Effect of Low-Level Laser therapy on the fungal proliferation of Candida albicans

NASA Astrophysics Data System (ADS)

Carneiro, Vanda S. M.; Araújo, Natália C.; Menezes, Rebeca F. d.; Moreno, Lara M.; Santos-Neto, Alexandrino d. P.; Gerbi, Marleny Elizabeth M.

2016-03-01

Candida albicans plays an important role in triggering infections in HIV+ patients. The indiscriminate use of antifungals has led to resistance to Candida albicans, which requires new treatment alternatives for oral candidiasis. Low-level laser therapy promotes a considerable improvement in the healing of wounds and in curing illnesses caused by microorganisms. The aim of the present study was to assess the effect of laser radiation on the cell proliferation of Candida albicans in immunosuppressed patients. Six Candida albicans strains that had been isolated from immunosuppressed patients were divided into a control group and experimental groups, which received eight sessions of laser therapy (InGaAlP, λ685nm, P = 30mW, CW, Φ~6 mm and GaAlAs, λ830nm, P = 40mW, CW, Φ~6 mm) using dosimetries of 6J/cm2, 8J/cm2, 10J/cm2 and 12J/cm2 for each wavelength and power. The results were not statistically significant (Kruskal Wallis, p > 0.05), although the proliferation of Candida albicans was lower in some of the experimental groups. The dosimetry of 6J/cm2 (GaAlAs, λ830nm, P = 40mW) provided lower mean scores than the other groups for the growth of Candida. Further studies are required to confirm whetehr laser therapy is a viable option in the treatment of fungal infections.

Effects of the GaAlAs diode laser (780 nm) on the periodontal tissues during orthodontic tooth movement in diabetes rats: histomorphological and immunohistochemical analysis.

PubMed

Gomes, Mônica Fernandes; da Graças Vilela Goulart, Maria; Giannasi, Lilian Chrystiane; Hiraoka, Cybelle Mori; de Fátima Santana Melo, Gabriela; de Sousa, Aretha Graziela Vilela; Nóbrega, Celestino José Prudente; Zangaro, Renato Amaro; Salgado, Miguel Angel Castillo

2017-09-01

The purposes of the present study are to assess the effects of the GaAlAs diode laser on the periodontal tissues and to investigate its action on the alveolar bone remodeling process during orthodontic tooth movement in normoglycemic and diabetic rats. Sixty adult male Wistar rats were divided into four groups of 15 rats: normoglycemic (N), diabetic (D), laser-normoglycemic (LN), and laser-diabetic (LD) rats. Diabetes mellitus was induced by a single intravenous injection of 40 mg/kg monohydrated alloxan. The orthodontically moved tooth underwent a force magnitude of 20 cN. The laser irradiation with a continuous emission of a 780-nm wavelength, an output power of 20 mW, and a fiber probe with a spot size of 0.04 cm in diameter and an area of 0.00126 cm 2 were used. Moreover, an energy density of 640 J/cm 2 was applied in an exposition time of 40 s. Histomorphological and immunohistochemical analysis was performed. The photobiomodulation (PBM) strongly stimulated the periodontal tissue response, establishing mainly the balance between the bone formation and resorption. Intense inflammatory cell infiltration and extensive loss of bone tissue were mainly found in the D group from 14 days. The number of osteopontin-positive osteocytes was significantly greater in the LN group, followed by the LD, especially at 7 and 14 days, whereas osteoprotegerin-positive osteoblasts were significantly higher in the LN and LD groups than in the N and D groups, respectively, in all periods. The PBM strongly stimulated the alveolar bone remodeling and favored the continuous reorganization of the soft periodontal tissues, leading to the maintenance and integrity of the periodontal microstructure under orthodontic force, especially in uncontrolled diabetic rats.

Molecular oxygen detection using frequency modulation diode laser spectroscopy

NASA Technical Reports Server (NTRS)

Wang, Liang-Guo; Sachse, Glen

1990-01-01

A high-sensitivity spectroscopic measurement of O2 using two-tone frequency modulation spectroscopy with a GaAlAs diode laser is presented. An oxygen sensor based on this technique would be non-intrusive, compact and possess high sensitivity and fast time response.

Long-term effect of diode laser irradiation compared to sodium fluoride varnish in the treatment of dentine hypersensitivity in periodontal maintenance patients: a randomized controlled clinical study.

PubMed

Yilmaz, Hasan Guney; Kurtulmus-Yilmaz, Sevcan; Cengiz, Esra

2011-11-01

The aim of this clinical study was to evaluate and compare the desensitizing effects of a gallium?aluminum?arsenide (GaAlAs) laser and sodium fluoride (NaF) varnish on dentine hypersensitivity (DH) in periodontal maintenance patients. The use of lasers opens a new dimension in the treatment of DH. Forty-eight patients with 244 teeth affected by DH were included in the trial. To be included in the study, the subjects had to have 4 or more hypersensitive teeth at different quadrants. Selected teeth were randomly assigned to a GaAlAs laser group, placebo laser group, NaF varnish group, or a placebo NaF varnish group. Laser therapy was performed at 8.5?J/cm(2) energy density. In the placebo laser group, the same laser without laser emission was used. In the NaF varnish group, the varnish was painted at the cervical region of the teeth. In the placebo NaF varnish group, the same treatment procedures were performed with a saline solution. DH was assessed with a visual analog scale (VAS); immediately, at 1 week, and at 1, 3, and 6 months after treatments. Intra-group time-dependent data were analyzed by Friedman's test, and Wilcoxon's rank sum test was used to evaluate the differences within groups. GaAlAs laser and NaF varnish treatments resulted in a significant reduction in the VAS scores immediately after treatments that were maintained throughout the study when compared to the baseline and placebo treatments. In the NaF group, there was a significant increase in the VAS scores at 3 and 6 months compared to at 1 week and 1 month. The placebo treatments showed no significant changes in VAS scores throughout the study period. Within the limits of the study, GaAlAs laser irradiation was effective in the treatment of DH, and it is a more comfortable and faster procedure than traditional DH treatment.

EFFECTS OF LASER RADIATION ON MATTER: Spectrum of the barium atom in a laser radiation field

NASA Astrophysics Data System (ADS)

Bondar', I. I.; Suran, V. V.

1990-08-01

An experimental investigation was made of the influence of a laser radiation field on the spectrum of barium atoms. The investigation was carried out by the method of three-photon ionization spectroscopy using dye laser radiation (ω = 14 800-18 700 cm - 1). The electric field intensity of the laser radiation was 103-106 V/cm. This laser radiation field had a strong influence on a number of bound and autoionizing states. The nature of this influence depended on the ratio of the excitation frequencies of bound and autoionizing states.

HO:LULF and HO:LULF Laser Materials

NASA Technical Reports Server (NTRS)

Barnes, Norman P. (Inventor); Morrison, Clyde A. (Inventor); Filer, Elizabeth D. (Inventor); Jani, Mahendra G. (Inventor); Murray, Keith E. (Inventor); Lockard, George E. (Inventor)

1998-01-01

A laser host material LULF (LuLiF4) is doped with holmium (Ho) and thulium (Tm) to produce a new laser material that is capable of laser light production in the vicinity of 2 microns. The material provides an advantage in efficiency over conventional Ho lasers because the LULF host material allows for decreased threshold and upconversion over such hosts as YAG and YLF. The addition of Tm allows for pumping by commonly available GaAlAs laser diodes. For use with flashlamp pumping, erbium (Er) may be added as an additional dopant. For further upconversion reduction, the Tm can be eliminated and the Ho can be directly pumped.

EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Spatial distribution of laser radiation scattered in a plasma formed by optical breakdown of a gas

NASA Astrophysics Data System (ADS)

Bufetov, Igor'A.; Bufetova, G. A.; Fyodorov, V. B.

1994-12-01

Spatial distributions of laser radiation scattered by a laser spark were determined at different laser radiation wavelengths (λ = 1060, 530, 353, and 265 nm) and gas pressures (air at 10-760 Torr). An interference structure of the cone of the scattered radiation behind the spark was detected for the first time. The structure was attributed to interference of the radiation scattered in two or more self-focusing centres in the laser-spark plasma in air. The dependences of the maximum scattering angle on the gas pressure and on the laser radiation wavelength were determined experimentally.

EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Microwave generation in an optical breakdown plasma created by modulated laser radiation

NASA Astrophysics Data System (ADS)

Antipov, A. A.; Grasyuk, Arkadii Z.; Losev, Leonid L.; Soskov, V. I.

1990-06-01

It was established that when laser radiation, intensity modulated at a frequency of 2.2 GHz, interacted with an optical breakdown plasma which it had created, a microwave component appeared in the thermal emf of the plasma. The amplitude of the microwave thermal emf reached 0.7 V for a laser radiation intensity of 6 GW/cm2. Laser radiation with λL = 1.06 μm was converted to the microwave range with λmω = 13 cm in the optical breakdown plasma. A microwave signal power of ~ 0.5 W was obtained from a laser power of ~ 5 MW.

Optical radiation hazards of laser welding processes. Part 1: Neodymium-YAG laser.

PubMed

Rockwell, R J; Moss, C E

1983-08-01

High power laser devices are being used for numerous metalworking processes such as welding, cutting and heat treating. Such laser devices are totally enclosed either by the manufacturer or the end-user. When this is done, the total laser system is usually certified by the manufacturer following the federal requirements of the Code of Federal Regulations (CFR) 1040.10 and 10.40.11 as a Class I laser system. Similarly, the end-user may also reclassify an enclosed high-power laser into the Class I category following the requirements of the American National Standards Institute (ANSI) Z-136.1 (1980) standard. There are, however, numerous industrial laser applications where Class IV systems are required to be used in an unenclosed manner. In such applications, there is concern for both ocular and skin hazards caused by direct and scattered laser radiation, as well as potential hazards caused by the optical radiation created by the laser beam's interaction with the metal (i.e. the plume radiation). Radiant energy measurements are reported for both the scattered laser radiation and the resultant plume radiations which were produced during typical unenclosed Class IV Neodymium-YAG laser welding processes. Evaluation of the plume radiation was done with both radiometric and spectroradiometric measurement equipment. The data obtained were compared to applicable safety standards.

INTERNATIONAL CONFERENCE ON SEMICONDUCTOR INJECTION LASERS SELCO-87: Transient heat conduction in laser diodes

NASA Astrophysics Data System (ADS)

Enders, P.; Galley, J.

1988-11-01

The dynamics of heat transfer in stripe GaAlAs laser diodes is investigated by solving the linear diffusion equation for a quasitwo-dimensional multilayer structure. The calculations are rationalized drastically by the transfer matrix method and also using for the first time the asymptotes of the decay constants. Special attention is given to the convergence of the Fourier series. A comparison with experimental results reveals however that this is essentially the Stefan problem (with moving boundary conditions).

Ultraviolet radiation induced discharge laser

DOEpatents

Gilson, Verle A.; Schriever, Richard L.; Shearer, James W.

1978-01-01

An ultraviolet radiation source associated with a suitable cathode-anode electrode structure, disposed in a gas-filled cavity of a high pressure pulsed laser, such as a transverse electric atmosphere (TEA) laser, to achieve free electron production in the gas by photoelectric interaction between ultraviolet radiation and the cathode prior to the gas-exciting cathode-to-anode electrical discharge, thereby providing volume ionization of the gas. The ultraviolet radiation is produced by a light source or by a spark discharge.

EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Conversion of the energy of fast electrons to thermal plasma radiation

NASA Astrophysics Data System (ADS)

Vergunova, G. A.; Rozanov, Vladislav B.

1992-01-01

An analysis is made of the conversion of the energy of highly energetic fast electrons, generated by the action of CO2 laser radiation on a target, into characteristic radiation emitted by a plasma formed from shell targets which, for instance, may be present inside targets irradiated by the CO2 laser. Analytical formulas are obtained for the temperature of the converted radiation. The results show that it is possible to control this radiation by choosing the parameters of the target and of the fast electron flux. The efficiency of conversion into characteristic thermal radiation is found numerically to be 95%. This method of conversion is more favorable than direct interaction of CO2 laser radiation with a target since the emitting region is localized in the target mass. When a laser interacts with a target the mass of this region increases with time and so the temperature of the emitted radiation is lower than in the case when fast electrons act on the target.

EFFECTS OF LASER RADIATION ON MATTER: Influence of the ambient air pressure on short-wavelength radiation from a laser plasma

NASA Astrophysics Data System (ADS)

Golovin, A. F.; Zemtsov, S. S.; Fedyushin, B. T.

1991-12-01

A detailed experimental investigation was made of the radiation from a plasma created on an aluminum target by a pulsed CO2 laser at different ambient gas pressures. Measurements were made of the energy and angular distribution of the radiation and of the efficiency of conversion of laser energy into reemitted plasma radiation. The intensity of this radiation was found to exhibit pressure-dependent pulsations. The maximum reflection of the laser radiation from the plasma was recorded at a pressure of ~ 40 Torr. An interpretation is given of the experimental data.

Effect of low-level laser therapy on irradiated parotid glands—study in mice

NASA Astrophysics Data System (ADS)

Acauan, Monique Dossena; Gomes, Ana Paula Neutziling; Braga-Filho, Aroldo; de Figueiredo, Maria Antonia Zancanaro; Cherubini, Karen; Salum, Fernanda Gonçalves

2015-10-01

The objective of this study was to evaluate the effect of low-level laser therapy (LLLT) on radiotherapy-induced morphological changes and caspase-3 immunodetection in parotids of mice. Forty-one Swiss mice were divided into control, radiotherapy, 2- and 4-J laser groups. The experimental groups were exposed to ionizing radiation in a single session of 10 Gy. In the laser groups, a GaAlAs laser (830 nm, 100 mW, 0.028 cm2, 3.57 W/cm2) was used on the region corresponding to the parotid glands, with 2-J energy (20 s, 71 J/cm2) or 4 J (40 s, 135 J/cm2) per point. LLLT was performed immediately before and 24 h after radiotherapy. One point was applied in each parotid gland. The animals were euthanized 48 h or 7 days after radiotherapy and parotid glands were dissected for morphological analysis and immunodetection of caspase-3. There was no significant difference between groups in the immunodetection of caspase-3, but the laser groups had a lower percentage compared to the radiotherapy group. LLLT promoted the preservation of acinar structure, reduced the occurrence of vacuolation, and stimulated parotid gland vascularization. Of the two LLLT protocols, the one using 4 J of energy showed better results.

Bracket debonding by mid-infrared laser radiation

NASA Astrophysics Data System (ADS)

Jelínková, H.; Šulc, J.; Dostálová, T.; Koranda, P.; Němec, M.; Hofmanova, P.

2009-03-01

The purpose of the study was to determine the proper laser radiation for ceramic bracket debonding and the investigation of the tooth root temperature injury. The debonding was investigated by diode-pumped continuously running Tm:YAP and Nd:YAG lasers, and by GaAs laser diode generating radiation with the wavelengths 1.997 μm, 1.444 μm, and 0.808 μm, respectively. The possibility of brackets removal by laser radiation was investigated together with the tooth and, it specifically, root temperature rise. From the results it follows that continuously running diode pumped Tm:YAG or Nd:YAG laser generating wavelengths 1.997 μm or 1.444 μm, respectively, having the output power 1 W can be good candidates for ceramic brackets debonding.

Optical-microwave interactions in semiconductor devices

NASA Astrophysics Data System (ADS)

Figueroa, L.; Slayman, C. W.; Yen, H. W.

1981-03-01

The results of an extensive characterization of microwave-optical devices is presented. The study has concentrated in the optical injection locking of IMPATT oscillators, high-speed analog modulation of (GaAl)As injection laser, mode-locking of (GaAl)As injection laser, and high-speed optical detectors.

Advanced optic fabrication using ultrafast laser radiation

NASA Astrophysics Data System (ADS)

Taylor, Lauren L.; Qiao, Jun; Qiao, Jie

2016-03-01

Advanced fabrication and finishing techniques are desired for freeform optics and integrated photonics. Methods including grinding, polishing and magnetorheological finishing used for final figuring and polishing of such optics are time consuming, expensive, and may be unsuitable for complex surface features while common photonics fabrication techniques often limit devices to planar geometries. Laser processing has been investigated as an alternative method for optic forming, surface polishing, structure writing, and welding, as direct tuning of laser parameters and flexible beam delivery are advantageous for complex freeform or photonics elements and material-specific processing. Continuous wave and pulsed laser radiation down to the nanosecond regime have been implemented to achieve nanoscale surface finishes through localized material melting, but the temporal extent of the laser-material interaction often results in the formation of a sub-surface heat affected zone. The temporal brevity of ultrafast laser radiation can allow for the direct vaporization of rough surface asperities with minimal melting, offering the potential for smooth, final surface quality with negligible heat affected material. High intensities achieved in focused ultrafast laser radiation can easily induce phase changes in the bulk of materials for processing applications. We have experimentally tested the effectiveness of ultrafast laser radiation as an alternative laser source for surface processing of monocrystalline silicon. Simulation of material heating associated with ultrafast laser-material interaction has been performed and used to investigate optimized processing parameters including repetition rate. The parameter optimization process and results of experimental processing will be presented.

[Induced thymus aging: radiation model and application perspective for low intensive laser radiation].

PubMed

Sevost'ianova, N N; Trofimov, A V; Lin'kova, N S; Poliakova, V O; Kvetnoĭ, I M

2010-01-01

The influence of gamma-radiation on morphofunctional state of thymus is rather like as natural thymus aging. However gamma-radiation model of thymus aging widely used to investigate geroprotectors has many shortcomings and limitations. Gamma-radiation can induce irreversible changes in thymus very often. These changes are more intensive in comparison with changes, which can be observed at natural thymus aging. Low intensive laser radiation can not destroy structure of thymus and its effects are rather like as natural thymus aging in comparison with gamma-radiation effects. There are many parameters of low intensive laser radiation, which can be changed to improve morphofunctional thymus characteristics in aging model. Using low intensive laser radiation in thymus aging model can be very perspective for investigations of aging immune system.

EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Feasibility of investigation of optical breakdown statistics using multifrequency lasers

NASA Astrophysics Data System (ADS)

Ulanov, S. F.

1990-06-01

A method proposed for investigating the statistics of bulk optical breakdown relies on multifrequency lasers, which eliminates the influence of the laser radiation intensity statistics. The method is based on preliminary recording of the peak intensity statistics of multifrequency laser radiation pulses at the caustic using the optical breakdown threshold of K8 glass. The probability density distribution function was obtained at the focus for the peak intensities of the radiation pulses of a multifrequency laser. This method may be used to study the self-interaction under conditions of bulk optical breakdown of transparent dielectrics.

Laser Irradiated Foam Targets: Absorption and Radiative Properties

NASA Astrophysics Data System (ADS)

Salvadori, Martina; Luigi Andreoli, Pier; Cipriani, Mattia; Consoli, Fabrizio; Cristofari, Giuseppe; De Angelis, Riccardo; di Giorgio, Giorgio; Giulietti, Danilo; Ingenito, Francesco; Gus'kov, Sergey Yu.; Rupasov, Alexander A.

2018-01-01

An experimental campaign to characterize the laser radiation absorption of foam targets and the subsequent emission of radiation from the produced plasma was carried out in the ABC facility of the ENEA Research Center in Frascati (Rome). Different targets have been used: plastic in solid or foam state and aluminum targets. The activated different diagnostics allowed to evaluate the plasma temperature, the density distribution, the fast particle spectrum and the yield of the X-Ray radiation emitted by the plasma for the different targets. These results confirm the foam homogenization action on laser-plasma interaction, mainly attributable to the volume absorption of the laser radiation propagating in such structured materials. These results were compared with simulation absorption models of the laser propagating into a foam target.

Laser radiation bracket debonding

NASA Astrophysics Data System (ADS)

Dostálová, Tat'jana; Jelínková, Helena; Šulc, Jan; Koranda, Petr; Nemec, Michal; Racek, Jaroslav; Miyagi, Mitsunobu

2008-02-01

Ceramic brackets are an aesthetic substitute for conventional stainless steel brackets in orthodontic patients. However, ceramic brackets are more brittle and have higher bond strengths, which can lead to bracket breakage and enamel damage during classical type of debonding. This study examined the possibility of laser radiation ceramic brackets removing as well as the possible damage of a surface structure of hard dental tissue after this procedure. Two types of lasers were used for the experiments - a laser diode LIMO HLU20F400 generating a wavelength of 808 nm with the maximum output power 20W at the end of the fiber (core diameter 400 μm, numerical aperture 0.22). As a second source, a diode-pumped Tm:YAP laser system generating a wavelength of 1.9 μm, with up to 3.8 W maximum output power was chosen. For the investigation, extracted incisors with ceramic brackets were used. In both cases, laser radiation was applied for 0.5 minute at a maximum power of 1 W. Temperature changes of the irradiated tissue was registered by camera Electrophysics PV320. After the interaction experiment, the photo-documentation was prepared by the stereomicroscope Nikon SMZ 2T, Japan. The surface tissue analysis was processed in "low vacuum" (30 Pa) regime without desiccation. This technique was used to record back-scattered electron images. Selecting the appropriate laser, resin, and bracket combination can minimize risks of enamel degradation and make debonding more safe.

Mathematical modeling of a photovoltaic-laser energy converter for iodine laser radiation

NASA Technical Reports Server (NTRS)

Walker, Gilbert H.; Heinbockel, John H.

1987-01-01

Space-based laser power systems will require converters to change laser radiation into electricity. Vertical junction photovoltaic converters are promising devices for this use. A promising laser for the laser power station is the t-C4F9I laser which emits radiation at a wavelength of 1.315 microns. This paper describes the results of mathematical modeling of a photovoltaic-laser energy converter for use with this laser. The material for this photovoltaic converter is Ga(53)In(47)As which has a bandgap energy of 0.94 eV, slightly below the energy of the laser photons (0.943 eV). Results of a study optimizing the converter parameters are presented. Calculated efficiency for a 1000 vertical junction converter is 42.5 percent at a power density of 1 x 10 to the 3d power w/sq cm.

Dichromatic laser radiation effects on DNA of Escherichia coli and plasmids

NASA Astrophysics Data System (ADS)

Martins, W. A.; Polignano, G. A. C.; Guimarães, O. R.; Geller, M.; Paoli, F.; Fonseca, A. S.

2015-04-01

Dichromatic and consecutive laser radiations have attracted increased attention for clinical applications as offering new tools for the treatment of dysfunctional tissues in situations where monochromatic radiation is not effective. This work evaluated the survival, filamentation and morphology of Escherichia coli cells, and the induction of DNA lesions, in plasmid DNA exposed to low-intensity consecutive dichromatic laser radiation. Exponential and stationary wild type and formamidopyrimidine DNA glycosylase/MutM protein deficient E. coli cultures were exposed to consecutive low-intensity dichromatic laser radiation (infrared laser immediately after red laser) to study the survival, filamentation and morphology of bacterial cells. Plasmid DNA samples were exposed to dichromatic radiation to study DNA lesions by electrophoretic profile. Dichromatic laser radiation affects the survival, filamentation and morphology of E. coli cultures depending on the growth phase and the functional repair mechanism of oxidizing lesions in DNA, but does not induce single/double strands breaks or alkali-labile DNA lesions. Results show that low-intensity consecutive dichromatic laser radiation induces biological effects that differ from those induced by monochromatic laser radiation, suggesting that other therapeutic effects could be obtained using dichromatic radiation.

Optical microwave interactions in semiconductor devices

NASA Astrophysics Data System (ADS)

Figueroa, L.; Slayman, C. W.; Yen, H. W.

1980-11-01

The results of an extensive characterization of high speed analog modulation of (GaAl)As injection lasers, high speed optical detectors, and mode locking of (GaAl)As injection lasers are presented. Commercial injection lasers were successfully modulated up to 5 GHz. The 5 GHz value represents a practical upper limit to the modulation bandwith of existing commercial lasers. The laser equivalent circuit was characterized and the parasitics were found to play a significant role in the high speed modulation of the injection laser.

Biological effects of a semiconductor diode laser on human periodontal ligament fibroblasts

PubMed Central

Choi, Eun-Jeong; Yim, Ju-Young; Koo, Ki-Tae; Seol, Yang-Jo; Lee, Yong-Moo; Ku, Young; Rhyu, In-Chul; Chung, Chong-Pyoung

2010-01-01

Purpose It has been reported that low-level semiconductor diode lasers could enhance the wound healing process. The periodontal ligament is crucial for maintaining the tooth and surrounding tissues in periodontal wound healing. While low-level semiconductor diode lasers have been used in low-level laser therapy, there have been few reports on their effects on periodontal ligament fibroblasts (PDLFs). We performed this study to investigate the biological effects of semiconductor diode lasers on human PDLFs. Methods Human PDLFs were cultured and irradiated with a gallium-aluminum-arsenate (GaAlAs) semiconductor diode laser of which the wavelength was 810 nm. The power output was fixed at 500 mW in the continuous wave mode with various energy fluencies, which were 1.97, 3.94, and 5.91 J/cm2. A culture of PDLFs without laser irradiation was regarded as a control. Then, cells were additionally incubated in 72 hours for MTS assay and an alkaline phosphatase (ALPase) activity test. At 48 hours post-laser irradiation, western blot analysis was performed to determine extracellular signal-regulated kinase (ERK) activity. ANOVA was used to assess the significance level of the differences among groups (P<0.05). Results At all energy fluencies of laser irradiation, PDLFs proliferation gradually increased for 72 hours without any significant differences compared with the control over the entire period taken together. However, an increment of cell proliferation significantly greater than in the control occurred between 24 and 48 hours at laser irradiation settings of 1.97 and 3.94 J/cm2 (P<0.05). The highest ALPase activity was found at 48 and 72 hours post-laser irradiation with 3.94 J/cm2 energy fluency (P<0.05). The phosphorylated ERK level was more prominent at 3.94 J/cm2 energy fluency than in the control. Conclusions The present study demonstrated that the GaAlAs semiconductor diode laser promoted proliferation and differentiation of human PDLFs. PMID:20607054

EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Temporal and thermodynamic characteristics of plasma formation

NASA Astrophysics Data System (ADS)

Ignatavichyus, M. V.; Kazakyavichyus, É.; Orshevski, G.; Danyunas, V.

1991-11-01

An investigation was made of plasma formation accompanying the interaction with aluminum, iron, and VK-6 alloy targets of nanosecond radiation from a YAG:Nd3+ laser (Emax = 50 mJ, τ = 3-8 ns). The duration of the plasma formation process depended weakly on the laser radiation parameters [the power density was varied in the range 1-3 GW/cm2, the pulse rise time in the range 2-8 ns, or the rate of rise of the power density in the range (1-8) × 108 W · cm - 2 · ns -1]. A study was made of the establishment of a local thermodynamic equilibrium in a plasma jet excited by radiation from nanosecond and picosecond (E = 30 mJ, τ = 40 ps) lasers. The maximum of the luminescence from an aluminum plasma excited by picosecond laser radiation was found to correspond to a local thermodynamic equilibrium. A local thermodynamic equilibrium could be absent in the case of excitation by nanosecond laser radiation.

Fast and broadband detector for laser radiation

NASA Astrophysics Data System (ADS)

Scorticati, Davide; Crapella, Giacomo; Pellegrino, Sergio

2018-02-01

We developed a fast detector (patent pending) based on the Laser Induced Transverse Voltage (LITV) effect. The advantage of detectors using the LITV effect over pyroelectric sensors and photodiodes for laser radiation measurements is the combination of an overall fast response time, broadband spectral acceptance, high saturation threshold to direct laser irradiation and the possibility to measure pulsed as well as cw-laser sources. The detector is capable of measuring the energy of single laser pulses with repetition frequencies up to the MHz range, adding the possibility to also measure the output power of cw-lasers. Moreover, the thermal nature of the sensor enables the capability to work in a broadband spectrum, from UV to THz as well as the possibility of operating in a broad-range (10-3-102 W/cm2 ) of incident average optical power densities of the laser radiation, without the need of adopting optical filters nor other precautions.

Medium-level laser in chronic tinnitus treatment.

PubMed

Dejakum, K; Piegger, J; Plewka, C; Gunkel, A; Thumfart, W; Kudaibergenova, S; Goebel, G; Kral, F; Freysinger, W

2013-01-01

The purpose of this study was to evaluate the effect of medium-level laser therapy in chronic tinnitus treatment. In a prospective double-blind placebo-controlled trial, either active laser (450 mW, 830 nm combined Ga-Al-As diode laser) or placebo irradiation was applied through the external acoustic meatus of the affected ear towards the cochlea. Fourty-eight patients with chronic tinnitus were studied. The main outcome was measured using the Goebel tinnitus questionnaire, visual analogue scales measuring the perceived loudness of tinnitus, the annoyance associated with tinnitus, and the degree of attention paid to tinnitus as well as psycho-acoustical matches of tinnitus pitch and loudness. The results did show only very moderate temporary improvement of tinnitus. Moreover, no statistically relevant differences between laser and placebo group could be found. We conclude that medium-level laser therapy cannot be regarded as an effective treatment of chronic tinnitus in our therapy regime considering the limited number of patients included in our study.

Terahertz plasmonic laser radiating in an ultra-narrow beam

DOE PAGES

Wu, Chongzhao; Khanal, Sudeep; Reno, John L.; ...

2016-07-07

Plasmonic lasers (spasers) generate coherent surface plasmon polaritons (SPPs) and could be realized at subwavelength dimensions in metallic cavities for applications in nanoscale optics. Plasmonic cavities are also utilized for terahertz quantum-cascade lasers (QCLs), which are the brightest available solid-state sources of terahertz radiation. A long standing challenge for spasers that are utilized as nanoscale sources of radiation, is their poor coupling to the far-field radiation. Unlike conventional lasers that could produce directional beams, spasers have highly divergent radiation patterns due to their subwavelength apertures. Here, we theoretically and experimentally demonstrate a new technique for implementing distributed feedback (DFB) thatmore » is distinct from any other previously utilized DFB schemes for semiconductor lasers. The so-termed antenna-feedback scheme leads to single-mode operation in plasmonic lasers, couples the resonant SPP mode to a highly directional far-field radiation pattern, and integrates hybrid SPPs in surrounding medium into the operation of the DFB lasers. Experimentally, the antenna-feedback method, which does not require the phase matching to a well-defined effective index, is implemented for terahertz QCLs, and single-mode terahertz QCLs with a beam divergence as small as 4°×4° are demonstrated, which is the narrowest beam reported for any terahertz QCL to date. Moreover, in contrast to a negligible radiative field in conventional photonic band-edge lasers, in which the periodicity follows the integer multiple of half-wavelengths inside the active medium, antenna-feedback breaks this integer limit for the first time and enhances the radiative field of the lasing mode. Terahertz lasers with narrow-beam emission will find applications for integrated as well as standoff terahertz spectroscopy and sensing. Furthermore, the antenna-feedback scheme is generally applicable to any plasmonic laser with a Fabry–Perot cavity

Generation and use of high power 213 nm and 266 nm laser radiation and tunable 210-400 nm laser radiation with BBO crystal matrix array

DOEpatents

Gruen, Dieter M.

2000-01-01

A 213 nm laser beam is capable of single photon ablative photodecomposition for the removal of a polymer or biological material substrate. Breaking the molecular bonds and displacing the molecules away from the substrate in a very short time period results in most of the laser photon energy being carried away by the displaced molecules, thus minimizing thermal damage to the substrate. The incident laser beam may be unfocussed and is preferably produced by quintupling the 1064 nm radiation from a Nd:YAG solid state laser, i.e., at 213 nm. In one application, the 213 nm laser beam is expanded in cross section and directed through a plurality of small beta barium borate (BBO) crystals for increasing the energy per photon of the laser radiation directed onto the substrate. The BBO crystals are arranged in a crystal matrix array to provide a large laser beam transmission area capable of accommodating high energy laser radiation without damaging the BBO crystals. The BBO crystal matrix array may also be used with 266 nm laser radiation for carrying out single or multi photon ablative photodecomposition. The BBO crystal matrix array may also be used in an optical parametric oscillator mode to generate high power tunable laser radiation in the range of 210-400 nm.

Optical radiation hazards of laser welding processes. Part II: CO2 laser.

