator. Reported experiments have successfully transported intense laser pulses in the hollow plasma column produced by a capillary discharge. The hollow plasma has an index of refraction which peaks on-axis, thus providing optical guiding which overcomes beam expansion due to diffraction. In more recent experiments at Hebrew University, 800 nm wavelength, 0.1 mJ, 100 fs pulses have been guided in {approximately}300 micron radius capillaries over distances as long as 6.6 cm. Simulations of these experiments using a 2-D nonlinear laser propagation model producemore » the expected optical guiding, with the laser pulse radius r{sub L} exhibiting oscillations about the equilibrium value predicted by an analytical envelope equation model. The oscillations are damped at the front of the pulse and grow in amplitude in the back of the pulse. This growth and damping is attributed to finite pulse length effects. Simulations also show that further ionization of the discharge plasma by the laser pulse may hollow the laser pulse and introduce modulations in the spot size. This ionization-defocusing effect is expected to be significant at the high intensities required for accelerator application. Capillary discharge experiments at much higher intensities are in progress on the Naval Research Laboratory T{sup 3} laser, and preliminary results are reported. {copyright} {ital 1999 American Institute of Physics.}« less

Intense laser pulse propagation in capillary discharge plasma channels

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

Hubbard, R. F.; Moore, C. I.; Sprangle, P.

Optical guiding of intense laser pulses is required for plasma-based accelerator concepts such as the laser wakefield accelerator. Reported experiments have successfully transported intense laser pulses in the hollow plasma column produced by a capillary discharge. The hollow plasma has an index of refraction which peaks on-axis, thus providing optical guiding which overcomes beam expansion due to diffraction. In more recent experiments at Hebrew University, 800 nm wavelength, 0.1 mJ, 100 fs pulses have been guided in {approx}300 micron radius capillaries over distances as long as 6.6 cm. Simulations of these experiments using a 2-D nonlinear laser propagation model producemore » the expected optical guiding, with the laser pulse radius r{sub L} exhibiting oscillations about the equilibrium value predicted by an analytical envelope equation model. The oscillations are damped at the front of the pulse and grow in amplitude in the back of the pulse. This growth and damping is attributed to finite pulse length effects. Simulations also show that further ionization of the discharge plasma by the laser pulse may hollow the laser pulse and introduce modulations in the spot size. This ionization-defocusing effect is expected to be significant at the high intensities required for accelerator application. Capillary discharge experiments at much higher intensities are in progress on the Naval Research Laboratory T{sup 3} laser, and preliminary results are reported.« less

Using laser irradiation for the surgical treatment of periodontal disease

NASA Astrophysics Data System (ADS)

Vieru, Rozana D.; Lefter, Agafita; Herman, Sonia

2002-10-01

In the marginal pr ogressive profound periodontities, we associated low level laser therapy (LLLT) to the classical surgical treatment with implant of biovitroceramics. From a total of 50 patients, 37 where irradiated with the laser. We used a diode laser, =830 nm, energy density up to 2 J cm2, in Nogier pulsed mode. The laser treatment is used in a complex of therapeutic procedures: odontal, local anti-inflammatory -- as well as in the cabinet and at home --, prosthetic, and for the morphologic and functional rebalancing. The immediate effects where: an evolution without bleeding and without post-surgical complications, as can appear at the patients who didn't benefit of laser irradiation (hematom, pain, functional alteration in the first post-surgical week). Operated tissue is recovering faster. The percentage of recurrences decreases and the success depends less on the biological potential and the immunity of each individual.

Elicitation of trans-resveratrol by laser resonant irradiation of table grapes

NASA Astrophysics Data System (ADS)

Jiménez Sánchez, J. B.; Crespo Corral, E.; Orea, J. M.; Santos Delgado, M. J.; González Ureña, A.

2007-05-01

Table grapes were irradiated with UV nanosecond laser pulses in searching for resonant photo-elicitation of trans-resveratrol, a known antioxidant compound naturally produced by grapevines and other plants. To this end, the irradiation time as well as the wavelength dependence of the induced trans-resveratrol content was investigated by comparing the elicitation level of this compound at two laser wavelengths. One wavelength was selected right at the maximum of the absorption band (302.1 nm, the resonant wavelength for this compound) while the second was selected (300 nm, a non-resonant wavelength) such that trans-resveratrol absorption is negligible. It was found that the resonant irradiation enhances the resveratrol content in grapes by up to six times more than that of non-resonant irradiation, the rest of the conditions being the same. This work demonstrates how selective laser excitation of fruits can open new possibilities for the development of functional foods with enhanced nutritional and beneficial properties.

Laser irradiation for central-type lung cancer

NASA Astrophysics Data System (ADS)

Sun, Kai

1993-03-01

Based on laser irradiation experiments on isolated lung specimens of animals done in 1989, 8 patients with central type lung cancer were treated with Nd:YAG laser irradiation via fiberoptic bronchoscope from January 1990 to August 1991 in our hospital. The patients recruited were all diagnosed by fiberoptic bronchoscopy and histology as having central type bronchopulmonary cancer without distal metastasis. All patients were male with a mean age of 64 (range 57 - 72). Of 8 patients, 4 had squamous cell carcinoma, 3 adenocarcinoma, and 1 undifferentiated small cell carcinoma, all being stage TUM 3. After laser treatment, 6 cases had a result of significant response and 2 had minor response. Among 6 cases of atelectasis, 4 were completely cured or partially improved and 4 recovered from their hemoptysis. The subjective symptoms in all cases remitted. A combined chemotherapy was carried out accompanying laser therapy for all, 6 of whom had a shrink of focus over 25%. Six cases were re-examined with fiberoptic bronchoscopy, showing a distinct reduction of the tumor. Four cases expectorated black charring tissues and residual tumorous tissues persistently as an outcome. Two typical cases are reported, the characteristics, indications, techniques, and side effects of laser therapy are analyzed and factors affecting efficacy discussed, indicating that the technique has such advantages as easy operation, accurate orientation, and safe outcome. The procedure is really an effective one for treating central type lung cancer in intermediate or late stage.

Polymers Used as Fuel for Laser Plasma Thrusters in Small Satellites

DTIC Science & Technology

2006-09-12

irradiation fluences 100 ns after the laser pulse . The velocity of the maximum intensity versus the irradiation fluence is plotted in Fig. 61. The...The first region can be assigned to ionized elements that have been accelerated by a fs laser pulse induced coulomb explosion on the sample surface...acquired for ns laser pulses , plasma studies for fs laser pulse irradiation were performed. This data allowed a comparison of thrust

The Use Of Laser Irradiation To Stimulate Adipose Derived Stem Cell Proliferation And Differentiation For Use In Autologous Grafts

NASA Astrophysics Data System (ADS)

Abrahamse, Heidi

2009-09-01

Stem cells are characterized by the qualities of self-renewal, long term viability, and the ability to differentiate into various cell types. Historically, stem cells have been isolated from the inner cell mass of blastocysts and harvesting these cells resulted in the death of the embryo leading to religious, political and ethical issues. The identification and subsequent isolation of adult stem cells from bone marrow stroma have been welcomed as an alternate source for stem cells. The clinical use of Mesenchymal Stem Cells (MSCs) presented problems such as limited cell number, pain and morbidity upon isolation. Adipose tissue is derived from the mesenchyme, is easily isolated, a reliable source of stem cells and able to differentiate into different cell types including smooth muscle. Over the past few years, the identification and characterization of stem cells has led the potential use of these cells as a promising alternative to cell replacement therapy. Smooth muscle is a major component of human tissues and is essential for the normal functioning of many different organs. Low intensity laser irradiation has been shown to increase viability, protein expression and migration of stem cells in vitro, and to stimulate proliferation of various types of stem cells. In addition, the use of laser irradiation to stimulate differentiation in the absence of growth factors has also been demonstrated in normal human neural progenitor cells (NHNPCs) in vitro where NHNPCs are not only capable of being sustained by light in the absence of growth factors, but that they are also able to differentiate normally as assessed by neurite formation. Our work has focused on the ability of laser irradiation to proliferate adipose derived stem cells (ADSCs), maintain ADSC character and increase the rate and maintenance of differentiation of ADSCs into smooth muscle and skin fibroblast cells. Current studies are also investigating the effect of different irradiation wavelengths and

Side-entry laser-beam zigzag irradiation of multiple channels in a microchip for simultaneous and highly sensitive detection of fluorescent analytes.

PubMed

Anazawa, Takashi; Yokoi, Takahide; Uchiho, Yuichi

2015-09-01

A simple and highly sensitive technique for laser-induced fluorescence detection on multiple channels in a plastic microchip was developed, and its effectiveness was demonstrated by laser-beam ray-trace simulations and experiments. In the microchip, with refractive index nC, A channels and B channels are arrayed alternately and respectively filled with materials with refractive indexes nA for electrophoresis analysis and nB for laser-beam control. It was shown that a laser beam entering from the side of the channel array traveled straight and irradiated all A channels simultaneously and effectively because the refractive actions by the A and B channels were counterbalanced according to the condition nA < nC < nB. This technique is thus called "side-entry laser-beam zigzag irradiation". As a demonstration of the technique, when nC = 1.53, nA = 1.41, nB = 1.66, and the cross sections of both eight A channels and seven B channels were the same isosceles trapezoids with 97° base angle, laser-beam irradiation efficiency on the eight A channels by the simulations was 89% on average and coefficient of variation was 4.4%. These results are far superior to those achieved by other conventional methods such as laser-beam expansion and scanning. Furthermore, fluorescence intensity on the eight A channels determined by the experiments agreed well with that determined by the simulations. Therefore, highly sensitive and uniform fluorescence detection on eight A channels was achieved. It is also possible to fabricate the microchips at low cost by plastic-injection molding and to make a simple and compact detection system, thereby promoting actual use of the proposed side-entry laser-beam zigzag irradiation in various fields.

Laser ablation of PMMA doped with benzyl

NASA Astrophysics Data System (ADS)

Wang, Jun; Niino, Hiroyuki; Yabe, Akira

1998-08-01

KrF-laser ablation of poly(methylmethacrylate) (PMMA) doped with benzil was studied from the viewpoint of nonlinear absorption of the PMMA film during the laser irradiation. After measuring the relationship between the transmission and incident laser intensity, we developed a novel method to obtain absorption coefficient depending on laser intensity. Using the nonlinear absorption coefficient of PMMA doped with benzil, we succeeded in fitting the relationship of etch depth and laser intensity. The dependence of concentration of benzil in PMMA film and the difference between benzil and pyrene were also discussed.

Thomson scattering in high-intensity chirped laser pulses

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

Holkundkar, Amol R., E-mail: amol.holkundkar@pilani.bits-pilani.ac.in; Harvey, Chris, E-mail: christopher.harvey@chalmers.se; Marklund, Mattias, E-mail: mattias.marklund@chalmers.se

2015-10-15

We consider the Thomson scattering of an electron in an ultra-intense laser pulse. It is well known that at high laser intensities, the frequency and brilliance of the emitted radiation will be greatly reduced due to the electron losing energy before it reaches the peak field. In this work, we investigate the use of a small frequency chirp in the laser pulse in order to mitigate this effect of radiation reaction. It is found that the introduction of a negative chirp means the electron enters a high frequency region of the field while it still has a large proportion ofmore » its original energy. This results in a significant enhancement of the frequency and intensity of the emitted radiation as compared to the case without chirping.« less

Semiconductor laser irradiation improves root canal sealing during routine root canal therapy

PubMed Central

Hu, Xingxue; Wang, Dashan; Cui, Ting; Yao, Ruyong

2017-01-01

Objective To evaluate the effect of semiconductor laser irradiation on root canal sealing after routine root canal therapy (RCT). Methods Sixty freshly extracted single-rooted human teeth were randomly divided into six groups (n = 10). The anatomic crowns were sectioned at the cementoenamel junction and the remaining roots were prepared endodontically with conventional RCT methods. Groups A and B were irradiated with semiconductor laser at 1W for 20 seconds; Groups C and D were ultrasonically rinsed for 60 seconds as positive control groups; Groups E and F without treatment of root canal prior to RCT as negative control groups. Root canal sealing of Groups A, C and E were evaluated by measurements of apical microleakage. The teeth from Groups B, D and F were sectioned, and the micro-structures were examined with scanning electron microscopy (SEM). One way ANOVA and LSD-t test were used for statistical analysis (α = .05). Results The apical sealing of both the laser irradiated group and the ultrasonic irrigated group were significantly different from the control group (p<0.5). There was no significant difference between the laser irradiated group and the ultrasonic irrigated group (p>0.5). SEM observation showed that most of the dentinal tubules in the laser irradiation group melted, narrowed or closed, while most of the dentinal tubules in the ultrasonic irrigation group were filled with tooth paste. Conclusion The application of semiconductor laser prior to root canal obturation increases the apical sealing of the roots treated. PMID:28957407

Low intensity infrared laser induces filamentation in Escherichia coli cells

NASA Astrophysics Data System (ADS)

Fonseca, A. S.; Presta, G. A.; Geller, M.; Paoli, F.

2011-10-01

Low intensity continuous wave and pulsed emission modes laser is used in treating many diseases and the resulting biostimulative effect on tissues has been described, yet the photobiological basis is not well understood. The aim of this wok was to evaluate, using bacterial filamentation assay, effects of laser on Escherichia coli cultures in exponential and stationary growth phase. E. coli cultures, proficient and deficient on DNA repair, in exponential and stationary growth phase, were exposed to low intensity infrared laser, aliquots were spread onto microscopic slides, stained by Gram method, visualized by optical microscopy, photographed and percentage of bacterial filamentation were determined. Low intensity infrared laser with therapeutic fluencies and different emission modes can induce bacterial filamentation in cultures of E. coli wild type, fpg/ mutM, endonuclease III and exonuclease III mutants in exponential and stationary growth phase. This study showed induction of bacterial, filamentation in E. coli cultures expose to low intensity infrared laser and attention to laser therapy protocols, which should take into account fluencies, wavelengths, tissue conditions, and genetic characteristics of cells before beginning treatment.

Temperature increasing in titanium implants using a high-intensity diode laser for peri-implantitis decontamination

NASA Astrophysics Data System (ADS)

Faustino, C. N.; Ana, A. P.; Bachman, L.

2018-02-01

Peri-implantitis is a destructive inflammatory process that affects the tissues that provide support to the dental implant, the bone and gingiva, and can lead to the loss of the implant. Among the treatments of this disease, the irradiation of the contaminated surface with high intensity lasers is considered a promising alternative; Thus, irradiation parameters must be correctly adjusted in order to promote an efficient and safe treatment. This study investigated the temperature changes at the implant-bone interface during simulated implant surface decontamination using an 808nm diode laser. Dental implants were inserted in bovine bone, in which an artificial periimplant bone defect was made. Access holes of 0.5mm diameter were drilled to allow the positioning of four Ktype thermocouples in different regions: T0 Implant-bone interface, T1 inside the implant, T2 In the bone defect, T3 In the apex of the implant. For laser irradiation, an optical fiber was used at a distance of 0.5mm from the implant surface, and the mean output power varied between 0.5 to 3.0W on both pulsed (PW) and continuous (CW) wave modes. Irradiations were performed by 60s, and the temperature rises were registered for a period of 180s. It was observed that the critical threshold of 47ºC was exceeded at T0, T1 e T2 thermocouples when irradiations were performed at 1.0W; for T3 thermocouple, the threshold was exceeded at 3.0W CW mode. For PW mode, the thermocouples T0, T1, T2 had the threshold exceeded at the power of 1,0W and for T3 the threshold was exceeded at 3.0W. Decontamination of implant surfaces using the diode laser did not excessively heat the implant-bone interface within the mean output power ranging from 0.5 to 1.0W; however, the temperature rise is critical when using the mean power of 0.5W CW and 1.0W PW. Thus, using the PW mode up to the power of 1W seems to be a promising parameter for a safe clinical application.

Laser induced periodic surface structures formation by nanosecond laser irradiation of poly (ethylene terephthalate) reinforced with Expanded Graphite

NASA Astrophysics Data System (ADS)

Rodríguez-Beltrán, René I.; Hernandez, Margarita; Paszkiewicz, Sandra; Szymczyk, Anna; Rosłaniec, Zbigniew; Ezquerra, Tiberio A.; Castillejo, Marta; Moreno, Pablo; Rebollar, Esther

2018-04-01

We report on the formation of Laser Induced Periodic Surface Structures in poly (ethylene terephthalate) and poly (ethylene terephthalate)/Expanded Graphite films by laser irradiation with nanosecond pulses at 266 nm. The characterization studies show that the quality of the ripples depends strongly on the irradiation time and fluence and the optimal conditions for obtaining LIPSS are affected by the amount of the expanded graphite present in the film due to the differences in crystallinity, thermal conductivity and thermal diffusivity of the nanocomposites. Physicochemical modifications in the materials were inspected by Raman spectroscopy, the colloidal probe technique and contact angle measurements using different liquids. Results show that there is an increase of the hydrophilicity of the surfaces after laser irradiation together with an increase of the surface free energy and in particular of its polar component. Additionally, the adhesion force estimated by the colloidal probe technique increases after laser nanostructuring.