PubMed

Rockwell, R J; Moss, C E

1989-08-01

There has been an extensive growth within the last five years in the use of high-powered lasers in various metalworking processes. The two types of lasers used most frequently for laser welding/cutting processes are the Neodymium-yttrium-aluminum-garnet (Nd:YAG) and the carbon dioxide (CO2) systems. When such lasers are operated in an open beam configuration, they are designated as a Class IV laser system. Class IV lasers are high-powered lasers that may present an eye and skin hazard under most common exposure conditions, either directly or when the beam has been diffusely scattered. Significant control measures are required for unenclosed (open beam), Class IV laser systems since workers may be exposed to scattered or reflected beams during the operation, maintenance, and service of these lasers. In addition to ocular and/or skin exposure hazards, such lasers also may present a multitude of nonlaser beam occupational concerns. Radiant energy measurements are reported for both the scattered laser radiation and the plasma-related plume radiations released during typical high-powered CO2 laser-target interactions. In addition, the application of the nominal hazard zone (NHZ) and other control measures also are discussed with special emphasis on Class IV industrial CO2 laser systems.

Laser Radiation-Induced Air Breakdown And Plasma Shielding

NASA Astrophysics Data System (ADS)

Smith, David C.

1981-12-01

Gas breakdown, or the ionization of the air in the path of a high power laser, is a limit on the maximum intensity which can be propagated through the atmosphere. When the threshold for breakdown is exceeded, a high density, high temperature plasma is produced which is opaque to visible and infrared wavelengths and thus absorbs the laser radiation. The threshold in the atmosphere is significantly lower than in pure gases because of laser interaction and vaporization of aerosols. This aspect of air breakdown is discussed in detail. Parametric studies have revealed the scaling laws of breakdown as to wavelength and laser pulse duration, and these will be discussed and compared with existing models. A problem closely related to breakdown is the plasma produc-tion when a high intensity laser interacts with a surface. In this case, the plasma can be beneficial for coupling laser energy into shiny surfaces. The plasma absorbs the laser radiation and reradiates the energy at shorter wavelengths; this shorter wavelength radiation is absorbed by the surface, thus increasing the coupling of energy into the surface. The conditions for the enhancement of laser coupling into surfaces will be discussed, particularly for cw laser beams, an area of recent experimen-tal investigation.

Numerical Investigation of Radiative Heat Transfer in Laser Induced Air Plasmas

NASA Technical Reports Server (NTRS)

Liu, J.; Chen, Y. S.; Wang, T. S.; Turner, James E. (Technical Monitor)

2001-01-01

Radiative heat transfer is one of the most important phenomena in the laser induced plasmas. This study is intended to develop accurate and efficient methods for predicting laser radiation absorption and plasma radiative heat transfer, and investigate the plasma radiation effects in laser propelled vehicles. To model laser radiation absorption, a ray tracing method along with the Beer's law is adopted. To solve the radiative transfer equation in the air plasmas, the discrete transfer method (DTM) is selected and explained. The air plasma radiative properties are predicted by the LORAN code. To validate the present nonequilibrium radiation model, several benchmark problems are examined and the present results are found to match the available solutions. To investigate the effects of plasma radiation in laser propelled vehicles, the present radiation code is coupled into a plasma aerodynamics code and a selected problem is considered. Comparisons of results at different cases show that plasma radiation plays a role of cooling plasma and it lowers the plasma temperature by about 10%. This change in temperature also results in a reduction of the coupling coefficient by about 10-20%. The present study indicates that plasma radiation modeling is very important for accurate modeling of aerodynamics in a laser propelled vehicle.

Beam shaping of laser diode radiation by waveguides with arbitrary cladding geometry written with fs-laser radiation.

PubMed

Beckmann, Dennis; Schnitzler, Daniel; Schaefer, Dagmar; Gottmann, Jens; Kelbassa, Ingomar

2011-12-05

Waveguides with arbitrary cross sections are written in the volume of Al(2)O(3)-crystals using tightly focused femtosecond laser radiation. Utilizing a scanning system with large numerical aperture, complex cladding geometries are realized with a precision around 0.5 µm and a scanning speed up to 100 mm/s. Individual beam and mode shaping of laser diode radiation is demonstrated by varying the design of the waveguide cladding. The influence of the writing parameters on the waveguide properties are investigated resulting in a numerical aperture of the waveguides in the range of 0.1. This direct laser writing technique enables optical devices which could possibly replace bulky beam shaping setups with an integrated solution.

Low-level Laser Therapy on Postoperative Pain after Mandibular Third Molar Surgery

PubMed Central

Hamid, May Ayad

2017-01-01

Introduction: The analgesic effect of low-level laser therapy (LLLT) after mandibular third molar (MTM) extraction is controversial. The aim is to evaluate the effect of intraoral LLLT on postoperative pain after MTMs extraction. Methods: Thirty patients with bilateral symmetrical impacted MTMs underwent surgical extractions. Experimental and control sides were randomly selected to receive LLLT or placebo. Following suturing, a dental assistant applied 810 nm gallium aluminum arsenide (GaAlAs) at three points for 30 s each with a total energy of 9 J. Pain was recorded on a visual analog scale on the 7 successive days. Results: Data analyzed by IBM SPSS Statistics 23 for Windows with P ≤ 0.05 significance level. LLLT appeared to have a high significant effect on pain reduction; however, there was a mild increase in pain after the 4th day. Conclusion: Intraoral 810 nm GaAlAs is effective in reducing postoperative pain when a dose of 32.86 J/cm2 is used. PMID:29264287

Laser phototherapy as topical prophylaxis against head and neck cancer radiotherapy-induced oral mucositis: comparison between low and high/low power lasers.

PubMed

Simões, Alyne; Eduardo, Fernanda P; Luiz, Ana Claudia; Campos, Luana; Sá, Pedro Henrique R N; Cristófaro, Márcio; Marques, Márcia M; Eduardo, Carlos P

2009-04-01

Oral mucositis is a dose-limiting and painful side effect of radiotherapy (RT) and/or chemotherapy in cancer patients. The purpose of the present study was to analyze the effect of different protocols of laser phototherapy (LPT) on the grade of mucositis and degree of pain in patients under RT. Thirty-nine patients were divided into three groups: G1, where the irradiations were done three times a week using low power laser; G2, where combined high and low power lasers were used three time a week; and G3, where patients received low power laser irradiation once a week. The low power LPT was done using an InGaAlP laser (660 nm/40 mW/6 J cm(-2)/0.24 J per point). In the combined protocol, the high power LPT was done using a GaAlAs laser (808 nm, 1 W/cm(2)). Oral mucositis was assessed at each LPT session in accordance to the oral-mucositis scale of the National Institute of the Cancer-Common Toxicity criteria (NIC-CTC). The patient self-assessed pain was measured by means of the visual analogue scale. All protocols of LPT led to the maintenance of oral mucositis scores in the same levels until the last RT session. Moreover, LPT three times a week also maintained the pain levels. However, the patients submitted to the once a week LPT had significant pain increase; and the association of low/high LPT led to increased healing time. These findings are desired when dealing with oncologic patients under RT avoiding unplanned radiation treatment breaks and additional hospital costs.

Laser-plasma-based Space Radiation Reproduction in the Laboratory

PubMed Central

Hidding, B.; Karger, O.; Königstein, T.; Pretzler, G.; Manahan, G. G.; McKenna, P.; Gray, R.; Wilson, R.; Wiggins, S. M.; Welsh, G. H.; Beaton, A.; Delinikolas, P.; Jaroszynski, D. A.; Rosenzweig, J. B.; Karmakar, A.; Ferlet-Cavrois, V.; Costantino, A.; Muschitiello, M.; Daly, E.

2017-01-01

Space radiation is a great danger to electronics and astronauts onboard space vessels. The spectral flux of space electrons, protons and ions for example in the radiation belts is inherently broadband, but this is a feature hard to mimic with conventional radiation sources. Using laser-plasma-accelerators, we reproduced relativistic, broadband radiation belt flux in the laboratory, and used this man-made space radiation to test the radiation hardness of space electronics. Such close mimicking of space radiation in the lab builds on the inherent ability of laser-plasma-accelerators to directly produce broadband Maxwellian-type particle flux, akin to conditions in space. In combination with the established sources, utilisation of the growing number of ever more potent laser-plasma-accelerator facilities worldwide as complementary space radiation sources can help alleviate the shortage of available beamtime and may allow for development of advanced test procedures, paving the way towards higher reliability of space missions. PMID:28176862

Facet joint laser radiation: tissue effects of a new clinical laser application

NASA Astrophysics Data System (ADS)

Werkmann, Klaus; Thal, Dietmar R.

1996-01-01

Chronic unilateral and bilateral back pain with pseudoradicular symptoms, is a common clinical syndrome, which in many cases can be related to the facet joint syndrome. The pain is caused by mechanical affection of synovial and capsular nerve terminals. Therefore, current therapeutical attempts including physical therapy, intra-articular injection of local anesthetics and steroids and thermocoagulation of the facet joint with a thermocoagulator, are performed. We confirmed laser coagulation of the facet joint. Porcine cadaveric spines were treated immediately after death by intra-articular facet joint laser radiation. With the pulsed Nd:YAG laser (1064 nm) altogether 600 J were applied in three different places 4 mm apart at the top of the facet joint. The results showed that facet joint laser radiation leads to a small (about 1 - 2 mm diameter) lesion restricted to the facet joint cavity and its synovia. Histologically, we found a central carbonization zone and necrosis, including almost the whole cartilage and approximately 0.2 mm of the adjacent bone. These changes are similar to Nd:Yag-laser applications in other skeletal regions. It is suggested that these changes may lead to facet joint denervation by coagulation of the synovial nerve terminals. Cicatration of the laser lesion might cause ankylosis of this joint. In sum, facet joint laser radiation could be an alternative therapeutical tool for lower back pain of the facet joint syndrome type. Therefore, future clinical application of this technique seems to be very promising.

Development of laser diode otolaryngological intracavity procedures and its clinical practice

NASA Astrophysics Data System (ADS)

Wang, Qingguo; Mao, Haitao; Bu, Hongjian; Dong, Xingfa; Li, Jikai; Li, Fangzheng; Zhang, Wenqing

1998-08-01

Because laser is diffusely reflected by the skin as well as scattered and absorbed by the subcutaneous tissue, the lasing intensity which enters into the tissue through the skin is exponentially attenuated with the increase in the depth. Therefore, when the medium-small energy laser is transmitted to the tissue depth through the skin, the lasing intensity is quite finite. However, a lot of diseases occur in the crooked and narrow tube, sinus or deep tissue, for these diseases, it is difficult to get the curative effect by normal laser radiation. As above, we have developed an otolaryngological intracavity therapeutic apparatus of laser diode. Visible GaAlAs laser diode is adopted on this apparatus, its lasing wavelength is 670 nm. The lasing beam is guided into the crooked and narrow tube, sinus or deep tissue, which passes through the optical fiber and the laser pins of different forms and sizes (such as straight, curved and sidelight etc.). Using the fiber-optic connector the laser pins can be changed conveniently. The lasing output power of laser pin can be adjusted from 0 to 20 mW. The lasing intensity may be modulated which changes the rectangular wave form 0 to 1 kHz. Five hundred patients were suffering from 35 kind of otolaryngological diseases were treated in the period of clinical test. The rate of efficiency (cure or improvement) is 89%. Nobody had the side effect or deteriorated. This apparatus has the best curative effect on the inflammation of the mucosa and shallow tissue, such as auris media dropsy, maxillary sinus inflammation, auris external inflammation, chronic laryngitis, otitis media, tinnitus, vertigo, and so on.

EFFECTS OF LASER RADIATION ON MATTER: Melting and thermocapillary convection under the action of pulsed laser radiation with an inhomogeneous spatial distribution

NASA Astrophysics Data System (ADS)

Uglov, A. A.; Smurov, I. Yu; Gus'kov, A. G.; Aksenov, L. V.

1990-08-01

A theoretical study is reported of melting and thermocapillary convection under the action of laser radiation with a nonmonotonic spatial distribution of the power density. An analysis is made of changes in the geometry of the molten bath with time. The transition from a nonmonotonic boundary of a melt, corresponding to the spatial distribution of the radiation, to a monotonic one occurs in a time of the order of 1 ms when the power density of laser radiation is 105 W/cm2. The vortex structure of the flow in the molten bath is governed by the spatial distribution of the laser radiation in such a way that each local power density maximum corresponds to two vortices with oppositely directed velocity components.

Effect of diode laser in the treatment of patients with nonspecific chronic low back pain: a randomized controlled trial.

PubMed

Vallone, Francesco; Benedicenti, Stefano; Sorrenti, Eugenio; Schiavetti, Irene; Angiero, Francesca

2014-09-01

Low back pain is a common, highly debilitating condition, whose severity is variable. This study evaluated the efficacy of treatment with Ga-Al-As diode laser (980 nm) with a large diameter spot (32 cm(2)), in association with exercise therapy, in reducing pain. The present study aimed to evaluate the pain reduction efficacy of treatment with the Ga-Al-As diode laser (980 nm) in combination with exercise therapy, in patients with chronic low back pain (CLBP). This study evaluated 100 patients with CLBP (mean age 60 years) who were randomly assigned to two groups. The laser plus exercises group (Laser+EX: 50 patients) received low-level laser therapy (LLLT) with a diode laser, 980 nm, with a specific handpiece [32 cm(2) irradiation spot size, power 20 W in continuous wave (CW), fluence 37.5J/cm(2), total energy per point 1200 J] thrice weekly, and followed a daily exercise schedule for 3 weeks (5 days/week). The exercises group (EX: 50 patients) received placebo laser therapy plus daily exercises. The outcome was evaluated on the visual analogue pain scale (VAS), before and after treatment. At the end of the 3 week period, the Laser+EX group showed a significantly greater decrease in pain than did the EX group. There was a significant difference between the two groups, with average Δ VAS scores of 3.96 (Laser+EX group) and 2.23 (EX group). The Student's t test demonstrated a statistically significant difference between the two groups, at p<0.001. This study demonstrated that the use of diode laser (980 nm) with large diameter spot size, in association with exercise therapy, appears to be effective. Such treatment might be considered a valid therapeutic option within rehabilitation programs for nonspecific CLBP.

Novel THz radiation from relativistic laser-plasmas

NASA Astrophysics Data System (ADS)

Sheng, Z. M.; Wu, H. C.; Wang, W. M.; Dong, X. G.; Chen, M.; Zhang, J.

2009-05-01

The interaction of ultrashort intense laser pulses with plasma can produce electromagnetic radiation of ultra-broad spectra ranging from terahertz (THz) radiation to keV x-rays and beyond. Here we present a review of our recent theoretical and numerical investigation on high power THz generation from tenuous plasma or gas targets irradiated by ultrashort intense laser pulses. Three mechanisms of THz emission are addressed, which include the linear mode conversion from laser wakefields in inhomogeneous plasma, transient current emission at the plasma-vacuum boundaries, and the emission from residual transverse currents produced by temporally-asymmetric laser pulses passing through gas or plasma targets. Since there is no breakdown limit for plasma under the irradiation of high power lasers, in principle, all these mechanisms can lead to terahertz pulse emission at the power of beyond megawatt with the field strength of MV/cm, suitable for the study of high THz field physics and other applications.

EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Low-threshold generation of harmonics and hard x radiation in a laser plasma. 2. Multipeak generation

NASA Astrophysics Data System (ADS)

Apollonov, V. V.; Derzhavin, S. I.; Kazakov, K. Kh

1993-02-01

The conditions for the generation of hard x radiation with a multipeak structure in a plasma pumped by a long pulse from a free-running CO2 laser at a low intensity (q≲10 GW/cm2) have been studied. This x-ray generation had been observed in a previous study by the present authors. It is shown that this generation of hard x radiation with a multipeak structure leads to a more than tenfold increase in the yield of hard x radiation per laser pulse, under optimum conditions. This increase results from the additional peaks in the x-ray signal. An explanation of this effect is proposed.

Laser amplification of incoherent radiation

NASA Technical Reports Server (NTRS)

Menegozzi, L. N.; Lamb, W. E., Jr.

1978-01-01

The amplification of noise in a laser amplifier is treated theoretically. The model for the active medium and its description using density-matrix techniques, are taken from the theory of laser operation. The spectral behavior of the radiation in the nonlinear regime is studied and the formalism is written from the onset in the frequency domain. The statistics of the light are gradually modified by the nonlinear amplification process, and expressions are derived for the rate of change of fluctuations in intensity as a measure of statistical changes. In addition, the range of validity of Litvak's Gaussian-statistics approximation is discussed. In the homogeneous-broadening case, the evolution of initially broadband Gaussian radiation toward quasimonochromatic oscillations with laserlike statistics is explored in several numerical examples. The connections of this study with the time-domain work on self-pulsing in a ring-laser configuration, are established. Finally, spectral-narrowing and -rebroadening effects in Doppler-broadened media are discussed both analytically and with numerical examples. These examples show the distinct contribution of pulsations in the population ('Raman-type terms'), and saturation phenomena.

The effects of two different low level laser therapies in the treatment of patients with chronic low back pain: A double-blinded randomized clinical trial.

PubMed

Koldaş Doğan, Şebnem; Ay, Saime; Evcik, Deniz

2017-01-01

The purpose of this study was to compare the effectiveness of two different laser therapy regimens on pain, lumbar range of motions (ROM) and functional capacity in patients with chronic low back pain (CLBP). Forty nine patients with CLBP were randomly assigned into two groups. Group 1 (n= 20) received hot-pack + laser therapy 1 (wavelength of 850 nm Gallium-Aluminum-Arsenide (Ga-Al-As) laser); group 2 (n= 29) received hot-pack + laser therapy 2 (wavelength of 650 nm Helyum-Neon (He-Ne), 785 ve 980 nm Gal-Al-As combined plaque laser) for 15 sessions. Pain severity, patient's and physician's global assessments were evaluated with visual analogue scale (VAS). Modified Schober test, right and left lateral flexion measurements were done. Modified Oswestry Disability Questionnaire (MODQ) was used for evaluation of functional disability. Measurements were done before and after the treatment. After treatment there were statistically significant improvements in pain severity, patient's and physician's global assessment, ROM and MODQ scores in both groups (P< 0.05). After the treatment there were statistically significant differences between the groups in lateral flexion measurements and MODQ scores (P< 0.05) except in pain severity, Modified Schober test, patient's and physician's global assessments (P> 0.05) in favor of those patients who received combined plaque laser therapy (group 2). Laser therapy applied with combined He-Ne and Ga-Al-As provides more improvements in lateral flexion measurements and disability of the patients, however no superiority of the two different laser devices to one another were detected on pain severity.

Medium-Level Laser in Chronic Tinnitus Treatment

PubMed Central

Dejakum, K.; Piegger, J.; Plewka, C.; Gunkel, A.; Thumfart, W.; Kudaibergenova, S.; Goebel, G.; Kral, F.; Freysinger, W.

2013-01-01

The purpose of this study was to evaluate the effect of medium-level laser therapy in chronic tinnitus treatment. In a prospective double-blind placebo-controlled trial, either active laser (450 mW, 830 nm combined Ga-Al-As diode laser) or placebo irradiation was applied through the external acoustic meatus of the affected ear towards the cochlea. Fourty-eight patients with chronic tinnitus were studied. The main outcome was measured using the Goebel tinnitus questionnaire, visual analogue scales measuring the perceived loudness of tinnitus, the annoyance associated with tinnitus, and the degree of attention paid to tinnitus as well as psycho-acoustical matches of tinnitus pitch and loudness. The results did show only very moderate temporary improvement of tinnitus. Moreover, no statistically relevant differences between laser and placebo group could be found. We conclude that medium-level laser therapy cannot be regarded as an effective treatment of chronic tinnitus in our therapy regime considering the limited number of patients included in our study. PMID:24294604

Thermomechanical effect of pulse-periodic laser radiation on cartilaginous and eye tissues

NASA Astrophysics Data System (ADS)

Baum, O. I.; Zheltov, G. I.; Omelchenko, A. I.; Romanov, G. S.; Romanov, O. G.; Sobol, E. N.

2013-08-01

This paper is devoted to theoretical and experimental studies into the thermomechanical action of laser radiation on biological tissues. The thermal stresses and strains developing in biological tissues under the effect of pulse-periodic laser radiation are theoretically modeled for a wide range of laser pulse durations. The models constructed allow one to calculate the magnitude of pressures developing in cartilaginous and eye tissues exposed to laser radiation and predict the evolution of cavitation phenomena occurring therein. The calculation results agree well with experimental data on the growth of pressure and deformations, as well as the dynamics of formation of gas bubbles, in the laser-affected tissues. Experiments on the effect of laser radiation on the trabecular region of the eye in minipigs demonstrated that there existed optimal laser irradiation regimens causing a substantial increase in the hydraulic permeability of the radiation-exposed tissue, which can be used to develop a novel glaucoma treatment method.

EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Formation of amplified spontaneous radiation in an expanding laser plasma allowing for refraction

NASA Astrophysics Data System (ADS)

Gulov, A. V.; Derzhiev, V. I.; Zhidkov, A. G.; Terskikh, A. O.; Yakovlenko, Sergei I.

1990-06-01

Calculations are made of the divergence of amplified spontaneous radiation in a laser plasma allowing for refraction by free electrons. An analysis is made of the divergence of the radiation generated due to a 3p→3s' transition in neon-like ions. Calculations are made of the divergence of the radiation due to the 4→3 transition in the O VIII ion allowing for refraction during expansion of a Formvar plasma.

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

EFFECTS OF LASER RADIATION ON MATTER: Growth of periodic structures on the surface of germanium subjected to pulsed laser radiation

NASA Astrophysics Data System (ADS)

Barsukov, D. O.; Gusakov, G. M.; Frolov, A. I.

1991-12-01

An experimental investigation was made of the dynamics of growth of periodic surface structures due to the interaction with pulsed laser radiation. Samples of Ge were subjected to laser pulses (λ = 1.06 μm, τ = 70 ns) with energy densities in the range 0.5-5.5 J/cm2. An investigation was made of the dynamics of the first-order diffraction of probe (λ = 0.53 μm) laser pulses with a time resolution 4 ns when p- and s-polarized laser radiation was incident at angles close to normal. A strong nonlinearity of the growth of such periodic surface structures was observed. The energy density from which such growth began depended on the quality of the polished Ge surface. The parameters of the dynamics of the growth of these structures were estimated.

Comparison of the ablation ability of nucleus pulposus after 1,064 nm Nd:YAG laser and 980 nm diode laser radiation.

PubMed

Yin, Jian; Han, Zhengfeng; Guo, Baofeng; Guo, Han; Zhang, Tongtong; Zeng, Yanjun; Ren, Longxi

2015-07-01

To compare the ablation ability of nucleus pulposus after 1,064 nm Nd:YAG laser and 980 nm diode laser radiation. Goat spine specimen (GSS) was radiated using Nd:YAG laser and 980 nm diode laser and then divided into five groups based on the final energy--200, 400, 600, 800 and 1,000 J groups. The ablation quality of nucleus pulposus after radiation was recorded. The ablation quality of GSS was greater at higher radiation energies in both lasers. When compared at the same energy level, the ablation quality of GSS was greater in 980 nm diode laser than in 1,064 nm Nd:YAG laser. Statistical significance was observed in 200 and 400 J groups (P < 0.05) and in 600, 800 and 1,000 J groups (P < 0.01). Radiation with 980 nm diode laser showed better ablation ability than 1,064 nm Nd:YAG laser.

Phase conjugation of Nd:YAG laser radiation

NASA Astrophysics Data System (ADS)

Chen, Jun

1988-06-01

The phase conjugation of Nd:YAG laser radiation by four-wave mixing in silicon and by stimulated Brillouin scattering in acetone and other organic liquids was experimentally and theoretically investigated. Due to nonlinear absorption in Si a saturation of the reflection of the phase conjugator was theoretically predicted, and experimentally observed. It is theoretically and experimentally shown that the radiation profile behind the Si-sample is annular due to defocusing. The experiments show that CS2 and acetone have the lowest thresholds for stimulated Brillouin scattering. A laser resonator was built using a Brillouin cell and two normal mirrors; the emitted laser beam is insensitive to phase perturbations in the resonator, and has a pulse duration of 5 ns and a pulse energy of 220 m.

LASER RADIATION CHARACTERISTICS (BRIEF COMMUNICATIONS): Conversion of KrCl and XeCl laser radiation to the visible spectral range by stimulated Raman scattering in lead vapor

NASA Astrophysics Data System (ADS)

Evtushenko, Gennadii S.; Mel'chenko, S. V.; Panchenko, Aleksei N.; Tarasenko, Viktor F.

1990-04-01

Conversion of KrCl and XeCl laser radiation by stimulated Raman scattering was achieved in lead vapor. The KrCl laser radiation was converted into three lines in the visible region at λ = 406, 590, and 723 nm by transitions from both the ground and first excited levels of the lead atom. The conversion efficiency of XeCl laser radiation of low spatial coherence was found to be limited by the activation of a competing nonlinear process.

INTERACTION OF LASER RADIATION WITH MATTER: Influence of surface breakdown on the process of drilling metals with pulsed CO2 laser radiation

NASA Astrophysics Data System (ADS)

Arutyunyan, R. V.; Baranov, V. Yu; Bobkov, I. V.; Bol'shov, Leonid A.; Dolgov, V. A.; Kanevskiĭ, M. F.; Malyuta, D. D.; Mezhevov, V. S.

1988-03-01

A report is given of the influence of low-threshold surface optical breakdown, occurring under the action of short (~ 5-μs) radiation pulses from a CO2 laser, on the process of the laser drilling of metals. Data are given on the difference between the interaction of radiation pulses having the same duration but differing in shape. A study was made of the influence of the pressure of the atmosphere surrounding a target on the results of laser drilling of metals. A theoretical explanation is given of the experimental results.

Counterpropagating Radiative Shock Experiments on the Orion Laser

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

Suzuki-Vidal, F.; Clayson, T.; Stehlé, C.

We present new experiments to study the formation of radiative shocks and the interaction between two counterpropagating radiative shocks. The experiments are performed at the Orion laser facility, which is used to drive shocks in xenon inside large aspect ratio gas cells. The collision between the two shocks and their respective radiative precursors, combined with the formation of inherently three-dimensional shocks, provides a novel platform particularly suited for the benchmarking of numerical codes. The dynamics of the shocks before and after the collision are investigated using point-projection x-ray backlighting while, simultaneously, the electron density in the radiative precursor was measuredmore » via optical laser interferometry. Modeling of the experiments using the 2D radiation hydrodynamic codes nym and petra shows very good agreement with the experimental results.« less

Counterpropagating Radiative Shock Experiments on the Orion Laser.

PubMed

Suzuki-Vidal, F; Clayson, T; Stehlé, C; Swadling, G F; Foster, J M; Skidmore, J; Graham, P; Burdiak, G C; Lebedev, S V; Chaulagain, U; Singh, R L; Gumbrell, E T; Patankar, S; Spindloe, C; Larour, J; Kozlova, M; Rodriguez, R; Gil, J M; Espinosa, G; Velarde, P; Danson, C

2017-08-04

We present new experiments to study the formation of radiative shocks and the interaction between two counterpropagating radiative shocks. The experiments are performed at the Orion laser facility, which is used to drive shocks in xenon inside large aspect ratio gas cells. The collision between the two shocks and their respective radiative precursors, combined with the formation of inherently three-dimensional shocks, provides a novel platform particularly suited for the benchmarking of numerical codes. The dynamics of the shocks before and after the collision are investigated using point-projection x-ray backlighting while, simultaneously, the electron density in the radiative precursor was measured via optical laser interferometry. Modeling of the experiments using the 2D radiation hydrodynamic codes nym and petra shows very good agreement with the experimental results.

Counterpropagating Radiative Shock Experiments on the Orion Laser

DOE PAGES

Suzuki-Vidal, F.; Clayson, T.; Stehlé, C.; ...

2017-08-02

We present new experiments to study the formation of radiative shocks and the interaction between two counterpropagating radiative shocks. The experiments are performed at the Orion laser facility, which is used to drive shocks in xenon inside large aspect ratio gas cells. The collision between the two shocks and their respective radiative precursors, combined with the formation of inherently three-dimensional shocks, provides a novel platform particularly suited for the benchmarking of numerical codes. The dynamics of the shocks before and after the collision are investigated using point-projection x-ray backlighting while, simultaneously, the electron density in the radiative precursor was measuredmore » via optical laser interferometry. Modeling of the experiments using the 2D radiation hydrodynamic codes nym and petra shows very good agreement with the experimental results.« less

LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Optimal two-mirror system for laser radiation focusing

NASA Astrophysics Data System (ADS)

Gitin, Andrey V.

2009-10-01

An optical system for laser radiation focusing, which consists of parabolic and elliptic mirrors, is considered. It is shown by the method of elementary reflections that the maximum concentration of laser radiation on the target can be achieved at a certain position of these mirrors.

Modelling of micromachining of human tooth enamel by erbium laser radiation

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

Belikov, A V; Skrypnik, A V; Shatilova, K V

We consider a 3D cellular model of human tooth enamel and a photomechanical cellular model of enamel ablation by erbium laser radiation, taking into account the structural peculiarities of enamel, energy distribution in the laser beam cross section and attenuation of laser energy in biological tissue. The surface area of the texture in enamel is calculated after its micromachining by erbium laser radiation. The influence of the surface area on the bond strength of enamel with dental filling materials is discussed. A good correlation between the computer simulation of the total work of adhesion and experimentally measured bond strength betweenmore » the dental filling material and the tooth enamel after its micromachining by means of YAG : Er laser radiation is attained. (laser biophotonics)« less

Betatron x-ray radiation from laser-plasma accelerators driven by femtosecond and picosecond laser systems

NASA Astrophysics Data System (ADS)

Albert, F.; Lemos, N.; Shaw, J. L.; King, P. M.; Pollock, B. B.; Goyon, C.; Schumaker, W.; Saunders, A. M.; Marsh, K. A.; Pak, A.; Ralph, J. E.; Martins, J. L.; Amorim, L. D.; Falcone, R. W.; Glenzer, S. H.; Moody, J. D.; Joshi, C.

2018-05-01

A comparative experimental study of betatron x-ray radiation from laser wakefield acceleration in the blowout and self-modulated regimes is presented. Our experiments use picosecond duration laser pulses up to 150 J (self-modulated regime) and 60 fs duration laser pulses up to 10 J (blowout regime), for plasmas with electronic densities on the order of 1019 cm-3. In the self-modulated regime, where betatron radiation has been very little studied compared to the blowout regime, electrons accelerated in the wake of the laser pulse are subject to both the longitudinal plasma and transverse laser electrical fields. As a result, their motion within the wake is relatively complex; consequently, the experimental and theoretical properties of the x-ray source based on self-modulation differ from the blowout regime of laser wakefield acceleration. In our experimental configuration, electrons accelerated up to about 250 MeV and betatron x-ray spectra with critical energies of about 10-20 keV and photon fluxes between 108 and 1010 photons/eV Sr are reported. Our experiments open the prospect of using betatron x-ray radiation for applications, and the source is competitive with current x-ray backlighting methods on multi-kilojoule laser systems.

Wavelength dependence of l/f noise in the light output of laser diodes; An experimental study

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

Fronen, R.J.

1990-10-01

The optical power emitted by a monomode GaAlAs laser is filtered with a monochromator. The 1/f noise in the filtered emission is found to be directly dependent on the noncoherent emission, such as S{sub p} {proportional to} P{sup m {sub nc}}. Here S{sub p} is the spectral density of the 1/f fluctuations, P{sub nc} is the average noncoherent power, m = 3/2 under spontaneous emission, and m=4 in the superradiation and laser regions. This paper reports that study of the 1/f noise in the optical power in a band centered at the laser wavelength and with variable bandwidth shows threemore » operating regions.« less

Modelling of micromachining of human tooth enamel by erbium laser radiation

NASA Astrophysics Data System (ADS)

Belikov, A. V.; Skrypnik, A. V.; Shatilova, K. V.

2014-08-01

We consider a 3D cellular model of human tooth enamel and a photomechanical cellular model of enamel ablation by erbium laser radiation, taking into account the structural peculiarities of enamel, energy distribution in the laser beam cross section and attenuation of laser energy in biological tissue. The surface area of the texture in enamel is calculated after its micromachining by erbium laser radiation. The influence of the surface area on the bond strength of enamel with dental filling materials is discussed. A good correlation between the computer simulation of the total work of adhesion and experimentally measured bond strength between the dental filling material and the tooth enamel after its micromachining by means of YAG : Er laser radiation is attained.

Clinical effectiveness of low-level laser treatment on peripheral somatosensory neuropathy.

PubMed

Fallah, Alireza; Mirzaei, Alireza; Gutknecht, Norbert; Demneh, Amir Saberi

2017-04-01

Peripheral sensory neuropathy treatment is one of the common treatment problems and causes morbidity and mortality in people suffering from that. Although treatment depends on the underlying cause of the condition, nevertheless, in some cases, there is no cure for it, and it requires palliative and symptomatic treatment. In laboratory studies, low-level laser has been effective in the nerves protection and restoration. The aim of this article is to investigate the clinical efficacy of low-level laser on improvement of the peripheral somatosensory neuropathy. Search in the articles published up to 30 October 2015 (full text and abstracts) in databases PubMed (Medline), Cochrane library, Physiotherapy Evidence Database was performed. The studies of low-level laser trials on patients with peripheral neuropathy were carried out and evaluated in terms of the exclusion criteria. There are 35 articles among which 10 articles had the intended and required criteria. 1, 3, and 6 articles study the patients with diabetes, neuropathy caused by trauma, and carpal tunnel syndrome, respectively. In six studies, laser led to a reduction in sensory impairment and improvement of the physiological function of the sensory nerves. In these articles, lasers (Diode, GaAlAs, He-Ne) had wavelength range 660-860 nm, radiation power 20-250 mW, energy density 0.45-70 J/cm 2 . The intervention sessions range was 6-21 times and patient follow-up was 0-6 months. According to the results of these studies, low-level laser therapy can improve sensory function in patients with peripheral somatosensory neuropathy, although little research have not been done, laser treatment regimens are varied and do not recommend a specific treatment protocol. It seems it requires more research to sum up better, particularly in relation to diabetes.

Laser therapy may be better than topical desensitizing agents for treating dentin hypersensitivity.

PubMed

Blatz, Markus B

2012-09-01

to 6 months. Most studies used Visual Analog Scale scores or other subjective tools to assess sensitivity. All 8 studies compared one kind of laser versus one kind of topical desensitizingagent. However, types of lasers as well as types of desensitizing agents differed among the reviewed studies. Half of the studies compared gallium-aluminum-arsenide (GaAlAs) lasers with various topical desensitizing agents; however, findings were conflicting. Two moderate-quality trials indicated that GaAlAs laser and the control desensitizing agents preformed similarly. Another moderate-quality trial demonstrated that the application of a bonding agent was significantly better than a GaAlAs laser in the reduction of hypersensitivity. The only reviewed study that was classified as an A-level study revealed a significantly greater immediate and long-term desensitizing effect than the control. The remaining studies involved Nd:YAG, Er:YAG, and CO(2) lasers, all of them reporting a slightly greater decrease in sensitivity as compared with topical desensitizing agents. Five of 8s tudies reported on the safety of laser application and did not find any detrimental pulpal effects, allergic reactions, or clinically detectable complications during follow-up. The authors concluded that the results obtained from the 8 studies included in this systematic review were conflicting but indicated a slight clinical advantage of laser therapy over topical medicaments in the treatment of dentin hypersensitivity. It was further concluded that application of lasers under controlled parameters for this indication may not lead to adverse effects. Copyright © 2012. Published by Mosby, Inc. All rights reserved.

Effects of femtosecond laser radiation on the skin

NASA Astrophysics Data System (ADS)

Rogov, P. Yu; Bespalov, V. G.

2016-08-01

A mathematical model of linear and nonlinear processes is presented occurring under the influence of femtosecond laser radiation on the skin. There was held an analysis and the numerical solution of an equation system describing the dynamics of the electron and phonon subsystems were received. The results can be used to determine the maximum permissible levels of energy generated by femtosecond laser systems and the establishment of Russian laser safety standards for femtosecond laser systems.

EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Emission of charged particles from the surface of a moving target acted on by cw CO2 laser radiation

NASA Astrophysics Data System (ADS)

Kuznetsov, S. I.; Petrov, A. L.; Shadrin, A. N.

1990-06-01

An experimental investigation was made of the emission of charged particles due to the irradiation of moving steel and graphite targets with cw CO2 laser radiation. The characteristics of the emission current signals were determined for different laser irradiation regimes. The maximum emission current density from the surface of a melt pool ( ~ 1.1 × 10 - 2 A/cm2) and the average temperature of the liquid metal (~ 2040 K) were measured for an incident radiation power density of 550 W and for horizontal and vertical target velocities of respectively ~ 1.5 mm/s and ~ 0.17 mm/s. The authors propose to utilize this phenomenon for monitoring the laser processing of materials.

Experimental comparison of laser energy losses in high-quality laser-oxygen cutting of low-carbon steel using radiation from fibre and CO{sub 2} lasers

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

Golyshev, A A; Malikov, A G; Orishich, A M

We report a comparative experimental study of laseroxygen cutting of low-carbon steel using a fibre laser with a wavelength of 1.07 μm and a CO{sub 2} laser with a wavelength of 10.6 μm at the sheet thickness of 3 – 16 mm. For the two lasers we have measured the dependence of the cutting speed on the radiation power and determined the cutting speed at which the surface roughness is minimal. The coefficient of laser radiation absorption in the laser cutting process is measured for these lasers at different values of the cutting speed and radiation power. It is foundmore » that the minimal roughness of the cut surface is reached at the absorbed laser energy per unit volume of the removed material, equal to 11 – 13 J mm{sup -3}; this value is the same for the two lasers and does not depend on the sheet thickness. (laser technologies)« less

Investigation of temperature feedback signal parameters during neoplasms treatment by diode laser radiation

NASA Astrophysics Data System (ADS)

Belikov, Andrey V.; Gelfond, Mark L.; Shatilova, Ksenia V.; Semyashkina, Yulia V.

2016-04-01

Dynamics of temperature signal in operation area and laser power at nevus, papilloma, and keratoma in vivo removal by a 980+/-10 nm diode laser with "blackened" tip operating in continuous (CW) mode and with temperature feedback (APC) mode are presented. Feedback allows maintaining temperature in the area of laser treatment at a preset level by regulating power of diode laser radiation (automatic power control). Temperature in the area of laser treatment was controlled by measuring the amplitude of thermal radiation, which occurs when tissue is heated by laser radiation. Removal of neoplasm was carried out in CW mode with laser radiation average power of 12.5+/-0.5 W; mean temperature in the area of laser treatment was 900+/-10°C for nevus, 800+/-15°C for papilloma, and 850+/-20°C for keratoma. The same laser radiation maximal power (12.5 W) and targeted temperature (900°C) were set for nevus removal in APC mode. The results of investigation are real time oscillograms of the laser power and temperature in the area of laser treatment at neoplasms removal in two described above modes. Simultaneously with the measurement of laser power and the temperature in the area of laser treatment video recording of surgeon manipulations was carried out. We discuss the correlation between the power of the laser radiation, the temperature in the area of laser treatment and consistency of surgeon manipulation. It is shown that the method of removal (excision with or without traction, scanning) influences the temperature in the area of laser treatment. It was found, that at removal of nevus with temperature feedback (APC) mode to achieve comparable with CW mode temperature in the area of laser treatment (900+/-10°C) 20-50% less laser power is required. Consequently, removing these neoplasms in temperature feedback mode can be less traumatic than the removal in CW mode.

EFFECTS OF LASER RADIATION ON MATTER: Efficient surface-erosion plasma formation in air due to the action of pulse-periodic laser radiation

NASA Astrophysics Data System (ADS)

Min'ko, L. Ya; Chumakou, A. N.; Bosak, N. A.

1990-11-01

A study was made of the interaction of a series of periodic laser (λ = 1.06 μm) pulses with a number of materials (aluminum, copper, graphite, ebonite) in air at laser radiation power densities q = 107-109 W/cm2 and repetition frequencies f<=50 kHz. The radiation was concentrated in spots of ~ 10 - 2 cm2 area. Efficient formation of plasma as a result of laser erosion (q > 2 × 108 W/cm2, f>=5 kHz) was observed. A screening layer of an air plasma created by the first pulse of the series was expelled from the interaction zone and this was followed by erosion plasma formation under conditions of slight screening of the target during the action of the subsequent laser pulses.

Dichromatic and monochromatic laser radiation effects on survival and morphology of Pantoea agglomerans

NASA Astrophysics Data System (ADS)

Thomé, A. M. C.; Souza, B. P.; Mendes, J. P. M.; Soares, L. C.; Trajano, E. T. L.; Fonseca, A. S.

2017-05-01

Despite the beneficial effects of low-level lasers on wound healing, their application for treatment of infected injuries is controversial because low-level lasers could stimulate bacterial growth exacerbating the infectious process. Thus, the aim of this work was to evaluate in vitro effects of low-level lasers on survival, morphology and cell aggregation of Pantoea agglomerans. P. agglomerans samples were isolated from human pressure injuries and cultures were exposed to low-level monochromatic and simultaneous dichromatic laser radiation to study the survival, cell aggregation, filamentation and morphology of bacterial cells in exponential and stationary growth phases. Fluence, wavelength and emission mode were those used in therapeutic protocols for wound healing. Data show no changes in morphology and cell aggregation, but dichromatic laser radiation decreased bacterial survival in exponential growth phase and monochromatic red and infrared lasers increased bacterial survival at the same fluence. Simultaneous dichromatic laser radiation induces biological effects that differ from those induced by monochromatic laser radiation and simultaneous dichromatic laser could be the option for treatment of infected pressure injuries by Pantoea agglomerans.

Study on the electromagnetic radiation characteristics of discharging excimer laser system

NASA Astrophysics Data System (ADS)

Zhao, Duliang; Liang, Xu; Fang, Xiaodong; Wang, Qingsheng

2016-10-01

Excimer laser in condition of high voltage, large current and fast discharge will produce strong electromagnetic pulse radiation and electromagnetic interference on the around electrical equipment. The research on characteristics and distribution of excimer laser electromagnetic radiation could provide important basis for electromagnetic shielding and suppressing electromagnetic interference, and further improving the electromagnetic compatibility of system. Firstly, electromagnetic radiation source is analyzed according to the working principle of excimer laser. The key test points of the electromagnetic radiation, hydrogen thyratron, main discharge circuit and laser outlet, are determined by the mechanical structure and the theory of electromagnetic radiation. Secondly, characteristics of electromagnetic field were tested using a near field probe on the key positions of the vertical direction at 20, 50, and 80 cm, respectively. The main radiation frequencies and the radiation field characteristics in the near field are obtained. The experimental results show that the main radiation frequencies distribute in 47, 65, and 130 MHz for electric field and the main radiation frequencies distribute in 34, 100, and 165 MHz for magnetic field. The intensity of electromagnetic field decreases rapidly with the increase of test distance. The higher the frequency increases, the faster the amplitude attenuate. Finally, several electromagnetic interference suppression measurement methods are proposed from the perspective of electromagnetic compatibility according to the test results.

EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Low-threshold generation of harmonics and hard x radiation in a laser plasma. 1. Single-peak generation

NASA Astrophysics Data System (ADS)

Apollonov, V. V.; Derzhavin, S. I.; Kazakov, K. Kh

1993-02-01

A source of hard x radiation based on a laser plasma has been studied under conditions such that parametric instabilities are driven in the plasma at low intensities of the pump radiation (below 10 GW/cm2). A qualitative interpretation of the observed effects is offered.

Simulation of free-electron lasers seeded with broadband radiation

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

Bajlekov, Svetoslav; Fawley, William; Schroeder, Carl

2011-03-10

The longitudinal coherence of free-electron laser (FEL) radiation can be enhanced by seeding the FEL with high harmonics of an optical laser pulse. The radiation produced by high-harmonic generation (HHG), however, has a fast-varying temporal profile that can violate the slowly varying envelope approximation and limited frequency window that is employed in conventional free-electron laser simulation codes. Here we investigate the implications of violating this approximation on the accuracy of simulations. On the basis of both analytical considerations and 1D numerical studies, it is concluded that, for most realistic scenarios, conventional FEL codes are capable of accurately simulating the FELmore » process even when the seed radiation violates the slowly varying envelope approximation. We additionally discuss the significance of filtering the harmonic content of broadband HHG seeds.« less

Heat effect of pulsed Er:YAG laser radiation

NASA Astrophysics Data System (ADS)

Hibst, Raimund; Keller, Ulrich

1990-06-01

Pulsed Er:YAG laser radiation has been found to be effective for dental enamel and dentin removal. Damage to the surrounding hard tissue is little, but before testing the Er:YAG laser clinically for the preparation of cavities, possible effects on the soft tissue of the pulp must be known. In order to estimate pulp damage , temperature rise in dentin caused by the laser radiation was measured by a thermocouple. Additionally, temperature distributions were observed by means of a thermal imaging system. The heat effect of a single Er:YAG laser pulse is little and limited to the vicinity of the impact side. Because heat energy is added with each additional pulse , the temperature distribution depends not only on the radiant energy, but also on the number of pulses and the repetition rate. Both irradiation conditions can be found , making irreversible pulp damage either likely or unlikely. The experimental observations can be explained qualitatively by a simple model of the ablation process.

EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Spectral and temporal characteristics of a laser plasma

NASA Astrophysics Data System (ADS)

Lipchak, A. I.; Solomonov, V. I.; Tel'nov, V. A.; Osipov, V. V.

1995-04-01

An experimental investigation was made of the spectral and temporal characteristics of a laser plasma formed by the interaction of a CO2 laser pulse with a target in atmospheric air. The results obtained indicate that the main role in the process of filling the excited states in a laser plasma is played by a recombination cascade and that both atoms and molecules of the atmospheric gases are excited. The result also show that a laser plasma can be used in spectroscopic analysis of multicomponent samples. The solution of the thermophysical problem of heating of a target by laser radiation supports the existing ideas on the process of formation of a plasma near the target surface in air.

Impact of Laser Radiation on Microhardness of a Semiconductor

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

Medvid', A.; Onufrijevs, P.; Chiradze, G.

2011-12-23

It was found that strongly absorbed Nd:YAG laser radiation leads to a non-monotonous dependence of microhardness of p- and n-type Si crystals on laser radiation. This dependence is characterized by two maxima for p-Si and one maximum for n-Si crystals. In both cases the increase of microhardness at higher laser intensity is explained by formation of mechanically compressed layer at the irradiated surface due to concentration of the interstitial atoms of Si at the surface in temperature gradient field. The decrease of the microhardness is explained by formation of nano-cones as a result of plastic deformation of the mechanically stressedmore » layer. The additional maximum at lower laser intensity for p-Si crystal is explained by p-n type inversion of Si conductivity.« less

The effect of MLS laser radiation on cell lipid membrane.

PubMed

Pasternak, Kamila; Wróbel, Dominika; Nowacka, Olga; Pieszyński, Ireneusz; Bryszewska, Maria; Kujawa, Jolanta

2018-03-14

Authors of numerous publications have proved the therapeutic effect of laser irradiation on biological material, but the mechanisms at cellular and subcellular level are not yet well understood. The aim of this study was to assess the effect of laser radiation emitted by the MLS M1 system (Multiwave Locked System) at two wavelengths (808 nm continuous and 905 nm pulsed) on the stability and fluidity of liposomes with a lipid composition similar to that of human erythrocyte membrane or made of phosphatidylocholine. Liposomes were exposed to low-energy laser radiation at surface densities 195 mW/cm² (frequency 1,000 Hz) and 230 mW/cm² (frequency 2,000 Hz). Different doses of radiation energy in the range 0-15 J were applied. The surface energy density was within the range 0.46 - 4.9 J/cm ². The fluidity and stability of liposomes subjected to such irradiation changed depending on the parameters of radiation used. Since MLS M1 laser radiation, depending on the parameters used, affects fluidity and stability of liposomes with the lipid content similar to erythrocyte membrane, it may also cause structural and functional changes in cell membranes.

Development of Technologies to Utilize Laser Plasma Radiations Sources for Radiation Effects Sciences

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

Davis, J F

2007-01-31

This final report will cover work performed over the period of November 11, 2005 to September 30, 2006 on the contract to develop technologies using laser sources for radiation effects sciences. The report will discuss four topic areas; the laser source experiments on the Gekko Laser at Osaka, Japan, planning for the Charge State Freeze Out experiments to be performed in calendar year 2007, a review of previous xenon gasbags on the LANL Trident laser to provide planning support to the May-June 2007 HELEN experiments.

A blackbody radiation-pumped CO2 laser experiment

NASA Technical Reports Server (NTRS)

Christiansen, W. H.; Insuik, R. J.; Deyoung, R. J.

1982-01-01

Thermal radiation from a high temperature oven was used as an optical pump to achieve lasing from CO2 mixtures. Laser output as a function of blackbody temperature and gas conditions is described. This achievement represents the first blackbody cavity pumped laser and has potential for solar pumping.

Evolution analysis of EUV radiation from laser-produced tin plasmas based on a radiation hydrodynamics model

PubMed Central

Su, M. G.; Min, Q.; Cao, S. Q.; Sun, D. X.; Hayden, P.; O’Sullivan, G.; Dong, C. Z.

2017-01-01

One of fundamental aims of extreme ultraviolet (EUV) lithography is to maximize brightness or conversion efficiency of laser energy to radiation at specific wavelengths from laser produced plasmas (LPPs) of specific elements for matching to available multilayer optical systems. Tin LPPs have been chosen for operation at a wavelength of 13.5 nm. For an investigation of EUV radiation of laser-produced tin plasmas, it is crucial to study the related atomic processes and their evolution so as to reliably predict the optimum plasma and experimental conditions. Here, we present a simplified radiation hydrodynamic model based on the fluid dynamic equations and the radiative transfer equation to rapidly investigate the evolution of radiation properties and dynamics in laser-produced tin plasmas. The self-absorption features of EUV spectra measured at an angle of 45° to the direction of plasma expansion have been successfully simulated and explained, and the evolution of some parameters, such as the plasma temperature, ion distribution and density, expansion size and velocity, have also been evaluated. Our results should be useful for further understanding of current research on extreme ultraviolet and soft X-ray source development for applications such as lithography, metrology and biological imaging. PMID:28332621

3D photomechanical model of tooth enamel ablation by Er-laser radiation

NASA Astrophysics Data System (ADS)

Belikov, Andrey V.; Shatilova, Ksenia V.; Skrypnik, Alexei V.

2014-02-01

The three-dimensional (3D) photomechanical model of human tooth enamel ablation is described. It takes into account: the structural peculiarities of enamel, Er-laser beam energy spatial distribution and laser radiation attenuation in the tissue. Dynamics change of enamel coefficient of absorption during ablation is also discussed. We consider the 3D photomechanical model of incomplete removal (modification) of the enamel rods by the pressure of water contained in the enamel pores and heated by laser radiation, and complete removal (ablation) of the enamel rods as result of hydroxyapatite heated by laser radiation and evaporation. Modeling results are in close agreement with the experimental results.

IV INTERNATIONAL CONFERENCE ON ATOM AND MOLECULAR PULSED LASERS (AMPL'99): Radiative and photochemical properties of organic compounds excited by high-power XeCl laser radiation

NASA Astrophysics Data System (ADS)

Kopylova, T. N.; Kuznetsova, Rimma T.; Svetlichnyi, Valerii A.; Sergeev, A. K.; Tel'minov, E. N.; Filinov, D. N.

2000-06-01

Radiative and photochemical properties of a number of laser dyes excited by focused radiation of a XeCl laser with intensity up to 200 MW cm-2 were studied. A method for measuring the gain of organic molecules under high-power excitation is proposed. The dependence of the dye transmittance for the pump radiation on its intensity was studied. It is shown that changes in energy, spectral, and time characteristics of radiation and the photostability of compounds under high-power excitation are associated with the formation of superluminescence.

Heat pump processes induced by laser radiation

NASA Technical Reports Server (NTRS)

Garbuny, M.; Henningsen, T.

1980-01-01

A carbon dioxide laser system was constructed for the demonstration of heat pump processes induced by laser radiation. The system consisted of a frequency doubling stage, a gas reaction cell with its vacuum and high purity gas supply system, and provisions to measure the temperature changes by pressure, or alternatively, by density changes. The theoretical considerations for the choice of designs and components are dicussed.

Absorption and scattering of laser radiation by the diffusion flame of aviation kerosene

NASA Astrophysics Data System (ADS)

Gvozdev, S. V.; Glova, A. F.; Dubrovskii, V. Yu; Durmanov, S. T.; Krasyukov, A. G.; Lysikov, A. Yu; Smirnov, G. V.; Solomakhin, V. B.

2012-04-01

The absorption coefficient of the radiation of a repetitively pulsed Nd : YAG laser with an average output power up to 6 W and of a cw ytterbium optical fibre laser with an output power up to 3 kW was measured in the diffusion flame of aviation kerosene burning on a free surface in the atmospheric air. The absorption coefficient as a function of flame length, radiation power, and radiation intensity, which was varied in the ~103 — 5×104 W cm-2 range, was obtained for two distances (1 and 2 cm) between the laser beam axis and the surface. The coefficient of radiation absorption by kerosene flame was compared with that in ethanol and kerosene — ethanol mixture flames. The radiation power scattered by a small segment of the kerosene flame irradiated by Nd : YAG laser radiation was measured as a function of longitudinal and azimuthal coordinates. An estimate was made of the total scattered radiation power.

Conversion of blackbody radiation into laser energy

NASA Technical Reports Server (NTRS)

Mcinville, R. M.; Hassan, H. A.

1982-01-01

By employing detailed kinetic models, three concepts which utilize a blackbody cavity for the conversion of solar energy into laser energy using a CO2 lasant are analyzed and compared. In the first, the blackbody radiation is used to excite flowing CO2 directly. The second and third employ a mixing laser concept with CO and N2 being the donor gases. The CO is optically pumped while thermal heating excites the N2. Blackbody temperatures ranging from 1500 deg K - 2500 deg K are considered. Based on calculated laser power output per unit flow rate of CO2, it appears that the N2-CO2 mixing laser is the most attractive system.

Argon laser phototherapy could eliminate the damage effects induced by the ionizing radiation "gamma radiation" in irradiated rabbits.

PubMed

Abdul-Aziz, Karolin Kamel; Tuorkey, M J

2010-04-02

The ionizing radiations could be taken in considerate as an integral part in our life, since, living organisms are actually exposed to a constant shower of ionizing radiations whether from the natural or artificial resources. The radio-protective efficiency of several chemicals has been confirmed in animal trails, whereas, due to their accumulative toxicity, their clinical utility is limited. Therefore, we aimed in the present work to investigate the possibility of using argon laser to recuperate the damaged tissues due to exposing to the ionizing radiation. The rabbits were used in this study, and they were designed as control, gamma irradiated, laser, and gamma plus laser groups. Lipid peroxidation, reduced glutathione (GSH), glutathione peroxidase (GSH-Px) and glucose-6-phosphate dehydrogenase (G-6-PD) in blood and liver were evaluated. As well as, the level of protein thiol was evaluated in the plasma among each group. Results of this study revealed the potential therapeutic performance of the treatment by laser argon to decline the damaging effect of the ionized radiation whether at systematic or local levels. In conclusion, argon laser therapy appears propitious protective effect against the hazard effects of gamma radiation. Copyright 2010 Elsevier B.V. All rights reserved.

Lithium niobate bulk crystallization promoted by CO2 laser radiation

NASA Astrophysics Data System (ADS)

Ferreira, N. M.; Costa, F. M.; Nogueira, R. N.; Graça, M. P. F.

2012-09-01

The crystallization induced by laser radiation is a very promising technique to promote glass/ceramic transformation, being already used to produce crystalline patterns on glass surfaces. In this work, a SiO2-Li2O-Nb2O5 glass, prepared by the sol-gel route, was submitted to CO2 laser radiation and conventional heat-treatments in order to induce the LiNbO3 crystallization. The structure and morphology of the samples prepared by both routes was analyzed as a function of exposure time, radiation power and heat-treatment temperatures by XRD, Raman spectroscopy and SEM. The results reveal a correlation between the crystallization degree of LiNbO3 particles and glass matrix with the heat treatment type and experimental parameters. An heat-treatment at 650 °C/4 h was necessary to induce crystallization in heat treatments samples while 4 W/500 s was enough for laser radiation ones, corresponding a reduction time processing of ˜14 000 s.

Experience of laser radiation for treatment of oral mucous lesions of different etiologies

NASA Astrophysics Data System (ADS)

Mosesyants, Elvira N.; Zazulevskaya, Lidiya Y.; Shevtsova, Elena

1997-05-01

Laser irradiation use for treatment of different manifestations of oral mucous diseases during the last 10 years. The aim of this research was study of the results of use He-Ne laser radiation in combination with main therapy for treatment of oral mucous lesions of different aetiology. He-Ne laser irradiation use for radiation of lesions were caused by different aetiology reasons. Under the observation was 116 patients 20 - 64 years old, who had and hadn't background pathology. There were biochemical, immunological controls. Data of research confirmed positive effect of use He-Ne laser radiation.

Absorption and scattering of laser radiation by the diffusion flame of aviation kerosene

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

Gvozdev, S V; Glova, A F; Dubrovskii, V Yu

2012-04-30

The absorption coefficient of the radiation of a repetitively pulsed Nd : YAG laser with an average output power up to 6 W and of a cw ytterbium optical fibre laser with an output power up to 3 kW was measured in the diffusion flame of aviation kerosene burning on a free surface in the atmospheric air. The absorption coefficient as a function of flame length, radiation power, and radiation intensity, which was varied in the {approx}10{sup 3} - 5 Multiplication-Sign 10{sup 4} W cm{sup -2} range, was obtained for two distances (1 and 2 cm) between the laser beammore » axis and the surface. The coefficient of radiation absorption by kerosene flame was compared with that in ethanol and kerosene - ethanol mixture flames. The radiation power scattered by a small segment of the kerosene flame irradiated by Nd : YAG laser radiation was measured as a function of longitudinal and azimuthal coordinates. An estimate was made of the total scattered radiation power.« less

Optically pumped carbon dioxide laser mixtures. [using solar radiation

NASA Technical Reports Server (NTRS)

Yesil, O.; Christiansen, W. H.

1979-01-01

This work explores the concept of blackbody radiation pumping of CO2 gas as a step toward utilization of solar radiation as a pumping source for laser action. To demonstrate this concept, an experiment was performed in which laser gas mixtures were exposed to 1500 K thermal radiation for brief periods of time. A gain of 2.8 x 10 to the -3rd reciprocal centimeters has been measured at 10.6 microns in a CO2-He gas mixture of 1 Torr pressure. A simple analytical model is used to describe the rate of change of energy of the vibrational modes of CO2 and to predict the gain. Agreement between the prediction and experiment is good.

Calculating the radiation characteristics of accelerated electrons in laser-plasma interactions

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

Li, X. F.; Graduate School of Engineering, Utsunomiya University, 7-1-2 Yohtoh, Utsunomiya 321-8585; Yu, Q.

2016-03-15

In this paper, we studied the characteristics of radiation emitted by electrons accelerated in a laser–plasma interaction by using the Lienard–Wiechert field. In the interaction of a laser pulse with a underdense plasma, electrons are accelerated by two mechanisms: direct laser acceleration (DLA) and laser wakefield acceleration (LWFA). At the beginning of the process, the DLA electrons emit most of the radiation, and the DLA electrons emit a much higher peak photon energy than the LWFA electrons. As the laser–plasma interaction progresses, the LWFA electrons become the major radiation emitter; however, even at this stage, the contribution from DLA electronsmore » is significant, especially to the peak photon energy.« less

Monitoring of catalyst performance in CO2 lasers using frequency modulation spectroscopy with diode lasers

NASA Technical Reports Server (NTRS)

Wang, Liang-Guo; Sachse, Glen

1990-01-01

Closed-cycle CO2 laser operation with removal of O2 and regeneration of CO2 can be achieved by catalytic CO-O2 recombination. Both parametric studies of the optimum catalyst formulation and long-term performance tests require on line monitoring of CO, O2 and CO2 concentrations. There are several existing methods for molecular oxygen detection. These methods are either intrusive (such as electrochemical method or mass spectrometry) or very expensive (such as CARS, UV laser absorption). Researchers demonstrated a high-sensitivity spectroscopic measurement of O2 using the two-tone frequency modulation spectroscopy (FMS) technique with a near infrared GaAlAs diode laser. Besides its inexpensive cost, fast response time, nonintrusive measurements and high sensitivity, this technique may also be used to differentiate between isotopes due to its high spectroscopic resolution. This frequency modulation spectroscopy technique could also be applied for the on-line monitoring of CO and CO2 using InGaAsP diode lasers operation in the 1.55 microns region and H2O in the 1.3 microns region. The existence of single mode optical fibers at the near infrared region makes it possible to combine FMS with optical fiber technology. Optical fiber FMS is particularly suitable for making point-measurements at one or more locations in the CO2 laser/catalyst system.

Strong terahertz radiation from relativistic laser interaction with solid density plasmas

NASA Astrophysics Data System (ADS)

Li, Y. T.; Li, C.; Zhou, M. L.; Wang, W. M.; Du, F.; Ding, W. J.; Lin, X. X.; Liu, F.; Sheng, Z. M.; Peng, X. Y.; Chen, L. M.; Ma, J. L.; Lu, X.; Wang, Z. H.; Wei, Z. Y.; Zhang, J.

2012-06-01

We report a plasma-based strong THz source generated in intense laser-solid interactions at relativistic intensities >1018 W/cm2. Energies up to 50 μJ/sr per THz pulse is observed when the laser pulses are incident onto a copper foil at 67.5°. The temporal properties of the THz radiation are measured by a single shot, electro-optic sampling method with a chirped laser pulse. The THz radiation is attributed to the self-organized transient fast electron currents formed along the target surface. Such a source allows potential applications in THz nonlinear physics and provides a diagnostic of transient currents generated in intense laser-solid interactions.

Cleaning of optical surfaces by excimer laser radiation

NASA Astrophysics Data System (ADS)

Mann, K.; Wolff-Rottke, B.; Müller, F.

1996-04-01

The effect of particle removal from Al mirror surfaces by the influence of pulsed UV laser radiation has been studied. The investigations are closely related to the demands of astronomers, who are looking for a more effective way to clean future very large telescope (VLT) mirrors [1]. A systematic parameter study has been performed in order to determine the irradiation conditions which yield the highest dust removal efficiency (i.e. reflectivity increase) on contaminated samples. The particle removal rate increases with increasing laser fluence, being limited however by the damage threshold of the coating. Data indicate that on Al coated BK7 and Zerodur samples KrF laser radiation yields the optimum result, with cleaning efficiencies comparable to polymer film stripping. The initial reflectivity of the clean coating can nearly be restored, in particular when an additional solvent film on the sample surface is applied.

Combined Impact of Gamma and Laser Radiation on Peripheral Blood of Rats in vivo

NASA Astrophysics Data System (ADS)

Zalesskaya, G. A.; Batay, L. E.; Koshlan, I. V.; Nasek, V. M.; Zilberman, R. D.; Milevich, T. I.; Govorun, R. D.; Koshlan, N. A.; Blaga, P.

2017-11-01

The impact of γ radiation of 137Cs (doses of 1 and 3 Gy), low-intensity laser radiation (λ = 670 nm, 5.3 or 10.6 J/cm2) as well as the influence of consecutive laser and γ radiation on peripheral blood and blood cells (erythrocytes, leukocytes, lymphocytes, granulocytes) were studied by analyzing the number of blood cells, blood absorption spectra, and activity of antioxidant defense enzymes. Two series of experiments were performed on four groups of rats. The rats of the control group (group 1) were not exposed to γ or laser radiation. In the experimental groups, single irradiation of the whole body of rats with γ radiation (group 2), three- or four-day over-vein irradiation of blood in the tail vein by low-intensity laser radiation (group 3), and successive three- or four-day irradiation of blood by laser and then a single irradiation of the whole body with γ radiation (group 4) were performed. It was shown that changes of the blood cell content in the experimental groups are accompanied by changes in the spectral characteristics of the blood and the activity of antioxidant defense enzymes. The radioprotective effect of low-intensity laser radiation is manifested as an increase in the average number of leukocytes and lymphocytes in the group as compared with the postradiation, as well as an increase in the activity of antioxidant protection enzymes. The possibility of using low-intensity optical radiation for correction of hematological disorders caused by ionizing radiation is discussed.