Guiding of High Laser Intensities in Long Plasma Channels

NASA Astrophysics Data System (ADS)

Levin, M.; Eisenmann, S.; Palchan, T.; Zigler, A.; Sugiyama, K.; Nakajima, K.; Kaganovich, D.; Hubbard, R. F.; Ting, A.; Gordon, D. F.; Sprangle, P.; Fraenkel, M.; Maman, S.; Henis, Z.

Plasma channels have been widely used to guide intense laser pulses over many Rayleigh lengths. Using optimized segmented capillary discharges, we demonstrated guided propagation of ultra short (100 fs) high intensity (1016 W/cm-2, limited by the laser system) pulses over distances up to 12.6 cm and intensities above 1018W/cm2 for 1.5cm boron nitride capillary. Both radial and longitudinal density profiles of plasma channels were studied under various discharge conditions. A new diagnostic technique is presented in which the transport of a guided laser pulse at different delay times from the initiation of the discharge is sampled on a single discharge shot. Using external, 10 nsec Nd YAG laser of several tenths of milijoules to ignite polyethylene capillaries we have demonstrated channels of various length in density range of 1017 - 1019 cm-3 and up to 25% deep. The longitudinal profiles were found to be remarkably uniform in both short and long capillaries. The Boron Nitride capillary has provided a guiding medium that can withstand more than 1000 shots. Using these capillaries we have guided laser intensities above 1018W/cm2. The laser ignition of capillary discharge provided reliable almost jitter free approach. The concerns related to influence of relatively high current density flow through capillary on the injected electrons were studied extensively by us both theoretically and experimentally using a simple injection method. The method is based on the interaction of a high intensity laser pulse with a thin wire placed near capillary entrance. The influence of magnetic fields was found to be insignificant. Using this method we have studied transport of electrons though capillary discharge.

Evaluation of irradiation effects of near-infrared free-electron-laser of silver alloy for dental application.

PubMed

Kuwada-Kusunose, Takao; Kusunose, Alisa; Wakami, Masanobu; Takebayashi, Chikako; Goto, Haruhiko; Aida, Masahiro; Sakai, Takeshi; Nakao, Keisuke; Nogami, Kyoko; Inagaki, Manabu; Hayakawa, Ken; Suzuki, Kunihiro; Sakae, Toshiro

2017-08-01

In the application of lasers in dentistry, there is a delicate balance between the benefits gained from laser treatment and the heat-related damage arising from laser irradiation. Hence, it is necessary to understand the different processes associated with the irradiation of lasers on dental materials. To obtain insight for the development of a safe and general-purpose laser for dentistry, the present study examines the physical effects associated with the irradiation of a near-infrared free-electron laser (FEL) on the surface of a commonly used silver dental alloy. The irradiation experiments using a 2900-nm FEL confirmed the formation of a pit in the dental alloy. The pit was formed with one macro-pulse of FEL irradiation, therefore, suggesting the possibility of efficient material processing with an FEL. Additionally, there was only a slight increase in the silver alloy temperature (less than 0.9 °C) despite the long duration of FEL irradiation, thus inferring that fixed prostheses in the oral cavity can be processed by FEL without thermal damage to the surrounding tissue. These results indicate that dental hard tissues and dental materials in the oral cavity can be safely and efficiently processed by the irradiation of a laser, which has the high repetition rate of a femtosecond laser pulse with a wavelength around 2900 nm.

Laser-irradiated drug chromatographic analysis and laser injection of drugs to treat staphyloccocal lesions of skin

NASA Astrophysics Data System (ADS)

Zharov, Vladimir P.; Latyshev, Alexei S.; Kovsh, Anna I.; Razumova, Svetlana A.; Masyukova, Svetlana A.; Volnukhin, Vladimir A.

2001-05-01

This article deals with further development of laser drug delivery methods. In order to estimate the effect of laser- drug interactions, we carried out the chromatographic fractionation of dexamethasone, hydrocortisone, and gentamicine, both prior to and after irradiating them by pulsed Er:YAG laser radiation. The laser radiation parameters were as follows: the wavelength, pulse energy, and pulse duration were, respectively, 2.94 micrometers , 0.7 J, and 100 microsecond(s) . The total laser radiation dose administered to a 100 (mu) l sample of these drug preparations amounted to 150 J. A chromatographic analysis revealed that drug samples exposed to Er:YAG laser radiation did not show any change. The results obtained made it possible to employ pulsed Er:YAG laser radiation to perform laser-acoustic injection of the above-mentioned drug preparations to study the treatment of staphylococcal lesions in 30 guinea pigs. The perforated channel depth was measured and the injected drug solution volume was calculated. It was found that laser injection enabled one to introduce therapeutic doses of drugs, and that it expedited the healing of lesions by 3 to 4 days, as compared to the control group that received the topical application of drugs without laser irradiation.

Low damage electrical modification of 4H-SiC via ultrafast laser irradiation

NASA Astrophysics Data System (ADS)

Ahn, Minhyung; Cahyadi, Rico; Wendorf, Joseph; Bowen, Willie; Torralva, Ben; Yalisove, Steven; Phillips, Jamie

2018-04-01

The electrical properties of 4H-SiC under ultrafast laser irradiation in the low fluence regime (<0.50 J/cm2) are presented. The appearance of high spatial frequency laser induced periodic surface structures is observed at a fluence near 0.25 J/cm2 and above, with variability in environments like in air, nitrogen, and a vacuum. In addition to the formation of periodic surface structures, ultrafast laser irradiation results in possible surface oxidation and amorphization of the material. Lateral conductance exhibits orders of magnitude increase, which is attributed to either surface conduction or modification of electrical contact properties, depending on the initial material conductivity. Schottky barrier formation on ultrafast laser irradiated 4H-SiC shows an increase in the barrier height, an increase in the ideality factor, and sub-bandgap photovoltaic responses, suggesting the formation of photo-active point defects. The results suggest that the ultrafast laser irradiation technique provides a means of engineering spatially localized structural and electronic modification of wide bandgap materials such as 4H-SiC with relatively low surface damage via low temperature processing.

Interaction of Intense Lasers with Plasmas

NASA Astrophysics Data System (ADS)

Shvets, Gennady

1995-01-01

This thesis addresses two important topics in nonlinear laser plasma physics: the interaction of intense lasers with a non thermal homogeneous plasma, the excitation of laser wakefields in hollow plasma channels, and the stability of channel guided propagation of laser pulses. In the first half of this thesis a new theoretical approach to the nonlinear interaction of intense laser pulses with underdense plasmas is developed. Unlike previous treatments, this theory is three-dimensional, relativistically covariant, and does not assume that a<<1, where a=eA/mc^2 is a dimensionless vector potential. This formalism borrows the diagrammatic techniques from quantum field theory, yet remains classical. This classical field theory, which treats cold plasma as a relativistic field interacting with the electromagnetic fields, introduces an artificial length scale which is smaller than any physically relevant spatial scale. By adopting a special (Arnowitt -Fickler) gauge, electromagnetic waves in a cold relativistic plasma are separated into "photons" and "plasmons" which are the relativistic extensions of electrostatic and electromagnetic waves in a cold stationary plasma. The field-theoretical formalism is applied to a variety of nonlinear problems including harmonic generation, parametric instabilities, and nonlinear corrections to the index of refraction. For the first time the rate of the second harmonic emission from a homogeneous plasma is calculated and its dependence on the polarization of the incident radiation is studied. An experimental check of this calculation is suggested, based on the predicted non-linear polarization rotation (the second harmonic is emitted polarized perpendicularly to polarization of the incident signal). The concept of renormalization is applied to the plasma and electromagnetic radiation (photons and plasmons). To the lowest order, this corresponds to relativistically correcting the electron mass for its oscillation in an intense EM field

High-Power, High-Intensity Laser Propagation and Interactions

DTIC Science & Technology

2014-03-10

wave Brillouin mixing [89,90]. transmitted beam is phase conjugated target initial wave front nn  1 turbulent air Figure 14. Using phase and...discussed in connection with both high-power and high-intensity lasers is propagation in a turbulent atmosphere . Laser propagation in atmospheric ... turbulence can results in beam centroid wander, spreading and intensity scintillation. A phase conjugation technique to mitigate the effects of atmospheric

Influence of laser irradiation on deposition characteristics of cold sprayed Stellite-6 coatings

NASA Astrophysics Data System (ADS)

Li, Bo; Jin, Yan; Yao, Jianhua; Li, Zhihong; Zhang, Qunli; Zhang, Xin

2018-03-01

Depositing hard materials such as Stellite-6 solely by cold spray (CS) is challengeable due to limited ability of plastic deformation. In this study, the deposition of Stellite-6 powder was achieved by supersonic laser deposition (SLD) which combines CS with synchronous laser irradiation. The surface morphology, deposition efficiency, track shape of Stellite-6 coatings produced over a range of laser irradiation temperatures were examined so as to reveal the effects of varying laser energy inputting on the deposition process of high strength material. The microstructure, phase composition and wear/corrosion resistant properties of the as-deposited Stellite-6 coatings were also investigated. The experimental results demonstrate that the surface flatness and deposition efficiency increase with laser irradiation temperature due to the softening effect induced by laser heating. The as-deposited Stellite-6 tracks show asymmetric shapes which are influenced by the relative configuration of powder stream and laser beam. The SLD coatings can preserve the original microstructure and phase of the feedstock material due to relatively low laser energy inputting, which result in the superior wear/corrosion resistant properties as compared to the counterpart prepared by laser cladding.

Genetic expression of adipose derived stem cell and smooth muscle cell markers to monitor differentiation potential following low intensity laser irradiation

NASA Astrophysics Data System (ADS)

Abrahamse, Heidi

2014-02-01

Mesenchymal stem cells (MSCs) have the capacity to differentiate into a variety of cell types that could potentially be used in tissue engineering and regenerative medicine. Low intensity laser irradiation (LILI) has been shown to induce a significant increase in cell viability and proliferation. Growth factors such as retinoic acid (RA) and transforming growth factor β1 (TGF-β1) play important roles in the differentiation of cells. The aim of this study was to investigate whether LILI in combination with growth factors could induce the differentiation of adipose derived stem cells (ADSCs) cocultured with smooth muscle cells (SMCs). The study used primary and continuous ADSC cell lines and a SMC line (SKUT-1) as control. Cells were co-cultured directly at a ratio of 1:1 using established methods, with and without growth factors and then exposed to LILI at 5 J/cm2 using a 636 nm diode laser. The cellular morphology, viability and proliferation of the co-cultures were assessed over a period of one week. The study also monitored the expression of cell specific markers over the same period of time. Genetic expression of the markers for both adipose derived stem cells (β1 Integrin and Thymidine 1) and smooth muscle cells (Heavy Myosin Chain) was monitored using flow cytometry. Cell viability and proliferation increased significantly in the co-cultured groups that were exposed to laser alone, as well as in combination with growth factors. Furthermore, there was a significant decrease in the expression of stem cell markers in the ADSCs over time. The results indicate that LILI in combination with growth factors not only increases the viability and proliferation of co-cultured cells but also decreases the expression of ADSC stem cell markers. This could indicate the possible differentiation of ADSCs into SMCs.

The intravascular low level laser irradiation (ILLLI) in treatment of psoriasis clinically

NASA Astrophysics Data System (ADS)

Zhu, Jing; Nie, Fan; Shi, Hong-Min

2005-07-01

Objective: The title is research curative effect of intravascular low level laser irradiation (ILLLI) in treatment of psoriasis. Method: 478 patients with psoriasis from five groups to observe their efficacy. Group1 were treated by He-Ne laser combined with drug. Group 2 were treated by semi-conductor laser combined with drug. Group 3 were treated only by He-He laser. Group 4 were treated by semi-conductor laser. Group 5 were treated only by drug. The Ridit statistical analysis was applied to all of these data. The treatment of intravascular low level laser irradiation is as follow: laser power:4-5mw, 1 hour per day and 10 days as a period combined with vit C 2.0 g iv and inhalation of O2. Results: The clinical results: the near efficient rate was 100%, in group1-4, if combined with drugs it would be better. Ridit statistical analysis showed no significant difference between group1-4, p>0.05. The efficient rate 72.97% in group5.There were showed very significant difference with group1-4, p<0.01. 2.There were no significant differences between He-Ne laser (632.8nm) and semiconductor laser(650nm); 3.The efficacy of ILLLI in psoriasis was positive correlation to the ILLLI times. Conclusions: It can improve curative effect of intravascular low levellaser irradiation (ILLLI) in treatment of psoriasis.

Bactericidal Effects of Diode Laser Irradiation on Enterococcus faecalis Using Periapical Lesion Defect Model

PubMed Central

Nagayoshi, Masato; Nishihara, Tatsuji; Nakashima, Keisuke; Iwaki, Shigetsugu; Chen, Ker-Kong; Terashita, Masamichi; Kitamura, Chiaki

2011-01-01

Objective. Photodynamic therapy has been expanded for use in endodontic treatment. The aim of this study was to investigate the antimicrobial effects of diode laser irradiation on endodontic pathogens in periapical lesions using an in vitro apical lesion model. Study Design. Enterococcus faecalis in 0.5% semisolid agar with a photosensitizer was injected into apical lesion area of in vitro apical lesion model. The direct effects of irradiation with a diode laser as well as heat produced by irradiation on the viability of microorganisms in the lesions were analyzed. Results. The viability of E. faecalis was significantly reduced by the combination of a photosensitizer and laser irradiation. The temperature caused by irradiation rose, however, there were no cytotoxic effects of heat on the viability of E. faecalis. Conclusion. Our results suggest that utilization of a diode laser in combination with a photosensitizer may be useful for clinical treatment of periapical lesions. PMID:21991489

Morphological changes produced by acid dissolution in Er:YAG laser irradiated dental enamel.

PubMed

Manuela Díaz-Monroy, Jennifer; Contreras-Bulnes, Rosalía; Fernando Olea-Mejía, Oscar; Emma Rodríguez-Vilchis, Laura; Sanchez-Flores, Ignacio

2014-06-01

Several scientific reports have shown the effects of Er:YAG laser irradiation on enamel morphology. However, there is lack of information regarding the morphological alterations produced by the acid attack on the irradiated surfaces. The aim of this study was to evaluate the morphological changes produced by acid dissolution in Er:YAG laser irradiated dental enamel. Forty-eight enamel samples were divided into four groups (n = 12). GI (control); Groups II, III, and IV were irradiated with Er:YAG at 100 mJ (12.7 J/cm(2) ), 200 mJ (25.5 J/cm(2) ), and 300 mJ (38.2 J/cm(2) ), respectively, at 10 Hz without water irrigation. Enamel morphology was evaluated before-irradiation, after-irradiation, and after-acid dissolution, by scanning electron microscopy (SEM). Sample coating was avoided and SEM analysis was performed in a low-vacuum mode. To facilitate the location of the assessment area, a reference point was marked. Morphological changes produced by acid dissolution of irradiated enamel were observed, specifically on laser-induced undesired effects. These morphological changes were from mild to severe, depending on the presence of after-irradiation undesired effects. © 2014 Wiley Periodicals, Inc.

What is the surface temperature of a solid irradiated by a Petawatt laser?

NASA Astrophysics Data System (ADS)

Kemp, A. J.; Divol, L.

2016-09-01

When a solid target is irradiated by a Petawatt laser pulse, its surface is heated to tens of millions of degrees within a few femtoseconds, facilitating a diffusive heat wave and the acceleration of electrons to MeV energies into the target. Using numerically converged collisional particle-in-cell simulations, we observe a competition between two surface heating mechanisms-inverse bremsstrahlung in solid density on the one hand and electron scattering on turbulent electric fields on the other. Collisionless heating effectively dominates above the relativistic intensity threshold. Our numerical results show that a high-contrast 40 fs, f/5 laser pulse with 1 J energy will heat the skin layer to 5 keV, and the inside of the target over several microns deep to bulk temperatures in the range of 10-100 eV at solid density.

ZnO synthesized in air by fs laser irradiation on metallic Zn thin films

NASA Astrophysics Data System (ADS)

Esqueda-Barrón, Y.; Herrera, M.; Camacho-López, S.

2018-05-01

We present results on rapid femtosecond laser synthesis of nanostructured ZnO. We used metallic Zn thin films to laser scan along straight tracks, until forming nanostructured ZnO. The synthesis dependence on laser irradiation parameters such as the per pulse fluence, integrated fluence, laser scan speed, and number of scans were explored carefully. SEM characterization showed that the morphology of the obtained ZnO is dictated by the integrated fluence and the laser scan speed; micro Raman and XRD results allowed to identify optimal laser processing conditions for getting good quality ZnO; and cathodoluminescence measurements demonstrated that a single laser scan at high per pulse laser fluence, but a medium integrated laser fluence and a medium laser scan speed favors a low density of point-defects in the lattice. Electrical measurements showed a correlation between resistivity of the laser produced ZnO and point-defects created during the synthesis. Transmittance measurements showed that, the synthesized ZnO can reach down to the supporting fused silica substrate under the right laser irradiation conditions. The physical mechanism for the formation of ZnO, under ultrashort pulse laser irradiation, is discussed in view of the distinct times scales given by the laser pulse duration and the laser pulse repetition rate.

Surface changes of composite and compomer materials following irradiation with an Er:YAG laser and a frequency doubled alexandrite laser

NASA Astrophysics Data System (ADS)

Pilgrim, Christian G.; Rechmann, Peter; Hennig, Thomas; Goldin, Dan S.

1999-05-01

Er:YAG laser as well as the frequency doubled Alexandrite laser have been suggested for the use in periodontal therapy and so for the elimination of calculus and the treatment of infected root cement. Intended is the laser application inside the gingival pocket. In consequence, both these lasers may be used in areas close to cervical or approximal location, or even on the fillings' surfaces. Light cured composite and compomer materials are in use for these types of fillings among others. Aim of the study presented here was to compare the effect of an Er:YAG laser (wavelength 2.94 μm, pulse duration 250 μs, free running. fluence 4.5 J/cm2 and 21.4 J/cm2) on compomers and composites with the result following irradiation with a frequency doubled Alexandrite laser (wavelength 377 nm, pulse duration 200 ns, fluence 3 Jcm-2 and 6 J/cm2). The surface of standardized compomer and composite samples were irradiated with both laser wavelengths (either frequency doubled Alexandrite or Er:YAG laser) using the same standardized application protocol. Scanning electron microscopic investigation showed that irradiation with both lasers causes surface changes in composites and compomers removing calculus with these lasers.

Laser- and Particle-Beam Chemical Processes on Surfaces. Volume 129

DTIC Science & Technology

1989-12-26

explosive decomposition of organometallic compounds with single pulse laser irradiation . This new... ultrashort , meaning ultra high intensity , excimer laser pulses , two-photon absorption becomes important and limits the penetration depth of the laser ...requires a higher photon load before suffering damage to its chemical structure. With extremely high light intensities , ultrashort excimer laser pulses

Sub ablative Er: YAG laser irradiation on surface roughness of eroded dental enamel.

PubMed

Curylofo-Zotti, Fabiana Almeida; Lepri, Taísa Penazzo; Colucci, Vivian; Turssi, Cecília Pedroso; Corona, Silmara Aparecida Milori

2015-11-01

This study evaluated the effects of Er:YAG laser irradiation applied at varying pulse repetition rate on the surface roughness of eroded enamel. Bovine enamel slabs (n = 10) were embedded in polyester resin, ground, and polished. To erosive challenges, specimens were immersed two times per day in 20mL of concentrated orange juice (pH = 3.84) under agitation, during a two-day period. Specimens were randomly assigned to irradiation with the Er:YAG laser (focused mode, pulse energy of 60 mJ and energy density of 3.79 J/cm(2) ) operating at 1, 2, 3, or 4 Hz. The control group was left nonirradiated. Surface roughness measurements were recorded post erosion-like formation and further erosive episodes by a profilometer and observed through atomic force microscopy (AFM). Analysis of variance revealed that the control group showed the lowest surface roughness, while laser-irradiated substrates did not differ from each other following post erosion-like lesion formation. According to analysis of covariance, at further erosive episodes, the control group demonstrated lower surface roughness (P > 0.05), than any of the irradiated groups (P < 0.05). The pulse repetition rate of the Er:YAG laser did not affect roughness of dental enamel eroded. The AFM images showed that the specimens irradiated by the Er:YAG laser at 1 Hz presented a less rough surface than those irradiated at 2, 3, and 4 Hz. © 2015 Wiley Periodicals, Inc.

Effect of Nd: YAG laser irradiation on surface properties and bond strength of zirconia ceramics.

PubMed

Liu, Li; Liu, Suogang; Song, Xiaomeng; Zhu, Qingping; Zhang, Wei

2015-02-01

This study investigated the effect of neodymium-doped yttrium aluminum garnet (Nd: YAG) laser irradiation on surface properties and bond strength of zirconia ceramics. Specimens of zirconia ceramic pieces were divided into 11 groups according to surface treatments as follows: one control group (no treatment), one air abrasion group, and nine laser groups (Nd: YAG irradiation). The laser groups were divided by applying with different output power (1, 2, or 3 W) and irradiation time (30, 60, or 90 s). Following surface treatments, the morphological characteristics of ceramic pieces was observed, and the surface roughness was measured. All specimens were bonded to resin cement. After, stored in water for 24 h and additionally aged by thermocycling, the shear bond strength was measured. Dunnett's t test and one-way ANOVA were performed as the statistical analyses for the surface roughness and the shear bond strength, respectively, with α = .05. Rougher surface of the ceramics could be obtained by laser irradiation with higher output power (2 and 3 W). However, cracks and defects were also found on material surface. The shear bond strength of laser groups was not obviously increased, and it was significantly lower than that of air abrasion group. No significant differences of the shear bond strength were found among laser groups treated with different output power or irradiation time. Nd: YAG laser irradiation cannot improve the surface properties of zirconia ceramics and cannot increase the bond strength of the ceramics. Enhancing irradiation power and extending irradiation time cannot induce higher bond strength of the ceramics and may cause material defect.

Effect of pulsed laser irradiation on the structural and the magnetic properties of NiMn/Co exchange bias system

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

Mohanan, Senthilnathan; Diebolder, Rolf; Hibst, Raimund

2008-04-01

We report about the influence of pulsed laser irradiation on the structural and magnetic properties of NiMn/Co thin films. Rocking curve measurements showed a significant improvement of the (111) texture of NiMn after laser irradiation which was accompanied by grain growth. We have studied the ordering transition in as-prepared and irradiated (laser fluence of 0.15 J/cm{sup 2}) samples during subsequent annealing. The onset of the fcc to fct phase transformation occurs at 325 deg. C irrespective of laser irradiation. Exchange bias fields for the laser irradiated samples are higher than those of the as-prepared samples. The observed increase in themore » exchange bias field for laser irradiated samples has been attributed to the increased grain size and the improved (111) texture of the NiMn layer after laser irradiation.« less

Electron dynamics characteristics in high-intensity laser fields

NASA Astrophysics Data System (ADS)

Kong, Q.; Ho, Y. K.; Cao, N.; Pang, J.; Wang, P. X.; Shao, L.

This paper addresses the conditions under which the vacuum laser acceleration scheme CAS (capture and acceleration scenario), newly proposed by the authors (see, e.g., P.X. Wang et al., Appl. Phys. Lett. 78, 2253 (2001)), can be observed. Specifically, the laser intensity threshold (a0)th and the range of the electron incident momentum for the CAS scheme to emerge are examined. We found that (a0)th is critically dependent on the laser beam width w0. At kw0=60, (a0)th=8, which is an intensity obtainable using present laser systems. The required energy of the incident electron is in the range 5-15 MeV. This study is of significance in designing an experimental setup to test CAS and helpful in understanding the basic physics of CAS.

Enhancing hair follicle regeneration by nonablative fractional laser: Assessment of irradiation parameters and tissue response.

PubMed

Wu, Yueh-Feng; Wang, Shiou-Han; Wu, Pei-Shan; Fan, Sabrina Mai-Yi; Chiu, Hsien-Yi; Tsai, Tsung-Hua; Lin, Sung-Jan

2015-04-01

Identification of methods to enhance anagen entry can be helpful for alopecia. Recently, nonablative laser has been proposed as a potential treatment for alopecia. However, how the laser parameters affect stem cell activity, hair cycles and the associated side effects have not been well characterized. Here we examine the effects of irradiation parameters of 1,550-nm fractional laser on hair cycles. The dorsal skin of eight-week-old female C57BL/6 mice with hair follicles in synchronized telogen was shaved and irradiated with a 1,550-nm fractional erbium-glass laser (Fraxel RE:STORE (SR1500) Laser System, Solta Medical, U.S.A.) with varied beam energies (5-35 mJ) and beam densities (500-3500 microthermal zones/cm(2) ). The cutaneous changes were evaluated both grossly and histologically. Hair follicle stem cell activity was detected by BrdU incorporation and changes in gene expression were quantified by real-time PCR. Direct thermal injury to hair follicles could be observed early after irradiation, especially at higher beam energy. Anagen induction in the irradiated skin showed an all-or-non change. Anagen induction and ulcer formation were affected by the combination of beam energy and density. The lowest beam energy of 5 mJ failed to promote anagen entry at all beam densities tested. As beam energy increased from 10 mJ to 35 mJ, we found a decreasing trend of beam density that could induce anagen entry within 7-9 days with activation of hair follicle stem cells. Beam density above the pro-regeneration density could lead to ulcers and scarring followed by anagen entry in adjacent skin. Analysis of inflammatory cytokines, including TNF-α, IL-1β, and IL-6, revealed that transient moderate inflammation was associated with anagen induction and intense prolonged inflammation preceded ulcer formation. To avoid side effects of hair follicle injury and scarring, appropriate combination of beam energy and density is required. Parameters outside the therapeutic

Application of Laser Irradiation for Restorative Treatments.

PubMed

Davoudi, Amin; Sanei, Maryam; Badrian, Hamid

2016-01-01

Nowadays, lasers are widely used in many fields of medicine. Also, they can be applied at many branches of dental practice such as diagnosis, preventive procedures, restorative treatments, and endodontic therapies. Procedures like caries removal, re-mineralization, and vital pulp therapy are the most noticeable effects of laser irradiation which has gained much attention among clinicians. With controlled and appropriate wavelength, they can help stimulating dentinogenesis, controlling pulpal hemorrhage, sterilization, healing of collagenic proteins, formation of a fibrous matrix, and inducing hard tissue barrier. Nevertheless, there are many controversies in literatures regarding their effects on the quality of bonded restorations. It hampered a wide application of lasers in some aspects of restorative dentistry and requirements to identify the best way to use this technology. The aim of this mini review is to explain special characteristics of laser therapy and to introduce the possible applications of laser devices for dental purposes.

Three-dimensional simulations of ion acceleration from a foil irradiated by a short-pulse laser.

PubMed

Pukhov, A

2001-04-16

Using 3D particle-in-cell simulations we study ion acceleration from a foil irradiated by a laser pulse at 10(19) W/cm(2) intensity. At the front side, the laser ponderomotive force pushes electrons inwards, thus creating the electric field by charge separation, which drags the ions. At the back side of the foil, the ions are accelerated by space charge of the hot electrons exiting into vacuum, as suggested by Hatchett et al. [Phys. Plasmas 7, 2076 (2000)]. The transport of hot electrons through the overdense plasma and their exit into vacuum are strongly affected by self-generated magnetic fields. The fast ions emerge from the rear surface in cones similar to those detected by Clark et al. [Phys. Rev. Lett. 84, 670 (2000)].

Cladding-like waveguide fabricated by cooperation of ultrafast laser writing and ion irradiation: characterization and laser generation.

PubMed

Lv, Jinman; Shang, Zhen; Tan, Yang; Vázquez de Aldana, Javier Rodríguez; Chen, Feng

2017-08-07

We report the surface cladding-like waveguide fabricated by the cooperation of the ultrafast laser writing and the ion irradiation. The ultrafast laser writes tracks near the surface of the Nd:YAG crystal, constructing a semi-circle columnar structure with a decreased refractive index of - 0.00208. Then, the Nd:YAG crystal is irradiated by the Carbon ion beam, forming an enhanced-well in the semi-circle columnar with an increased refractive index of + 0.0024. Tracks and the enhanced-well consisted a surface cladding-like waveguide. Utilizing this cladding-like waveguide as the gain medium for the waveguide lasing, optimized characterizations were observed compared with the monolayer waveguide. This work demonstrates the refractive index of the Nd:YAG crystal can be well tailored by the cooperation of the ultrafast laser writing and the ion irradiation, which provides an convenient way to fabricate the complex and multilayered photonics devices.

Intense excitation source of blue-green laser

NASA Astrophysics Data System (ADS)

Han, K. S.

1985-10-01

An intense and efficient excitation source for blue-green lasers useful for the space-based satellite laser applications, underwater strategic communication, and measurement of ocean bottom profile is being developed. The source in use, hypocycloidal pinch plasma (HCP), and a newly designed dense-plasma focus (DPF) can produce intense UV photons (200 to 300 nm) which match the absorption spectra of both near UV and blue green dye lasers (300 to 400 nm). During the current project period, the successful enhancement of blue-green laser output of both Coumarin 503 and LD490 dye through the spectral conversion of the HCP pumping light has been achieved with a converter dye BBQ. The factor of enhancement in the blue-green laser output energy of both Coumarin 503 and LD490 is almost 73%. This enhancement will definitely be helpful in achieving the direct high power blue-green laser (> 1 MW) with the existing blue green dye laser. On the other hand the dense-plasma focus (DPF) with new optical coupling has been designed and constructed. For the optimization of the DPF device as the UV pumping light source, the velocity of current sheath and the formation of plasma focus have been measured as function of argon or argon-deuterium fill gas pressure. Finally, the blue-green dye laser (LD490) has been pumped with the DPF device for preliminary tests. Experimental results with the DPF device show that the velocity of the current sheath follows the inverse relation of sq st. of pressure as expected. The blue-green dye (LD490) laser output exceeded 3.1 m at the best cavity tuning of laser system. This corresponds to 3J/1 cu cm laser energy extraction.

Intense excitation source of blue-green laser

NASA Astrophysics Data System (ADS)

Han, Kwang S.

1986-10-01

An intense and efficient source for blue green laser useful for the space-based satellite laser applications, underwater strategic communication, and measurement of ocean bottom profile is being developed. The source in use, the hypocycloidal pinch plasma (HCP), and the dense plasma focus (DPF) can produce intense uv photons (200 to 400nm) which match the absorption spectra of both near UV and blue green dye lasers (300 to 400nm). As a result of optimization of the DPF light at 355nm, the blue green dye (LD490) laser output exceeding 4mJ was obtained at the best cavity tunning of the laser system. With the HCP pumped system a significant enhancement of the blue green laser outputs with dye LD490 and coumarin 503 has been achieved through the spectrum conversion of the pumping light by mixing a converter dye BBQ. The maximum increase of laser output with the dye mixture of LD490+BBQ and coumarin 503+BBQ was greater than 80%. In addition, the untunned near UV lasers were also obtained. The near UV laser output energy of P-terphenyl dye was 0.5mJ at lambda sub C=337nm with the bandwidth of 3n m for the pulse duration of 0.2us. Another near UV laser output energy obtained with BBQ dye was 25 mJ at lambda sub C=383nm with the bandwidth of 3nm for the pulse duration of 0.2us. Another near UV laser output energy obtained with BBQ dye was 25 mJ at lambda sub C=383nm with the bandwidth of 3nm for the pulse duration of 0.2microsec.

Laser-irradiated Kondo insulators: Controlling the Kondo effect and topological phases

NASA Astrophysics Data System (ADS)

Takasan, Kazuaki; Nakagawa, Masaya; Kawakami, Norio

2017-09-01

We investigate theoretically the nature of laser-irradiated Kondo insulators. Using Floquet theory and the slave-boson approach, we study a periodic Anderson model and derive an effective model that describes laser-irradiated Kondo insulators. In this model, we find two generic effects induced by laser light. One is dynamical localization, which suppresses hopping and hybridization. The other is laser-induced hopping and hybridization, which can be interpreted as synthetic spin-orbit coupling or a magnetic field. The first effect drastically changes the behavior of the Kondo effect. In particular, the Kondo effect under laser light qualitatively changes its character depending on whether the hybridization is on-site or off-site. The second effect triggers topological phase transitions. In topological Kondo insulators, linearly polarized laser light realizes phase transitions between trivial, weak topological, and strong topological Kondo insulators. Moreover, circularly polarized laser light breaks time-reversal symmetry and induces Weyl semimetallic phases. Our results make it possible to dynamically control the Kondo effect and topological phases in heavy-fermion systems. We also discuss experimental setups to detect the signatures.