Radiation reabsorption in a laser-produced plasma

NASA Astrophysics Data System (ADS)

Brunner, W.; John, R. W.; Paul, H.; Steudel, H.

1988-11-01

Taking into account the emission and absorption of resonance radiation in a recombining laser-produced plasma of intermediate density, the system of rate equations for the population densities coupled with the radiative transfer equation is approximately treated. In the case of spatially varying absorption, an approximate form of the rate equation determining the population density of the upper resonance level is derived. By applying this relation to an axially symmetric plasma, a simple formula that describes the effect of radiation reabsorption on the spatial behavior of the population density is obtained.

Ultraviolet out-of-band radiation studies in laser tin plasma sources

NASA Astrophysics Data System (ADS)

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

2017-11-01

Out-of-band long wavelength emission measurements from high power, high-repetition-rate extreme-ultra-violet lithography (EUVL) laser plasma sources are imperative to estimating heat deposition in EUV mirrors, and the impact of short wavelength light transported through the imaging system to the wafer surface. This paper reports a series of experiments conducted to measure the absolute spectral irradiances of laser-plasmas produced from planar tin targets over the wavelength region of 124 to 164 nm by 1.06 μm wavelength, 10 ns full-width-at-half-maximum Gaussian laser pulses. The use of spherical targets is relevant to the EUVL source scenario. Although plasmas produced from planar surfaces evolve differently, there is a close similarity to the evolution of current from 10.6 μm CO2 laser EUVL sources, which use a pre-pulse from a lower energy solid-state laser to melt and reform an initial spherical droplet into a thin planar disc target. The maximum of radiation conversion efficiency in the 124-164 nm wavelength band (1%/2πsr) occurs at the laser intensity of 1010 W cm-2. A developed collisional-radiative model reveals the strong experimental spectra that originate mainly from the 4d105p2-4d105s5p, 4d105p-4d105s resonance lines, and 4d95p-4d95s unresolved transition arrays from Sn III, Sn IV, and Sn V ions, respectively. The calculated conversion efficiencies using a 2D radiation-hydrodynamics model are in agreement with the measurements. The model predicts the out-of-band (100-400 nm) radiation conversion efficiencies generated by both 1.06 and 10.6 μm pulses. The 10.6 μm laser pulse produces a higher conversion efficiency (12%/2πsr) at the lower laser intensity of 109 W cm-2.

UV and IR laser radiation's interaction with metal film and teflon surfaces

NASA Astrophysics Data System (ADS)

Fedenev, A. V.; Alekseev, S. B.; Goncharenko, I. M.; Koval', N. N.; Lipatov, E. I.; Orlovskii, V. M.; Shulepov, M. A.; Tarasenko, V. F.

2003-04-01

The interaction of Xe ([lambda] [similar] 1.73 [mu]m) and XeCl (0.308 [mu]m) laser radiation with surfaces of metal and TiN-ceramic coatings on glass and steel substrates has been studied. Correlation between parameters of surface erosion versus laser-specific energy was investigated. Monitoring of laser-induced erosion on smooth polished surfaces was performed using optical microscopy. The correlation has been revealed between characteristic zones of thin coatings damaged by irradiation and energy distribution over the laser beam cross section allowing evaluation of defects and adhesion of coatings. The interaction of pulsed periodical CO2 ([lambda] [similar] 10.6 [mu]m), and Xe ([lambda] [similar] 1.73 [mu]m) laser radiation with surfaces of teflon (polytetrafluoroethylene—PTFE) has been studied. Monitoring of erosion track on surfaces was performed through optical microscopy. It has been shown that at pulsed periodical CO2-radiation interaction with teflon the sputtering of polymer with formation of submicron-size particles occurs. Dependencies of particle sizes, form, and sputtering velocity on laser pulse duration and target temperature have been obtained.

Effect of active-region “volume” on the radiative properties of laser heterostructures with radiation output through the substrate

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

Nekorkin, S. M.; Zvonkov, B. N.; Baidus, N. V.

2017-01-15

The radiative properties of InGaAs/GaAs/InGaP laser structures with radiation output through the substrate depending on the number of quantum wells in the active region and laser diodes on their basis are investigated. It is established that the presence of six–eight quantum wells in the active region is optimum from the viewpoint of observable values of the threshold current and the output optical power of lasers.

The laser radiation action on the crystal formation processes in the biological fluids

NASA Astrophysics Data System (ADS)

Malov, Alexander N.; Vaichas, Andrey A.; Novikova, Evgeniya A.

2016-11-01

The results of an experimental study of the laser radiation effect on the crystal`s formation in the volume of biological fluids that are complex multi-component solutions have been discussing. Are investigated white and natural bile in vitro. The qualitative changes were observed. Thus, at the bottom of the cell in which bile is not exposed to the laser radiation, the crystals are formed. In the irradiated bile gallstone has a thin layer of a homogeneous viscous colloidal liquid with very small, visible in polarized light crystalline formations was got. Irradiated laser bile's gallstone was covered evenly white deposit without surface defect unlike gallstone in bile without radiation exposure. A possible mechanism to explain the laser radiation action on the mineral formation in biological fluids and also practical application of this effect have been suggesting too.

Laser radiography forming bremsstrahlung radiation to image an object

DOEpatents

Perry, Michael D.; Sefcik, Joseph A.

2004-01-13

A method of imaging an object by generating laser pulses with a short-pulse, high-power laser. When the laser pulse strikes a conductive target, bremsstrahlung radiation is generated such that hard ballistic high-energy electrons are formed to penetrate an object. A detector on the opposite side of the object detects these electrons. Since laser pulses are used to form the hard x-rays, multiple pulses can be used to image an object in motion, such as an exploding or compressing object, by using time gated detectors. Furthermore, the laser pulses can be directed down different tubes using mirrors and filters so that each laser pulse will image a different portion of the object.

Radiation reaction effect on laser driven auto-resonant particle acceleration

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

Sagar, Vikram; Sengupta, Sudip; Kaw, P. K.

2015-12-15

The effects of radiation reaction force on laser driven auto-resonant particle acceleration scheme are studied using Landau-Lifshitz equation of motion. These studies are carried out for both linear and circularly polarized laser fields in the presence of static axial magnetic field. From the parametric study, a radiation reaction dominated region has been identified in which the particle dynamics is greatly effected by this force. In the radiation reaction dominated region, the two significant effects on particle dynamics are seen, viz., (1) saturation in energy gain by the initially resonant particle and (2) net energy gain by an initially non-resonant particlemore » which is caused due to resonance broadening. It has been further shown that with the relaxation of resonance condition and with optimum choice of parameters, this scheme may become competitive with the other present-day laser driven particle acceleration schemes. The quantum corrections to the Landau-Lifshitz equation of motion have also been taken into account. The difference in the energy gain estimates of the particle by the quantum corrected and classical Landau-Lifshitz equation is found to be insignificant for the present day as well as upcoming laser facilities.« less

The measurement of atmospheric visibility with Lidar: TSC field test results

DOT National Transportation Integrated Search

1974-03-01

The report represents a technical feasibility study of the use of lidar for determining the atmospheric extinction coefficient in low visibility. Measurements were made with three laser sources: a Q-switched ruby laser, a GaAlAs diode laser array, an...

The changes in the electronic spectra of ascorbic acid induced by laser radiation

NASA Astrophysics Data System (ADS)

Danyaeva, J. S.; Kutsenko, S. A.

2018-04-01

The results of research the changes in the absorption spectra of aqueous solutions of ascorbic acid under the influence of laser radiation are presented. The solutions were irradiated with the radiation of semiconductor lasers with wavelengths of 408 and 532 nm, YAG: Nd3+ laser with a wavelength of 1064 nm and a nitrogen laser with a wavelength of 337.1 nm. The photoinduced changes in the spectrum are revealed, which indicate the breakage of π -> π bonds in the molecule of ascorbic acid during its destruction.

LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Modification of biological objects in water media by CO2-laser radiation

NASA Astrophysics Data System (ADS)

Baranov, G. A.; Belyaev, A. A.; Onikienko, S. B.; Smirnov, S. A.; Khukharev, V. V.

2005-09-01

The modification of biological objects (polysaccharides and cells) by CO2-laser radiation in water added drop by drop into the interaction region is studied theoretically and experimentally. Calculations are performed by using the models describing gas-dynamic and heterogeneous processes caused by absorption of laser radiation by water drops. It is found experimentally that the laser modification of polysaccharides leads to the formation of low-molecular derivatives with immunostimulating properties. A dose of the product of laser activation of the yeast culture Saccharamyces cerevisiae prevented the development of a toxic emphysema in mice and protected them against lethal grippe and also prevented a decrease of survival rate, increased the average life, and prevented the development of metabolic and immune disorders in mice exposed to sublethal gamma-radiation doses.

Ultraviolet laser beam monitor using radiation responsive crystals

DOEpatents

McCann, Michael P.; Chen, Chung H.

1988-01-01

An apparatus and method for monitoring an ultraviolet laser beam includes disposing in the path of an ultraviolet laser beam a substantially transparent crystal that will produce a color pattern in response to ultraviolet radiation. The crystal is exposed to the ultraviolet laser beam and a color pattern is produced within the crystal corresponding to the laser beam intensity distribution therein. The crystal is then exposed to visible light, and the color pattern is observed by means of the visible light to determine the characteristics of the laser beam that passed through crystal. In this manner, a perpendicular cross sectional intensity profile and a longitudinal intensity profile of the ultraviolet laser beam may be determined. The observation of the color pattern may be made with forward or back scattered light and may be made with the naked eye or with optical systems such as microscopes and television cameras.

EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Characteristics of the evolution of a plasma formed by cw and pulse-periodic CO2 laser radiation in various gases

NASA Astrophysics Data System (ADS)

Kanevskiĭ, M. F.; Stepanova, M. A.

1990-06-01

An investigation was made of the interaction between high-power cw and pulse-periodic CO2 laser radiation and a low-threshold optical breakdown plasma near a metal surface. Characteristics of the breakdown plasma were studied as a function of the experimental conditions. A qualitative analysis was made of the results using a simple one-dimensional model for laser combustion waves.

Generation of coherent terahertz radiation in ultrafast laser-gas interactionsa)

NASA Astrophysics Data System (ADS)

Kim, Ki-Yong

2009-05-01

The generation of intense terahertz radiation in ultrafast laser-gas interactions is studied on a basis of transient electron current model. When an ultrashort pulse laser's fundamental and its second harmonic fields are mixed to ionize a gas, a nonvanishing, directional photoelectron current can be produced, which simultaneously emits terahertz radiation in the far field. Here, the generation mechanism is examined with an analytic derivation and numerical simulations, in which tunneling ionization and subsequent electron motion in the combined laser field play a key role. In the simulations, three types of laser-gas interactions are considered: (i) mixing the fundamental and its second harmonic fields, (ii) mixing nonharmonic, two-color fields, and (iii) focusing single-color, few-cycle pulses. In these interactions, terahertz generation and other nonlinear effects driven by the transient current are investigated. In particular, anticorrelation between terahertz and second (or third) harmonic generation is observed and analyzed.

Laser ablation of single-crystalline silicon by radiation of pulsed frequency-selective fiber laser

NASA Astrophysics Data System (ADS)

Veiko, V. P.; Skvortsov, A. M.; Huynh, C. T.; Petrov, A. A.

2015-07-01

We have studied the process of destruction of the surface of a single-crystalline silicon wafer scanned by the beam of a pulsed ytterbium-doped fiber laser radiation with a wavelength of λ = 1062 nm. It is established that the laser ablation can proceed without melting of silicon and the formation of a plasma plume. Under certain parameters of the process (radiation power, beam scan velocity, and beam overlap density), pronounced oxidation of silicon microparticles with the formation of a characteristic loose layer of fine powdered silicon dioxide has been observed for the first time. The range of lasing and beam scanning regimes in which the growth of SiO2 layer takes place is determined.

Quantum radiation reaction in laser-electron-beam collisions.

PubMed

Blackburn, T G; Ridgers, C P; Kirk, J G; Bell, A R

2014-01-10

It is possible using current high-intensity laser facilities to reach the quantum radiation reaction regime for energetic electrons. An experiment using a wakefield accelerator to drive GeV electrons into a counterpropagating laser pulse would demonstrate the increase in the yield of high-energy photons caused by the stochastic nature of quantum synchrotron emission: we show that a beam of 10(9) 1 GeV electrons colliding with a 30 fs laser pulse of intensity 10(22)  W cm(-2) will emit 6300 photons with energy greater than 700 MeV, 60× the number predicted by classical theory.

Interaction of laser radiation with metal island films

NASA Astrophysics Data System (ADS)

Benditskii, A. A.; Viduta, L. V.; Ostranitsa, A. P.; Tomchuk, P. M.; Iakovlev, V. A.

1986-08-01

The emission phenomena arising during the interaction of pulsed laser emission with island films are examined with reference to experimental results obtained for island films of gold irradiated by a CO2 laser at a wavelength of 10.6 microns. Well reproducible emission pulses that are also accompanied by light pulses are produced at intensities less than 10 to the 5th W/sq cm, with the film structure remaining unchanged. The maximum energy of the electrons emitted under the effect of laser radiation is estimated at 3 eV; the work function is 2.1 eV.

Laser system for testing radiation imaging detector circuits

NASA Astrophysics Data System (ADS)

Zubrzycka, Weronika; Kasinski, Krzysztof

2015-09-01

Performance and functionality of radiation imaging detector circuits in charge and position measurement systems need to meet tight requirements. It is therefore necessary to thoroughly test sensors as well as read-out electronics. The major disadvantages of using radioactive sources or particle beams for testing are high financial expenses and limited accessibility. As an alternative short pulses of well-focused laser beam are often used for preliminary tests. There are number of laser-based devices available on the market, but very often their applicability in this field is limited. This paper describes concept, design and validation of laser system for testing silicon sensor based radiation imaging detector circuits. The emphasis is put on keeping overall costs low while achieving all required goals: mobility, flexible parameters, remote control and possibility of carrying out automated tests. The main part of the developed device is an optical pick-up unit (OPU) used in optical disc drives. The hardware includes FPGA-controlled circuits for laser positioning in 2 dimensions (horizontal and vertical), precision timing (frequency and number) and amplitude (diode current) of short ns-scale (3.2 ns) light pulses. The system is controlled via USB interface by a dedicated LabVIEW-based application enabling full manual or semi-automated test procedures.

LASERS IN MEDICINE: Structure of matrices for the transformation of laser radiation by biofractals

NASA Astrophysics Data System (ADS)

Angel'skii, O. V.; Ushenko, A. G.; Arkhelyuk, A. D.; Ermolenko, S. B.; Burkovets, D. N.

1999-12-01

The changes in the state of polarisation of laser radiation transformed by biofractal objects are examined. The orientational angular structure of the matrix elements of the operator representing the optical properties of biofractals with different morphological structures (mineralised collagen fibres and myosin bundles) is investigated. An optical model for the description of fractal laser fields under the conditions of single light scattering is proposed.

Experimental Evidence of Radiation Reaction in the Collision of a High-Intensity Laser Pulse with a Laser-Wakefield Accelerated Electron Beam

NASA Astrophysics Data System (ADS)

Cole, J. M.; Behm, K. T.; Gerstmayr, E.; Blackburn, T. G.; Wood, J. C.; Baird, C. D.; Duff, M. J.; Harvey, C.; Ilderton, A.; Joglekar, A. S.; Krushelnick, K.; Kuschel, S.; Marklund, M.; McKenna, P.; Murphy, C. D.; Poder, K.; Ridgers, C. P.; Samarin, G. M.; Sarri, G.; Symes, D. R.; Thomas, A. G. R.; Warwick, J.; Zepf, M.; Najmudin, Z.; Mangles, S. P. D.

2018-02-01

The dynamics of energetic particles in strong electromagnetic fields can be heavily influenced by the energy loss arising from the emission of radiation during acceleration, known as radiation reaction. When interacting with a high-energy electron beam, today's lasers are sufficiently intense to explore the transition between the classical and quantum radiation reaction regimes. We present evidence of radiation reaction in the collision of an ultrarelativistic electron beam generated by laser-wakefield acceleration (ɛ >500 MeV ) with an intense laser pulse (a0>10 ). We measure an energy loss in the postcollision electron spectrum that is correlated with the detected signal of hard photons (γ rays), consistent with a quantum description of radiation reaction. The generated γ rays have the highest energies yet reported from an all-optical inverse Compton scattering scheme, with critical energy ɛcrit>30 MeV .

Recycling of laser and plasma radiation energy for enhancement of extreme ultraviolet sources for nanolithography

NASA Astrophysics Data System (ADS)

Sizyuk, V.; Sizyuk, T.; Hassanein, A.; Johnson, K.

2018-01-01

We have developed comprehensive integrated models for detailed simulation of laser-produced plasma (LPP) and laser/target interaction, with potential recycling of the escaping laser and out-of-band plasma radiation. Recycling, i.e., returning the escaping laser and plasma radiation to the extreme ultraviolet (EUV) generation region using retroreflective mirrors, has the potential of increasing the EUV conversion efficiency (CE) by up to 60% according to our simulations. This would result in significantly reduced power consumption and/or increased EUV output. Based on our recently developed models, our High Energy Interaction with General Heterogeneous Target Systems (HEIGHTS) computer simulation package was upgraded for LPP devices to include various radiation recycling regimes and to estimate the potential CE enhancement. The upgraded HEIGHTS was used to study recycling of both laser and plasma-generated radiation and to predict possible gains in conversion efficiency compared to no-recycling LPP devices when using droplets of tin target. We considered three versions of the LPP system including a single CO2 laser, a single Nd:YAG laser, and a dual-pulse device combining both laser systems. The gains in generating EUV energy were predicted and compared for these systems. Overall, laser and radiation energy recycling showed the potential for significant enhancement in source efficiency of up to 60% for the dual-pulse system. Significantly higher CE gains might be possible with optimization of the pre-pulse and main pulse parameters and source size.

EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Physics of the plasma corona in the problem of laser controlled thermonuclear fusion

NASA Astrophysics Data System (ADS)

Andreev, N. E.; Gorbunov, Leonid M.; Tikhonchuk, Vladimir T.

1994-09-01

A brief analysis is made of the most important nonlinear processes which result from the interaction of laser radiation with thermonuclear targets. lt is shown that problems in the physics of the plasma corona should be an essential part of any programme of research on laser controlled thermonuclear fusion. A list is given of the problems that have to be solved first before going to the next level of laser energies.

Biostimulation effects of low-energy laser radiation on yeast cell suspensions

NASA Astrophysics Data System (ADS)

Anghel, Sorin; Stanescu, Constantin S.; Giosanu, Dana; Neagu, Ionica; Savulescu, Geta; Iorga-Siman, Ion

2000-02-01

This paper presents work to determine the effects produced by low energy laser radiation on the metabolism and growth of a yeast cell suspension. As experimental material, we used young yeast culture in liquid medium, then distributed on a solid medium, to obtain isolated colonies. As laser source, we used a He-Ne laser, and the irradiation was made with different exposure times. Form each irradiated material, a sample of white grape sterile must was sowed, that has fermented at 18 divided by 20 degrees C for 10 divided by 15 days, after that some properties was tested. Some microscopic studies were also made. The results prove some influence of low energy laser irradiation, which can induce mutations, with new properties of the irradiated material. These mutations can be obtained in a positive sense, with new and important perspectives in wine industry. Also, we observed an inhibitory effect of the laser radiation on the yeast cell growth, due, probably to the too high values of the exposure.

Benefits of low-power lasers on oral soft tissue

NASA Astrophysics Data System (ADS)

Eduardo, Carlos d. P.; Cecchini, Silvia C. M.; Cecchini, Renata C.

1996-04-01

The last five years have represented a great advance in relation to laser development. Countries like Japan, United States, French, England, Israel and others, have been working on the association of researches and clinical applications, in the field of laser. Low power lasers like He-Ne laser, emitting at 632,8 nm and Ga-As-Al laser, at 790 nm, have been detached acting not only as a coadjutant but some times as an specific treatment. Low power lasers provide non thermal effect at wavelengths believed to stimulate circulation and cellular activity. These lasers have been used to promote wound healing and reduce inflammation edema and pain. This work presents a five year clinical study with good results related to oral tissue healing. Oral cavity lesions, like herpes and aphthous ulcers were irradiated with Ga-Al- As laser. In both cases, an excellent result was obtained. The low power laser application decrease the painful sintomatology immediately and increase the reparation process of these lesions. An excellent result was obtained with application of low power laser in herpetic lesions associated with a secondary infection situated at the lip commissure covering the internal tissue of the mouth. The healing occurred after one week. An association of Ga-Al-As laser and Nd:YAG laser have been also proven to be good therapy for these kind of lesions. This association of low and high power laser has been done since 1992 and it seems to be a complement of the conventional therapies.

Comparison of diode laser and Er:YAG lasers in the treatment of ankyloglossia.

PubMed

Aras, Mutan Hamdi; Göregen, Mustafa; Güngörmüş, Metin; Akgül, Hayati Murat

2010-04-01

The purpose of this study was to compare the tolerance of lingual frenectomy with regard to a local anesthesia requirement and comparison of postsurgical discomfort experienced by patients operated on with both diode and erbium:yttrium-aluminium-garnet (Er:YAG) lasers. Ankyloglossia, commonly known as tongue-tie, is a congenital oral anomaly characterized by a short lingual frenulum. A short lingual frenulum may contribute to feeding, speech, and mechanical tongue problems. Sixteen referred patients with tongue mobility complaints were included in this study. A GaAlAs laser device with a continuous wavelength of 808 nm was used in the diode group. Frenulums were incised by applying 2 W of laser power. The Er:YAG laser device with a continuous wavelength of 2940 nm was used in the Er:YAG group. Frenulums were incised by applying 1 W of laser power. The acceptability of the lingual frenectomy without local anesthesia and the degree of the postsurgical discomfort were evaluated. Although the majority of patients (six) could be operated on without local anesthesia in the Er:YAG group, all patients could not be operated on without local anesthetic agent in the diode group. There were no differences between the two groups with regard to pain, chewing, and speaking on the first or seventh day after surgery, whereas patients had more pain in the Er:YAG group than in the diode group the first 3 h after surgery. The results indicate that only the Er:YAG laser can be used for lingual frenectomy without local anesthesia, and there was no difference between the two groups regarding the degree of the postsurgical discomfort except in the first 3 h. In conclusion, these results indicate that the Er:YAG laser is more advantageous than the diode laser in minor soft-tissue surgery because it can be performed without local anesthesia and with only topical anesthesia.

Calculation of laser induced impulse based on the laser supported detonation wave model with dissociation, ionization and radiation

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

Gan, Li, E-mail: ligan0001@gmail.com; Mousen, Cheng; Xiaokang, Li

In the laser intensity range that the laser supported detonation (LSD) wave can be maintained, dissociation, ionization and radiation take a substantial part of the incidence laser energy. There is little treatment on the phenomenon in the existing models, which brings obvious discrepancies between their predictions and the experiment results. Taking into account the impact of dissociation, ionization and radiation in the conservations of mass, momentum and energy, a modified LSD wave model is developed which fits the experimental data more effectively rather than the existing models. Taking into consideration the pressure decay of the normal and the radial rarefaction,more » the laser induced impulse that is delivered to the target surface is calculated in the air; and the dependencies of impulse performance on laser intensity, pulse width, ambient pressure and spot size are indicated. The results confirm that the dissociation is the pivotal factor of the appearance of the momentum coupling coefficient extremum. This study focuses on a more thorough understanding of LSD and the interaction between laser and matter.« less

Effect of low-level laser therapy (λ780 nm) on the mechanically damaged dentin-pulp complex in a model of extrusive luxation in rat incisors.

PubMed

de Santana, Dandara Andrade; Fonseca, Gabriela Ferraz; Ramalho, Luciana Maria Pedreira; Rodriguez, Tânia Tavares; Aguiar, Marcio Cajazeira

2017-12-01

In order to regenerate the dental pulp, many strategies have been developed as phototherapy. In the pulp repair, we do not know if gallium-aluminum-arsenide (GaAlAs) laser preserves the primary odontoblasts or stimulates the formation of more dentin matrix when dental pulp is damaged. The aim of the present study was to examine the effect of laser phototherapy (λ780 nm) on vascularization, inflammation, density of the primary odontoblast layer, and formation of reactionary and reparative dentin in the dental pulp by provoking extrusion of the rat incisor. The upper incisors were extruded 3 mm and then repositioned into their original sockets followed by a laser irradiation of the palatal mucosa (λ = 780 nm; p = 70 mW; CW; 4.2 J/cm 2 ; 60 s) every 48 h. Non-traumatized and/or non-irradiated incisors were used as the controls. At 8 and 30 days after surgery, incisors were processed for histological and histomorphometric analysis. Morphological analysis revealed no differences in vascularization between groups, but showed discrete inflammation in some non-irradiated and injured specimens, which correlated with a more irregular reparative dentin. The density of primary odontoblasts in the groups treated with lasers was higher when compared to non-irradiated groups, but no statistically significant difference between groups (p > 0.05). The thickness of the tertiary dentin was increased in both traumatized groups with no statistically significant difference between non-irradiated and irradiated groups (p > 0.05).The present findings revealed that the GaAlAs laser induced small changes on dentin-pulp complex, with more regular dentin matrix in the irradiated dental pulps.

Frequency conversion of cw chemical HF laser radiation in nonlinear crystals

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

Klement'ev, V.M.; Kolpakov, Y.G.; Pecherskii, Y.Y.

1977-07-01

A description is given of a cw chemical HF laser and its characteristics. The results are reported of investigations of the efficiency of conversion of the HF laser radiation into second harmonics and combination frequencies in LiNbO/sub 3/, LiIO/sub 3/, and Ag/sub 3/AsS/sub 3/ crystals. The most efficient conversion was achieved in proustite (Ag/sub 3/AsS/sub 3/) when the second-harmonic power was approx.3..mu..W and the fundamental-frequency power was approx.100 mW. Twenty-one emission lines were obtained in the 1.39--1.49 ..mu.. range. The HF laser radiation was converted to the visible range (0.522--0.516 ..mu..).

Atmospheric propagation of high power laser radiation at different weather conditions

NASA Astrophysics Data System (ADS)

Pargmann, Carsten; Hall, Thomas; Duschek, Frank; Handke, Jürgen

2016-05-01

Applications based on the propagation of high power laser radiation through the atmosphere are limited in range and effect, due to weather dependent beam wandering, beam deterioration, and scattering processes. Security and defense related application examples are countermeasures against hostile projectiles and the powering of satellites and aircrafts. For an examination of the correlations between weather condition and laser beam characteristics DLR operates at Lampoldshausen a 130 m long free transmission laser test range. Sensors around this test range continuously monitor turbulence strength, visibility, precipitation, temperature, and wind speed. High power laser radiation is obtained by a TruDisk 6001 disk laser (Trumpf company) yielding a maximum output power of 6 kW at a wavelength of 1030 nm. The laser beam is expanded to 180 mm and focused along the beam path. Power and intensity distribution are measured before and after propagation, providing information about the atmospheric transmission and alterations of diameter and position of the laser beam. Backscattered laser light is acquired by a photo receiver. As a result, measurements performed at different weather conditions show a couple of correlations to the characteristics of the laser beam. The experimental results are compared to a numerical analysis. The calculations are based on the Maxwell wave equation in Fresnel approximation. The turbulence is considered by the introduction of phase screens and the "von Karman" spectrum.

Cleaning of copper traces on circuit boards with excimer laser radiation

NASA Astrophysics Data System (ADS)

Wesner, D. A.; Mertin, M.; Lupp, F.; Kreutz, E. W.

1996-04-01

Cleaning of Cu traces on circuit boards is studied using pulsed excimer laser radiation (pulse width ˜ 20 ns, wavelength 248 nm), with the goal of improving the properties of the Cu surface for soldering and bonding. Traces with well-defined oxide overlayers are cleaned by irradiation in air using ≤ 10 3 laser pulses at fluences per pulse of ≤ 2 J cm -2. After treatment the surface morphology is analyzed using optical microscopy, optical profilometry, and scanning electron microscopy, while the chemical state of the surface is investigated with X-ray photoelectron (XPS) spectroscopy. Ellipsometry is used to determine the oxide overlayer thickness. Prior to cleaning samples exhibit a contamination overlayer about 15-25 nm in thickness containing Cu 2O and C. Cleaning reduces the overlayer thickness to ≤ 10 nm by material removal. The process tends to be self-limiting, since the optical reflectivity of the oxidized Cu surface for laser radiation is smaller than that of the cleaned surface. Additionally, the interaction with the laser radiation results in surface segregation of a minor alloy component out of the bulk (e.g. Zn), which may help to passivate the surface for further chemical reactions.

Laser therapy by noncoherent light field of radiation.

PubMed

Djibladze, M I; Melikishvili, Z G; Uchaneishvili, S D

1997-01-01

Conducted researches on study of interaction of radiation with blood have shown, that the interaction is the most effective for light with wavelengths in the range of 600-1000 nm that corresponds to the minimum absorption factor of the whole blood. Calculations show, that at interaction of radiation with blood considerably grows effective (electronic) temperature of biological environment, that results in sharp increase of speed of biochemical reactions. The absence of necessity of application of laser radiation coherence in lasertherapy permits to create high efficient noncoherent sources of light on the basis of the GaALAs(Zn) crystals, radiating with two maxima of wavelengths 675 and 900 nm. The radiation spectrum of GaALAs(Zn) crystals falls in the most favourable area of a blood absorption spectrum.

Generation of nano-voids inside polylactide using femtosecond laser radiation

NASA Astrophysics Data System (ADS)

Viertel, Tina; Pabst, Linda; Olbrich, Markus; Ebert, Robby; Horn, Alexander; Exner, Horst

2017-12-01

The arrangement of nanometer-sized voids, induced by focusing intense laser radiation within transparent material can allow the generation of transparent components with dimensions in the micrometer to nanometre range due to internal contour cut and thus satisfy the progressive miniaturization of products in micro-optics and medical technologies. For further improvements in the precision of those components, a deep understanding of the involved processes during the interaction of laser radiation within the material is necessary. In this work, voids inside bulk polylactide (PLA), a bioabsorbable polymer, were generated using a femtosecond laser ( λ = 1030 nm, τH = 180 fs) with single and multiple pulse irradiation. The dependence of the spot size was examined by the use of four microscope objectives with focus radii of 4.9, 3.3, 2 and 1.2 µm. For the experiments, the pulse energy and focusing depth into the material were varied. The dimensions of the voids were experimentally determined as function of the intensity. Differences in the lateral and axial extents of the voids were obtained for different focus radii and focusing depths at same intensities. Furthermore, the intensity distribution of the laser radiation inside the material for the different focus radii and focusing depths, and their dependence on the lateral and axial sizes of the voids was simulated and compared with the experimental results.

Apparatus and method for generating continuous wave 16. mu. m laser radiation using gaseous CF/sub 4/

DOEpatents

Telle, J.M.

1984-05-01

Apparatus and method for generating continuous wave 16 ..mu..m laser radiation using gaseous CF/sub 4/. Laser radiation at 16 ..mu..m has been observed in a cooled static cell containing low pressure CF/sub 4/ optically pumped by an approximately 3 W output power c-w CO/sub 2/ laser. The laser cavity employed was a multiple-pass off-axis-path two spherical mirror ring resonator. Unidirectional CF/sub 4/ laser output power at 615 cm/sup -1/ exceeded 2 mW. Computer calculations indicate that for modest pump powers of about 40 W, approximately 1 W of emitted laser radiation at 16 ..mu..m might be obtained.

Apparatus and method for generating continuous wave 16 .mu.m laser radiation using gaseous CF.sub.4

DOEpatents

Telle, John M.