Flying Focus: Spatiotemporal Control of the Laser Beam Intensity

NASA Astrophysics Data System (ADS)

Froula, D. H.; Turnbull, D.; Kessler, T. J.; Haberberger, D.; Bahk, S.-W.; Begishev, I. A.; Boni, R.; Bucht, S.; Davies, A.; Katz, J.; Sefkow, A. B.; Shaw, J. L.

2017-10-01

A ``flying focus'' is presented: this advanced focusing scheme provides unprecedented spatiotemporal control over the laser focal volume. A chromatic focusing system combined with chirped laser pulses enabled the speed of a small-diameter laser focus to propagate over nearly 100 × its Rayleigh length. Furthermore, the flying focus decouples the speed at which the peak intensity propagates from the group velocity of the laser pulse, allowing the laser focus to co- or counter-propagate along its axis at any velocity. Experiments have demonstrated a nearly constant intensity over 4.5 mm while the velocity of the focus ranged from subluminal (0.01 c) to superluminal (15 c) . These properties could provide the opportunity to overcome current fundamental limitations in laser-plasma amplifiers, laser-wakefield accelerators, photon accelerators, ion accelerators, and high-order frequency conversion. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944.

[Gastric ulcers in liver cirrhosis and their exposure to low-intensity infrared laser radiation].

PubMed

Vorozheĭkin, V M; Nazyrov, F G; Artykov, Sh N; Baĭbekov, I M

1992-01-01

By means of light, scanning electron microscopy and planimetry, the pathomorphology of gastric ulcers (GU) was investigated in patients who had died from liver cirrhosis (LC) and in rats with experimental portal hypertension (PH). It was noticed that GU are frequent (13.3%) in patients with LC. Experimental GU induced in rats with PH persist longer and their areas are larger than in ulcers without cirrhosis. The treatment of ulcers through abdominal wall with low-intensive infrared laser irradiation (LILR) causes significant acceleration of their epithelialization in the rat without cirrhosis. Ulcers in the animals with cirrhosis do not repair under LILR influence, but their area significantly decreases after forming collateral shunting. The congestion in the portal system is the main pathogenetic element in gastroesophageal ulcerogenesis. The laser therapy without decreasing portal hypertension is not efficient.

Morphological alterations of periodontal pocket epithelium following Nd:YAG laser irradiation.

PubMed

Ting, Chun-Chan; Fukuda, Mitsuo; Watanabe, Tomohisa; Sanaoka, Atsushi; Mitani, Akio; Noguchi, Toshihide

2014-12-01

The purpose of this in vivo study was to examine morphologic alterations in the periodontal pocket epithelium with presence or absence of clinical inflammation following the use of the Neodymium: Yttrium-Aluminum-Garnet (Nd:YAG) laser irradiation. Subgingival Nd:YAG laser irradiation has been proposed as an alternative technique for treatment of chronic periodontitis. Several published studies have reported the clinical outcomes of such treatment. Twenty patients, diagnosed with moderate chronic periodontitis, were selected for the study. A total of 32 sites was identified and divided into a control (n=18) and laser-treated test groups (n=14). Probing depth (PD) and bleeding on probing (BOP) were recorded for all sites. Test sites were irradiated with an Nd:YAG laser using parameters of 2 W, 200 mJ pulse energy, and 10 pps delivered through a 320 μm diameter tip. Total laser treatment time ranged from 1 to 2 min. Following treatment, all specimens were harvested via biopsy and processed for scanning electron microscopy (SEM) and histologic examination. Control group specimens, depending upon initial PD, exhibited either a relatively smooth and intact epithelium with little desquamation (PD≤3 mm), or increasing degrees of epithelial desquamation and leukocytic infiltration at a PD of ≥4 mm. In the laser-treated test group, the specimens with PD≤3 mm that were BOP negative (-) exhibited a thin layer of epithelium that was disrupted. In the specimens with initial PD of ≥4 mm, complete removal of the epithelium whose extent and degree were increasing, was observed in the inflamed portion, while epithelium remained in the uninflamed portion. The SEM and histologic findings demonstrated the feasibility of ablating pocket epithelium with an Nd:YAG laser irradiation using parameters of 2 W of power (200 mJ, 10 pps). Furthermore, the presence or absence of clinical inflammation appeared to have an impact on the degree of laser

Probing the photoresponse of individual Nb2O5 nanowires with global and localized laser beam irradiation.

PubMed

Tamang, Rajesh; Varghese, Binni; Mhaisalkar, Subodh G; Tok, Eng Soon; Sow, Chorng Haur

2011-03-18

Photoresponse of isolated Nb(2)O(5) nanowires (NW) padded with platinum (Pt) at both ends were studied with global irradiation by a laser beam and localized irradiation using a focused laser beam. Global laser irradiation on individual NW in ambient and vacuum conditions revealed photocurrent contributions with different time characteristics (rapid and slowly varying components) arising from defect level excitations, thermal heating effect, surface states and NW-Pt contacts. With a spot size of < 1 µm, localized irradiation highlighted the fact that the measured photocurrent in this single NW device (with and without applied bias) depended sensitively on the photoresponse at the NW-Pt contacts. At applied bias, unidirectional photocurrent was observed and higher photocurrent was achieved with localized laser irradiation at reverse-biased NW-Pt contacts. At zero bias, the opposite polarity of photocurrents was detected when the two NW-Pt contacts were subjected to focused laser beam irradiation. A reduced Schottky barrier/width resulting from an increase in charge carriers and thermoelectric effects arising from the localized thermal heating due to focused laser beam irradiation were proposed as the mechanisms dictating the photocurrent at the NW-Pt interface. Comparison of photocurrents generated upon global and localized laser irradiation showed that the main contribution to the photocurrent was largely due to the photoresponse of the NW-Pt contacts.

Near-infrared laser irradiation improves the development of mouse pre-implantation embryos.

PubMed

Yokoo, Masaki; Mori, Miho

2017-05-27

The aim of the present study was to assess the effects of near-infrared laser irradiation on the in vitro development of mouse embryos. Female ICR mice were superovulated with pregnant mare serum gonadotropin and human chorionic gonadotropin (hCG), and mated with male mice. Two-cell stage embryos were collected 40 h after administering hCG and cultured in M16 medium. Two-cell embryos (0 h after culture), 8-cell embryos (approx. 30 h after culture), morula (approx. 48 h after culture), and blastocysts (approx. 73 h after culture) were irradiated at 904 nm for 60 s. These embryos were cultured in a time-lapse monitoring system and the timing of blastocyst hatching was evaluated. Some of the irradiated blastocysts were transferred to the uterine horns of pseudopregnant recipients immediately after irradiation. Pregnancy rates, and offspring growth and fertility, were evaluated. Near-infrared laser irradiation increased the speed of in vitro mouse embryo development. In irradiated blastocysts, hatching was faster than in control (non-irradiated) blastocysts (18.4 vs. 28.2 h, P < 0.05). When 195 irradiated blastocysts were transferred to 18 pseudopregnant mice, all became pregnant and 92 (47.2%) normal-looking pups were born alive. When 182 control blastocysts were transferred to 17 pseudopregnant mice, 14 (82.4%) became pregnant and 54 (29.7%) normal-looking pups were born alive. The growth trajectories (up to 5 weeks) of offspring from irradiated blastocysts were similar to those from control blastocysts. Second generation offspring from transplanted animals were all fertile. These results indicate that near-infrared laser irradiation improves the quality of mouse embryo development in vitro, and increases the live birth rate without affecting the normality of the offspring. Thus, the near-infrared laser method may enhance the quality of embryos and contribute to improvements in reproductive technologies in mammals. Copyright © 2017 Elsevier Inc. All rights

Novel high-energy physics studies using intense lasers and plasmas

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

Leemans, Wim P.; Bulanov, Stepan; Esarey, Eric

2015-06-29

In the framework of the project “Novel high-energy physics studies using intense lasers and plasmas” we conducted the study of ion acceleration and “flying mirrors” with high intensity lasers in order to develop sources of ion beams and high frequency radiation for different applications. Since some schemes of laser ion acceleration are also considered a good source of “flying mirrors”, we proposed to investigate the mechanisms of “mirror” formation. As a result we were able to study the laser ion acceleration from thin foils and near critical density targets. We identified several fundamental factors limiting the acceleration in the RPAmore » regime and proposed the target design to compensate these limitations. In the case of near critical density targets, we developed a concept for the laser driven ion source for the hadron therapy. Also we studied the mechanism of “flying mirror” generation during the intense laser interaction with thin solid density targets. As for the laser-based positron creation and capture we initially proposed to study different regimes of positron beam generation and positron beam cooling. Since the for some of these schemes a good quality electron beam is required, we studied the generation of ultra-low emittance electron beams. In order to understand the fundamental physics of high energy electron beam interaction with high intensity laser pulses, which may affect the efficient generation of positron beams, we studied the radiation reaction effects.« less

Short Pulse Laser Absorption and Energy Partition at Relativistic Laser Intensities

NASA Astrophysics Data System (ADS)

Ping, Yuan

2005-10-01

We present the first absorption measurements at laser intensity between 10^17 to 10^20 W/cm^2 using an intergrating sphere and a suite of diagnostics that measures scale length, hot electrons and laser harmonics. A much-enhanced absorption in the regime of relativestic electron heating was observed. Furthermore, we present measurements on the partitioning of absorbed laser energy into thermal and non-thermal electrons when illuminating solid targets from 10^17 to 10^19 W/cm^2. This was measured using a sub-picosecond x-ray streak camera interfaced to a dual crystal von H'amos crystal spectrograph, a spherical crystal x-ray imaging spectrometer, an electron spectrometer and optical spectrometer. Our data suggests an intensity dependent energy-coupling transition with greater energy portion into non-thermal electrons that rapidly transition to thermal electrons. The details of these experimental results and modeling simulations will be presented.

Loss of structural water and carbonate of Nd:YAG laser-irradiated human enamel.

PubMed

Corrêa-Afonso, Alessandra Marques; Bachmann, Luciano; de Almeida, Cíntia Guimarães; Dibb, Regina Guenka Palma; Borsatto, Maria Cristina

2015-05-01

The objective of this study was to use Fourier Transform Infrared (FTIR) spectroscopy and Scanning Electron Microscopy (SEM) to assess whether Nd:YAG laser irradiation associated with a dye or not alters the chemical constitution of the enamel. Fourteen enamel sections were randomly divided into two groups: (1) Nd:YAG and (2) dye + Nd:YAG. First, the untreated enamel surfaces were analyzed by FTIR to acquire the control absorption spectrum. Next, Group 2 received a layer of inactivated coal diluted in deionized water before laser treatment. Enamel samples belonging to groups 1 and 2 were then irradiated with a 1,064-nm Nd:YAG laser (80 mJ, 10 Hz) in the contact mode; the carbonate absorption band and the water absorption band were measured in each sample after irradiation. The water band was measured again 24 h, 48 h, and 7 days after irradiation. Group 1 had statistically similar water and carbonate contents before and after irradiation. Group 2 displayed significantly lower (p < 0.05) water content after irradiation, which remained constant along time at 24 and 48 h. After 7 days, the water content increased slightly, being statistically higher than in the other experimental periods, except for the control. The carbonate/phosphate ratio was measured only at the beginning, and after irradiation, it decreased only in Group 2 indicating carbonate loss (p < 0.05). Irradiation with 1,064-nm Nd:YAG laser associated with a dye reduces the carbonate and structural water content in the enamel.

FT-Raman spectroscopic characterization of enamel surfaces irradiated with Nd:YAG and Er:YAG lasers

PubMed Central

Shahabi, Sima; Fekrazad, Reza; Johari, Maryam; Chiniforoush, Nasim; Rezaei, Yashar

2016-01-01

Background. Despite recent advances in dental caries prevention, caries is common and remains a serious health problem. Laser irradiation is one of the most common methods in preventive measures in recent years. Raman spectroscopy technique is utilized to study the microcrystalline structure of dental enamel. In this study, FT-Raman spectroscopy was used to evaluate chemical changes in enamel structure irradiated with Nd:YAG and Er:YAG lasers. Methods. We used 15 freshly-extracted, non-carious, human molars that were treated as follows: No treatment was carried out in group A (control group); Group B was irradiated with Er:YAG laser for 10 seconds under air and water spray; and Group C was irradiated with Nd:YAG laser for 10 seconds under air and water spray. After treatment, the samples were analyzed by FT-Raman spectroscopy. Results. The carbonate content evaluation with regard to the integrated area under the curve (1065/960 cm–1) exhibited a significant reduction in its ratio in groups B and C. The organic content (2935/960 cm-1) area exhibited a significant decrease after laser irradiation in group B and C. Conclusion. The results showed that the mineral and organic matrices of enamel structure were affected by laser irradiation; therefore, it might be a suitable method for caries prevention. PMID:28096945

Enhancement of stability of aqueous suspension of alumina nanoparticles by femtosecond laser irradiation

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

Seo, Youngsang; Ha, Jeonghong; Kim, Dongsik, E-mail: dskim87@postech.ac.kr

2015-09-21

In this work, we report substantially enhanced colloidal stability of aqueous nanoparticle suspensions by ultrashort laser pulse irradiation. A Ti:Sapphire femtosecond laser (wavelength: 800 nm; pulse duration: 50 fs at full width at half maximum) was used to modify the electrochemical properties of nanoparticle suspensions at laser fluences below the particle ablation threshold. The colloidal stability of the suspension was evaluated by zeta potential and dynamic light scattering (DLS). The DLS results along with the images from transmission electron microscopy revealed that the laser irradiation caused no distinct morphological change to the individual alumina particles, but a substantial portion of themore » clustered particles was fragmented by the laser pulses, decreasing the apparent size of the suspended particles. Also, X-ray photoelectron spectroscopy analysis indicates that the laser irradiation modified the surface chemistry of the alumina particles. The stabilizing capability of the proposed technique was turned out to be better than that of conventional ultrasonic treatments. The stability of the laser-treated sample with no added surfactant was maintained for up to 30 days, without requiring an additional homogenizing process such as magnetic stirring.« less

Apparatus and process for active pulse intensity control of laser beam

DOEpatents

Wilcox, Russell B.

1992-01-01

An optically controlled laser pulse energy control apparatus and process is disclosed wherein variations in the energy of a portion of the laser beam are used to vary the resistance of a photodetector such as a photoresistor through which a control voltage is fed to a light intensity controlling device through which a second portion of the laser beam passes. Light attenuation means are provided to vary the intensity of the laser light used to control the resistance of the photodetector. An optical delay path is provided through which the second portion of the beam travels before reaching the light intensity controlling device. The control voltage is supplied by a variable power supply. The apparatus may be tuned to properly attenuate the laser beam passing through the intensity controlling device by adjusting the power supply, the optical delay path, or the light attenuating means.

Investigation of longitudinal proton acceleration in exploded targets irradiated by intense short-pulse laser

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

Gauthier, M.; CEA, DAM, DIF, 91297 Arpajon; Lévy, A.

2014-01-15

It was recently shown that a promising way to accelerate protons in the forward direction to high energies is to use under-dense or near-critical density targets instead of solids. Simulations have revealed that the acceleration process depends on the density gradients of the plasma target. Indeed, under certain conditions, the most energetic protons are predicted to be accelerated by a collisionless shock mechanism that significantly increases their energy. We report here the results of a recent experiment dedicated to the study of longitudinal ion acceleration in partially exploded foils using a high intensity (∼5 × 10{sup 18} W/cm{sup 2}) picosecond laser pulse. Wemore » show that protons accelerated using targets having moderate front and rear plasma gradients (up to ∼8 μm gradient length) exhibit similar maximum proton energy and number compared to proton beams that are produced, in similar laser conditions, from solid targets, in the well-known target normal sheath acceleration regime. Particle-In-Cell simulations, performed in the same conditions as the experiment and consistent with the measurements, allow laying a path for further improvement of this acceleration scheme.« less

Mass removal by oxidation and sublimation of porous graphite during fiber laser irradiation

NASA Astrophysics Data System (ADS)

Phillips, Grady T.; Bauer, William A.; Fox, Charles D.; Gonzales, Ashley E.; Herr, Nicholas C.; Gosse, Ryan C.; Perram, Glen P.