1986-01-01

Apparatus and method for generating continuous wave 16 .mu.m laser radiation using gaseous CF.sub.4. Laser radiation at 16 .mu.m has been observed in a cooled static cell containing low pressure CF.sub.4 optically pumped by an approximately 3 W output power cw CO.sub.2 laser. The laser cavity employed was a multiple-pass off-axis-path two spherical mirror ring resonator. Unidirectional CF.sub.4 laser output power at 615 cm.sup.-1 exceeded 2 mW. Computer calculations indicate that for modest pump powers of about 40 W, approximately 1 W of emitted laser radiation at 16 .mu.m might be obtained.

The suppression of radiation reaction and laser field depletion in laser-electron beam interaction

NASA Astrophysics Data System (ADS)

Ong, J. F.; Moritaka, T.; Takabe, H.

2018-03-01

The effects of radiation reaction (RR) have been studied extensively by using the interaction of ultraintense lasers with a counter-propagating relativistic electron. At the laser intensity at the order of 1023 W/cm2, the effects of RR are significant in a few laser periods for a relativistic electron. However, a laser at such intensity is tightly focused and the laser energy is usually assumed to be fixed. Then, the signal of RR and energy conservation cannot be guaranteed. To assess the effects of RR in a tightly focused laser pulse and the evolution of the laser energy, we simulated this interaction with a beam of 109 electrons by means of a Particle-In-Cell method. We observe that the effects of RR are suppressed due to the ponderomotive force and accompanied by a non-negligible amount of laser field energy reduction. This is because the ponderomotive force prevents the electrons from approaching the center of the laser pulse and leads to an interaction at the weaker field region. At the same time, the laser energy is absorbed through ponderomotive acceleration. Thus, the kinetic energy of the electron beam has to be carefully selected such that the effects of RR become obvious.

High resolution laser micro sintering / melting using q-switched and high brilliant laser radiation

NASA Astrophysics Data System (ADS)

Exner, H.; Streek, A.

2015-03-01

Since the discovery of selective laser sintering/melting, numerous modifications have been made to upgrade or customize this technology for industrial purposes. Laser micro sintering (LMS) is one of those modifications: Powders with particles in the range of a few micrometers are used to obtain products with highly resolved structures. Pulses of a q-switched laser had been considered necessary in order to generate sinter layers from the micrometer scaled metal powders. LMS has been applied with powders from metals as well as from ceramic and cermet feedstock's to generate micro parts. Recent technological progress and the application of high brilliant continuous laser radiation have now allowed an efficient laser sintering/melting of micrometer scaled metal powders. Thereby it is remarkable that thin sinter layers are generated using high continuous laser power. The principles of the process, the state of the art in LMS concerning its advantages and limitations and furthermore the latest results of the recent development of this technology will be presented. Laser Micro Sintering / Laser Micro Melting (LMM) offer a vision for a new dimension of additive fabrication of miniature and precise parts also with application potential in all engineering fields.

Interaction of high-intensity laser radiation with metals.

NASA Technical Reports Server (NTRS)

Linlor, W. I.

1971-01-01

The interaction is characterized by the production of plasma, within which the primary absorption occurs. Absorption of laser radiation by a plasma may occur by several processes. The absorption process called 'inverse bremsstrahlung' is discussed. The interaction of a laser beam with the plasma produced from a thick metal target was studied. The results of the measurements of the ion kinetic energies are presented in a graph. In addition to measurements with thick targets, information was also obtained with a thin foil of gold.

3D Finite Element Model for Writing Long-Period Fiber Gratings by CO2 Laser Radiation

PubMed Central

Coelho, João M. P.; Nespereira, Marta; Abreu, Manuel; Rebordão, José

2013-01-01

In the last years, mid-infrared radiation emitted by CO2 lasers has become increasing popular as a tool in the development of long-period fiber gratings. However, although the development and characterization of the resulting sensing devices have progressed quickly, further research is still necessary to consolidate functional models, especially regarding the interaction between laser radiation and the fiber's material. In this paper, a 3D finite element model is presented to simulate the interaction between laser radiation and an optical fiber and to determine the resulting refractive index change. Dependence with temperature of the main parameters of the optical fiber materials (with special focus on the absorption of incident laser radiation) is considered, as well as convection and radiation losses. Thermal and residual stress analyses are made for a standard single mode fiber, and experimental results are presented. PMID:23941908

EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Doppler backscattered-signal diagnostics of laser-induced surface hydrodynamic processes

NASA Astrophysics Data System (ADS)

Gordienko, Vyacheslav M.; Kurochkin, Nikolay N.; Markov, V. N.; Panchenko, Vladislav Ya; Pogosov, G. A.; Chastukhin, E. M.

1995-02-01

A method is proposed for on-line monitoring of laser industrial processing. The method is based on optical heterodyne measurements of the Doppler backscattering signal generated in the interaction zone. Qualitative and quantitative information on hydrodynamic flows in the interaction zone can be obtained. A report is given of measurements, carried out at cw CO2 laser radiation intensities up to 1 kW cm-2, on the surfaces of a number of condensed materials irradiated in the monostatic interaction configuration.

Hawking radiation from ultrashort laser pulse filaments.

PubMed

Belgiorno, F; Cacciatori, S L; Clerici, M; Gorini, V; Ortenzi, G; Rizzi, L; Rubino, E; Sala, V G; Faccio, D

2010-11-12

Event horizons of astrophysical black holes and gravitational analogues have been predicted to excite the quantum vacuum and give rise to the emission of quanta, known as Hawking radiation. We experimentally create such a gravitational analogue using ultrashort laser pulse filaments and our measurements demonstrate a spontaneous emission of photons that confirms theoretical predictions.

A radiatively pumped CW CO2 laser

NASA Technical Reports Server (NTRS)

Insuik, R. J.; Christiansen, W. H.

1984-01-01

A proof of principle experiment to demonstrate the physics of a radiatively pumped laser has been carried out. For the first time, a blackbody cavity has optically pumped a CW CO2 laser. Results are presented from a series of experiments using mixtures of CO2, He, and Ar in which maximum output power was obtained with a 20 percent CO2-15 percent He-65 percent Ar mixture. The dependence of the output power on the blackbody temperature and the cooling gas flow rate is also discussed. By appropriately varying these parameters, continuous output powers of 8-10 mW have been achieved.

Terahertz Radiation from Laser Created Plasma by Applying a Transverse Static Electric Field

NASA Astrophysics Data System (ADS)

Fukuda, Takuya; Katahira, Koji; Yugami, Noboru; Sentoku, Yasuhiko; Sakagami, Hitoshi; Nagatomo, Hideo

2016-10-01

Terahertz (THz) radiation, which is emitted in narrow cone in the forward direction from laser created plasma has been observed by N.Yugami et al.. Additionally, Löffler et al. have observed that a significantly increased THz emission intensity in the forward direction when the transverse static electric field is applied to the plasma. The purpose of our study is to derive the mechanism of the THz radiation from laser created plasma by applying the transverse static electric field. To study the radiation mechanism, we conducted 2D-PIC simulation. With the static electric field of 10 kV/cm and gas density of 1020 cm-3, we obtain 1.2 THz single cycle pulse radiation, whose intensity is 1.3 ×105 W/cm2. The magnetic field called ``picket fence mode'' is generated in the laser created plasma. At the boundary surface between the plasma and vacuum, the magnetic field is canceled because eddy current flows. We conclude that the temporal behavior of the magnetic field at the boundary surface radiates the THz wave.

Optical properties modification induced by laser radiation in noble-metal-doped glasses

NASA Astrophysics Data System (ADS)

Nedyalkov, N.; Stankova, N. E.; Koleva, M. E.; Nikov, R.; Atanasov, P.; Grozeva, M.; Iordanova, E.; Yankov, G.; Aleksandrov, L.; Iordanova, R.; Karashanova, D.

2018-03-01

We present results on laser-induced color changes in gold- and silver-doped glass. The doped borosilicate glass was prepared by conventional melt quenching. The study was focused on the change of the optical properties after irradiation of the glass by femtosecond laser pulses. Under certain conditions, the laser radiation induces defects associated with formation of color centers in the material. We studied this process in a broad range of laser radiation wavelengths – from UV to IR, and observed changes in the color of the irradiated areas after annealing of the processed glass samples, the color being red for the gold-doped glass red and yellow for the silver-doped glass. The structural and morphological analyses performed indicated that this effect is related to formation of metal nanoparticles inside the material. The results obtained show that femtosecond laser processing of noble-metal-doped glasses can be used for fabrication of 3D-nanoparticles systems in transparent materials with application as novel optical components.

Surface treatment of CFRP composites using femtosecond laser radiation

NASA Astrophysics Data System (ADS)

Oliveira, V.; Sharma, S. P.; de Moura, M. F. S. F.; Moreira, R. D. F.; Vilar, R.

2017-07-01

In the present work, we investigate the surface treatment of carbon fiber-reinforced polymer (CFRP) composites by laser ablation with femtosecond laser radiation. For this purpose, unidirectional carbon fiber-reinforced epoxy matrix composites were treated with femtosecond laser pulses of 1024 nm wavelength and 550 fs duration. Laser tracks were inscribed on the material surface using pulse energies and scanning speeds in the range 0.1-0.5 mJ and 0.1-5 mm/s, respectively. The morphology of the laser treated surfaces was investigated by field emission scanning electron microscopy. We show that, by using the appropriate processing parameters, a selective removal of the epoxy resin can be achieved, leaving the carbon fibers exposed. In addition, sub-micron laser induced periodic surface structures (LIPSS) are created on the carbon fibers surface, which may be potentially beneficial for the improvement of the fiber to matrix adhesion in adhesive bonds between CFRP parts.

Systems and methods for imaging using radiation from laser produced plasmas

DOEpatents

Renard-Le Galloudec, Nathalie; Cowan, Thomas E.; Sentoku, Yasuhiko; Rassuchine, Jennifer

2009-06-30

In particular embodiments, the present disclosure provides systems and methods for imaging a subject using radiation emitted from a laser produced plasma generating by irradiating a target with a laser. In particular examples, the target includes at least one radiation enhancing component, such as a fluor, cap, or wire. In further examples, the target has a metal layer and an internal surface defining an internal apex, the internal apex of less than about 15 .mu.m, such as less than about 1 .mu.m. The targets may take a variety of shapes, including cones, pyramids, and hemispheres. Certain aspects of the present disclosure provide improved imaging of a subject, such as improved medical images of a radiation dose than typical conventional methods and systems.

Simulation of planetary entry radiative heating with a CO2 gasdynamic laser

NASA Technical Reports Server (NTRS)

Lundell, J. H.; Dickey, R. R.; Howe, J. T.

1975-01-01

Heating encountered during entry into the atmospheres of Jupiter, Saturn, and Uranus is described, followed by a discussion of the use of a CO2 gasdynamic laser to simulate the radiative component of the heating. Operation and performance of the laser is briefly described. Finally, results of laser tests of some candidate heat-shield materials are presented.

Design considerations for the use of laser-plasma accelerators for advanced space radiation studies

NASA Astrophysics Data System (ADS)

Königstein, T.; Karger, O.; Pretzler, G.; Rosenzweig, J. B.; Hidding, B.; Hidding

2012-08-01

We present design considerations for the use of laser-plasma accelerators for mimicking space radiation and testing space-grade electronics. This novel application takes advantage of the inherent ability of laser-plasma accelerators to produce particle beams with exponential energy distribution, which is a characteristic shared with the hazardous relativistic electron flux present in the radiation belts of planets such as Earth, Saturn and Jupiter. Fundamental issues regarding laser-plasma interaction parameters, beam propagation, flux development, and experimental setup are discussed.

INTERACTION OF LASER RADIATION WITH MATTER: Influence of a target on operation of a pulsed CO2 laser emitting microsecond pulses

NASA Astrophysics Data System (ADS)

Baranov, V. Yu; Dolgov, V. A.; Malyuta, D. D.; Mezhevov, V. S.; Semak, V. V.

1987-12-01

The profile of pulses emitted by a TEA CO2 laser with an unstable resonator changed as a result of interaction of laser radiation with the surface of a metal in the presence of a breakdown plasma. This influence of a target on laser operation and its possible applications in laser processing of materials are analyzed.

EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Spatial-temporal distribution of a mechanical load resulting from interaction of laser radiation with a barrier (analytic model)

NASA Astrophysics Data System (ADS)

Fedyushin, B. T.

1992-01-01

The concepts developed earlier are used to propose a simple analytic model describing the spatial-temporal distribution of a mechanical load (pressure, impulse) resulting from interaction of laser radiation with a planar barrier surrounded by air. The correctness of the model is supported by a comparison with experimental results.

Multiline CO2 laser with Q-switching for generation of terahertz radiation

NASA Astrophysics Data System (ADS)

Ionin, A. A.; Kinyaevskiy, I. O.; Klimachev, Yu M.; Stepanishchev, V. V.; Khafizov, I. Zh

2017-12-01

In this paper we consider the method of obtaining THz radiation by difference frequency generation (DFG) of multiline CO2 laser. For this purpose a multiline CO2 laser with Q-switching was created. The three strongest lines, 9 R(18), 9 P(20) and 9 P(22) with wavelengths ∼9.28, ∼9.55 and ∼9.57 μm respectively, held 85% of CO2 laser power, and can be used to obtain difference frequency at a wavelength of ∼310 μm. DFG of other spectral lines fall within the range of 263 ÷ 8100 μm. Different nonlinear crystals for DFG and filters to separate THz radiation were considered.

Laser radiation frequency doubling in a single-crystal fibre based on a stoichiometric LiNbO3 crystal

NASA Astrophysics Data System (ADS)

Kashin, V. V.; Nikolaev, D. A.; Rusanov, S. Ya; Tsvetkov, V. B.

2015-01-01

We demonstrate the employment of single-crystal optical fibres based on lithium niobate for doubling the laser radiation frequency. The measured characteristics of the fibre confirm its high quality and spatial homogeneity. Parameters of the frequency doublers for neodymium laser radiation (λ = 1 mm) based on fibre and bulk single crystals are compared. Single crystals are grown by the method of laser-heated pedestal growing with heating by radiation of a CO2 laser (LHPG-method).

Radiation characteristics of femtosecond laser-induced plasma channel Vee antenna

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

Choe, Yun-Sik; Department of Physics, University of Science, Pyongyang, North Korea; Hao, Zuoqiang

A virtual reconfigurable plasma Vee antenna consisting of a set of laser plasma filaments produced by femtosecond laser pulses in air is investigated in this paper. The calculation results show that radiation pattern becomes more complex and gain shows initially rapid rise but gradually saturate as the leg length increases, but the pattern and gain are not seriously affected by the plasma conductivity; particularly, the gain of the Vee antenna with plasma conductivity σ = 100S/m can reach about 80% of that of a copper antenna. Radiation efficiency of the antenna has shown a strong dependence on radius of the antenna leg,more » and an efficiency of 65%, considered to have a proper performance, can be obtained with the channel radius of about 10 mm. Apex angle variation can lead to significant change of the radiation pattern and influence the gain; the best apex angle corresponding to maximal gain and good directivity for the third resonance antenna leg length is found to be at 74° at 600 MHz and σ = 100 S/m. The calculation has shown that at terawatt laser power level, the plasma channel conductivity is close to that of conventional plasma antenna, and peak gain of the Vee antenna is more than 8 dB with a good directivity. In addition, the radiation pattern of special Vee antennas with apex angle 180°-dipole antennas, for first and third resonance leg lengths, is compared and underneath physics of the difference is given. The laser-induced plasma channel antenna is especially suitable for achieving good directivity and gain, which has advantage over conventional plasma antenna with gas discharge tube or metal antenna.« less

Terahertz radiation generation by beating of two laser beams in a collisional plasma with oblique magnetic field

NASA Astrophysics Data System (ADS)

Hematizadeh, Ayoob; Jazayeri, Seyed Masud; Ghafary, Bijan

2018-02-01

A scheme for excitation of terahertz (THz) radiation is presented by photo mixing of two super-Gaussian laser beams in a rippled density collisional magnetized plasma. Lasers having different frequencies and wave numbers but the same electric fields create a ponderomotive force on the electrons of plasma in the beating frequency. Super-Gaussian laser beam has the exclusive features such as steep gradient in laser intensity distribution, wider cross-section in comparison with Gaussian profiles, which make stronger ponderomotive force and higher THz radiation. The magnetic field is considered oblique to laser beams propagation direction; in this case, depending on the phase matching conditions different mode waves can propagate in plasma. It is found that amplitude and efficiency of the emitted THz radiation not only are sensitive to the beating frequency, collision frequency, and magnetic field strength but to the angle between laser beams and static magnetic field. The efficiency of THz radiation can be optimized in a certain angle.

Generation of terahertz radiation by intense hollow Gaussian laser beam in magnetised plasma under relativistic-ponderomotive regime

NASA Astrophysics Data System (ADS)

Rawat, Priyanka; Rawat, Vinod; Gaur, Bineet; Purohit, Gunjan

2017-07-01

This paper explores the self-focusing of hollow Gaussian laser beam (HGLB) in collisionless magnetized plasma and its effect on the generation of THz radiation in the presence of relativistic-ponderomotive nonlinearity. The relativistic change of electron mass and electron density perturbation due to the ponderomotive force leads to self-focusing of the laser beam in plasma. Nonlinear coupling between the intense HGLB and electron plasma wave leads to generation of THz radiation in plasma. Resonant excitation of THz radiation at different frequencies of laser and electron plasma wave satisfies proper phase matching conditions. Appropriate expressions for the beam width parameter of the laser beam and the electric vector of the THz wave have been evaluated under the paraxial-ray and Wentzel-Kramers Brillouin approximations. It is found that the yield of THz amplitude depends on the focusing behaviour of laser beam, magnetic field, and background electron density. Numerical simulations have been carried out to investigate the effect of laser and plasma parameters on self-focusing of the laser beam and further its effect on the efficiency of the generated THz radiation.

The Effect of Intense Laser Radiation on Atomic Collisions

NASA Astrophysics Data System (ADS)

Young, Stephen Michael Radley

1991-02-01

Available from UMI in association with The British Library. Requires signed TDF. We have carried out theoretical and experimental studies into the effect of intense laser radiation on atomic collisions. The first experiment used neon. Excitation by electron impact in a gas discharge demanded a pressure of at least 0.075 Torr. Measurement of the intensity of 3^1S_0to 3^1P_1 fluorescence has been made for the case where high intensity ASE wings in the laser profile and background laser scatter are unimportant, with the laser tuned to resonance. The field intensity required to produce strong field fluorescence (exemplified by the Mollow triplet) was found to give rise to complications capable of screening the effects sought. Our theoretical model has suggested that at finite detunings, line-centre fluorescence will dominate Rayleigh scatter and omega_3 fluorescence. Our measurements provide information on the saturation of neon fluorescence but not of the variation of the intense field collision rate. Absorption of weak field 253.7 nm laser photons by ground state mercury atoms yielded a high 6 ^3P_1 population at a lower pressure of 0.02 Torr. The Mollow triplet has been observed in the self-broadened mercury system. Dressing of the upper transition (6^3P_1rightarrow 7^3S_1) by an intense laser close to 435.8 nm yielded the strong field signal. Polarisation studies were made possible by the 3-level mercury system (radiation trapping in a 2-level system would depolarise fluorescence) perturbed by argon. The studies yielded results that were explainable in terms of the selective population of Stark shifted dressed states by a detuned, weak probe field. Use has been made of the electric-dipole radiation selection rule m_{J}=0 rightarrow m_{J^' } = 0 unless J=J^' to devise a 'Stark shift collision switch'. The competition between collision and radiation induced transitions within the mercury atom has then been studied. The resonant, strong lambda 435.8 nm field was used

ARTICLES: Physical laws governing the interaction of pulse-periodic CO2 laser radiation with metals

NASA Astrophysics Data System (ADS)

Vedenov, A. A.; Gladush, G. G.; Drobyazko, S. V.; Pavlovich, Yu V.; Senatorov, Yu M.

1985-01-01

It is shown theoretically and experimentally that the efficiency of welding metals with a pulse-periodic CO2 laser beam of low duty ratio, at low velocities, can exceed that of welding with cw lasers and with electron beams. For the first time an investigation was made of the influence of the laser radiation parameters (energy and frequency) and of the welding velocity on the characteristics of the weld and on the shape of the weldpool. The influence of the laser radiation polarization on the efficiency of deep penetration was analyzed.

Thermal effects of λ = 808 nm GaAlAs diode laser irradiation on different titanium surfaces.

PubMed

Giannelli, Marco; Lasagni, Massimo; Bani, Daniele

2015-12-01

Diode lasers are widely used in dental laser treatment, but little is known about their thermal effects on different titanium implant surfaces. This is a key issue because already a 10 °C increase over the normal body temperature can induce bone injury and compromise osseo-integration. The present study aimed at evaluating the temperature changes and surface alterations experienced by different titanium surfaces upon irradiation with a λ = 808 nm diode laser with different settings and modalities. Titanium discs with surfaces mimicking different dental implant surfaces including TiUnite and anodized, machined surfaces were laser-irradiated in contact and non-contact mode, and with and without airflow cooling. Settings were 0.5-2.0 W for the continuous wave mode and 10-45 μJ, 20 kHz, 5-20 μs for the pulsed wave mode. The results show that the surface characteristics have a marked influence on temperature changes in response to irradiation. The TiUnite surface, corresponding to the osseous interface of dental implants, was the most susceptible to thermal rise, while the machined surfaces, corresponding to the implant collar, were less affected. In non-contact mode and upon continuous wave emission, the temperature rose above the 50 °C tissue damage threshold. Scanning electron microscopy investigation of surface alterations revealed that laser treatment in contact mode resulted in surface scratches even when no irradiation was performed. These findings indicate that the effects of diode laser irradiation on implant surfaces depend on physical features of the titanium coating and that in order to avoid thermal or physical damage to implant surface the irradiation treatment has to be carefully selected.

An improved maximum permissible exposure meter for safety assessments of laser radiation

NASA Astrophysics Data System (ADS)

Corder, D. A.; Evans, D. R.; Tyrer, J. R.

1997-12-01

Current interest in laser radiation safety requires demonstration that a laser system has been designed to prevent exposure to levels of laser radiation exceeding the Maximum Permissible Exposure. In some simple systems it is possible to prove this by calculation, but in most cases it is preferable to confirm calculated results with a measurement. This measurement may be made with commercially available equipment, but there are limitations with this approach. A custom designed instrument is presented in which the full range of measurement issues have been addressed. Important features of the instrument are the design and optimisation of detector heads for the measurement task, and consideration of user interface requirements. Three designs for detector head are presented, these cover the majority of common laser types. Detector heads are designed to optimise the performance of relatively low cost detector elements for this measurement task. The three detector head designs are suitable for interfacing to photodiodes, low power thermopiles and pyroelectric detectors. Design of the user interface was an important aspect of the work. A user interface which is designed for the specific application minimises the risk of user error or misinterpretation of the measurement results. A palmtop computer was used to provide an advanced user interface. User requirements were considered in order that the final implement was well matched to the task of laser radiation hazard audits.

EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Effect of compression of a laser plasma on the generation of harmonics and hard x radiation

NASA Astrophysics Data System (ADS)

Apollonov, V. V.; Derzhavin, S. I.; Kazakov, K. Kh

1993-02-01

A compression of a plasma produced at a conical target by a low-intensity beam (q≲10 GW/cm2) from a CO2 laser has been studied. The effect of this compression on the onset of the parametric instability responsible for the generation of harmonics and of hard x radiation has also been studied. A qualitative interpretation of the results is offered.

Xenon plasma sustained by pulse-periodic laser radiation

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

Rudoy, I. G.; Solovyov, N. G.; Soroka, A. M.

2015-10-15

The possibility of sustaining a quasi-stationary pulse-periodic optical discharge (POD) in xenon at a pressure of p = 10–20 bar in a focused 1.07-μm Yb{sup 3+} laser beam with a pulse repetition rate of f{sub rep} ⩾ 2 kHz, pulse duration of τ ⩾ 200 μs, and power of P = 200–300 W has been demonstrated. In the plasma development phase, the POD pulse brightness is generally several times higher than the stationary brightness of a continuous optical discharge at the same laser power, which indicates a higher plasma temperature in the POD regime. Upon termination of the laser pulse,more » plasma recombines and is then reinitiated in the next pulse. The initial absorption of laser radiation in successive POD pulses is provided by 5p{sup 5}6s excited states of xenon atoms. This kind of discharge can be applied in plasma-based high-brightness broadband light sources.« less

Skin welding using pulsed laser radiation and a dye

NASA Astrophysics Data System (ADS)

Fried, Nathaniel M.; Walsh, Joseph T., Jr.

1998-07-01

Previous skin welding studies have used continuous wave (CW) delivery of radiation. However, heat diffusion during irradiation prevents strong welds from being achieved without creating large zones of thermal damage to surrounding tissue. This damage may prevent normal wound healing. Strong welds and minimal thermal damage can be achieved by introducing a dye and delivering the radiation in a pulsed mode. Two-cm-long, full-thickness incisions were made in guinea pig skin. India ink was used as an absorber, and egg white albumin was used as an adhesive. A 5-mm-diameter spot of CW, 1.06-micrometer Nd:YAG laser radiation was scanned over the weld site, producing 100 millisecond pulses. The cooling time between scans and number of scans was varied. Thermal damage zones were measured using a transmission polarizing microscope to identify birefringence changes in tissue. Tensile strengths were measured using a tensiometer. For pulsed welding and long cooling times, weld strengths of 2.4 kg/cm2 were measured, and thermal damage to the epidermis was limited to approximately 500 micrometers. With CW welding, comparable weld strengths resulted in approximately 2700 micrometer of thermal damage. CW laser radiation weld strengths were only 0.6 kg/cm2 when thermal damage in the epidermis was limited to approximately 500 micrometers.

Response of antioxidant defense system to laser radiation apical meristem of Isatis indigotica seedlings exposed to UV-B.

PubMed

Chen, Yi-Ping

2009-07-01

To determine the response of antioxidant defense system to laser radiation apical meristem of Isatis indigotica seedlings, Isatis indigotica seedlings were subjected to UV-B radiation (10.08 kJ m(-2)) for 8 h day(-1) for 8 days (PAR, 220 micromol m(-2) s(-1)) and then exposed to He-Ne laser radiation (633 nm; 5.23 mW mm(-2); beam diameter: 1.5 mm) for 5 min each day without ambient light radiation. Changes in free radical elimination systems were measured, the results indicate that: (1) UV-B radiation enhanced the concentration of Malondialdahyde (MDA) and decreased the activities of superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) in seedlings compared with the control. The concentration of MDA was decreased and the activities of SOD, CAT and POD were increased when seedlings were subjected to elevated UV-B damage followed by laser; (2) the concentration of UV absorbing compounds and proline were increased progressively with UV-B irradiation, laser irradiation and He-Ne laser irradiation plus UV-B irradiation compared with the control. These results suggest that laser radiation has an active function in repairing UV-B-induced lesions in seedlings.

Beam power-dependent laser-induced fluorescence radiation quenching of silver-ion-exchanged glasses

NASA Astrophysics Data System (ADS)

Nahal, Arashmid; Khalesifard, Hamid Reza M.

2007-04-01

In this article, results of an investigation about the modification of silver ions embedded in a glass matrix under the action of a CW high-power Ar + laser beam, by means of laser-induced fluorescence, is reported. It is known [A. Nahal, H.R.M. Khalesifard, J. Mostafavi-Amjad, Appl. Phys. B 79 (2004) 513-518] that, as a result of the interaction of the laser beam with the sample, the embedded silver ions reduce to neutral ones and silver clusters are formed. We observed that the fluorescence radiation of the central part of the interaction area, on the sample, diminishes simultaneously with the formation of the neutral clusters. Further increase in the exposure time or the power of the beam results in reappearance of the fluorescence radiation, in the central part of the interaction area. We found that, during and after the interaction the spectrum of the fluorescence radiation changes. This makes it possible to study the laser-induced changes in the embedded silver ions and clusters, in real-time.

Thermal Investigation of Interaction between High-power CW-laser Radiation and a Water-jet

NASA Astrophysics Data System (ADS)

Brecher, Christian; Janssen, Henning; Eckert, Markus; Schmidt, Florian

The technology of a water guided laser beam has been industrially established for micro machining. Pulsed laser radiation is guided via a water jet (diameter: 25-250 μm) using total internal reflection. Due to the cylindrical jet shape the depth of field increases to above 50 mm, enabling parallel kerfs compared to conventional laser systems. However higher material thicknesses and macro geometries cannot be machined economically viable due to low average laser powers. Fraunhofer IPT has successfully combined a high-power continuous-wave (CW) fiber laser (6 kW) and water jet technology. The main challenge of guiding high-power laser radiation in water is the energy transferred to the jet by absorption, decreasing its stability. A model of laser water interaction in the water jet has been developed and validated experimentally. Based on the results an upscaling of system technology to 30 kW is discussed, enabling a high potential in cutting challenging materials at high qualities and high speeds.

Laser treatment of oral vascular malformations

NASA Astrophysics Data System (ADS)

Romeo, U.; Gaimari, G.; Mohsen, M.; Tenore, G.; Palaia, G.

2014-01-01

Oral Vascular Malformations (OVM) are congenital anomalies characterized by morph-structural and/or functional changes of nature in severity and extension. OVM can affect any type of vessels arterial, venous or lymphatic and any capillary or anatomical. They are divided into two categories: low and high flow. In this study were treated 40 patients with OVM with a range size from 2 mm to 44 mm; they were subjected to clinical examination supported by Colour-Doppler Ultrasound instrumental examination and only for doubt cases the Magnetic Resonance Imaging (MRI) was prescribed. Only low flow venous and capillary malformations were treated by GaAlAs laser (Wiser®, Lambda, Brindole,Italy, 980nm) and KTP laser (SmartLite®, DEKA, Florence, Italy, 532nm) with two different techniques: the Transmucosal Thermophotocoagulation (TMT) and the Intralesional Photocoagulation (ILP). These techniques permitted a good control of haemostasis, avoiding bleeding both during surgery and in the postoperative. It is obtained an excellent and good healing respectively in 10% and 60% of cases, a moderate and poor resolution respectively in 22.5% and 7.5% of cases. A clear diagnosis allowed the management of Venous malformations (VM) by laser devices with wavelengths highly absorbed in haemoglobin in safety and efficacy and according to the principles of minimal invasive surgery. The aim of this study was to verify if the laser is effective in the treatment of OVM for the purpose of the clinical findings and the postoperative course. The Authors concluded that the laser can be considered the "gold standard" for treating OVM.

Biochemical Studies Of The Effect Of Two Laser Radiation Wavelengths On The Khapra Beetle Trogoderma Granarium Everts (Coleoptera : Dermestidae)

NASA Astrophysics Data System (ADS)

Abdel-Kader, Mahmoud H.; El-Nozahy, Adel M.; Ahmed, Salwa M. S.; Khalifa, Ibtesam A.

2007-02-01

The present work was carried out to evaluate the actual effect of subleathal dosage of LD30 of two different lasers (Argon-ion and CO2 lasers) on the main metabolites, phosphatases enzymes, transaminases, acetylcholinestrase and peroxidases in the one day adult stage of Trogoderma granarium treated as 2-3 days old pupae. Our results clearly indicated that two different wavelengths of laser radiation increased significantly the total proteins content, whereas no significant changes occurred in the total lipids for the two laser radiation wavelenghts. On the other hand the total carbohydrates were significantly decreased when irradiating using CO2 laser wavelength which is not the case for the Argon-ion laser radiation. Significant changes of phosphatases occurred for both wavelengths. Inhibition of transaminases GOT (glutamic oxaloacetic transaminases) and insignificant changes of GPT (glutamic pyruvic oxaloacetic transaminases) was observed for both laser wavelengths. Significant inhibition of acetyl cholinestrase was observed using CO2 laser and insignificant changes were recorded for Argon ion laser radiation where as insignificant decrease of peroxideses was observed for both lasers.

Regeneration of spine disc and joint cartilages under temporal and space modulated laser radiation

NASA Astrophysics Data System (ADS)

Sobol, E.; Shekhter, A.; Baskov, A.; Baskov, V.; Baum, O.; Borchshenko, I.; Golubev, V.; Guller, A.; Kolyshev, I.; Omeltchenko, A.; Sviridov, A.; Zakharkina, O.

2009-02-01

The effect of laser radiation on the generation of hyaline cartilage in spine disc and joints has been demonstrated. The paper considers physical processes and mechanisms of laser regeneration, presents results of investigations aimed to optimize laser settings and to develop feedback control system for laser reconstruction of spine discs. Possible mechanisms of laser-induced regeneration include: (1) Space and temporary modulated laser beam induces nonhomogeneous and pulse repetitive thermal expansion and stress in the irradiated zone of cartilage. Mechanical effect due to controllable thermal expansion of the tissue and micro and nano gas bubbles formation in the course of the moderate (up to 45-50 oC) heating of the NP activate biological cells (chondrocytes) and promote cartilage regeneration. (2) Nondestructive laser radiation leads to the formation of nano and micro-pores in cartilage matrix. That promotes water permeability and increases the feeding of biological cells. Results provide the scientific and engineering basis for the novel low-invasive laser procedures to be used in orthopedics for the treatment cartilages of spine and joints. The technology and equipment for laser reconstruction of spine discs have been tested first on animals, and then in a clinical trial. Since 2001 the laser reconstruction of intervertebral discs have been performed for 340 patients with chronic symptoms of low back or neck pain who failed to improve with non-operative care. Substantial relief of back pain was obtained in 90% of patients treated who returned to their daily activities. The experiments on reparation of the defects in articular cartilage of the porcine joints under temporal and spase modulated laser radiation have shown promising results.

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.

Dark solitons in laser radiation build-up dynamics.

PubMed

Woodward, R I; Kelleher, E J R

2016-03-01

We reveal the existence of slowly decaying dark solitons in the radiation build-up dynamics of bright pulses in all-normal dispersion mode-locked fiber lasers, numerically modeled in the framework of a generalized nonlinear Schrödinger equation. The evolution of noise perturbations to quasistationary dark solitons is examined, and the significance of background shape and soliton-soliton collisions on the eventual soliton decay is established. We demonstrate the role of a restoring force in extending soliton interactions in conservative systems to include the effects of dissipation, as encountered in laser cavities, and generalize our observations to other nonlinear systems.

EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA Annealing of induced absorption in quartz glasses by ArF laser radiation

NASA Astrophysics Data System (ADS)

Sergeev, P. B.; Sergeev, A. P.

2010-11-01

Annealing of individual bands of electron-beam-induced absorption (IA) in the region of 150 — 400 nm in KS-4V, KU-1, and Corning 7980 (ArF Grade) quartz glasses by ArF laser radiation is studied. It is shown that the phototransformation of the IA spectra occurs mainly due to a significant decrease in the amplitudes of bands at λ = 183.5, 213, and 260 nm. The role played by interstitial oxygen, hydrogen, and chlorine in the formation and relaxation of glass defects is considered.

Precision drilling of fused silica with 157-nm excimer laser radiation

NASA Astrophysics Data System (ADS)

Temme, Thorsten; Ostendorf, Andreas; Kulik, Christian; Meyer, Klaus

2003-07-01

μFor drilling fused silica, mechanical techniques like with diamond drills, ultrasonic machining, sand blasting or water jet machining are used. Also chemical techniques like laser assisted wet etching or thermal drilling with CO2-lasers are established. As an extension of these technologies, the drilling of micro-holes in fused silica with VUV laser radiation is presented here. The high absorption of the 157 nm radiation emitted by the F2 excimer laser and the short pulse duration lead to a material ablation with minimised impact on the surrounding material. Contrary to CO2-laser drilling, a molten and solidified phase around the bore can thus be avoided. The high photon energy of 7.9 eV requires either high purity nitrogen flushing or operation in vacuum, which also effects the processing results. Depending on the required precision, the laser can be used for percussion drilling as well as for excimer laser trepanning, by applying rotating masks. Rotating masks are especially used for high aspect ratio drilling with well defined edges and minimised debris. The technology is suitable particularly for holes with a diameter below 200 μm down to some microns in substrates with less than 200 μm thickness, that can not be achieved with mechanical methods. Drilling times in 200 μm fused silica substrates are in the range of ten seconds, which is sufficient to compete with conventional methods while providing similar or even better accuracy.

Strong Field-Induced Frequency Conversion of Laser Radiation in Plasma Plumes: Recent Achievements

PubMed Central

Ganeev, R. A.

2013-01-01

New findings in plasma harmonics studies using strong laser fields are reviewed. We discuss recent achievements in the growth of the efficiency of coherent extreme ultraviolet (XUV) radiation sources based on frequency conversion of the ultrashort pulses in the laser-produced plasmas, which allowed for the spectral and structural studies of matter through the high-order harmonic generation (HHG) spectroscopy. These studies showed that plasma HHG can open new opportunities in many unexpected areas of laser-matter interaction. Besides being considered as an alternative method for generation of coherent XUV radiation, it can be used as a powerful tool for various spectroscopic and analytical applications. PMID:23864818

Broad Area Distributed Gain, Distributed Index Profile GaAlAs Semiconductor Laser Diodes

DTIC Science & Technology

1991-02-14

active region. The external and electron mobilities . This, along with the difference differential quantum efficiency and light-current slope ef- [91...nternotionoi .-. rnri in Circuit Thteor\\ 1991. and Aplications He also has served o~n iechnical and orovrai committees 1 -1 H C Case,, and NI B...sample temperatures. these defects are mobile and cause atomic diffusion, usually called radiation-enhanced diffusion (RED). Since this diffusion

Analytical modeling of polarization transformation of laser radiation of various spectral ranges by birefringent structures

NASA Astrophysics Data System (ADS)

Motrich, A. V.; Ushenko, O. G.

2018-01-01

The results of statistical dependence and correlation structures of two-dimensional Mueller matrix elements in various spectral regions of laser radiation by changes in the distribution of orientations of optical axes and birefringence of protein crystals. Namely, a two-wave ("red-blue") approach - layer of biological tissues irradiated by He-Ne laser (λ1 = 0,63μm ) and He-Cd laser (λ1 = 0,41μm )was used Conducted analysis of polarimetric sensitivity was made, a state of polarization points that contain volumetric structures of biological objects to spectral region of laser radiation was detected.

Focusers of obliquely incident laser radiation

NASA Astrophysics Data System (ADS)

Goncharskiy, A. V.; Danilov, V. A.; Popov, V. V.; Prokhorov, A. M.; Sisakyan, I. N.; Sayfer, V. A.; Stepanov, V. V.

1984-08-01

Focusing obliquely incident laser radiation along a given line in space with a given intensity distribution is treated as a problem of synthesizing a mirror surface. The intricate shape of such a surface, characterized by a function z= z (u,v) in the approximation of geometrical optics, is determined from the equation phi (u,v,z) - phi O(u,v,z)=O, which expresses that the incident field and the reflected field have identical eikonals. Further calculations are facilitated by replacing continuous mirror with a more easily manufactured piecewise continuous one. The problem is solved for the simple case of a plane incident wave with a typical iconal phi O(u,v,z)= -z cos0 at a large angle to a focus mirror in the z-plane region. Mirrors constructed on the basis of the theoretical solution were tested in an experiment with a CO2 laser. A light beam with Gaussian intensity distribution was, upon incidence at a 45 deg angle, focused into a circle or into an ellipse with uniform intensity distribution. Improvements in amplitudinal masking and selective tanning technology should reduce energy losses at the surface which results in efficient laser focusing mirrors.

Smith-Purcell terahertz radiation from laser modulated electron beam over a metallic grating

NASA Astrophysics Data System (ADS)

Kumar, Pawan; Bhasin, Lalita; Tripathi, V. K.; Kumar, Ashok; Kumar, Manoj

2016-09-01

We propose a novel scheme of terahertz (THz) radiation generation from the beat frequency modulation of an electron beam by two co-propagating lasers and the generation of terahertz radiation by the modulated beam passing over a periodic metallic grating. The lasers cause velocity modulation of the beam by exerting a longitudinal ponderomotive force on it. In the drift space between the modulator and metallic grating, the velocity modulation translates into density and current modulation. The modulated beam, propagating over the grating of specific wave number, induces space periodic image current in the conductor that emits beat frequency Smith-Purcell radiation. With 1 μm, 4 × 1016 W/cm2 lasers, beam current modulation of the order of 50% can be achieved at optimum lengths of the modulator and drift space. Employing 10 mA, 0.5 MeV short-period electron beam, propagating at a height of 50 μ m above the grating of period 150 μm, one may obtain THz radiated power of the order of 6 mW at 10 THz.

Spectrum and Angular Distribution of γ-rays from Radiative Damping in Extremely Relativistic Laser-Plasma Interaction

NASA Astrophysics Data System (ADS)

Pandit, Rishi; Sentoku, Yasuhiko

2013-10-01

Effects of the radiative damping in the interaction of extremely intense laser (> 1022 W/cm2) with dense plasma is studied via a relativistic collisional particle-in-cell simulation, PICLS. When the laser intensity is getting close to 1024 W/cm2, the effect of quantum electrodynamics (QED) appears. We had calculated γ-rays from the radiative damping processes based on the classical model [1], but had taken into account the QED effect [2] in the spectrum calculation. In ultra-intense laser-plasma interaction, electrons are accelerated by the strong laser fields and emit γ-ray photons mainly via two processes, namely, Bremsstrahlung and radiative damping. Such relativistic γ-ray has wide range of frequencies and the angular distribution depends on the hot electron source. Comparing the details of γ-rays from the Bremsstrahlung and the radiative damping in simulations, we will discuss the laser parameters and the target conditions (geometry and material) to distinguish the photons from each process and also the QED effect in the γ-rays spectrum at the extremely relativistic intensity. Supported by US DOE DE-SC0008827.

LASER MEDICINE: Effect of laser radiation absorption in water and blood on the optimal wavelength for endovenous obliteration of varicose veins

NASA Astrophysics Data System (ADS)

Zhilin, K. M.; Minaev, V. P.; Sokolov, Aleksandr L.

2009-08-01

This work examines laser radiation absorption in water and blood at the wavelengths that are used in endovenous laser treatment (EVLT): 0.81-1.06, 1.32, 1.47, 1.5 and 1.56 μm. It is shown that the best EVLT conditions are ensured by 1.56-μm radiation. Analysis of published data suggests that even higher EVLT efficacy may be achieved at wavelengths of 1.68 and 1.7 μm.

Endoscopic diode laser therapy for chronic radiation proctitis.

PubMed

Polese, Lino; Marini, Lucia; Rizzato, Roberto; Picardi, Edgardo; Merigliano, Stefano

2018-01-01

The purpose of this study is to determine the effectiveness of endoscopic diode laser therapy in patients presenting rectal bleeding due to chronic radiation proctitis (CRP). A retrospective analysis of CRP patients who underwent diode laser therapy in a single institution between 2010 and 2016 was carried out. The patients were treated by non-contact fibers without sedation in an outpatient setting. Fourteen patients (median age 77, range 73-87 years) diagnosed with CRP who had undergone high-dose radiotherapy for prostatic cancer and who presented with rectal bleeding were included. Six required blood transfusions. Antiplatelet (three patients) and anticoagulant (two patients) therapy was not suspended during the treatments. The patients underwent a median of two sessions; overall, a mean of 1684 J of laser energy per session was used. Bleeding was resolved in 10/14 (71%) patients, and other two patients showed improvement (93%). Only one patient, who did not complete the treatment, required blood transfusions after laser therapy; no complications were noted during or after the procedures. Study findings demonstrated that endoscopic non-contact diode laser treatment is safe and effective in CRP patients, even in those receiving antiplatelet and/or anticoagulant therapy.

Interaction of repetitively pulsed high energy laser radiation with matter

NASA Astrophysics Data System (ADS)

Hugenschmidt, M.

1986-05-01

Laser target interaction processes and methods of improving the overall energy balance are discussed. This can be achieved with high repetition rate pulsed lasers even for initially highly reflecting materials, such as metals. Experiments were performed using a pulsed CO2 laser at mean powers up to 2 KW and repetition rates up to 100 Hz. The rates of temperature rise of aluminum for example are increased by more than a factor of 3 as compared to cw-radiation of comparable power density. Similar improvements are found for the overall absorptivities, that are increased by more than an order of magnitude.

A new method and device of aligning patient setup lasers in radiation therapy.

PubMed

Hwang, Ui-Jung; Jo, Kwanghyun; Lim, Young Kyung; Kwak, Jung Won; Choi, Sang Hyuon; Jeong, Chiyoung; Kim, Mi Young; Jeong, Jong Hwi; Shin, Dongho; Lee, Se Byeong; Park, Jeong-Hoon; Park, Sung Yong; Kim, Siyong

2016-01-08

The aim of this study is to develop a new method to align the patient setup lasers in a radiation therapy treatment room and examine its validity and efficiency. The new laser alignment method is realized by a device composed of both a metallic base plate and a few acrylic transparent plates. Except one, every plate has either a crosshair line (CHL) or a single vertical line that is used for alignment. Two holders for radiochromic film insertion are prepared in the device to find a radiation isocenter. The right laser positions can be found optically by matching the shadows of all the CHLs in the gantry head and the device. The reproducibility, accuracy, and efficiency of laser alignment and the dependency on the position error of the light source were evaluated by comparing the means and the standard deviations of the measured laser positions. After the optical alignment of the lasers, the radiation isocenter was found by the gantry and collimator star shots, and then the lasers were translated parallel to the isocenter. In the laser position reproducibility test, the mean and standard deviation on the wall of treatment room were 32.3 ± 0.93 mm for the new method whereas they were 33.4 ± 1.49 mm for the conventional method. The mean alignment accuracy was 1.4 mm for the new method, and 2.1 mm for the conventional method on the walls. In the test of the dependency on the light source position error, the mean laser position was shifted just by a similar amount of the shift of the light source in the new method, but it was greatly magnified in the conventional method. In this study, a new laser alignment method was devised and evaluated successfully. The new method provided more accurate, more reproducible, and faster alignment of the lasers than the conventional method.

A new method and device of aligning patient setup lasers in radiation therapy

PubMed Central

Hwang, Ui‐Jung; Jo, Kwanghyun; Kwak, Jung Won; Choi, Sang Hyoun; Jeong, Chiyoung; Kim, Mi Young; Jeong, Jong Hwi; Shin, Dongho; Lee, Se Byeong; Park, Jeong‐Hoon; Park, Sung Yong; Kim, Siyong

2016-01-01

The aim of this study is to develop a new method to align the patient setup lasers in a radiation therapy treatment room and examine its validity and efficiency. The new laser alignment method is realized by a device composed of both a metallic base plate and a few acrylic transparent plates. Except one, every plate has either a crosshair line (CHL) or a single vertical line that is used for alignment. Two holders for radiochromic film insertion are prepared in the device to find a radiation isocenter. The right laser positions can be found optically by matching the shadows of all the CHLs in the gantry head and the device. The reproducibility, accuracy, and efficiency of laser alignment and the dependency on the position error of the light source were evaluated by comparing the means and the standard deviations of the measured laser positions. After the optical alignment of the lasers, the radiation isocenter was found by the gantry and collimator star shots, and then the lasers were translated parallel to the isocenter. In the laser position reproducibility test, the mean and standard deviation on the wall of treatment room were 32.3±0.93 mm for the new method whereas they were 33.4±1.49 mm for the conventional method. The mean alignment accuracy was 1.4 mm for the new method, and 2.1 mm for the conventional method on the walls. In the test of the dependency on the light source position error, the mean laser position was shifted just by a similar amount of the shift of the light source in the new method, but it was greatly magnified in the conventional method. In this study, a new laser alignment method was devised and evaluated successfully. The new method provided more accurate, more reproducible, and faster alignment of the lasers than the conventional method. PACS numbers: 87.56.Fc, 87.53.Bn, 87.53.Kn, 87.53.Ly, 87.55.Gh PMID:26894331

TEA HF laser with a high specific radiation energy

NASA Astrophysics Data System (ADS)

Puchikin, A. V.; Andreev, M. V.; Losev, V. F.; Panchenko, Yu. N.

2017-01-01

Results of experimental studies of the chemical HF laser with a non-chain reaction are presented. The possibility of the total laser efficiency of 5 % is shown when a traditional C-to-C pumping circuit with the charging voltage of 20-24 kV is used. It is experimentally shown that the specific radiation output energy of 21 J/l is reached at the specific pump energy of 350 J/l in SF6/H2 = 14/1 mixture at the total pressure of 0.27 bar.

PHYSICAL EFFECTS OCCURRING DURING GENERATION AND AMPLIFICATION OF LASER RADIATION: Enhancement of the efficiency of flashlamp-pumped lasers by conversion of the spectral composition of the exciting radiation

NASA Astrophysics Data System (ADS)

Levin, M. B.; Cherkasov, A. S.

1989-02-01

An account is given of the published investigations of ways of increasing the efficiency of flashlamp-pumped lasers by frequency conversion of the exciting radiation with the aid of luminescent filters. An analysis is made of the method for calculating the efficiency of luminescent filters absorbing short-wavelength radiation and reemitting it in the absorption region of the active medium. It is shown that the use of rhodamine 6G and other phosphors as luminescent filters can double the efficiency of neodymium glass lasers, increase the efficiency of YAG:Nd3+ lasers by a factor of 1.5, and improve the efficiency of lasers activated with Ti3+ by more than an order of magnitude. The use of luminescent filters in dye lasers can double the efficiency and make it possible to reach average output powers of hundreds of watts. Promising materials for luminescent filters are considered and margins for increasing their efficiency are analyzed. The main results are reported of studies of plasma pump-spectrum converters and it is shown that promising results can be expected by combining luminescent filters and an optimized plasma converter system in an "optical boiler" enclosure.

Biological Effects of Laser Radiation. Volume II. Review of Our Studies on Biological Effects of Laser Radiation-1965-1971.

DTIC Science & Technology

1978-10-17

alter the immunological capability/virulence ratio of influenza virus ; gross and microscopic descriptions of lesions, their natural history, and...with Viruses 4 Chapter 4 Studies on Normal Animals 6 Chapter 5 Tumor-Related Laser Radiation Studies and Potential for Carcinogenesis 17 Chapter 6...affect the immunological capability/virulence ratio of influenza virus in order to explore facilitation of vaccine production; 5) extensive gross and

Method and apparatus for producing laser radiation following two-photon excitation of a gaseous medium

DOEpatents

Bischel, William K. [Menlo Park, CA; Jacobs, Ralph R. [Livermore, CA; Prosnitz, Donald [Hamden, CT; Rhodes, Charles K. [Palo Alto, CA; Kelly, Patrick J. [Fort Lewis, WA

1979-02-20

Method and apparatus for producing laser radiation by two-photon optical pumping of an atomic or molecular gaseous medium and subsequent lasing action. A population inversion is created as a result of two-photon absorption of the gaseous species. Stark tuning is utilized, if necessary, in order to tune the two-photon transition into exact resonance. In particular, gaseous ammonia (NH.sub.3) or methyl fluoride (CH.sub.3 F) is optically pumped by a pair of CO.sub.2 lasers to create a population inversion resulting from simultaneous two-photon excitation of a high-lying vibrational state, and laser radiation is produced by stimulated emission of coherent radiation from the inverted level.

Method and apparatus for producing laser radiation following two-photon excitation of a gaseous medium

DOEpatents

Bischel, W.K.; Jacobs, R.R.; Prosnitz, D.P.; Rhodes, C.K.; Kelly, P.J.

1979-02-20

Method and apparatus are disclosed for producing laser radiation by two-photon optical pumping of an atomic or molecular gaseous medium and subsequent lasing action. A population inversion is created as a result of two-photon absorption of the gaseous species. Stark tuning is utilized, if necessary, in order to tune the two-photon transition into exact resonance. In particular, gaseous ammonia (NH[sub 3]) or methyl fluoride (CH[sub 3]F) is optically pumped by a pair of CO[sub 2] lasers to create a population inversion resulting from simultaneous two-photon excitation of a high-lying vibrational state, and laser radiation is produced by stimulated emission of coherent radiation from the inverted level. 3 figs.

Application of laser radiation and magnetostimulation in therapy of patients with multiple sclerosis.

PubMed

Kubsik, Anna; Klimkiewicz, Robert; Janczewska, Katarzyna; Klimkiewicz, Paulina; Jankowska, Agnieszka; Woldańska-Okońska, Marta

2016-01-01

Multiple sclerosis is one of the most common neurological disorders. It is a chronic inflammatory demyelinating disease of the CNS, whose etiology is not fully understood. Application of new rehabilitation methods are essential to improve functional status. The material studied consisted of 120 patients of both sexes (82 women and 38 men) aged 21-81 years. The study involved patients with a diagnosis of multiple sclerosis. The aim of the study was to evaluate the effect of laser radiation and other therapies on the functional status of patients with multiple sclerosis. Patients were randomly divided into four treatment groups. The evaluation was performed three times - before the start of rehabilitation, immediately after rehabilitation (21 days of treatment) and subsequent control - 30 days after the patients leave the clinic. The following tests were performed for all patients to assess functional status: Expanded Disability Status Scale (EDSS) of Kurtzke and Barthel Index. Results of all testing procedures show that the treatment methods are improving the functional status of patients with multiple sclerosis, with the significant advantage of the synergistic action of laser and magneto stimulation. The combination of laser and magneto stimulation significantly confirmed beneficial effect on quality of life. The results of these studies present new scientific value and are improved compared to program of rehabilitation of patients with multiple sclerosis by laser radiation which was previously used. This study showed that synergic action of laser radiation and magneto stimulation has a beneficial effect on improving functional status, and thus improves the quality of life of patients with multiple sclerosis. The effects of all methods of rehabilitation are persisted after cessation of treatment applications, with a particular advantage of the synergistic action of laser radiation and magneto stimulation, which indicates the possibility to elicitation in these

Microsecond enamel ablation with 10.6μm CO2 laser radiation

NASA Astrophysics Data System (ADS)

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

2016-02-01

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

Kinetics of UV laser radiation defects in high performance glasses

NASA Astrophysics Data System (ADS)

Natura, U.; Feurer, T.; Ehrt, D.

2000-05-01

High purity fluoride phosphate glasses are attractive candidates as UV transmitting materials. The calculated values for the ultraviolet resonance wavelength are comparable with those of pure silica glass or fluoride single crystal CaF2. The formation of radiation-induced defect centers leads to additional absorption bands in the VUV-UV-vis range. The damage and the healing behavior by lamps and lasers are investigated in dependence on phosphate content and the content of impurities, mainly transition metals. Experiments were carried out using pulsed lasers with a duration of femto- and nanoseconds at a wavelength of 248 nm. The initial slope of the induced absorption shows a nonlinear dependence on the pulse energy density. Resonant and non-resonant two-photon mechanisms were observed. Two-photon-absorption coefficients at 248 nm for samples with different phosphate contents were measured. Models of the kinetics of the radiation-induced defects were developed. The inclusion of energy transfer was necessary to explain the difference in the damage behavior for nanosecond (248 nm, 193 nm) and femtosecond (248 nm) laser pulses.

Effects of radiation reaction in the interaction between cluster media and high intensity lasers in the radiation dominant regime

NASA Astrophysics Data System (ADS)

Iwata, Natsumi; Nagatomo, Hideo; Fukuda, Yuji; Matsui, Ryutaro; Kishimoto, Yasuaki

2016-06-01

Interaction between media composed of clusters and high intensity lasers in the radiation dominant regime, i.e., intensity of 10 22 - 23 W / cm 2 , is studied based on the particle-in-cell simulation that includes the radiation reaction. By introducing target materials that have the same total mass but different internal structures, i.e., uniform plasma and cluster media with different cluster radii, we investigate the effect of the internal structure on the interaction dynamics, high energy radiation emission, and its reaction. Intense radiation emission is found in the cluster media where electrons exhibit non-ballistic motions suffering from strong accelerations by both the penetrated laser field and charge separation field of clusters. As a result, the clustered structure increases the energy conversion into high energy radiations significantly at the expense of the conversion into particles, while the total absorption rate into radiation and particles remains unchanged from the absorption rate into particles in the case without radiation reaction. The maximum ion energy achieved in the interaction with cluster media is found to be decreased through the radiation reaction to electrons into the same level with that achieved in the interaction with the uniform plasma. The clustered structure thus enhances high energy radiation emission rather than the ion acceleration in the considered intensity regime.

Ablation of biological tissues by radiation of strontium vapor laser

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

Soldatov, A. N., E-mail: general@tic.tsu.ru; Vasilieva, A. V., E-mail: anita-tomsk@mail.ru

2015-11-17

A two-stage laser system consisting of a master oscillator and a power amplifier based on sources of self- contained transitions in pairs SrI and SrII has been developed. The radiation spectrum contains 8 laser lines generating in the range of 1 – 6.45 μm, with a generation pulse length of 50 – 150 ns, and pulse energy of ∼ 2.5 mJ. The divergence of the output beam was close to the diffraction and did not exceed 0.5 mrad. The control range of the laser pulse repetition rate varied from 10 to 15 000 Hz. The given laser system has allowed to perform ablationmore » of bone tissue samples without visible thermal damage.« less

Laser Radiation in Active Amplifying Media Treated as a Transport Problem - Transfer Equation Derived and Exactly Solved

NASA Astrophysics Data System (ADS)

Das Gupta, Santanu; Das Gupta, S. R.

1991-10-01

The flow of laser radiation in a plane-parallel cylindrical slab of active amplifying medium with axial symmetry is treated as a problem in radiative transfer. The appropriate one-dimensional transfer equation describing the transfer of laser radiation has been derived by an appeal to Einstein'sA, B coefficients (describing the processes of stimulated line absorption, spontaneous line emission, and stimulated line emission sustained by population inversion in the medium) and considering the ‘rate equations’ to completely establish the rational of the transfer equation obtained. The equation is then exactly solved and the angular distribution of the emergent laser beam intensity is obtained; its numerically computed values are given in tables and plotted in graphs showing the nature of peaks of the emerging laser beam intensity about the axis of the laser cylinder.

Laser radiation in active amplifying media treated as a transport problem - Transfer equation derived and exactly solved

NASA Astrophysics Data System (ADS)

Gupta, S. R. D.; Gupta, Santanu D.

1991-10-01

The flow of laser radiation in a plane-parallel cylindrical slab of active amplifying medium with axial symmetry is treated as a problem in radiative transfer. The appropriate one-dimensional transfer equation describing the transfer of laser radiation has been derived by an appeal to Einstein's A, B coefficients (describing the processes of stimulated line absorption, spontaneous line emission, and stimulated line emission sustained by population inversion in the medium) and considering the 'rate equations' to completely establish the rational of the transfer equation obtained. The equation is then exactly solved and the angular distribution of the emergent laser beam intensity is obtained; its numerically computed values are given in tables and plotted in graphs showing the nature of peaks of the emerging laser beam intensity about the axis of the laser cylinder.

Fabrication of versatile cladding light strippers and fiber end-caps with CO2 laser radiation

NASA Astrophysics Data System (ADS)

Steinke, M.; Theeg, T.; Wysmolek, M.; Ottenhues, C.; Pulzer, T.; Neumann, J.; Kracht, D.

2018-02-01

We report on novel fabrication schemes of versatile cladding light strippers and end-caps via CO2 laser radiation. We integrated cladding light strippers in SMA-like connectors for reliable and stable fiber-coupling of high-power laser diodes. Moreover, the application of cladding light strippers in typical fiber geometries for high-power fiber lasers was evaluated. In addition, we also developed processes to fuse end-caps to fiber end faces via CO2 laser radiation and inscribe the fibers with cladding light strippers near the end-cap. Corresponding results indicate the great potential of such devices as a monolithic and low-cost alternative to SMA connectors.

Laser-plasma accelerator and femtosecond photon sources-based ultrafast radiation chemistry and biophysics

NASA Astrophysics Data System (ADS)

Gauduel, Y. A.

2017-02-01

The initial distribution of energy deposition triggered by the interaction of ionizing radiations (far UV and X rays, electron, proton and accelerated ions) with molecular targets or integrated biological systems is often decisive for the spatio-temporal behavior of radiation effects that take place on several orders of magnitude. This contribution deals with an interdisciplinary approach that concerns cutting-edge advances on primary radiation events, considering the potentialities of innovating strategies based on ultrafast laser science, from femtosecond photon sources to laser-driven relativistic particles acceleration. Recent advances of powerful TW laser sources (~ 1019 Wcm-2) and laser-plasma interactions providing ultrashort relativistic particle beams in the energy domain 2.5-150 MeV open exciting opportunities for the development of high-energy radiation femtochemistry (HERF). Early radiation damages being dependent on the survival probability of secondary electrons and radial distribution of short-lived radicals inside ionization clusters, a thorough knowledge of these processes involves the real-time probing of primary events in the temporal range 10-14-10-11 s. In the framework of a closed synergy between low-energy radiation femtochemistry (LERF) and the emerging domain of HERF, the paper focuses on early phenomena that occur in the prethermal regime of low-energy secondary electrons, considering very short-lived quantum effects in aqueous environments. A high dose-rate delivered by femtosecond electron beam (~ 1011-1013 Gy s-1) can be used to investigate early radiation processes in native ionization tracks, down to 10-12 s and 10-9 m. We explain how this breakthrough favours the innovating development of real-time nanodosimetry in biologically relevant environments and open new perspectives for spatio-temporal radiation biophysics. The emerging domain of HERF would provide guidance for understanding the specific bioeffects of ultrashort particle

Comparison of the effect of UV laser radiation and of a radiomimetic substance on chromatin

NASA Astrophysics Data System (ADS)

Radulescu, Irina; Radu, Liliana; Serbanescu, Ruxandra; Nelea, V. D.; Martin, C.; Mihailescu, Ion N.

1998-07-01

The damages of the complex of deoxyribonucleic acid (DNA) and proteins from chromatin, produced by the UV laser radiation and/or by treatment with a radiomimetic substance, bleomycin, were compared. The laser radiation and bleomycin effects on chromatin structure were determined by the static and dynamic fluorimetry of chromatin complexes with the DNA specific ligand-- proflavine and by the analysis of tryptophan chromatin intrinsic fluorescence. Time resolved spectroscopy is a sensitive technique which allows to determine the excited state lifetimes of chromatin--proflavine complexes. Also, the percentage contributions to the fluorescence of proflavine, bound and unbound to chromatin DNA, were evaluated. The damages produced by the UV laser radiation on chromatin are similar with those of radiomimetic substance action and consists in DNA and proteins destruction. The DNA damage degree has been determined. The obtained results may constitute some indications in the laser utilization in radiochimiotherapy.

Spacecraft system study: A study to define the impact of laser communication systems on their host spacecraft

NASA Technical Reports Server (NTRS)

1984-01-01

The mutual influence of a laser communication system and its host spacecraft and the degree to which the mutual influence limited acquisition, tracking and pointing processes were investigated. A laser klink between a low earth orbiting (LEO) satellite and a geosynchronous earth orbiting (GEO) satellite was used as a baseline. The laser link between satellites was a generic channel transferring 500 Mbps data from the LEO to GEO using the GaAlAs laser as the laser light source. Major aspects of pointing and tracking with a satelliteborne optical system were evaluated including: (1) orbital aspects such as spacecraft relative motions, point ahead, and Sun snd Moon optical noise; (2) burst errors introduced by the electronic and optical noise levels; (3) servo system design and configurations, and the noise sources such as, sensor noise, base motion disturbances, gimbal friction torque noise; (4) an evaluation of the tracking and beacon link and the type of sensors used; (5) the function of the acquisition procedure and an evaluation of the sensors employed; and (6) an estimate of the size, weight and power needed for the satellite system.

Dichromatic and monochromatic laser radiation effects on antibiotic resistance, biofilm formation, and division rate of Pantoea agglomerans

NASA Astrophysics Data System (ADS)

Thomé, A. M. C.; Souza, B. P.; Mendes, J. P. M.; Cardoso, A. F. R.; Soares, L. C.; Trajano, E. T. L.; Fonseca, A. S.