2017-01-01

The various effects of laser heating of carbon materials are key to assessing laser weapon effectiveness. Porous graphite plates, cylinders, and cones with densities of 1.55 to 1.82 g/cm3 were irradiated by a 10-kW fiber laser at 0.075 to 3.525 kW/cm2 for 120 s to study mass removal and crater formation. Surface temperatures reached steady state values as high as 3767 K. The total decrease in sample mass ranged from 0.06 to 6.29 g, with crater volumes of 0.52 to 838 mm3, and penetration times for 12.7-mm-thick plates as short as 38 s. Minor contaminants in the graphite samples produced calcium and iron oxide to be redeposited on the graphite surface. Dramatic graphite crystalline structures are also produced at higher laser irradiances. Significantly increased porosity of the sample is observed even outside the laser-irradiated region. Total mass removed increases with deposited laser energy at a rate of 4.83 g/MJ for medium extruded graphite with an apparent threshold of 0.15 MJ. At ˜3.5 kW/cm2, the fractions of the mass removed from the cylindrical samples in the crater, surrounding trench, and outer region of decreased porosity are 38%, 47%, and 15%, respectively. Graphite is particularly resistant to damage by high power lasers. The new understanding of graphite combustion and sublimation during laser irradiation is vital to the more complex behavior of carbon composites.

Does laser diode irradiation improve the degree of conversion of simplified dentin bonding systems?

PubMed

Brianezzi, Leticia Ferreira de Freitas; Maenosono, Rafael Massunari; Bim, Odair; Zabeu, Giovanna Speranza; Palma-Dibb, Regina Guenka; Ishikiriama, Sérgio Kiyoshi

2017-01-01

This study aimed to investigate the effect of laser diode irradiation on the degree of conversion (DC), water sorption (WS), and water solubility (WSB) of these bonding systems in an attempt to improve their physico-mechanical resistance. Two bonding agents were tested: a two-step total-etch system [Adper™ Single Bond 2, 3M ESPE (SB)] and a universal system [Adper™ Single Bond Universal, 3M ESPE (SU)]. Square-shaped specimens were prepared and assigned into 4 groups (n=5): SB and SU (control groups - no laser irradiation) and SB-L and SU-L [SB and SU laser (L) - irradiated groups]. DC was assessed using Fourier transform infrared spectroscopy with attenuated total reflectance. Additional uncured resin samples (≈3.0 µL, n=5) of each adhesive were also scanned for final DC calculation. For WS/WSB tests, similar specimens (n=10) were prepared and measured by monitoring the mass changes after dehydration/water storage cycles. For both tests, adhesive fluids were dropped into standardized Teflon molds (6.0×6.0×1.0 mm), irradiated with a 970-nm laser diode, and then polymerized with an LED-curing unit (1 W/cm2). Laser irradiation immediately before photopolymerization increased the DC (%) of the tested adhesives: SB-L>SB>SU-L>SU. For WS/WSB (μg/mm3), only the dentin bonding system (DBS) was a significant factor (p<0.05): SB>SU. Irradiation with a laser diode improved the degree of conversion of all tested simplified dentin bonding systems, with no impact on water sorption and solubility.

Pyrolysis responses of kevlar/epoxy composite materials on laser irradiating

NASA Astrophysics Data System (ADS)

Liu, Wei-ping; Wei, Cheng-hua; Zhou, Meng-lian; Ma, Zhi-liang; Song, Ming-ying; Wu, Li-xiong

2017-05-01

The pyrolysis responses of kevlar/epoxy composite materials are valuable to study in a case of high temperature rising rate for its widely application. Distinguishing from the Thermal Gravimetric Analysis method, an apparatus is built to research the pyrolysis responses of kevlar/epoxy composite materials irradiated by laser in order to offer a high temperature rising rate of the sample. By deploying the apparatus, a near real-time gas pressure response can be obtained. The sample mass is weighted before laser irradiating and after an experiment finished. Then, the gas products molecular weight and the sample mass loss evolution are derived. It is found that the pressure and mass of the gas products increase with the laser power if it is less than 240W, while the molecular weight varies inversely. The variation tendency is confusing while the laser power is bigger than 240W. It needs more deeper investigations to bring it to light.

Improving oxidation resistance and thermal insulation of thermal barrier coatings by intense pulsed electron beam irradiation

NASA Astrophysics Data System (ADS)

Mei, Xianxiu; Liu, Xiaofei; Wang, Cunxia; Wang, Younian; Dong, Chuang

2012-12-01

In this paper, intense pulsed electron beam was used for the irradiation treatment of 6-8% Y2O3-stablized ZrO2 thermal barrier coating prepared by electron beam-physical vapor deposition to achieve the "sealing" of columnar crystals, thus improving their thermal insulation properties and high temperature oxidation resistance. The electron beam parameters used were: pulse duration 200 μs, electron voltage 15 kV, energy density 3, 5, 8, 15, 20 J/cm2, and pulsed numbers 30. 1050 °C cyclic oxidation and static oxidation experiments were used for the research on oxidation resistance of the coatings. When the energy density of the electron beam was larger than 8 J/cm2, ZrO2 ceramic coating surface was fully re-melted and became smooth, dense and shiny. The coating changed into a smooth polycrystalline structure, thus achieving the "sealing" effect of the columnar crystals. After irradiations with the energy density of 8-15 J/cm2, the thermally grown oxide coating thickness decreased significantly in comparison with non-irradiated coatings, showing that the re-melted coating improved the oxidation resistance of the coatings. The results of thermal diffusivity test by laser flash method showed that the thermal diffusion rate of the irradiated coating was lower than that of the coating without irradiation treatment, and the thermal insulation performance of irradiated coating was improved.

Low Level Laser Irradiation of Nerve Cells In Vitro

DTIC Science & Technology

1996-01-01

Advisor Michael Miloro, D.M.D., M.D. College of Dentistry ABSTRACT Low energy laser treatment of patients with nerve injuries has been reported to achieve...Isolation and Culture 15 vii Cell Lines 17 Cell Expansion 19 Cell Freezing 20 Experimental Design 20 GaA1As Laser Diode 22 Radiation Schedule 23...of 1 six well plate. Two groups served as controls. The remaining groups were irradiated with a 70 mW GaA1As laser diode , wavelength 820-830 nm

Non-contact profilometry of eroded and abraded enamel irradiated with an Er:YAG laser

PubMed Central

Scatolin, Renata Siqueira; Colucci, Vivian; Lepri, Taísa Penazzo; de Alexandria, Adílis Kalina; Maia, Lucianne Cople; Galo, Rodrigo; Borsatto, Maria Cristina; Corona, Silmara Aparecida Milori

2018-01-01

Abstract Literature has reported positive results regarding the use of lasers in the control of erosive lesions; however, evaluating whether they are effective in the control of the progression of erosive/abrasive lesions is important. Objectives This study aimed to evaluate the effect of the Er:YAG laser irradiation in controlling the progression of erosion associated with abrasive lesions in enamel. Material and methods Bovine incisors were sectioned, flattened and polished. Forty-eight enamel slabs were subjected to treatment in an intraoral phase. Twelve volunteers used an intraoral appliance containing one slab that was irradiated with an Er:YAG laser (5.2 J/cm2, 85 mJ, 2 Hz) and another non-irradiated slab on each side of the appliance, during one phase of 5 d, under a split-mouth design. Devices were subjected to erosive challenges (1% citric acid, 5 min, 3 times a day) and abrasive challenges one h after (brushing force of 1.5 N for 15 s) randomly and independently on each side of the device. Measurements of enamel loss were performed via 3D optical profilometry (μm). We analyzed data using the Kruskal-Wallis and Mann-Whitney tests and morphological characteristics via scanning electron microscopy. Results Following erosive and abrasive challenges, the group that was irradiated with the Er:YAG laser presented less loss of structure than the non-irradiated group. The group that underwent erosion and irradiation did not exhibit a significant difference from the non-irradiated group. Conclusion Irradiation with the Er:YAG laser did not control the loss of structure of enamel subjected to erosion but did control abrasion after erosion. PMID:29742259

Non-contact profilometry of eroded and abraded enamel irradiated with an Er:YAG laser.

PubMed

Scatolin, Renata Siqueira; Colucci, Vivian; Lepri, Taísa Penazzo; Alexandria, Adílis Kalina de; Maia, Lucianne Cople; Galo, Rodrigo; Borsatto, Maria Cristina; Corona, Silmara Aparecida Milori

2018-01-01

Literature has reported positive results regarding the use of lasers in the control of erosive lesions; however, evaluating whether they are effective in the control of the progression of erosive/abrasive lesions is important. Objectives This study aimed to evaluate the effect of the Er:YAG laser irradiation in controlling the progression of erosion associated with abrasive lesions in enamel. Material and methods Bovine incisors were sectioned, flattened and polished. Forty-eight enamel slabs were subjected to treatment in an intraoral phase. Twelve volunteers used an intraoral appliance containing one slab that was irradiated with an Er:YAG laser (5.2 J/cm2, 85 mJ, 2 Hz) and another non-irradiated slab on each side of the appliance, during one phase of 5 d, under a split-mouth design. Devices were subjected to erosive challenges (1% citric acid, 5 min, 3 times a day) and abrasive challenges one h after (brushing force of 1.5 N for 15 s) randomly and independently on each side of the device. Measurements of enamel loss were performed via 3D optical profilometry (μm). We analyzed data using the Kruskal-Wallis and Mann-Whitney tests and morphological characteristics via scanning electron microscopy. Results Following erosive and abrasive challenges, the group that was irradiated with the Er:YAG laser presented less loss of structure than the non-irradiated group. The group that underwent erosion and irradiation did not exhibit a significant difference from the non-irradiated group. Conclusion Irradiation with the Er:YAG laser did not control the loss of structure of enamel subjected to erosion but did control abrasion after erosion.

Polymer Morphological Change Induced by Terahertz Irradiation

PubMed Central

Hoshina, Hiromichi; Suzuki, Hal; Otani, Chiko; Nagai, Masaya; Kawase, Keigo; Irizawa, Akinori; Isoyama, Goro

2016-01-01

As terahertz (THz) frequencies correspond to those of the intermolecular vibrational modes in a polymer, intense THz wave irradiation affects the macromolecular polymorph, which determines the polymer properties and functions. THz photon energy is quite low compared to the covalent bond energy; therefore, conformational changes can be induced “softly,” without damaging the chemical structures. Here, we irradiate a poly(3-hydroxybutylate) (PHB) / chloroform solution during solvent casting crystallization using a THz wave generated by a free electron laser (FEL). Morphological observation shows the formation of micrometer-sized crystals in response to the THz wave irradiation. Further, a 10−20% increase in crystallinity is observed through analysis of the infrared (IR) absorption spectra. The peak power density of the irradiating THz wave is 40 MW/cm2, which is significantly lower than the typical laser intensities used for material manipulation. We demonstrate for the first time that the THz wave effectively induces the intermolecular rearrangement of polymer macromolecules. PMID:27272984

Polymer Morphological Change Induced by Terahertz Irradiation

NASA Astrophysics Data System (ADS)

Hoshina, Hiromichi; Suzuki, Hal; Otani, Chiko; Nagai, Masaya; Kawase, Keigo; Irizawa, Akinori; Isoyama, Goro

2016-06-01

As terahertz (THz) frequencies correspond to those of the intermolecular vibrational modes in a polymer, intense THz wave irradiation affects the macromolecular polymorph, which determines the polymer properties and functions. THz photon energy is quite low compared to the covalent bond energy; therefore, conformational changes can be induced “softly,” without damaging the chemical structures. Here, we irradiate a poly(3-hydroxybutylate) (PHB) / chloroform solution during solvent casting crystallization using a THz wave generated by a free electron laser (FEL). Morphological observation shows the formation of micrometer-sized crystals in response to the THz wave irradiation. Further, a 10-20% increase in crystallinity is observed through analysis of the infrared (IR) absorption spectra. The peak power density of the irradiating THz wave is 40 MW/cm2, which is significantly lower than the typical laser intensities used for material manipulation. We demonstrate for the first time that the THz wave effectively induces the intermolecular rearrangement of polymer macromolecules.

Angiogenic response in the chick chorioallantoic membrane model to laser-irradiated cartilage

NASA Astrophysics Data System (ADS)

Karamzadeh, Amir M.; Wong, Brian J.; Milner, Thomas E.; Wilson, Marie; Liaw, Lih-Huei L.; Nelson, J. Stuart

1999-06-01

Laser radiation can be used to reshape cartilage grafts via thermally mediated stress relaxation. While several studies have addressed the biophysical changes accompanying reshaping, cartilage viability following laser irradiation has not been extensively investigated. The objective of this study was to determine the extent of angioinvasion of irradiated cartilage explant placed onto the chick chorioallantoic membrane (CAM) model. Angioinvasion of the tissue matrix does not occur in viable cartilage tissue, whereas denatured tissue is readily vasculairzed and/or resorbed in vivo. Porcine septal cartilage specimens were removed from freshly sacrificed animals and divided into three protocols (n=10 each group) consisting of an untreated control, cartilage boiled in saline solution for one hour, and a laser irradiated group (Nd:YAG, λ=1.32 μm, 30.8 W/cm2, irradiation time = 10 sec). Following laser irradiation, tissue specimens were washed in antibiotic solution sand cut into small cubes (~1.5 mm3). The cartilage specimens were placed onto the surface of twenty CAMs, six of which, survived the entire 14 days incubation period. After incubation, the membranes and specimens were fixed in situ with formaldehyde, an then photographed using a dissection microscope. Cartilage specimens were prepared for histologic evaluation and stained with hematoxylin and eosin. Examination with a dissecting microscope showed no obvious vascular invasion of the cartilage or loss of gross tissue integrity in both the control and laser treated groups. In contrast, boiled specimens appeared to be partially or completely resorbed by the surrounding CAM vascular network. These gross findings were also confirmed by histological examination. In summary, our preliminary studies suggest that cartilage specimens treated using the present laser parameters remain resistant to angioinvasion or metabolism by the CAM, whereas boiled tissue undergoes resorption. Clinically, uncontrolled heating may

Low-intensity red and infrared lasers on XPA and XPC gene expression

NASA Astrophysics Data System (ADS)

Fonseca, A. S.; Magalhães, L. A. G.; Mencalha, A. L.; Ferreira-Machado, S. C.; Geller, M.; Paoli, F.

2014-09-01

Laser devices emit monochromatic, coherent, and highly collimated intense beams of light that are useful for a number of biomedical applications. However, for low-intensity lasers, possible adverse effects of laser light on DNA are still controversial. In this work, the expression of XPA and XPC genes in skin and muscle tissue exposed to low-intensity red and infrared lasers was evaluated. Skin and muscle tissue of Wistar rats were exposed to low-intensity red and infrared lasers at different fluences in continuous mode emission. Skin and muscle tissue samples were withdrawn for total RNA extraction, cDNA synthesis, and evaluation of actin gene expression by quantitative polymerase chain reaction. Data obtained show that laser radiation alters the expression of XPA and XPC mRNA differently in skin and muscle tissue of Wistar rats, depending on physical (fluence and wavelength) and biological (tissue) parameters. Laser light could modify expression of genes related to the nucleotide excision repair pathway at fluences and wavelengths used in clinical protocols.

Basic study of charring detection at the laser catheter-tip using back scattering light measurement during therapeutic laser irradiation in blood.

PubMed

Takahashi, Mei; Ito, Arisa; Kajihara, Takuro; Matsuo, Hiroki; Arai, Tsunenori

2010-01-01

The purpose of this study is to investigate transient process of the charring at the laser catheter-tip in blood during therapeutic laser irradiation by the back scattering light measurement to detect precursor state of the charring. We took account of using photodynamic therapy for arrhythmia in blood through the laser catheter. We observed the influence of the red laser irradiation (λ=663 nm) upon the shape of red blood cells (RBCs). The RBCs aggregation, round formation, and hemolysis were took place sequentially before charring. With a model blood sandwiched between glass plates simulated as a catheter-tip boundary, we measured diffuse-reflected-light power and transmitted-light power simultaneously and continuously by a microscopic optics during the laser irradiation. We found that measured light power changes were originated with RBCs shape change induced by temperature rise due to the laser irradiation. A gentle peak following a slow descending was observed in the diffuse-reflected-light power history. This history might indicate the precursor state of the charring, in which the hemolysis might be considered to advance rapidly. We think that the measurement of diffuse-reflected-light power history might be able to detect precursor state of charring at the catheter-tip in blood.

Vacuum aperture isolator for retroreflection from laser-irradiated target

DOEpatents

Benjamin, Robert F.; Mitchell, Kenneth B.

1980-01-01

The disclosure is directed to a vacuum aperture isolator for retroreflection of a laser-irradiated target. Within a vacuum chamber are disposed a beam focusing element, a disc having an aperture and a recollimating element. The edge of the focused beam impinges on the edge of the aperture to produce a plasma which refracts any retroreflected light from the laser's target.

Influence of laser frequency chirp on deuteron energy from laser-driven deuterated methane cluster expansion

NASA Astrophysics Data System (ADS)

Li, H. Y.; Liu, J. S.

2010-06-01

The simulations of three-dimensional particle dynamics are carried out to investigate the Coulomb explosion dynamics of deuterated methane clusters under the irradiation of an ultrashort intense laser pulse. The final kinetic energy of deuterons produced from the cluster explosion is calculated as a function of the pulse width, the laser intensity and the pulse chirp. It is found that the deuteron energy obtained in an intense laser pulse with negative chirp is higher than that with positive chirp, which agrees qualitatively with the experimental results reported by Fukuda et al. [Y. Fukuda et al., Phys. Rev. A 67, 061201 (2003)].

Plasma-based polarizer and waveplate at large laser intensity

NASA Astrophysics Data System (ADS)

Lehmann, G.; Spatschek, K. H.

2018-06-01

A plasma photonic crystal consists of a plasma density grating which is created in underdense plasma by counterpropagating laser beams. When a high-power laser pulse impinges the crystal, it might be reflected or transmitted. So far only one type of pulse polarization, namely the so-called s wave (or TE mode) was investigated (when the electric field vector is perpendicular to the plane of incidence). Here, when investigating also so-called p waves (or TM modes, where the magnetic field vector is perpendicular to the plane of incidence), it is detected that the transmission and reflection properties of the plasma photonic crystal depend on polarization. A simple analytic model of the crystal allows one to make precise predictions. The first conclusion is that in some operational regime the crystal can act as a plasma polarizer for high-intensity laser pulses. Also, differences in phase velocities for grazing incidence between s and p polarization are found. Thus, secondly, the crystal can be utilized as a waveplate, e.g., transforming linearly polarized laser light into circular polarization. All these processes extend to laser intensities beyond the damage intensities of so far used solid state devices.

Thermal effects in tissues induced by interstitial irradiation of near infrared laser with a cylindrical diffuser

NASA Astrophysics Data System (ADS)

Le, Kelvin; Johsi, Chet; Figueroa, Daniel; Goddard, Jessica; Li, Xiaosong; Towner, Rheal A.; Saunders, Debra; Smith, Nataliya; Liu, Hong; Hode, Tomas; Nordquist, Robert E.; Chen, Wei R.

2011-03-01

Laser immunotherapy (LIT), using non-invasive laser irradiation, has resulted in promising outcomes in the treatment of late-stage cancer patients. However, the tissue absorption of laser light limits the clinical applications of LIT in patients with dark skin, or with deep tumors. The present study is designed to investigate the thermal effects of interstitial irradiation using an 805-nm laser with a cylindrical diffuser, in order to overcome the limitations of the non-invasive mode of treatment. Cow liver and rat tumors were irradiated using interstitial fiber. The temperature increase was monitored by thermocouples that were inserted into the tissue at different sites around the cylinder fiber. Three-dimensional temperature distribution in target tissues during and after interstitial laser irradiation was also determined by Proton Resonance Frequency. The preliminary results showed that the output power of laser and the optical parameters of the target tissue determined the light distribution in the tissue. The temperature distributions varied in the tissue according to the locations relative to the active tip of the cylindrical diffuser. The temperature increase is strongly related to the laser power and irradiation time. Our results using thermocouples and optical sensors indicated that the PRF method is reliable and accurate for temperature determination. Although the inhomogeneous biological tissues could result in temperature fluctuation, the temperature trend still can be reliable enough for the guidance of interstitial irradiation. While this study provides temperature profiles in tumor tissue during interstitial irradiation, the biological effects of the irradiation remain unclear. Future studies will be needed, particularly in combination with the application of immunostimulant for inducing tumor-specific immune responses in the treatment of metastatic tumors.

Ablation of dentin by irradiation of violet diode laser

NASA Astrophysics Data System (ADS)

Hatayama, H.; Kato, J.; Akashi, G.; Hirai, Y.; Inoue, A.

2006-02-01

Several lasers have been used for clinical treatment in dentistry. Among them, diode lasers are attractive because of their compactness compared with other laser sources. Near-infrared diode lasers have been practically used for cutting soft tissues. Because they penetrate deep to soft tissues, they cause sufficiently thick coagulation layer. However, they aren't suitable for removal of carious dentin because absorption by components in dentin is low. Recently, a violet diode laser with a wavelength of 405nm has been developed. It will be effective for cavity preparation because dentin contains about 20% of collagen whose absorption coefficient at a violet wavelength is larger than that at a near-infrared wavelength. In this paper, we examined cutting performance of the violet diode laser for dentin. To our knowledge, there have been no previous reports on application of a violet laser to dentin ablation. Bovine teeth were irradiated by continuous wave violet diode laser with output powers in a range from 0.4W to 2.4W. The beam diameter on the sample was about 270μm and an irradiation time was one second. We obtained the crater ablated at more than an output power of 0.8W. The depth of crater ranged from 20μm at 0.8W to 90μm at 2.4W. Furthermore, the beam spot with an output power of 1.7W was scanned at a speed of 1mm/second corresponding to movement of a dentist's hand in clinical treatment. Grooves with the depth of more than 50μm were also obtained. From these findings, the violet diode laser has good potential for cavity preparation. Therefore, the violet diode laser may become an effective tool for cavity preparation.

Effect of Doping on the Properties of Hydrogenated Amorphous Silicon Irradiated with Femtosecond Laser Pulses

NASA Astrophysics Data System (ADS)

Denisova, K. N.; Il'in, A. S.; Martyshov, M. N.; Vorontsov, A. S.

2018-04-01

A comparative analysis of the effect of femtosecond laser irradiation on the structure and conductivity of undoped and boron-doped hydrogenated amorphous silicon ( a-Si: H) is performed. It is demonstrated that the process of nanocrystal formation in the amorphous matrix under femtosecond laser irradiation is initiated at lower laser energy densities in undoped a-Si: H samples. The differences in conductivity between undoped and doped a-Si: H samples vanish almost completely after irradiation with an energy density of 150-160 mJ/cm2.

Microhardness evaluations of CAD/CAM ceramics irradiated with CO2 or Nd:YAP laser

PubMed Central

Rocca, Jean Paul; Fornaini, Carlo; Medioni, Etienne; Brulat-Bouchard, Nathalie

2017-01-01

Background and aims The aim of this study was to measure the microhardness values of irradiated computer-aided design/computer-aided manufacturing (CAD/CAM) ceramics surfaces before and after thermal treatment. Materials and Methods Sixty CAD/CAM ceramic discs were prepared and grouped by material, i.e. lithium disilicate ceramic (Emax CAD) and zirconia ceramic (Emax ZirCAD). Laser irradiation at the material surface was performed with a carbon dioxide laser at 5 Watt (W) or 10 W power in continuous mode (CW mode), or with a neodymium:yttrium aluminum perovskite (Nd:YAP) laser at 10 W on graphite and non-graphite surfaces. Vickers hardness was tested at 0.3 kgf for lithium disilicate and 1 kgf for zirconia. Results Emax CAD irradiated with CO2 at 5 W increased microhardness by 6.32 GPa whereas Emax ZirCAD irradiated with Nd:YAP decreased microhardness by 17.46 GPa. Conclusion CO2 laser effectively increases the microhardness of lithium disilicate ceramics (Emax CAD). PMID:28740324

Effect of high-frequency near-infrared diode laser irradiation on periodontal tissues during experimental tooth movement in rats.

PubMed

Gunji, Hidemi; Kunimatsu, Ryo; Tsuka, Yuji; Yoshimi, Yuki; Sumi, Keisuke; Awada, Tetsuya; Nakajima, Kengo; Kimura, Aya; Hiraki, Tomoka; Hirose, Naoto; Yanoshita, Makoto; Tanimoto, Kotaro

2018-02-05

Tooth movement during orthodontic treatment is associated with bone neoplasticity and bone resorption on the tension and pressure sides. Previous clinical studies have suggested that low-power laser irradiation can accelerate tooth movement during orthodontic treatment, although the underlying mechanism remains unclear. In this study, we used a high-frequency near-infrared diode laser that generates less heat and examined the histologic changes in periodontal tissue during experimental tooth movement with laser irradiation. A nickel-titanium closed coil was mounted between the maxillary left side first molar and incisor of rats to model experimental tooth movement. The laser-irradiation and the control groups were set, and the amount of movement of the first molar on 7th and 14th days after the start of pulling of the first molar tooth on the maxillary left was measured by three-dimensional analysis of µCT. After tooth movement, tissue samples from the mesial and tension sides were collected, and successive horizontal sections were prepared and examined using hematoxylin-eosin and TRAP staining and immunohistochemical staining for RANKL, OPG, ALP, and proliferating cell nuclear antigen (PCNA). Changes in tissue temperature following laser irradiation were also examined. Laser irradiation significantly increased tooth movement compared with non-irradiated controls. Histologic staining of the pressure-side mesial root in laser-irradiated rats revealed enhanced RANKL expression and increased numbers of TRAP-positive cells compared with controls. By contrast, on the tension side, laser irradiation led to increased expression of ALP and PCNA. These data indicate that high-frequency near-infrared diode laser irradiation on the pressure side upregulates RANKL expression and accelerates osteoclast differentiation, facilitating bone resorption, whereas bone formation is induced on the tension side. This study demonstrates that high-frequency near-infrared diode laser

Dependence of the correlated-momentum patterns in double ionization on the carrier-envelope phase and intensity of a few-cycle laser pulse

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

Xin, G. G.; Ye, D. F.; Graduate School, China Academy of Engineering Physics, Beijing 100088

2010-12-15

In the present paper, we investigate the correlated electron emission of atoms irradiated by a few-cycle laser pulse, with emphasis on the correlated longitudinal momentum spectra. We find that the spectra show clear v-shaped structures, in analogy to what was observed recently in long-pulse experiments. Moreover, the patterns of the spectra depend sensitively on the carrier-envelope phase as well as the laser intensity. The v-shaped structure is more pronounced at lower and higher intensities and becomes obscure at medium intensity. At a lower intensity, upon change of the phase from 0 to {pi}/2, the v-shaped structure shifts from the firstmore » quadrant to the third quadrant and the ratios between the double ionization yields in the first and third quadrants are found to increase by a few orders of magnitude. The semiclassical rescattering model is exploited in the preceding calculations and the underlying mechanisms are uncovered by analyzing the subcycle dynamics of classical trajectories.« less

Effects of erbium, chromium:YSGG laser irradiation on root surface: morphological and atomic analytical studies.

PubMed

Kimura, Y; Yu, D G; Kinoshita, J; Hossain, M; Yokoyama, K; Murakami, Y; Nomura, K; Takamura, R; Matsumoto, K

2001-04-01

The purpose of this study was to investigate the morphological and atomic changes on the root surface by stereoscopy, field emission-scanning electron microscopy (FE-SEM), and energy dispersive X-ray spectroscopy (SEM-EDX) after erbium, chromium:yttrium, scandium, gallium, garnet (Er,Cr:YSGG) laser irradiation in vitro. There have been few reports on morphological and atomic analytical study on root surface by Er,Cr:YSGG laser irradiation. Eighteen extracted human premolar and molar teeth were irradiated on root surfaces at a vertical position with water-air spray by an Er,Cr:YSGG laser at the parameter of 5.0 W and 20 Hz for 5 sec while moving. The samples were then morphologically observed by stereoscopy and FE-SEM and examined atomic-analytically by SEM-EDX. Craters having rough but clean surfaces and no melting or carbonization were observed in the samples. An atomic analytical examination showed that the calcium ratio to phosphorus showed no significant changes between the control and irradiated areas (p > 0.01). These results showed that the Er,Cr:YSGG laser has a good cutting effect on root surface and causes no burning or melting after laser irradiation.

Computational Modeling of Ablation on an Irradiated Target

NASA Astrophysics Data System (ADS)

Mehmedagic, Igbal; Thangam, Siva

2017-11-01

Computational modeling of pulsed nanosecond laser interaction with an irradiated metallic target is presented. The model formulation involves ablation of the metallic target irradiated by pulsed high intensity laser at normal atmospheric conditions. Computational findings based on effective representation and prediction of the heat transfer, melting and vaporization of the targeting material as well as plume formation and expansion are presented along with its relevance for the development of protective shields. In this context, the available results for a representative irradiation from 1064 nm laser pulse is used to analyze various ablation mechanisms, variable thermo-physical and optical properties, plume expansion and surface geometry. Funded in part by U. S. Army ARDEC, Picatinny Arsenal, NJ.

Optothermal transfer simulation in laser-irradiated human dentin.

PubMed

Moriyama, Eduardo H; Zangaro, Renato A; Lobo, Paulo D C; Villaverde, Antonio Balbin; Pacheco, Marcos T; Watanabe, Ii-Sei; Vitkin, Alex

2003-04-01

Laser technology has been studied as a potential replacement to the conventional dental drill. However, to prevent pulpal cell damage, information related to the safety parameters using high-power lasers in oral mineralized tissues is needed. In this study, the heat distribution profiles at the surface and subsurface regions of human dentine samples irradiated with a Nd:YAG laser were simulated using Crank-Nicolson's finite difference method for different laser energies and pulse durations. Heat distribution throughout the dentin layer, from the external dentin surface to the pulp chamber wall, were calculated in each case, to investigate the details of pulsed laser-hard dental tissue interactions. The results showed that the final temperature at the pulp chamber wall and at the dentin surface are strongly dependent on the pulse duration, exposure time, and the energy contained in each pulse.

Analyses of surface coloration on TiO 2 film irradiated with excimer laser

NASA Astrophysics Data System (ADS)

Zheng, H. Y.; Qian, H. X.; Zhou, W.

2008-01-01

TiO 2 film of around 850 nm in thickness was deposited on a soda-lime glass by PVD sputtering and irradiated using one pulse of krypton-fluorine (KrF) excimer laser (wavelength of 248 nm and pulse duration of 25 ns) with varying fluence. The color of the irradiated area became darker with increasing laser fluence. Irradiated surfaces were characterized using optical microscopy, scanning electron microscopy, Raman spectroscopy and atomic force microscopy. Surface undergoes thermal annealing at low laser fluence of 400 and 590 mJ/cm 2. Microcracks at medium laser fluence of 1000 mJ/cm 2 are attributed to surface melting and solidification. Hydrodynamic ablation is proposed to explain the formation of micropores and networks at higher laser fluence of 1100 and 1200 mJ/cm 2. The darkening effect is explained in terms of trapping of light in the surface defects formed rather than anatase to rutile phase transformation as reported by others. Controlled darkening of TiO 2 film might be used for adjustable filters.

The neuroprotective effects of intravascular low level laser irradiation on cerebral ischemia rats

NASA Astrophysics Data System (ADS)

Qiu, Yongming; Lu, Zhaofeng; Wang, Zhongguang; Jiang, Jiyao

2005-07-01

The effects of intravascular low level laser irradiation of He-Ne on rat MCAo-induced cerebral injury were studied. The results showed that control rats (subjected to MCAo injury without laser treatment) at 7d exhibited striatal and cortical brain infarction in the right hemisphere from approximately 3 to 11mm from the front pole. the total infarct volume in this group was 34.5+/-8.1mm3. For experimental rats (with laser management), the total infarct volume was 29.0+/-9.0mm3. P was gained less than 0.05. The neurological score of control group was 4.7+/-0.6 and it was 5.2+/-1.0 in experimental group, comparison by statistical analysis showed P less than 0.05. The cerebral pathological damages in the control group were more severe than in experimental group. We concluded that the intravascular low level laser irradiation has no remarked complication and is helpful to reduce ischemic damage. There is clinically potential for the application of intravascular He-Ne low level laser irradiation in ischemia stroke.

Propagation of intense short laser pulses in the atmosphere.