2018-06-01

Since infection is a common cause of delayed wound healing, it is important to understand the effect of low-level laser therapy (LLLT) in bacterial mechanisms. In this study we evaluated the effects of LLLT on antibiotic resistance, division rate, and biofilm formation of Pantoea agglomerans. P. agglomerans samples were isolated from human pressure injuries in humans and cultures were exposed to low-level monochromatic and simultaneous dichromatic laser radiation to study the susceptibility of an antimicrobial to ampicillin and piperacillin  +  tazobactam, quantification of areas of bacterial colonies, and biofilm formation of bacterial cells. Fluence, wavelength, and emission mode were used in the therapeutic protocols for wound healing. The data showed no changes in the areas of the colonies, but dichromatic laser radiation decreased biofilm formation, while a monochromatic red laser at low dose increased biofilm formation and infrared at high dose decreased antibiotic resistance to ampicillin. LLLT modulates antibiotic resistance and biofilm formation of P. agglomerans, but these depend on the laser irradiation parameters, since dichromatic laser radiation induces biological effects that differ from those induced by monochromatic laser radiation. Thus, simultaneous dichromatic low-level red and infrared lasers could be a new option for the treatment of infected wounds, reducing biofilm formation, without altering antibiotic resistance and the division rate of P. agglomerans cultures.

The effect of laser radiation on the diffraction of X-rays in crystals

NASA Astrophysics Data System (ADS)

Trushin, V. N.; Chuprunov, E. V.; Khokhlov, A. F.

1988-10-01

The effect of laser radiation on the intensity of the X-ray diffraction peaks of KDP, ADP, and CuSO4-5H2O crystals was studied experimentally. This intensity was found to increase as a function of the laser beam power. This result suggests that it is possible to use laser beams to control X-ray intensity in the crystals considered.

Removal of dust particles from metal-mirror surfaces by excimer-laser radiation

NASA Astrophysics Data System (ADS)

Mann, Klaus R.; Wolff-Rottke, B.; Mueller, F.

1995-07-01

The effect of particle desorption from Al mirror surfaces by the influence of pulsed UV laser radiation has been studied. The investigations are closely related to the demands of astronomers, who are looking for a more effective way of cleaning the Al coatings of future very large telescope mirrors. A systematic parameter study has been performed in order to determine the irradiation conditions which yield the highest dust removal efficiency (i.e. reflectivity increase) on contaminated samples, taking particularly into account laser-induced damage and degradation effects of coating and substrate. The particle removal rate increases with increasing laser fluence, being limited however by the damage threshold of the coating. Therefore, parameters influencing the damage threshold of metal coatings like wavelength, pulse width, and number of pulses have been studied in detail. Data indicate that on Al coated BK7 and Zerodur samples KrF laser radiation yields the optimum result, with cleaning efficiencies comparable to polymer film stripping. The initial reflectivity of the clean coating can nearly be reinstalled, in particular when an additional solvent film on the sample surface is applied. Hence, laser desorption seems to be a viable method of cleaning large Al mirrors for telescopes.

Spectral and angular distribution of photons via radiative damping in extreme ultra-intense laser-plasma interaction

NASA Astrophysics Data System (ADS)

Pandit, Rishi; Sentoku, Yasuhiko

2012-10-01

Spectral and angular distribution of photons produced in the interaction of extremely intense laser (> 10^22,/cm^2) with dense plasma are studied with a help of a collisional particle-in-cell simulation, PICLS. In ultra-intense laser-plasma interaction, electrons are accelerated by the strong laser fields and emit γ-ray photons mainly via two processes, namely, Bremsstrahlung and radiative damping. We had developed numerical models of these processes in PICLS and study the spectrum and the angular distribution of γ-rays produced in the relativistic laser regime. Such relativistic γ-rays have wide range of frequencies and the angular distribution depends on the hot electron source. From the power loss calculation in PICLS we found that the Bremsstrahlung will get saturated at I > 10^22,/cm^2 while the radiative damping will continuously increase. Comparing the details of γ-rays from the Bremsstrahlung and the radiative damping in simulations, we will discuss the laser parameters and the target conditions (geometry and material) to distinguish the photons from each process and how to catch the signature of the radiative damping in future experiments.

Effects of low-level laser therapy on orthodontic tooth movement and root resorption after artificial socket preservation.

PubMed

Seifi, Massoud; Atri, Faezeh; Yazdani, Mohammad Masoud

2014-01-01

Low- level laser therapy has been used to stimulate the orthodontic tooth movements (OTM) previously. Furthermore, in the orthodontic treatments accompanying tooth extractions, the adjacent teeth move towards the extraction sites and close the space in some cases. Then, the adjacent tooth movements must be prevented in the treatments requiring space. Laser stimulates and at some doses decelerates tooth movement; it also improves healing process and enhances osteogenesis. Hence, it can prevent movement by osteogenesis adjacent to the tooth. The present study investigated the effects of low-level laser therapy on the OTM and root resorption following artificial socket preservation. In this experimental animal trial, 16 male albino rabbits were selected with similar characteristics and randomly divided in two groups. Under general anesthesia, an artificial socket, 8 mm in height, was created in the mesial aspect of the first premolars of the rabbits and filled with demineralized freeze dried bone allograft (DFDBA). The first premolars were connected to the incisors using nickel titanium coil springs. In experimental group, gallium-aluminum-arsenide (GaAlAs) laser was irritated mesial to first premolar where artificial socket was created continuously (808 nm). The cycle was 10 days irritation, 14 days rest, 10 days irritation, 14 days rest (Biostimulation mode). Control group was not laser irradiated. All animals were sacrificed after 48 days and the distance between the distal aspect of the first premolars, and the mesial surface of the second premolars was measured with leaf gauge. The specimens underwent histological assessments. Integrity of root and its resorption was observed under microscope calibration. The size of resorption lacunae was calculated in mm(2). Normality of data was proved according to Kolmogorov-Smirnov analysis, and Student's t-test was done. P value less than 0.05 was considered as significant. The mean OTM were 5.68 ± 1.21 mm in the control

Double-pulse THz radiation bursts from laser-plasma acceleration

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

Bosch, R. A.

2006-11-15

A model is presented for coherent THz radiation produced when an electron bunch undergoes laser-plasma acceleration and then exits axially from a plasma column. Radiation produced when the bunch is accelerated is superimposed with transition radiation from the bunch exiting the plasma. Computations give a double-pulse burst of radiation comparable to recent observations. The duration of each pulse very nearly equals the electron bunch length, while the time separation between pulses is proportional to the distance between the points where the bunch is accelerated and where it exits the plasma. The relative magnitude of the two pulses depends upon bymore » the radius of the plasma column. Thus, the radiation bursts may be useful in diagnosing the electron bunch length, the location of the bunch's acceleration, and the plasma radius.« less

Generation of 369.4 nm Radiation by Efficient Doubling of a Diode Laser

NASA Technical Reports Server (NTRS)

Williams, A.; Seidel, D. J.; Maleki, J.

1993-01-01

A resonant cavity second harmonic generation system has been developed to produce 369.4 nm radiation from a 738.8 nm diode laser with 10 mW nominal output power. This system utilizes a polarization technique to lock the cavity to the laser frequency. In this paper we report on an evaluation of the system using a Titanium:Sapphire laser as the input source, and preliminary results with a diode laser source. To our knowledge, this is the deepest uv light ever produced by frequency-doubling a diode laser.

Designing a Broadband Pump for High-Quality Micro-Lasers via Modified Net Radiation Method.

PubMed

Nechayev, Sergey; Reusswig, Philip D; Baldo, Marc A; Rotschild, Carmel

2016-12-07

High-quality micro-lasers are key ingredients in non-linear optics, communication, sensing and low-threshold solar-pumped lasers. However, such micro-lasers exhibit negligible absorption of free-space broadband pump light. Recently, this limitation was lifted by cascade energy transfer, in which the absorption and quality factor are modulated with wavelength, enabling non-resonant pumping of high-quality micro-lasers and solar-pumped laser to operate at record low solar concentration. Here, we present a generic theoretical framework for modeling the absorption, emission and energy transfer of incoherent radiation between cascade sensitizer and laser gain media. Our model is based on linear equations of the modified net radiation method and is therefore robust, fast converging and has low complexity. We apply this formalism to compute the optimal parameters of low-threshold solar-pumped lasers. It is revealed that the interplay between the absorption and self-absorption of such lasers defines the optimal pump absorption below the maximal value, which is in contrast to conventional lasers for which full pump absorption is desired. Numerical results are compared to experimental data on a sensitized Nd 3+ :YAG cavity, and quantitative agreement with theoretical models is found. Our work modularizes the gain and sensitizing components and paves the way for the optimal design of broadband-pumped high-quality micro-lasers and efficient solar-pumped lasers.

Designing a Broadband Pump for High-Quality Micro-Lasers via Modified Net Radiation Method

PubMed Central

Nechayev, Sergey; Reusswig, Philip D.; Baldo, Marc A.; Rotschild, Carmel

2016-01-01

High-quality micro-lasers are key ingredients in non-linear optics, communication, sensing and low-threshold solar-pumped lasers. However, such micro-lasers exhibit negligible absorption of free-space broadband pump light. Recently, this limitation was lifted by cascade energy transfer, in which the absorption and quality factor are modulated with wavelength, enabling non-resonant pumping of high-quality micro-lasers and solar-pumped laser to operate at record low solar concentration. Here, we present a generic theoretical framework for modeling the absorption, emission and energy transfer of incoherent radiation between cascade sensitizer and laser gain media. Our model is based on linear equations of the modified net radiation method and is therefore robust, fast converging and has low complexity. We apply this formalism to compute the optimal parameters of low-threshold solar-pumped lasers. It is revealed that the interplay between the absorption and self-absorption of such lasers defines the optimal pump absorption below the maximal value, which is in contrast to conventional lasers for which full pump absorption is desired. Numerical results are compared to experimental data on a sensitized Nd3+:YAG cavity, and quantitative agreement with theoretical models is found. Our work modularizes the gain and sensitizing components and paves the way for the optimal design of broadband-pumped high-quality micro-lasers and efficient solar-pumped lasers. PMID:27924844

Quantitative analysis of vacuum-ultraviolet radiation from nanosecond laser-zinc interaction

NASA Astrophysics Data System (ADS)

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

2018-07-01

The paper reports measurements of the vacuum-ultraviolet spectral irradiances of a flat zinc target over a wavelength region of 124-164 nm generated by 10 and 60 ns duration low-intensities, 5 ×109 - 3 ×1010 W cm-2, 1.06 μm wavelength laser pulses. Maximum radiation conversion efficiencies of 2.5%/2πsr and 0.8%/2πsr were measured for 60 and 10 ns laser pulses at the intensities of 5 ×109 and 1.4 ×1010 W cm-2, respectively. Atomic structure calculations using a relativistic configuration-interaction, flexible atomic code and a developed non-local thermodynamic equilibrium population kinetics model in comparison to the experimental spectra detected by the Seya-Namioka type monochromator reveal the strong broadband experimental emission originates mainly from 3d94p-3d94s, 3d94d-3d94p and 3d84p-3d84s, 3d84d-3d84p unresolved-transition arrays of double and triple ionized zinc, respectively. Two-dimensional radiation-hydrodynamics code is used to investigate time-space plasma evolution and spectral radiation of a 10 ns full-width-at-half-maximum Gaussian laser pulse-zinc interaction.

Propagation of intense laser radiation through a diffusion flame of burning oil

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

Gvozdev, S V; Glova, A F; Dubrovskii, V Yu

2015-06-30

We report the results of measuring the absorption coefficient of radiation from a cw ytterbium fibre single-mode laser with the power up to 1.5 kW by a diffusion flame of oil, burning in the atmosphere air at normal pressure on a free surface. For the constant length (30 mm) and width (30 mm) of the flame and the distance 10 mm between the laser beam axis and the oil surface the dependence of the absorption coefficient, averaged over the flame length, on the mean radiation intensity (varied from 4.5 × 10{sup 3} to 1.2 × 10{sup 6} W cm{sup -2})more » entering the flame is obtained. The qualitative explanation of nonmonotonic behaviour of the absorption coefficient versus the intensity is presented. (laser applications and other topics in quantum electronics)« less

Characterization of x- and gamma- radiation in relativistically intense laser-solid interactions

NASA Astrophysics Data System (ADS)

Hou, Bixue; Zulick, Calvin; Zhao, Zhen; Nees, John; Batson, Thomas; Maksimchuk, Anatoly; Thomas, Alexander G. R.; Krushelnick, Karl; CenterUltrafast Optical Science Team

2013-10-01

Using a high resolution (λ/ Δλ > 100) high purity germanium detector, the angular and material dependence, and the intensity scaling, of bremsstrahlung gamma radiation from relativistically intense (I > 1018 W/cm2) laser-solid interactions have been characterized at energies between 0.1 and 1 MeV with the high-repetition rate (500 Hz) Lambda-Cubed laser facility. The bremsstrahlung spectra of SiO2, Mo, and Eu2O3 were observed to have two-temperature energy distributions, corresponding to two different groups of electrons and depending on both laser intensity and observation angle. The spectra and source sizes of hard x-radiation under 0.1 MeV are also studied. These x-ray sources are being developed for phase-contrast imaging. Support provided by DHS (EECS-0833499), AFOSR (FA99550-12-1-0310), ARO (W911NF-11-1-0116).

Simulation study of terahertz radiation generation by circularly polarized laser pulses propagating in axially magnetized plasma

NASA Astrophysics Data System (ADS)

Saroch, Akanksha; Jha, Pallavi

2017-12-01

This paper deals with a two-dimensional simulation study of terahertz radiation emission in the wake of circularly polarized laser pulses propagating in uniformly magnetized plasma, using the XOOPIC code. The external magnetic field is applied along the direction of propagation of the laser pulse. It is seen that linearly polarized terahertz radiation is emitted off-axis, along the propagation direction, in plasma. This emitted radiation is also seen to be transmitted in vacuum. Simulation studies reveal that no such radiation is generated on-axis for the given configuration.

EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Characteristics of the scattering of neutral atoms by two counterpropagating pulsed optical fields

NASA Astrophysics Data System (ADS)

Grinchuk, V. A.; Grishina, I. A.; Kuzin, E. F.; Nagaeva, M. L.; Ryabenko, G. A.; Yakovlev, V. P.

1994-04-01

The scattering of neutral sodium atoms by a strong field of two counterpropagating (incident on and reflected from a mirror) short laser pulses was used in an experimental investigation of a stimulated radiation pressure. The reasons for the anomalous frequency structure in the scattering of atoms were identified. The oscillatory nature of the dependence of the scattering on the detuning from resonance was found to be significant in strong laser radiation fields. The oscillation period depended on the distance between the reflecting mirror and the atomic beam.

Response of dosemeters in the radiation field generated by a TW-class laser system.

PubMed

Olšovcová, V; Klír, D; Krása, J; Krůs, M; Velyhan, A; Zelenka, Z; Rus, B

2014-10-01

State-of-the-art laser systems are able to generate ionising radiation of significantly high energies by focusing ultra-short and intense pulses onto targets. Thus, measures ensuring the radiation protection of both working personnel and the general public are required. However, commercially available dosemeters are primarily designed for measurement in continuous fields. Therefore, it is important to explore their response to very short pulses. In this study, the responses of dosemeters in a radiation field generated by iodine high-power and Ti:Sapphire laser systems are examined in proton and electron acceleration experiments. Within these experiments, electron bunches of femtosecond pulse duration and 100-MeV energy and proton bunches with sub-nanosecond pulse duration and energy of several megaelectronvolts were generated in single-shot regimes. Responses of typical detectors (TLD, films and electronic personal dosemeter) were analysed and compared. Further, a first attempt was carried out to characterise the radiation field generated by TW-class laser systems. © The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Contamination and Radiation Effects on Nonlinear Crystals for Space Laser Systems

NASA Technical Reports Server (NTRS)

Abdeldayem, Hossain A.; Dowdye, Edward; Jamison, Tracee; Canham, John; Jaeger, Todd

2005-01-01

Space Lasers are vital tools for NASA s space missions and military applications. Although, lasers are highly reliable on the ground, several past space laser missions proved to be short-lived and unreliable. In this communication, we are shedding more light on the contamination and radiation issues, which are the most common causes for optical damages and laser failures in space. At first, we will present results based on the study of liquids and subsequently correlate these results to the particulates of the laser system environment. We present a model explaining how the laser beam traps contaminants against the optical surfaces and cause optical damages and the role of gravity in the process. We also report the results of the second harmonic generation efficiency for nonlinear optical crystals irradiated with high-energy beams of protons. In addition, we are proposing to employ the technique of adsorption to minimize the presence of adsorbing molecules present in the laser compartment.

Simulations of radiation pressure ion acceleration with the VEGA Petawatt laser

NASA Astrophysics Data System (ADS)

Stockhausen, Luca C.; Torres, Ricardo; Conejero Jarque, Enrique

2016-09-01

The Spanish Pulsed Laser Centre (CLPU) is a new high-power laser facility for users. Its main system, VEGA, is a CPA Ti:Sapphire laser which, in its final phase, will be able to reach Petawatt peak powers in pulses of 30 fs with a pulse contrast of 1 :1010 at 1 ps. The extremely low level of pre-pulse intensity makes this system ideally suited for studying the laser interaction with ultrathin targets. We have used the particle-in-cell (PIC) code OSIRIS to carry out 2D simulations of the acceleration of ions from ultrathin solid targets under the unique conditions provided by VEGA, with laser intensities up to 1022 W cm-2 impinging normally on 20 - 60 nm thick overdense plasmas, with different polarizations and pre-plasma scale lengths. We show how signatures of the radiation pressure-dominated regime, such as layer compression and bunch formation, are only present with circular polarization. By passively shaping the density gradient of the plasma, we demonstrate an enhancement in peak energy up to tens of MeV and monoenergetic features. On the contrary linear polarization at the same intensity level causes the target to blow up, resulting in much lower energies and broader spectra. One limiting factor of Radiation Pressure Acceleration is the development of Rayleigh-Taylor like instabilities at the interface of the plasma and photon fluid. This results in the formation of bubbles in the spatial profile of laser-accelerated proton beams. These structures were previously evidenced both experimentally and theoretically. We have performed 2D simulations to characterize this bubble-like structure and report on the dependency on laser and target parameters.

Multidisciplinary approaches to radiation-balanced lasers (MARBLE): a MURI program by AFOSR (Conference Presentation)

NASA Astrophysics Data System (ADS)

Sheik-Bahae, Mansoor

2017-02-01

An overview of the diverse research activities under the newly funded MURI project by AFOSR will be presented. The main goal is to advance the science of radiation-balanced lasers, also known as athermal lasers, in order to mitigate the thermal degradation of the high-power laser beams. The MARBLE project involves researchers from four universities and spans research activities in rare-earth doped crystals and fibers to semiconductor disc lasers.

Laser beat wave excitation of terahertz radiation in a plasma slab

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

Chauhan, Santosh; Parashar, Jetendra, E-mail: j.p.parashar@gmail.com

2014-10-15

Terahertz (THz) radiation generation by nonlinear mixing of lasers, obliquely incident on a plasma slab is investigated. Two cases are considered: (i) electron density profile is parabolic but density peak is below the critical density corresponding to the beat frequency, (ii) plasma boundaries are sharp and density is uniform. In both cases, nonlinearity arises through the ponderomotive force that gives rise to electron drift at the beat frequency. In the case of inhomogeneous plasma, non zero curl of the nonlinear current density gives rise to electromagnetic THz generation. In case of uniform plasma, the sharp density variation at the plasmamore » boundaries leads to radiation generation. In a slab width of less than a terahertz wavelength, plasma density one fourth of terahertz critical density, laser intensities ∼10{sup 17 }W/cm{sup 2} at 1 μm, one obtains the THz intensity ∼1 GW/cm{sup 2} at 3 THz radiation frequency.« less

Comparative study of the thermal effects of four semiconductor lasers on the enamel and pulp chamber of a human tooth.

PubMed

Arrastia, A M; Machida, T; Smith, P W; Matsumoto, K

1994-01-01

An in vitro thermometric study was conducted on various GaAlAs semiconductor lasers emitting at wavelengths between 750 nm and 905 nm, to verify whether these lasers produce significant heating during application to tooth structure. Measurements were conducted in vitro, using a thermal camera and a thermocouple during a 60, 120, and 180 s laser exposure at energy densities between 1.5 and 2,400 J/cm2. Mean temperature changes on surface enamel were statistically significant in all groups at P < or = .05 and P < or = .01. The higher the energy density applied to a surface area, the greater the temperature rise observed using the same spot size, operation mode, and wavelength. Intrapulpal temperature elevations measured > or = 3 degrees C. An in vivo study was also conducted to determine whether perceptible stimuli are experienced by patients during this time of laser treatment and to verify results of the in vitro study. The results did not conform well with the in vitro study because of uncontrollable variables. None of the patients who received irradiation treatment described any perceptible stimuli.

Latest results on solarization of optical glasses with pulsed laser radiation

NASA Astrophysics Data System (ADS)

Jedamzik, Ralf; Petzold, Uwe

2017-02-01

Femtosecond lasers are more and more used for material processing and lithography. Femtosecond laser help to generate three dimensional structures in photoresists without using masks in micro lithography. This technology is of growing importance for the field of backend lithography or advanced packaging. Optical glasses used for beam shaping and inspection tools need to withstand high laser pulse energies. Femtosecond laser radiation in the near UV wavelength range generates solarization effects in optical glasses. In this paper results are shown of femtosecond laser solarization experiments on a broad range of optical glasses from SCHOTT. The measurements have been performed by the Laser Zentrum Hannover in Germany. The results and their impact are discussed in comparison to traditional HOK-4 and UVA-B solarization measurements of the same materials. The target is to provide material selection guidance to the optical designer of beam shaping lens systems.

EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Laser—ultrasonic formation of melts of high-speed tool steels

NASA Astrophysics Data System (ADS)

Gureev, D. M.

1994-09-01

A study was made of the influence of ultrasonic vibrations on the processes of heat and mass transfer, and of structure formation during ultrafast crystallisation of laser melts of T1 high-speed tool steel. Acoustic flows which appeared in laser melts effectively smoothed out the temperature inhomogeneities and flattened the relief of the molten surface even when the laser radiation acted for just ~1 ms. The transformation of the mechanical energy of ultrasonic vibrations into heat increased the depth of the laser melt baths and suppressed crack formation. The observed changes in the structural and phase composition appeared as a change in the microhardness of the solidified laser melts. The geometry of coupling of ultrasound into a laser melt influenced the changes in the microhardness, suggesting a need for a more detailed analysis of the structure formation processes in the course of ultrafast crystallisation of laser melts in an ultrasonic field.

Self-mixing detection of backscattered radiation in a single-mode erbium fibre laser for Doppler spectroscopy and velocity measurements

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

Dmitriev, A K; Konovalov, A N; Ul'yanov, V A

2014-04-28

We report an experimental study of the self-mixing effect in a single-mode multifrequency erbium fibre laser when radiation backscattered from an external moving object arrives at its cavity. To eliminate resulting chaotic pulsations in the laser, we have proposed a technique for suppressing backscattered radiation through the use of multimode fibre for radiation delivery. The multifrequency operation of the laser has been shown to lead to strong fluctuations of the amplitude of the Doppler signal and a nonmonotonic variation of the amplitude with distance to the scattering object. In spite of these features, the self-mixing signal was detected with amore » high signal-to-noise ratio (above 10{sup 2}) when the radiation was scattered by a rotating disc, and the Doppler frequency shift, evaluated as the centroid of its spectrum, had high stability (0.15%) and linearity relative to the rotation rate. We conclude that the self-mixing effect in this type of fibre laser can be used for measuring the velocity of scattering objects and in Doppler spectroscopy for monitoring the laser evaporation of materials and biological tissues. (control of laser radiation parameters)« less

Behavioral reactions in rats exposed to low-energy laser radiation

NASA Astrophysics Data System (ADS)

Sieron, Aleksander; Mrowiec, Janina; Plech, Andrzej; Cieslar, Grzegorz; Biniszkiewicz, Tomasz

1995-03-01

The effect on their behavior of chronic exposure to infrared laser radiation applied to the skull of rats was evaluated. The experiment was carried out on 20 Wistar white male rats. A semiconductive infrared laser (wavelength -- 904 nm, frequency -- 100 Hz, pulse duration -- 10 ns, mean power 10 mW, energy density 1.5 J/cm2) was used. A skull fornix of rats was irradiated with use of multidiode probe, 10 minutes daily for 14 consecutive days. A locomotor activity was determined in the `open field' test. Simultaneously, an exploratory activity was examined in the `hole' test. Space memory was determined by means of a water maze test. Afterwards, an irritability was investigated by means of the score of Nakamura and Thoenen. The evaluation of behavior was made 24 hours after a single irradiation, at the 7th and 14th day of repeated everyday irradiation and then at the 7th and 14th day after the end of the cycle of irradiations. Obtained data show that low-energy laser radiation does not affect the rats central nervous system, resulting in persistent changes of behavior.

Blood absorption during 970 and 1470 nm laser radiation in vitro.

PubMed

Shaydakov, E; Ilyukhin, E; Rosukhovskiy, D

2015-10-01

Soon after introduction of water lasers in medical practice for EVLA, less power and energy line density have been used. However, there are no experimental grounds for different energy modes and there is no clear evidence for a difference in the effect of the two wavelengths dealt with in this study. The goal of this study was to evaluate the temperature profile of various laser action modes with testing devices. Three experimental testing devices consisted of cylinders filled with whole donor blood and a set of temperature sensors installed in different positions. We have determined the range of temperatures around the fiber tip of 970 and 1470 nm lasers. The average temperature of 970 nm laser at 1 mm distance along the axis from the fiber tip substantially differed from that of 1470 nm laser, power being equal. Statistically substantial differences were found in endovenous laser ablation simulation in vitro for the 970 nm and 1470 nm laser radiation. Similar temperatures can be reached with 970 nm lasers if power is increased.

LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Phase locking of the radiation of ring waveguide CO2 lasers

NASA Astrophysics Data System (ADS)

Glova, A. F.; Lebedev, E. A.; Lysikov, A. Yu; Shchetnikov, S. B.

1999-12-01

Phase locking of the radiation of two ring waveguide CO2 lasers with a common cavity and unidirectional lasing was achieved for an output power of about 20 W. Measurements of the fringe visibility of the radiation intensity distributions in the far-field zone agreed qualitatively with the calculations for plane waves.

Influence of MLS laser radiation on erythrocyte membrane fluidity and secondary structure of human serum albumin.

PubMed

Pasternak, Kamila; Nowacka, Olga; Wróbel, Dominika; Pieszyński, Ireneusz; Bryszewska, Maria; Kujawa, Jolanta

2014-03-01

The biostimulating activity of low level laser radiation of various wavelengths and energy doses is widely documented in the literature, but the mechanisms of the intracellular reactions involved are not precisely known. The aim of this paper is to evaluate the influence of low level laser radiation from an multiwave locked system (MLS) of two wavelengths (wavelength = 808 nm in continuous emission and 905 nm in pulsed emission) on the human erythrocyte membrane and on the secondary structure of human serum albumin (HSA). Human erythrocytes membranes and HSA were irradiated with laser light of low intensity with surface energy density ranging from 0.46 to 4.9 J cm(-2) and surface energy power density 195 mW cm(-2) (1,000 Hz) and 230 mW cm(-2) (2,000 Hz). Structural and functional changes in the erythrocyte membrane were characterized by its fluidity, while changes in the protein were monitored by its secondary structure. Dose-dependent changes in erythrocyte membrane fluidity were induced by near-infrared laser radiation. Slight changes in the secondary structure of HSA were also noted. MLS laser radiation influences the structure and function of the human erythrocyte membrane resulting in a change in fluidity.

Linear lesions in heart tissue using diffused laser radiation

NASA Astrophysics Data System (ADS)

Fried, Nathaniel M.; Lardo, Albert C.; Berger, Ronald D.; Calkins, Hugh; Halperin, Henry R.

2000-05-01

Transmural, continuous, and linear lesions may be necessary for successful catheter ablation of cardiac arrythmias such as atrial fibrillation. Laser ablation was studied as an alternative to radiofrequency ablation, which is noted to produce superficial and discontinuous lesions as well as tissue charring and vaporization. Samples of canine myocardium were placed in a saline bath and irradiated with an 1.06- micrometer Nd:YAG laser operated in either pulsed or continuous mode. For pulsed mode, the laser pulse duration was 10 s with 10 s cooling between pulses. Laser radiation was delivered radially through diffusing optical fiber tips oriented parallel to the endocardial surface. In CW mode, transmural (6-mm-deep), linear (16-mm-long), and continuous lesions were produced using a laser power of 30 W and an irradiation time of 180 s. Peak tissue temperatures measured 51 plus or minus 1 degree Celsius at the endocardial surface, 61 plus or minus 6 degrees Celsius in the mid-myocardium, and 55 plus or minus 6 degree Celsius at the epicardial surface. There was no evidence of tissue charring or vaporization. Pulsed laser irradiation produced comparable lesion depths to CW irradiation with more uniform heating of the subsurface myocardium, but at the expense of longer operation times. Further in vivo study of laser ablation is warranted for possible clinical applications.

Interaction of Repetitively Pulsed High Energy Laser Radiation With Matter

NASA Astrophysics Data System (ADS)

Hugenschmidt, Manfred

1986-10-01

The paper is concerned with laser target interaction processes involving new methods of improving the overall energy balance. As expected theoretically, this can be achieved with high repetition rate pulsed lasers even for initially highly reflecting materials, such as metals. Experiments were performed by using a pulsed CO2 laser at mean powers up to 2 kW and repetition rates up to 100 Hz. The rates of temperature rise of aluminium for example were thereby increased by lore than a factor of 3 as compared to cw-radiation of comparable power density. Similar improvements were found for the overall absorptivities that were increased by this method by more than an order of magnitude.

Removal of dust particles from metal mirror surfaces by excimer laser radiation

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

Mann, K.; Wolff-Rottke, B.; Mueller, F.

1995-12-31

The effect of particle desorption from Al mirror surfaces by the influence of pulsed UV laser radiation has been studied. The investigations are closely related to the demands of astronomers, who are looking for a more effective way of cleaning the Al coatings of future very large telescope (VLT) mirrors. A systematic parameter study has been performed in order to determine the irradiation conditions which yield the highest dust removal efficiency (i.e. reflectivity increase) on contaminated samples, taking particularly into account laser induced damage and degradation effects of coating and substrate. The particle removal rate increases with increasing laser fluence,more » being limited however by the damage threshold of the coating. Therefore, parameters influencing the damage threshold of metal coatings like wavelength, pulse width and number of pulses have been studied in detail. Data indicate that on Al coated BK7 and Zerodur samples KrF laser radiation yields the optimum result, with cleaning efficiencies comparable to polymer film stripping. The initial reflectivity of the clean coating can nearly be reinstalled, in particular when an additional solvent film on the sample surface is applied. Hence, laser desorption seems to be a viable method of cleaning large Al mirrors for telescopes.« less

Characterization of Tin/Ethylene Glycol Solar Nanofluids Synthesized by Femtosecond Laser Radiation.

PubMed

Torres-Mendieta, Rafael; Mondragón, Rosa; Puerto-Belda, Verónica; Mendoza-Yero, Omel; Lancis, Jesús; Juliá, J Enrique; Mínguez-Vega, Gladys

2017-05-05

Solar energy is available over wide geographical areas and its harnessing is becoming an essential tool to satisfy the ever-increasing demand for energy with minimal environmental impact. Solar nanofluids are a novel solar receiver concept for efficient harvesting of solar radiation based on volumetric absorption of directly irradiated nanoparticles in a heat transfer fluid. Herein, the fabrication of a solar nanofluid by pulsed laser ablation in liquids was explored. This study was conducted with the ablation of bulk tin immersed in ethylene glycol with a femtosecond laser. Laser irradiation promotes the formation of tin nanoparticles that are collected in the ethylene glycol as colloids, creating the solar nanofluid. The ability to trap incoming electromagnetic radiation, thermal conductivity, and the stability of the solar nanofluid in comparison with conventional synthesis methods is enhanced. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Attenuation of laser radiation by the flame of burning hydrocarbons and efficiency of remote cutting of metals

NASA Astrophysics Data System (ADS)

Gvozdev, S. V.; Glova, A. F.; Dubrovskii, V. Yu; Durmanov, S. T.; Krasyukov, A. G.; Lysikov, A. Yu; Smirnov, G. V.; Pleshkov, V. M.