PubMed

Sprangle, P; Peñano, J R; Hafizi, B

2002-10-01

The propagation of short, intense laser pulses in the atmosphere is investigated theoretically and numerically. A set of three-dimensional (3D), nonlinear propagation equations is derived, which includes the effects of dispersion, nonlinear self-focusing, stimulated molecular Raman scattering, multiphoton and tunneling ionization, energy depletion due to ionization, relativistic focusing, and ponderomotively excited plasma wakefields. The instantaneous frequency spread along a laser pulse in air, which develops due to various nonlinear effects, is analyzed and discussed. Coupled equations for the power, spot size, and electron density are derived for an intense ionizing laser pulse. From these equations we obtain an equilibrium for a single optical-plasma filament, which involves a balancing between diffraction, nonlinear self-focusing, and plasma defocusing. The equilibrium is shown to require a specific distribution of power along the filament. It is found that in the presence of ionization a self-guided optical filament is not realizable. A method for generating a remote spark in the atmosphere is proposed, which utilizes the dispersive and nonlinear properties of air to cause a low-intensity chirped laser pulse to compress both longitudinally and transversely. For optimally chosen parameters, we find that the transverse and longitudinal focal lengths can be made to coincide, resulting in rapid intensity increase, ionization, and white light generation in a localized region far from the source. Coupled equations for the laser spot size and pulse duration are derived, which can describe the focusing and compression process in the low-intensity regime. More general examples involving beam focusing, compression, ionization, and white light generation near the focal region are studied by numerically solving the full set of 3D, nonlinear propagation equations.

Modification of graphene oxide by laser irradiation: a new route to enhance antibacterial activity

NASA Astrophysics Data System (ADS)

Buccheri, Maria A.; D'Angelo, Daniele; Scalese, Silvia; Spanò, Simon F.; Filice, Simona; Fazio, Enza; Compagnini, Giuseppe; Zimbone, Massimo; Brundo, Maria V.; Pecoraro, Roberta; Alba, Anna; Sinatra, Fulvia; Rappazzo, Giancarlo; Privitera, Vittorio

2016-06-01

The antibacterial activity and possible toxicity of graphene oxide and laser-irradiated graphene oxide (iGO) were investigated. Antibacterial activity was tested on Escherichia coli and shown to be higher for GO irradiated for at least three hours, which seems to be correlated to the resulting morphology of laser-treated GO and independent of the kind and amount of oxygen functionalities. X-ray photoelectron spectroscopy, Raman spectroscopy, dynamic light scattering and scanning electron microscopy (SEM) show a reduction of the GO flakes size after visible laser irradiation, preserving considerable oxygen content and degree of hydrophilicity. SEM images of the bacteria after the exposure to the iGO flakes confirm membrane damage after interaction with the laser-modified morphology of GO. In addition, a fish embryo toxicity test on zebrafish displayed that neither mortality nor sublethal effects were caused by the different iGO solutions, even when the concentration was increased up to four times higher than the one effective in reducing the bacteria survival. The antibacterial properties and the absence of toxicity make the visible laser irradiation of GO a promising option for water purification applications.

Effects of Er:YAG laser irradiation on human cartilage

NASA Astrophysics Data System (ADS)

Glinkowski, Wojciech; Brzozowska, Malgorzata; Ciszek, Bogdan; Rowinski, Jan; Strek, Wieslaw

1996-03-01

Irradiation of the hyaline or fibrous cartilage excised from the body of a human cadaver with Er:YAG laser beam, single pulse with a dose of 1 J, produces a crater with a depth of approximately 500 micrometers and a diameter varying from 5 to 300 micrometers. Histological examination has revealed that the laser-made craters were surrounded by a thin rim (2-10 micrometer) of charred and coagulated tissue. No damage was observed in the cartilage surrounding the rim. The presence of sharp demarcation between the tissue areas ablated by laser energy and the undamaged areas argues for the potential usefulness of the Er:YAG laser in surgery of cartilages.

Long-Range Coulomb Effect in Intense Laser-Driven Photoelectron Dynamics.

PubMed

Quan, Wei; Hao, XiaoLei; Chen, YongJu; Yu, ShaoGang; Xu, SongPo; Wang, YanLan; Sun, RenPing; Lai, XuanYang; Wu, ChengYin; Gong, QiHuang; He, XianTu; Liu, XiaoJun; Chen, Jing

2016-06-03

In strong field atomic physics community, long-range Coulomb interaction has for a long time been overlooked and its significant role in intense laser-driven photoelectron dynamics eluded experimental observations. Here we report an experimental investigation of the effect of long-range Coulomb potential on the dynamics of near-zero-momentum photoelectrons produced in photo-ionization process of noble gas atoms in intense midinfrared laser pulses. By exploring the dependence of photoelectron distributions near zero momentum on laser intensity and wavelength, we unambiguously demonstrate that the long-range tail of the Coulomb potential (i.e., up to several hundreds atomic units) plays an important role in determining the photoelectron dynamics after the pulse ends.

Long-Range Coulomb Effect in Intense Laser-Driven Photoelectron Dynamics

PubMed Central

Quan, Wei; Hao, XiaoLei; Chen, YongJu; Yu, ShaoGang; Xu, SongPo; Wang, YanLan; Sun, RenPing; Lai, XuanYang; Wu, ChengYin; Gong, QiHuang; He, XianTu; Liu, XiaoJun; Chen, Jing

2016-01-01

In strong field atomic physics community, long-range Coulomb interaction has for a long time been overlooked and its significant role in intense laser-driven photoelectron dynamics eluded experimental observations. Here we report an experimental investigation of the effect of long-range Coulomb potential on the dynamics of near-zero-momentum photoelectrons produced in photo-ionization process of noble gas atoms in intense midinfrared laser pulses. By exploring the dependence of photoelectron distributions near zero momentum on laser intensity and wavelength, we unambiguously demonstrate that the long-range tail of the Coulomb potential (i.e., up to several hundreds atomic units) plays an important role in determining the photoelectron dynamics after the pulse ends. PMID:27256904

Laser induced white lighting of tungsten filament

NASA Astrophysics Data System (ADS)

Strek, W.; Tomala, R.; Lukaszewicz, M.

2018-04-01

The sustained bright white light emission of thin tungsten filament was induced under irradiation with focused beam of CW infrared laser diode. The broadband emission centered at 600 nm has demonstrated the threshold behavior on excitation power. Its intensity increased non-linearly with excitation power. The emission occurred only from the spot of focused beam of excitation laser diode. The white lighting was accompanied by efficient photocurrent flow and photoelectron emission which both increased non-linearly with laser irradiation power.

Effects of Radiation Damping in Extreme Ultra-intense Laser-Plasma Interaction

NASA Astrophysics Data System (ADS)

Pandit, Rishi R.

Recent advances in the development of intense short pulse lasers are significant. Now it is available to access a laser with intensity 1021W/cm2 by focusing a petawatt class laser. In a few years, the intensity will exceed 1022W/cm2 , at which intensity electrons accelerated by the laser get energy more than 100 MeV and start to emit radiation strongly. Resultingly, the damping of electron motion can become large. In order to study this problem, we developed a code to solve a set of equations describing the evolution of a strong electromagnetic wave interacting with a single electron. Usually the equation of motion of an electron including radiation damping under the influence of electromagnetic fields is derived from the Lorentz-Dirac equation treating the damping as a perturbation. So far people had used the first order damping equation. This is because the second order term seems to be small and actually it is negligible under 1022W/cm2 intensity. The derivation of 2nd order equation is also complicated and challenging. We derived the second order damping equations for the first time and implemented in the code. The code was then tested via single particle motion in the extreme intensity laser. It was found that the 1st order damping term is reasonable up to the intensity 1022W/cm2, but the 2nd oder term becomes not negligible and comparable in magnitude to the first order term beyond 1023W/cm2. The radiation damping model was introduced using a one-dimensional particle-in-cell code (PIC), and tested in the laser-plasma interaction at extreme intensity. The strong damping of hot electrons in high energy tail was demonstrated in PIC simulations.

What is the surface temperature of a solid irradiated by a Petawatt laser?

NASA Astrophysics Data System (ADS)

Kemp, Andreas; Divol, Laurent

2016-10-01

When a solid target is irradiated by a Petawatt laser pulse, its surface is heated to tens of millions of degrees within a few femtoseconds, facilitating a diffusive heat wave and the acceleration of electrons to MeV energies into the target. Using numerically converged collisional particle-in-cell simulations, we observe a competition between two surface heating mechanisms - inverse bremsstrahlung in solid density on one hand, and electrons scattering on turbulent electric fields on the other. Collision-less heating effectively dominates above the relativistic intensity threshold. Our numerical results show that a high-contrast 40fs, f/5 laser pulse with 1J energy will heat the skin layer to 5keV, and the inside of the target over several microns deep to a bulk temperature of 100s eV at solid density. Work performed under the auspices of the U.S. Department of Energy by the Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Patterning and reduction of graphene oxide using femtosecond-laser irradiation

NASA Astrophysics Data System (ADS)

Kang, SeungYeon; Evans, Christopher C.; Shukla, Shobha; Reshef, Orad; Mazur, Eric

2018-07-01

Graphene has emerged as one of the most versatile materials ever discovered due to its extraordinary electronic, optical, thermal, and mechanical properties. However, device fabrication is a well-known challenge and requires novel fabrication methods to realize the complex integration of graphene-based devices. Here, we demonstrate direct laser writing of reduced graphene oxide using femtosecond-laser irradiation at λ = 795 nm. We perform a systematic study of the reduction process of graphene oxide to graphene by varying both the laser fluence and the pulse repetition rate. Our observations show that the reduction has both thermal and non-thermal features, and suggest that we can achieve better resolution and conductivity using kHz pulse trains than using MHz pulse trains or a continuous wave laser. Our reduced graphene oxide lines written at 10-kHz exhibit a 5 order-of-magnitude decrease in resistivity compared to a non-irradiated control sample. This study provides new insight into the reduction process of graphene oxide and opens doors to achieving a high degree of flexibility and control in the fabrication of graphene layers.

Increased viability of odontoblast-like cells subjected to low-level laser irradiation

NASA Astrophysics Data System (ADS)

Oliveira, C. F.; Basso, F. G.; Lins, E. C.; Kurachi, C.; Hebling, J.; Bagnato, V. S.; de Souza Costa, C. A.

2010-07-01

Studies have shown that the increase of cell metabolism depends on the low level laser therapy (LLLT) parameters used to irradiate the cells. However, the optimal laser dose to up-regulate pulp cell activity remains unknown. Consequently, the aim of this study was to evaluate the metabolic response of odontoblast-like cells (MDPC-23) exposed to different LLLT doses. Cells at 20000 cells/cm2 were seeded in 24-well plates using plain culture medium (DMEM) and were incubated in a humidified incubator with 5% CO2 at 37°C. After 24 h, the culture medium was replaced by fresh DMEM supplemented with 5% (stress by nutritional deficit) or 10% fetal bovine serum (FBS). The cells were exposed to different laser doses from a near infrared diode laser prototype designed to provide a uniform irradiation of the wells. The experimental groups were: G1: 1.5 J/cm2 + 5% FBS; G2: 1.5 J/cm2 + 10% FBS; G3: 5 J/cm2 + 5% FBS; G4: 5 J/cm2 + 10% FBS; G5: 19 J/cm2 + 5% FBS; G6: 19 J/cm2 + 10% FBS. LLLT was performed in 3 consecutive irradiation cycles with a 24-hour interval. Non-irradiated cells cultured in DMEM supplemented with either 5 or 10% FBS served as control groups. The analysis of the metabolic response was performed by the MTT assay 3 h after the last irradiation. G1 presented an increase in SDH enzyme activity and differed significantly (Mann-Whitney test, p < 0.05) from the other groups. Analysis by scanning electron microscopy showed normal cell morphology in all groups. Under the tested conditions, LLLT stimulated the metabolic activity of MDPC-23 cultured in DMEM supplemented with 5% FBS and exposed to a laser dose of 1.5 J/cm2. These findings are relevant for further studies on the action of near infrared lasers on cells with odontoblast phenotype.

Laboratory investigation of the efficacy of holmium:YAG laser irradiation in removing intracanal debris

NASA Astrophysics Data System (ADS)

Nuebler-Moritz, Michael; Gutknecht, Norbert; Sailer, Hermann F.; Hering, Peter; Prettl, Wilhelm

1997-05-01

Current endodontic therapy involves debridement and disinfection of the root canal by means of mechanical instrumentation and chemical irrigation. However, several studies have shown that these techniques fail to achieve complete cleansing. Recently, lasers have been suggested for use within root canals. This study was conducted to determine the efficacy of Holmium:YAG laser irradiation in removing intracanal debris and smear layer. Root canal surfaces of freshly-extracted human teeth were exposed to pulsed Ho:YAG laser radiation. Subsequently, laser induced structural changes were investigated using scanning electron microscopy. Temperature measurements during irradiation were performed by means of thermocouples. The result of this survey give a preliminary indication of the ability of the Ho:YAG laser to improve current endodontic treatment survey give a preliminary indication of the ability of the Ho:YAG laser to improve current endodontic treatment modalities. However, limitations exist with regard to circumscribed and well-quantified irradiation of root canal surfaces, due to the lack of perpendicular delivery of the laser beam. Additional studies will be required to develop suitable optical transmission systems, in order to achieve complete cleansing and to avoid damage to the periradicular tissues, respectively.

Preliminary study of laser welding for aortic dissection in a porcine model using a diode laser with indocyanine green.

PubMed

Fujita, Masanori; Morimoto, Yuji; Ohmori, Sayaka; Usami, Noriko; Arai, Tsunenori; Maehara, Tadaaki; Kikuchi, Makoto

2003-01-01

The objective of this study was to determine whether a dissected aorta could be welded by a diode laser with a solder using an in vitro porcine aortic dissection model. Porcine aortic strips were dissected into two flaps and the dissected faces were immersed in a solution of indocyanine green. The two flaps were pressed at 0.2 kg/cm2 with contact between the two immersed faces. The pressed flaps were irradiated with a diode laser (810 nm) at intensities of 170-425 W/cm2 for 8 seconds. The welded flaps were studied by light microscopy and the adhesive strengths were measured. The irradiated flaps were successfully welded. The breaking stress, the maximum stress recorded in a stress-strain curve, increased with increase in irradiation intensity up to 396 W/cm2 (2.7 x 10(2) mmHg) and decreased when the intensity reached 425 W/cm2. In the specimen irradiated at 396 W/cm2, the welded faces showed continuous fusion of elastin layers, while some voids were seen between the welded faces in the specimen irradiated at 425 W/cm2. The dissected porcine aortas were successfully welded using a laser with solder. The results suggest that the welded aorta can bear physiological blood pressure. Copyright 2003 Wiley-Liss, Inc.

Correlation-induced superconductivity dynamically stabilized and enhanced by laser irradiation.

PubMed

Ido, Kota; Ohgoe, Takahiro; Imada, Masatoshi

2017-08-01

Studies on out-of-equilibrium dynamics have paved a way to realize a new state of matter. Superconductor-like properties above room temperatures recently suggested to be in copper oxides achieved by selectively exciting vibrational phonon modes by laser have inspired studies on an alternative and general strategy to be pursued for high-temperature superconductivity. We show that the superconductivity can be enhanced by irradiating laser to correlated electron systems owing to two mechanisms: First, the effective attractive interaction of carriers is enhanced by the dynamical localization mechanism, which drives the system into strong coupling regions. Second, the irradiation allows reaching uniform and enhanced superconductivity dynamically stabilized without deteriorating into equilibrium inhomogeneities that suppress superconductivity. The dynamical superconductivity is subject to the Higgs oscillations during and after the irradiation. Our finding sheds light on a way to enhance superconductivity that is inaccessible in equilibrium in strongly correlated electron systems.

Does laser diode irradiation improve the degree of conversion of simplified dentin bonding systems?

PubMed Central

BRIANEZZI, Leticia Ferreira de Freitas; MAENOSONO, Rafael Massunari; BIM, Odair; ZABEU, Giovanna Speranza; PALMA-DIBB, Regina Guenka; ISHIKIRIAMA, Sérgio Kiyoshi

2017-01-01

Abstract Simplified dentin-bonding systems are clinically employed for most adhesive procedures, and they are prone to hydrolytic degradation. Objective This study aimed to investigate the effect of laser diode irradiation on the degree of conversion (DC), water sorption (WS), and water solubility (WSB) of these bonding systems in an attempt to improve their physico-mechanical resistance. Material and Methods Two bonding agents were tested: a two-step total-etch system [Adper™ Single Bond 2, 3M ESPE (SB)] and a universal system [Adper™ Single Bond Universal, 3M ESPE (SU)]. Square-shaped specimens were prepared and assigned into 4 groups (n=5): SB and SU (control groups – no laser irradiation) and SB-L and SU-L [SB and SU laser (L) – irradiated groups]. DC was assessed using Fourier transform infrared spectroscopy with attenuated total reflectance. Additional uncured resin samples (≈3.0 µL, n=5) of each adhesive were also scanned for final DC calculation. For WS/WSB tests, similar specimens (n=10) were prepared and measured by monitoring the mass changes after dehydration/water storage cycles. For both tests, adhesive fluids were dropped into standardized Teflon molds (6.0×6.0×1.0 mm), irradiated with a 970-nm laser diode, and then polymerized with an LED-curing unit (1 W/cm2). Results Laser irradiation immediately before photopolymerization increased the DC (%) of the tested adhesives: SB-L>SB>SU-L>SU. For WS/WSB (μg/mm3), only the dentin bonding system (DBS) was a significant factor (p<0.05): SB>SU. Conclusion Irradiation with a laser diode improved the degree of conversion of all tested simplified dentin bonding systems, with no impact on water sorption and solubility. PMID:28877276

X-ray Emission Characteristics of Ultra-High Energy Density Relativistic Plasmas Created by Ultrafast Laser Irradiation of Nanowire Arrays

NASA Astrophysics Data System (ADS)

Hollinger, R. C.; Bargsten, C.; Shlyaptsev, V. N.; Pukhov, A.; Purvis, M. A.; Townsend, A.; Keiss, D.; Wang, Y.; Wang, S.; Prieto, A.; Rocca, J. J.

2014-10-01

Irradiation of ordered nanowire arrays with high contrast femtosecond laser pulses of relativistic intensity creates volumetrically heated near solid density plasmas characterized by multi-KeV temperatures and extreme degrees of ionization. The large hydrodynamic-to-radiative lifetime ratio of these plasmas results in very efficient X-ray generation. Au nanowire array plasmas irradiated at I 5×1018 Wcm-2 are measured to convert ~ 5 percent of the laser energy into h ν > 0.9 KeV X-rays, and >1 × 10-4 into h ν > 9 KeV photons, creating bright picosecond X-ray sources. The angular distribution of the higher energy photons is measured to change from isotropic into annular as the intensity increases, while softer X-ray emission (h ν >1 KeV) remains isotropic and nearly unchanged. Model simulations suggest the unexpected annular distribution of the hard X-rays might result from bremsstrahlung of fast electrons confined in a high aspect ratio near solid density plasma in which the electron-ion collision mean free-path is of the order of the plasma thickness. Work supported by the U.S Department of Energy, Fusion Energy Sciences and the Defense Threat Reduction Agency Grant HDTRA-1-10-1-0079. A.P was supported by of DFG-funded project TR18.

Controllable photoinduced optical attenuation in a single-mode optical fiber by irradiation of a femtosecond pulse laser.

PubMed

Himei, Yusuke; Qiu, Jianrong; Nakajima, Sotohiro; Sakamoto, Akihiko; Hirao, Kazuyuki

2004-12-01

Novel optical attenuation fibers were fabricated by the irradiation of a focused infrared femtosecond pulsed laser onto the core of a silica glass single-mode optical fiber. Optical attenuation at a wavelength of 1.55 microm proportionally increased with increasing numbers of irradiation points and was controllable under laser irradiation conditions. The single-mode property of the waveguide and the mode-field diameter of the optical fiber were maintained after irradiation of the femtosecond laser. It is suggested that the attenuation results from optical scattering at photoinduced spots formed inside the fiber core.

Effect of laser irradiation on crystalline structure of enamel surface during whitening treatment with hydrogen peroxide.

PubMed

Son, Jung-Hyun; An, Ji-Hae; Kim, Byung-Kuk; Hwang, In-Nam; Park, Yeong-Joon; Song, Ho-Jun

2012-11-01

This study is to evaluate the effect of laser activation on the whitening and crystalline structure of enamel surface during whitening treatment with hydrogen peroxide. Bovine teeth were treated with whitening gel containing 35% hydrogen peroxide. A whitening gel was applied on the enamel surface for a period of 5 min, and then irradiated using a diode laser (740 nm) during whitening treatment for 0, 30, 60, 120 and 180s for the GL0-W, GL30-W, GL60-W, GL120-W and GL180-W groups, respectively. The total whitening application time was 30 min for all groups. Laser-irradiated enamel groups showed a similar lightness compared to the GL0-W group. The thickness of porous layer observed on the enamel surface of GL0-W group was decreased by increasing the laser irradiation time. While the Ca and P contents of the GL0-W group were lower than those of the non-whitening treated group (GL0-C), the Ca and P contents of the GL180-W group were similar to those of the GL180-C group. The enamel crystallinity was dramatically decreased by whitening treatment without laser irradiation. However, the decrease of crystallinity was protected by laser irradiation during whitening treatment. Raman measurement verified that laser irradiation could prevent the loss of mineral compositions on enamel and maintain its crystalline structure. The professional whitening treatment with hydrogen peroxide and diode laser activation improves not only the whitening effect but also protects the change of enamel structure compared to the treatment with only gel. Copyright © 2012 Elsevier Ltd. All rights reserved.

In Situ analysis of CO2 laser irradiation on controlling progression of erosive lesions on dental enamel.

PubMed

Lepri, Taísa Penazzo; Scatolin, Renata Siqueira; Colucci, Vivian; De Alexandria, Adílis Kalina; Maia, Lucianne Cople; Turssi, Cecília Pedroso; Corona, Silmara Aparecida Milori

2014-08-01

The present study aimed to evaluate in situ the effect of CO2 laser irradiation to control the progression of enamel erosive lesions. Fifty-six slabs of bovine incisors enamel (5 × 3 × 2.5 mm(3) ) were divided in four distinct areas: (1) sound (reference area), (2) initial erosion, (3) treatment (irradiated or nonirradiated with CO2 laser), (4) final erosion (after in situ phase). The initial erosive challenge was performed with 1% citric acid (pH = 2.3), for 5 min, 2×/day, for 2 days. The slabs were divided in two groups according to surface treatment: irradiated with CO2 laser (λ = 10.6 µm; 0.5 W) and nonirradiate. After a 2-day lead-in period, 14 volunteers wore an intraoral palatal appliance containing two slabs (irradiated and nonirradiated), in two intraoral phases of 5 days each. Following a cross-over design during the first intraoral phase, half of the volunteers immersed the appliance in 100 mL of citric acid for 5 min, 3×/day, while other half of the volunteers used deionized water (control). The volunteers were crossed over in the second phase. Enamel wear was determined by an optical 3D profilometer. Three-way ANOVA for repeated measures revealed that there was no significant interaction between erosive challenge and CO2 laser irradiation (P = 0.419). Erosive challenge significantly increased enamel wear (P = 0.001), regardless whether or not CO2 laser irradiation was performed. There was no difference in enamel wear between specimens CO2 -laser irradiated and non-irradiated (P = 0.513). Under intraoral conditions, CO2 laser irradiation did not control the progression of erosive lesions in enamel caused by citric acid. © 2014 Wiley Periodicals, Inc.

Thermodynamic effects of laser irradiation of implants placed in bone: an in vitro study.

PubMed

Leja, Chris; Geminiani, Alessandro; Caton, Jack; Romanos, Georgios E

2013-11-01

Lasers have been proposed for various applications involving dental implants, including uncovering implants and treating peri-implantitis. However, the effect of laser irradiation on the implant surface temperature is only partially known. The aim of this pilot study was to determine the effect of irradiation with diode, carbon dioxide, and Er:YAG lasers on the surface temperature of dental implants placed in bone, in vitro. For this study, one dental implant was placed in a bovine rib. A trephine bur was used to create a circumferential defect to simulate peri-implantitis, and thermocouples were placed at the coronal and apical aspect of the implant. The implant was irradiated for 60 s using four different lasers independently and change in temperature as well as time to reach a 10 °C increase in temperature were recorded. There was wide variability in results among the lasers and settings. Time for a 10 °C increase ranged from 0.9 to over 60 s for the coronal thermocouple and from 18 to over 60 s for the apical thermocouple. Maximum temperature ranged from 5.9 to 70.9 °C coronally and from 1.4 to 23.4 °C apically. During laser irradiation of dental implants, a surface temperature increase beyond the "critical threshold" of 10 °C can be reached after only 18 s.

Efficiency and threshold pump intensity of CW solar-pumped solid-state lasers

NASA Technical Reports Server (NTRS)

Hwang, In H.; Lee, Ja H.

1991-01-01

The authors consider the relation between the threshold pumping intensity, the material properties, the resonator parameters, and the ultimate slope efficiencies of various solid-state laser materials for solar pumping. They clarify the relation between the threshold pump intensity and the material parameters and the relation between the ultimate slope efficiency and the laser resonator parameters such that a design criterion for the solar-pumped solid-state laser can be established. Among the laser materials evaluated, alexandrite has the highest slope efficiency of about 12.6 percent; however, it does not seem to be practical for a solar-pumped laser application because of its high threshold pump intensity. Cr:Nd:GSGG is the most promising for solar-pumped lasing. Its threshold pump intensity is about 100 air-mass-zero (AM0) solar constants and its slope efficiency is about 12 percent when thermal deformation is completely prevented.

Effects of high-frequency near-infrared diode laser irradiation on the proliferation and migration of mouse calvarial osteoblasts.

PubMed

Kunimatsu, Ryo; Gunji, Hidemi; Tsuka, Yuji; Yoshimi, Yuki; Awada, Tetsuya; Sumi, Keisuke; Nakajima, Kengo; Kimura, Aya; Hiraki, Tomoka; Abe, Takaharu; Naoto, Hirose; Yanoshita, Makoto; Tanimoto, Kotaro

2018-07-01

Laser irradiation activates a range of cellular processes and can promote tissue repair. Here, we examined the effects of high-frequency near-infrared (NIR) diode laser irradiation on the proliferation and migration of mouse calvarial osteoblastic cells (MC3T3-E1). MC3T3-E1 cells were cultured and exposed to high-frequency (30 kHz) 910-nm diode laser irradiation at a dose of 0, 1.42, 2.85, 5.7, or 17.1 J/cm 2 . Cell proliferation was evaluated with BrdU and ATP concentration assays. Cell migration was analyzed by quantitative assessment of wound healing using the Incucyt ® ZOOM system. In addition, phosphorylation of mitogen-activated protein kinase (MAPK) family members including p38 mitogen-activated protein kinase (p38), stress-activated protein kinase/Jun-amino-terminal kinase (SAPK/JNK), and extracellular signal-regulated protein kinase (ERK)1/2) after laser irradiation was examined with western blotting. Compared to the control, cell proliferation was significantly increased by laser irradiation at a dose of 2.85, 5.7, or 17.1 J/cm 2 . Laser irradiation at a dose of 2.85 J/cm 2 induced MC3T3-E1 cells to migrate more rapidly than non-irradiated control cells. Irradiation with the high-frequency 910-nm diode laser at a dose of 2.85 J/cm 2 induced phosphorylation of MAPK/ERK1/2 15 and 30 min later. However, phosphorylation of p38 MAPK and SAPK/JNK was not changed by NIR diode laser irradiation at a dose of 2.85 J/cm 2 . Irradiation with a high-frequency NIR diode laser increased cell division and migration of MT3T3-E1 cells, possibly via MAPK/ERK signaling. These observations may be important for enhancing proliferation and migration of osteoblasts to improve regeneration of bone tissues.

Suppressing the memory state of floating gate transistors with repeated femtosecond laser backside irradiations

NASA Astrophysics Data System (ADS)

Chambonneau, Maxime; Souiki-Figuigui, Sarra; Chiquet, Philippe; Della Marca, Vincenzo; Postel-Pellerin, Jérémy; Canet, Pierre; Portal, Jean-Michel; Grojo, David

2017-04-01

We demonstrate that infrared femtosecond laser pulses with intensity above the two-photon ionization threshold of crystalline silicon induce charge transport through the tunnel oxide in floating gate Metal-Oxide-Semiconductor transistor devices. With repeated irradiations of Flash memory cells, we show how the laser-produced free-electrons naturally redistribute on both sides of the tunnel oxide until the electric field of the transistor is suppressed. This ability enables us to determine in a nondestructive, rapid and contactless way the flat band and the neutral threshold voltages of the tested device. The physical mechanisms including nonlinear ionization, quantum tunneling of free-carriers, and flattening of the band diagram are discussed for interpreting the experiments. The possibility to control the carriers in memory transistors with ultrashort pulses holds promises for fast and remote device analyses (reliability, security, and defectivity) and for considerable developments in the growing field of ultrafast microelectronics.

The Experimental Study of Characterized Noble Gas Puffs Irradiated by Ultra-Short Laser Pulses Compared with X-Pinches as an X-Ray Source

NASA Astrophysics Data System (ADS)

Schultz, Kimberly Ann

The goal of this dissertation is to study the basic physics and X-ray emission (1-10 keV) of two X-ray sources: X-pinch plasmas and a clustered gas-puff irradiated by an ultrashort laser pulse. X-pinches and other typical X-ray sources using solid targets create hot debris that can damage sensitive equipment. Therefore, to perform sensitive backlighting or X-ray effects testing, debris-free sources of radiation must be investigated. In this work, the author presents a broad study of clustered noble gas puffs including characterization measurements and laser heating experiments using several gas nozzles and multiple gases. Ultimately, the goal is to compare the laser-irradiated gas-puff and X-pinch plasmas as X-ray sources. Characterization of the gas puffs is performed at the Radiation Physics Laboratory at the University of Nevada, Reno (UNR) Physics Department using optical interferometry and Rayleigh scattering to determine density and cluster radius. By changing the gas-puff variables control of both the density and cluster size of the gas jets is obtained. Two laser systems provide the high intensities desired for the laser-irradiated gas puff experiments: the UNR Leopard Laser (1-2x1019 W/cm2) and the Lawrence Livermore National Laboratory's Titan Laser (7x1019 W/cm2). X-ray emission is studied as a function of laser pulse parameters, gas target type, gas puff density, and the gas-delay timing between puff initiation and laser interaction with the puff. The tested gases are Ar, Kr, Xe, and four mixtures of the noble gases. Time-resolved X-ray measurements are captured with Silicon diodes and photoconducting diamond detectors. Electron beam detectors include Faraday cups and a high-energy (> 1 MeV) electron spectrometer. Modeling of spectra from X-ray crystal spectrometers provides plasma density and temperature measurement and a molecular dynamics (MD) code describes cluster interactions with the laser pulse. The conversion of laser energy into X rays is also

Particle characteristics of different materials after ultra-short pulsed laser (USPL) irradiation

NASA Astrophysics Data System (ADS)

Meister, Joerg; Schelle, Florian; Kowalczyk, Philip; Frentzen, Matthias

2012-01-01

The exposition of nanoparticles caused by laser application in dental health care is an open discussion. Based on the fact that nanoparticles can penetrate through the mucosa, the knowledge about particle characteristics after irradiation with an USPL is of high importance. Therefore, the aim of this study was to investigate the particle characteristics, especially the size of the ablated debris after USPL irradiation. The irradiation was carried out with an USP Nd:YVO4 laser with a center wavelength of 1064 nm. Based on the pulse duration of 8 ps and a pulse repetition rate of 500 kHz the laser emits an average power of 9 W. The materials investigated were dental tissues and dental restorative materials (composite and amalgam), ceramic and different metals (gold and aluminium). The samples were irradiated with a power density in the order of 300 GW/cm2 at distances of 5, 10, 15, and 20 mm. The debris was collected on an object plate. SEM pictures were used for analysis of the ablation debris. Depending on the irradiated material, we observed different kinds of structures: vitreous, flocculent, and pellet-like. The mean particle sizes were 10 x 10 up to 30 x 30 μm2. In addition, a cluster of ablated matter (nanometer range) distributed over the whole irradiated area was found. With increasing distances the cluster structure reduced from multi-layer to mono-layer clusters. Particle sizes in the micrometer and nanometer range were found after irradiation with an USPL. The nanoparticles create a cluster structure which is influenced by increasing distances.

Demonstration of a neonlike argon soft-x-ray laser with a picosecond-laser-irradiated gas puff target.

PubMed

Fiedorowicz, H; Bartnik, A; Dunn, J; Smith, R F; Hunter, J; Nilsen, J; Osterheld, A L; Shlyaptsev, V N

2001-09-15

We demonstrate a neonlike argon-ion x-ray laser, using a short-pulse laser-irradiated gas puff target. The gas puff target was formed by pulsed injection of gas from a high-pressure solenoid valve through a nozzle in the form of a narrow slit and irradiated with a combination of long, 600-ps and short, 6-ps high-power laser pulses with a total of 10 J of energy in a traveling-wave excitation scheme. Lasing was observed on the 3p (1)S(0)?3s (1)P(1) transition at 46.9 nm and the 3d (1)P(1)?3p (1)P(1) transition at 45.1 nm. A gain of 11 cm(-1) was measured on these transitions for targets up to 0.9 cm long.

Effects Of Continuous Argon Laser Irradiation On Canine And Autopsied Human Cardiac Tissue