2017-12-01

Mobile laser technological complex MLTC-20 with radiation power 20 kW and radiation wavelength 1.07 μm created in SRC RF TRINITI on the base of a three cw fiber Yb lasers is used successfully at remote cutting of the metalworks at carrying out of the emergency-reduction works on the out of control gas wells. In this work the results of the investigation of the possibility and the efficiency of laser radiation application for remote cutting of metals on the emergency oil wells have been presented. Measurements of the mean absorption coefficient of the radiation of a cw fiber Yb laser under its propagation in a flame of burning oil in dependence on radiation intensity have been carried out. It was shown that at the intensity ~104 W/cm2 the absorption coefficient traverses the maximum where its value is equal to ~0.1 cm-1, and at the intensity increasing to the values 105 - 106 W/cm2 it stabilizes on a small level ~5·10-3 - 10-2 cm-1. It is established that the maximal velocity and the efficiency of remote cutting of the steel plates with a thickness up to 10 mm by the radiation with the intensity 106 W/cm2 exceed these factors at the intensity 104 W/cm2. The possibility of the efficient remote cutting of steel plate with a thickness of 60 mm by laser radiation having the power 7.5 kW and the intensity 105 W/cm2 has been demonstrated.

Analytical model for electromagnetic radiation from a wakefield excited by intense short laser pulses in an unmagnetized plasma

NASA Astrophysics Data System (ADS)

Chen, Zi-Yu; Chen, Shi; Dan, Jia-Kun; Li, Jian-Feng; Peng, Qi-Xian

2011-10-01

A simple one-dimensional analytical model for electromagnetic emission from an unmagnetized wakefield excited by an intense short-pulse laser in the nonlinear regime has been developed in this paper. The expressions for the spectral and angular distributions of the radiation have been derived. The model suggests that the origin of the radiation can be attributed to the violent sudden acceleration of plasma electrons experiencing the accelerating potential of the laser wakefield. The radiation process could help to provide a qualitative interpretation of existing experimental results, and offers useful information for future laser wakefield experiments.

High-energy coherent terahertz radiation emitted by wide-angle electron beams from a laser-wakefield accelerator

NASA Astrophysics Data System (ADS)

Yang, Xue; Brunetti, Enrico; Jaroszynski, Dino A.

2018-04-01

High-charge electron beams produced by laser-wakefield accelerators are potentially novel, scalable sources of high-power terahertz radiation suitable for applications requiring high-intensity fields. When an intense laser pulse propagates in underdense plasma, it can generate femtosecond duration, self-injected picocoulomb electron bunches that accelerate on-axis to energies from 10s of MeV to several GeV, depending on laser intensity and plasma density. The process leading to the formation of the accelerating structure also generates non-injected, sub-picosecond duration, 1–2 MeV nanocoulomb electron beams emitted obliquely into a hollow cone around the laser propagation axis. These wide-angle beams are stable and depend weakly on laser and plasma parameters. Here we perform simulations to characterise the coherent transition radiation emitted by these beams if passed through a thin metal foil, or directly at the plasma–vacuum interface, showing that coherent terahertz radiation with 10s μJ to mJ-level energy can be produced with an optical to terahertz conversion efficiency up to 10‑4–10‑3.

Efficient injection of radiation-pressure-accelerated sub-relativistic protons into laser wakefield acceleration based on 10 PW lasers

NASA Astrophysics Data System (ADS)

Liu, M.; Weng, S. M.; Wang, H. C.; Chen, M.; Zhao, Q.; Sheng, Z. M.; He, M. Q.; Li, Y. T.; Zhang, J.

2018-06-01

We propose a hybrid laser-driven ion acceleration scheme using a combination target of a solid foil and a density-tailored background plasma. In the first stage, a sub-relativistic proton beam can be generated by radiation pressure acceleration in intense laser interaction with the solid foil. In the second stage, this sub-relativistic proton beam is further accelerated by the laser wakefield driven by the same laser pulse in a near-critical-density background plasma with decreasing density profile. The propagating velocity of the laser front and the phase velocity of the excited wakefield wave are effectively lowered at the beginning of the second stage. By decreasing the background plasma density gradually from near critical density along the laser propagation direction, the wake travels faster and faster, while it accelerates the protons. Consequently, the dephasing between the protons and the wake is postponed and an efficient wakefield proton acceleration is achieved. This hybrid laser-driven proton acceleration scheme can be realized by using ultrashort laser pulses at the peak power of 10 PW for the generation of multi-GeV proton beams.

Intense Nanosecond-Pulsed Cavity-Dumped Laser Radiation at 1.04 THz

NASA Astrophysics Data System (ADS)

Wilson, Thomas

2013-03-01

We report first results of intense far-infrared (FIR) nanosecond-pulsed laser radiation at 1.04 THz from a previously described[2] cavity-dumped, optically-pumped molecular gas laser. The gain medium, methyl fluoride, is pumped by the 9R20 line of a TEA CO2 laser[3] with a pulse energy of 200 mJ. The THz laser pulses contain of 30 kW peak power in 5 nanosecond pulse widths at a pulse repetition rate of 10 Hz. The line width, measured by a scanning metal-mesh FIR Fabry-Perot interferometer, is 100 MHz. The novel THz laser is being used in experiments to resonantly excite coherent ns-pulsed 1.04 THz longitudinal acoustic phonons in silicon doping-superlattices. The research is supported by NASA EPSCoR NNX11AM04A and AFOSR FA9550-12-1-0100 awards.

Low-level laser therapy induces an upregulation of collagen gene expression during the initial process of bone healing: a microarray analysis

NASA Astrophysics Data System (ADS)

Tim, Carla Roberta; Bossini, Paulo Sérgio; Kido, Hueliton Wilian; Malavazi, Iran; von Zeska Kress, Marcia Regina; Carazzolle, Marcelo Falsarella; Rennó, Ana Cláudia; Parizotto, Nivaldo Antonio

2016-08-01

This study investigates the histological modifications produced by low level laser therapy (LLLT) on the first day of bone repair, as well as evaluates the LLLT effects on collagen expression on the site of a fracture. Twenty Wistar rats were distributed into a control group (CG) and a laser group (LG). Laser irradiation of Ga-Al-As laser 830 nm, 30 mW, 94 s, 2.8 J was performed in five sessions. Animals were euthanized on day 5 postsurgery. Histopathological analysis showed that LLLT was able to increase deposition of granulation tissue and newly formed bone at the site of the injury. In addition, picrosirius analysis showed that collagen fiber organization in the LG was enhanced compared to CG. Microarray analysis demonstrated that LLLT produced an upregulation type I collagen (COL-I). Immunohistochemical analysis revealed that the subjects that were treated presented a higher immunoexpression of COL-I. Our findings indicated that LLLT improves bone healing by producing a significant increase in the expression of collagen genes.

Energy exchange between a laser beam and charged particles using inverse transition radiation and method for its use

DOEpatents

Kimura, Wayne D.; Romea, Richard D.; Steinhauer, Loren C.

1998-01-01

A method and apparatus for exchanging energy between relativistic charged particles and laser radiation using inverse diffraction radiation or inverse transition radiation. The beam of laser light is directed onto a particle beam by means of two optical elements which have apertures or foils through which the particle beam passes. The two apertures or foils are spaced by a predetermined distance of separation and the angle of interaction between the laser beam and the particle beam is set at a specific angle. The separation and angle are a function of the wavelength of the laser light and the relativistic energy of the particle beam. In a diffraction embodiment, the interaction between the laser and particle beams is determined by the diffraction effect due to the apertures in the optical elements. In a transition embodiment, the interaction between the laser and particle beams is determined by the transition effect due to pieces of foil placed in the particle beam path.

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

NASA Astrophysics Data System (ADS)

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

1999-06-01

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

Formation of short high-power laser radiation pulses in excimer mediums

NASA Astrophysics Data System (ADS)

Losev, V. F., Sr.; Ivanov, N. G.; Panchenko, Yu. N.

2007-06-01

Presently an excimer mediums continue are examined as one of variants for formation of powerful and over powerful pulses of laser radiation with duration from units of nanosecond up to tens femtosecond. The researches on such powerful installations as "NIKE" (USA) and << SUPER ASHURA >>, Japan) proceed in this direction. The main advantage of excimer mediums is the opportunity to work in a frequency mode, absence of restriction on the size of active area, high uniformity of a gas working medium, high efficiency (up to 10 %) and wide spectral range of laser radiation (KrF, XeCl ~ 2nm, XeF (C-A), Xe IICl ~ 50-100 nanometers). Research in area of high quality laser beams formation in excimer mediums and its amplification in high power amplifiers are carried out the long time in Institute of High Current Electronics SB RAS, Tomsk, Russia. The wide aperture XeCl laser system of MELS-4k is used for these investigations. Last time we take part in program on development of high power excimer laser system with a petawatt level of power. This system supposes the formation and amplification high quality laser beams with different pulse duration from units of nanosecond up to tens femtosecond. We research the possibility of laser beams formation in excimer mediums with ps-ns pulse duration having the low noise and divergence near to diffraction limit. In other hand, we are developing the wide aperture XeF(C-A) amplifier with optical pump on base electron accelerator. According to our estimations of the XeF(C-A) amplifier based on the converter of e-beam energy to the Xe II* fluorescence at 172 nm will allow to obtain up to 100 TW peak power in a 30 fs pulse.

A comparative evaluation to assess the efficacy of 5% sodium fluoride varnish and diode laser and their combined application in the treatment of dentin hypersensitivity

PubMed Central

Suri, Isha; Singh, Poonam; Shakir, Quaid Johar; Shetty, Arvind; Bapat, Ranjeet; Thakur, Roshani

2016-01-01

Background: Dentin hypersensitivity (DH) is an age old complaint with a great number of treatment modalities, but none of these are totally effective till date. Lasers being one of the latest treatment options in periodontics, a study was conducted to test the efficacy of diode laser (DL) in DH alone and in comparison with 5% sodium fluoride (NaF) varnish. Aim: The aim of the present study was to compare the effectiveness of 5% topical NaF varnish and 980 nm gallium aluminum arsenide (GaAlAs) DL alone and combination of 5% NaF + 980 nm GaAlAs DL in the management of DH. Materials and Methods: The study was conducted on 120 teeth in thirty patients with DH assessed by tactile and air blast (AB) stimuli measured by visual analog scale (VAS). Teeth were randomly divided into Group 1 (P) placebo-treated control group, Group 2 (NaF) treated by 5% NaF varnish, Group 3 (DL) treated with 980 nm DL, and Group 4 (NaF + DL) treated with both 5% NaF varnish and 980 nm DL (combination group). Results: There was a significant reduction in DH. The VAS reduction percentages were calculated, and there was a significant decrease in DH above all in G4 (NaF + DL) than G3 (DL) and G2 (NaF). Conclusion: Even though all the three groups (2, 3, and 4) showed improvement in terms of DH reduction, 5% NaF varnish with DL showed the best results among all the groups. PMID:27563205

Formation and dynamics of a plasma in superstrong laser fields including radiative and quantum electrodynamics effects

NASA Astrophysics Data System (ADS)

Artemenko, I. I.; Golovanov, A. A.; Kostyukov, I. Yu.; Kukushkina, T. M.; Lebedev, V. S.; Nerush, E. N.; Samsonov, A. S.; Serebryakov, D. A.

2016-12-01

Studies of phenomena accompanying the interaction of superstrong electromagnetic fields with matter, in particular, the generation of an electron-positron plasma, acceleration of electrons and ions, and the generation of hard electromagnetic radiation are briefly reviewed. The possibility of using thin films to initiate quantum electrodynamics cascades in the field of converging laser pulses is analyzed. A model is developed to describe the formation of a plasma cavity behind a laser pulse in the transversely inhomogeneous plasma and the generation of betatron radiation by electrons accelerated in this cavity. Features of the generation of gamma radiation, as well as the effect of quantum electrodynamics effects on the acceleration of ions, at the interaction of intense laser pulses with solid targets are studied.

New approaches in clinical application of laser-driven ionizing radiation

NASA Astrophysics Data System (ADS)

Hideghéty, Katalin; Szabó, Rita Emilia; Polanek, Róbert; Szabó, Zoltán.; Brunner, Szilvia; Tőkés, Tünde

2017-05-01

The planned laser-driven ionizing beams (photon, very high energy electron, proton, carbon ion) at laser facilities have the unique property of ultra-high dose rate (>Gy/s-10), short pulses, and at ELI-ALPS high repetition rate, carry the potential to develop novel laser-driven methods towards compact hospital-based clinical application. The enhanced flexibility in particle and energy selection, the high spatial and time resolution and extreme dose rate could be highly beneficial in radiotherapy. These approaches may increase significantly the therapeutic index over the currently available advanced radiation oncology methods. We highlight two nuclear reactionbased binary modalities and the planned radiobiology research. Boron Neutron Capture Therapy is an advanced cell targeted modality requiring 10B enriched boron carrier and appropriate neutron beam. The development of laser-based thermal and epithermal neutron source with as high as 1010 fluence rate could enhance the research activity in this promising field. Boron-Proton Fusion reaction is as well as a binary approach, where 11B containing compounds are accumulated into the cells, and the tumour selectively irradiated with protons. Due to additional high linear energy transfer alpha particle release of the BPFR and the maximum point of the Bragg-peak is increased, which result in significant biological effect enhancement. Research at ELI-ALPS on detection of biological effect differences of modified or different quality radiation will be presented using recently developed zebrafish embryo and rodent models.

Radiation from particles moving in small-scale magnetic fields created in solid-density laser-plasma laboratory experiments

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

Keenan, Brett D., E-mail: bdkeenan@ku.edu; Medvedev, Mikhail V.

2015-11-15

Plasmas created by high-intensity lasers are often subject to the formation of kinetic-streaming instabilities, such as the Weibel instability, which lead to the spontaneous generation of high-amplitude, tangled magnetic fields. These fields typically exist on small spatial scales, i.e., “sub-Larmor scales.” Radiation from charged particles moving through small-scale electromagnetic (EM) turbulence has spectral characteristics distinct from both synchrotron and cyclotron radiation, and it carries valuable information on the statistical properties of the EM field structure and evolution. Consequently, this radiation from laser-produced plasmas may offer insight into the underlying electromagnetic turbulence. Here, we investigate the prospects for, and demonstrate themore » feasibility of, such direct radiative diagnostics for mildly relativistic, solid-density laser plasmas produced in lab experiments.« less

Three dimensional radiation fields in free electron lasers using Lienard-Wiechert fields

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

Elias, L.R.; Gallardo, J.

1981-10-28

In a free electron laser a relativistic electron beam is bunched under the action of the ponderomotive potential and is forced to radiate in close phase with the input wave. Until recently, most theories of the FEL have dealt solely with electron beams of infinite transverse dimension radiating only one-dimensional E.M. waves (plane waves). Although these theories describe accurately the dynamics of the electrons during the FEL interaction process, neither the three dimensional nature of the radiated fields nor its non-monochromatic features can be properly studied by them. As a result of this, very important practical issues such as themore » gain per gaussian-spherical optical mode in a free electron laser have not been well addressed, except through a one dimensional field model in which a filling factor describes crudely the coupling of the FEL induced field to the input field.« less

High-power laser radiation in atmospheric aerosols: Nonlinear optics of aerodispersed media

NASA Astrophysics Data System (ADS)

Zuev, V. E.; Zemlianov, A. A.; Kopytin, Iu. D.; Kuzikovskii, A. V.

The bulk of this book contains the results of investigations carried out at the Institute of Atmospheric Optics, Siberian Branch, USSR Academy of Science with the participation of the authors. The microphysical and optical characteristics of atmospheric aerosols are considered, taking into account light scattering by a single aerosol particle, light scattering by a system of particles, the scattering phase matrix, light scattering by clouds and fogs, light scattering by hazes, and scattering phase functions of polydispersed aerosols. Other topics studies are related to low-energy (subexplosive) effects of radiation on individual particles, the formation of clear zones in clouds and fogs due to the vaporization of droplets under regular regimes, self-action of a wave beam in a water aerosol under conditions of regular droplet vaporization, laser beam propagation through an explosively evaporating water-droplet aerosol, the propagation of high-power laser radiation through hazes, the ionization and optical breakdown in aerosol media, and laser monitoring of a turbid atmosphere using nonlinear effects.

Dependence of injection locking of a TEA CO2 laser on intensity of injected radiation

NASA Technical Reports Server (NTRS)

Oppenheim, U. P.; Menzies, R. T.; Kavaya, M. J.

1982-01-01

The results of an experimental study to determine the minimum required injected power to control the output frequency of a TEA CO2 laser are reported. A CW CO2 waveguide laser was used as the injection oscillator. Both the power and the frequency of the injected radiation were varied, while the TEA resonator cavity length was adjusted to match the frequency of the injected signal. Single-longitudinal mode (SLM) TEA laser radiation was produced for injected power levels which are several orders of magnitude below those previously reported. The ratio of SLM output power to injection power exceeded 10 to the 12th at the lowest levels of injected intensity.

Description of high-power laser radiation in the paraxial approximation

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

Milant'ev, V P; Karnilovich, S P; Shaar, Ya N

2015-11-30

We consider the feasibility of an adequate description of a laser pulse of arbitrary shape within the framework of the paraxial approximation. In this approximation, using a parabolic equation and an expansion in the small parameter, expressions are obtained for the field of a sufficiently intense laser radiation given in the form of axially symmetric Hermite – Gaussian beams of arbitrary mode and arbitrary polarisation. It is shown that in the case of sufficiently short pulses, corrections to the transverse components of the laser field are the first-order rather than the secondorder quantities in the expansion in the small parameter.more » The peculiarities of the description of higher-mode Hermite – Gaussian beams are outlined. (light wave transformation)« less

Gold-coated copper cone detector as a new standard detector for F2 laser radiation at 157 nm.

PubMed

Kück, Stefan; Brandt, Friedhelm; Taddeo, Mario

2005-04-20

A new standard detector for high-accuracy measurements of F2 laser radiation at 157 nm is presented. This gold-coated copper cone detector permits the measurement of average powers up to 2 W with an uncertainty of approximately 1%. To the best of our knowledge, this is the first highly accurate standard detector for F2 laser radiation for this power level. It is fully characterized according to Guide to the Expression of Uncertainty in Measurement of the International Organization for Standardization and is connected to the calibration chain for laser radiation established by the German National Metrology Institute.

X-ray laser system, x-ray laser and method

DOEpatents

London, Richard A.; Rosen, Mordecai D.; Strauss, Moshe

1992-01-01

Disclosed is an x-ray laser system comprising a laser containing generating means for emitting short wave length radiation, and means external to said laser for energizing said generating means, wherein when the laser is in an operative mode emitting radiation, the radiation has a transverse coherence length to width ratio of from about 0.05 to 1. Also disclosed is a method of adjusting the parameters of the laser to achieve the desired coherence length to laser width ratio.

Undulator radiation from laser-plasma-accelerated electron beams

NASA Astrophysics Data System (ADS)

Shaw, B.; van Tilborg, J.; Gonsalves, A.; Nakamura, K.; Sokollik, T.; Shiraishi, S.; Mittal, R.; Esarey, E.; Schroeder, C.; Toth, C.; Leemans, W. P.

2012-12-01

Recent experiments coupled electron beams from the LOASIS TREX laser plasma accelerator (LPA) [1, 2, 3] to the Tapered Hybrid Undulator (THUNDER). Using the 1.5m, 66 period undulator, followed by an XUV spectrometer, spontaneous radiation was observed at photon energies extending to 100 eV. Previous experiments have reported visible [4] and soft-x-ray [5] radiation. The purpose of our experiments is to do highly precise, single shot diagnostics of the energy spread and emittance for each electron beam. We present recent results including measurements of electron beam transport through the undulator with and without the use of permanent magnetic quadrapoles, and measurements of XUV spectra up to 100 eV from LPA produced e-beams.

Waveform-controlled terahertz radiation from the air filament produced by few-cycle laser pulses.

PubMed

Bai, Ya; Song, Liwei; Xu, Rongjie; Li, Chuang; Liu, Peng; Zeng, Zhinan; Zhang, Zongxin; Lu, Haihe; Li, Ruxin; Xu, Zhizhan

2012-06-22

Waveform-controlled terahertz (THz) radiation is of great importance due to its potential application in THz sensing and coherent control of quantum systems. We demonstrated a novel scheme to generate waveform-controlled THz radiation from air plasma produced when carrier-envelope-phase (CEP) stabilized few-cycle laser pulses undergo filamentation in ambient air. We launched CEP-stabilized 10 fs-long (~1.7 optical cycles) laser pulses at 1.8 μm into air and found that the generated THz waveform can be controlled by varying the filament length and the CEP of driving laser pulses. Calculations using the photocurrent model and including the propagation effects well reproduce the experimental results, and the origins of various phase shifts in the filament are elucidated.

Stimulated Brillouin scattering of laser radiation in a compensated magnetoactive semiconductor

NASA Astrophysics Data System (ADS)

Ferdous, T.; Salahuddin, M.; Amin, M. R.; Salimullah, M.

1995-09-01

In the present paper we have studied the stimulated Brillouin scattering of laser radiation in a compensated magnetoactive semiconductor. The nonlinearity in the low-frequency ion-acoustic wave arises through the ponderomotive force on both electrons and holes. The high-frequency nonlinearity arises through the nonlinear current density. For typical plasma parameters in compensated Ge, ɛL=16, T0=77 K, n00=1017 cm-3, Bs=60 kG, θ=30°, laser power density corresponding to a CO2 laser ~=0.1 MW cm-2, the growth rate of the low-frequency ion-acoustic wave turns out to be ~=107 rad sec-1.

Absorption of the laser radiation by the laser plasma with gas microjet targets

NASA Astrophysics Data System (ADS)

Borisevichus, D. A.; Zabrodskii, V. V.; Kalmykov, S. G.; Sasin, M. E.; Seisyan, R. P.

2017-01-01

An upper limit of absorption of the laser radiation in the plasma produced in a gas jet Xe target with the average density of (3-6) × 1018 cm-3 and the effective diameter of 0.7 mm is found. It is equal to ≈50% and remains constant under any variation in this range of densities. This result contradicts both theoretical assessments that have predicted virtually complete absorption and results of earlier experiments with the laser spark in an unlimited stationary Xe gas with the same density, where the upper limit of absorption was close to 100%. An analysis shows that nonlinearity of absorption and plasma nonequilibrium lead to the reduction of the absorption coefficient that, along with the limited size of plasma, can explain the experimental results.

Numerical simulation of a soft-x-ray Li laser pumped with synchrotron radiation

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

Rozsnyai, B.; Watanabe, H.; Csonka, P.L.

1985-07-01

Results of a computer simulation are reported for a lithium soft-x-ray laser pumped by synchro- tron radiation. Coherent stimulated emission of the photons of interest occurs in Li II 1s2p..-->..Li II 1s/sup 2/ transitions. Calculated results include the dominant ion and photon densities and the laser gain.

Peculiarities of the statistics of spectrally selected fluorescence radiation in laser-pumped dye-doped random media

NASA Astrophysics Data System (ADS)

Yuvchenko, S. A.; Ushakova, E. V.; Pavlova, M. V.; Alonova, M. V.; Zimnyakov, D. A.

2018-04-01

We consider the practical realization of a new optical probe method of the random media which is defined as the reference-free path length interferometry with the intensity moments analysis. A peculiarity in the statistics of the spectrally selected fluorescence radiation in laser-pumped dye-doped random medium is discussed. Previously established correlations between the second- and the third-order moments of the intensity fluctuations in the random interference patterns, the coherence function of the probe radiation, and the path difference probability density for the interfering partial waves in the medium are confirmed. The correlations were verified using the statistical analysis of the spectrally selected fluorescence radiation emitted by a laser-pumped dye-doped random medium. Water solution of Rhodamine 6G was applied as the doping fluorescent agent for the ensembles of the densely packed silica grains, which were pumped by the 532 nm radiation of a solid state laser. The spectrum of the mean path length for a random medium was reconstructed.

Increase in the nitric oxide release without changes in cell viability of macrophages after laser therapy with 660 and 808 nm lasers.

PubMed

Silva, Igor Henrique Morais; de Andrade, Samantha Cardoso; de Faria, Andreza Barkokebas Santos; Fonsêca, Deborah Daniela Diniz; Gueiros, Luiz Alcino Monteiro; Carvalho, Alessandra Albuquerque Tavares; da Silva, Wylla Tatiana Ferreira; de Castro, Raul Manhães; Leão, Jair Carneiro

2016-12-01

The aim of this study was to evaluate the influence of low-level laser therapy (LLLT) with different parameters and wavelengths on nitric oxide (NO) release and cell viability. Irradiation was performed with Ga-Al-As laser, continuous mode and wavelengths of 660 and 808 nm at different energy and power densities. For each wavelength, powers of 30, 50, and 100 mW and times of 10, 30, and 60 s were used. NO release was measured using Griess reaction, and cell viability was evaluated by mitochondrial reduction of bromide 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) to formazan. LLLT promoted statistically significant changes in NO release and MTT value only at the wavelength of 660 nm (p < 0.05). LLLT also promoted an increase in the NO release and cell viability when the energy densities 64 (p = 0.04) and 214 J/cm 2 (p = 0.012), respectively, were used. LLLT has a significant impact on NO release without affecting cell viability, but the significance of these findings in the inflammatory response needs to be further studied.

The optical effect of a semiconductor laser on protecting wheat from UV-B radiation damage.

PubMed

Qiu, Zong-Bo; Zhu, Xin-Jun; Li, Fang-Min; Liu, Xiao; Yue, Ming

2007-07-01

Lasers have been widely used in the field of biology along with the development of laser technology, but the mechanism of the bio-effect of lasers is not explicit. The objective of this paper was to test the optical effect of a laser on protecting wheat from UV-B damage. A patent instrument was employed to emit semiconductor laser (wavelength 650 nm) and incoherent red light, which was transformed from the semiconductor laser. The wavelength, power and lightfleck diameter of the incoherent red light are the same as those of the semiconductor laser. The semiconductor laser (wavelength 650 nm, power density 3.97 mW mm(-2)) and incoherent red light (wavelength 650 nm, power density 3.97 mW mm(-2)) directly irradiated the embryo of wheat seeds for 3 min respectively, and when the seedlings were 12-day-old they were irradiated by UV-B radiation (10.08 kJ m(-2)) for 12 h in the dark. Changes in the concentration of malondialdehyde (MDA), hydrogen peroxide (H(2)O(2)), glutathione (GSH), ascorbate (AsA), carotenoids (CAR), the production rate of superoxide radical (O(2)(-)), the activities of peroxidase (POD), catalase (CAT), superoxide dismutase (SOD) and the growth parameters of seedlings (plant height, leaf area and fresh weight) were measured to test the optical effect of the laser. The results showed that the incoherent red light treatment could not enhance the activities of SOD, POD and CAT and the concentration of AsA and CAR. When the plant cells were irradiated by UV-B, the incoherent red light treatment could not eliminate active oxygen and prevent lipid peroxidation in wheat. The results also clearly demonstrate that the plant DNA was damaged by UV-B radiation and semiconductor laser irradiance had the capability to protect plants from UV-B-induced DNA damage, while the incoherent red light could not. This is the first investigation reporting the optical effect of a semiconductor laser on protecting wheat from UV-B radiation damage.

Simulation study of enhancing laser-driven multi-keV line-radiation through application of external magnetic fields

NASA Astrophysics Data System (ADS)

Kemp, G. Elijah; Colvin, J. D.; Fournier, K. B.; May, M. J.; Barrios, M. A.; Patel, M. V.; Koning, J. M.; Scott, H. A.; Marinak, M. M.

2015-11-01

Laser-driven, spectrally tailored, high-flux x-ray sources have been developed over the past decade for testing the radiation hardness of materials used in various civilian, space and military applications. The optimal electron temperatures for these x-ray sources occur around twice the desired photon energy. At the National Ignition Facility (NIF) laser, the available energy can produce plasmas with ~ 10keV electron temperatures which result in highly-efficient ~ 5keV radiation but less than optimal emission from the > 10keV sources. In this work, we present a possible venue for enhancing multi-keV x-ray emission on existing laser platforms through the application of an external magnetic field. Preliminary radiation-hydrodynamics calculations with Hydra suggest as much as 2 - 14 × increases in laser-to-x-ray conversion efficiency for 22 - 68keV K-shell sources are possible on the NIF laser - without any changes in laser-drive conditions - through the application of an external axial 50 T field. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract No. DE-AC52-07NA27344.

X-ray radiation from nonlinear Thomson scattering of an intense femtosecond laser on relativistic electrons in a helium plasma.

PubMed

Ta Phuoc, K; Rousse, A; Pittman, M; Rousseau, J P; Malka, V; Fritzler, S; Umstadter, D; Hulin, D

2003-11-07

We have generated x-ray radiation from the nonlinear Thomson scattering of a 30 fs/1.5 J laser beam on plasma electrons. A collimated x-ray radiation with a broad continuous spectrum peaked at 0.15 keV with a significant tail up to 2 keV has been observed. These characteristics are found to depend strongly on the laser strength parameter a(0). This radiative process is dominant for a(0) greater than unity at which point the relativistic scattering of the laser light originates from MeV energy electrons inside the plasma.

Endocavitary Ir-192 radiation and laser treatment for palliation of obstructive rectal cancer.

PubMed

Mischinger, H J; Hauser, H; Cerwenka, H; Stücklschweiger, G; Geyer, E; Schweiger, W; Rosanelli, G; Kohek, P H; Werkgartner, G; Hackl, A

1997-10-01

Endoscopic laser therapy (ELT) either alone or combined with endocavitary Ir-192 radiation is performed for advanced, inoperable rectal cancer and when patients are ineligible for surgery due to severe concomitant medical illness. During the period from January 1984 to January 1997 we treated 81 patients (51 males, 30 females). Sixty-seven patients had ELT only using a ND-Yag Laser system. Twenty-five patients (average age: 80.5 years) were ineligible for surgery (Group I). Forty-two patients (74.1 years) had an advanced locally inoperable tumour (Group II). Fourteen patients (76.5 years) underwent a combined therapeutic regime with endocavitary Ir-192 afterloading following ELT (Group III). Adequate desobliteration was achieved in 100% (groups I and III) and 97% (group II) of the patients. The average interval to aftertreatment was 8.4 weeks in group I and 9.4 weeks in group II, compared to 11.5 weeks in group III. Serious complications (perianal abscess, rectovaginal fistula) occurred in 3.7%, minor complications (laser-induced bleedings, unclear fever) in 12.3%. All laser-induced bleedings could be dealt with using laser therapy. The frequency of treatment was governed by tumour mass and the patient's survival. The results suggest that additional endocavitary radiation significantly prolongs the maintenance of normal bowel function compared with laser therapy alone.

INTERACTION OF LASER RADIATION WITH MATTER: Calculation of the kinetics of heating and structural changes in the cartilaginous tissue under the action of laser radiation

NASA Astrophysics Data System (ADS)

Sobol', E. N.; Kitai, M. S.

1998-07-01

A theoretical model is developed for the calculation of the temperature fields and determination of the size of a zone with structural changes in the cartilaginous tissue. The model is based on a simultaneous analysis of the heat and mass transfer processes and it takes into account the bulk absorption of laser radiation by the tissue, surface evaporation of water, and temperature dependences of the diffusion coefficients. It is assumed that under the influence of a phase transition between free and bound water, caused by heating of the cartilage to 70°C, the proteoglycans of the cartilage matrix become mobile and, as a result of such mass transfer, structural changes are induced in the cartilaginous tissue causing relaxation of stresses or denaturation. It is shown that the maximum temperature is then reached not on the irradiated surface but at some distance from it, and that the size of the zones of structural changes (denaturation depth) depends strongly on the energy density of the laser radiation and its wavelength, on the duration of the irradiation, and on the cartilage thickness. This model makes it possible to calculate the temperature fields and the depth of structural changes in laser-induced relaxation of stresses and changes in the shape of the cartilaginous tissue.

Eczematous Dermatitis Occurring on a Café-au-Lait Spot Long after Laser Radiation.

PubMed

Mihara, Motoyuki

2013-05-01

A 40-year-old woman presented with an itchy erythematosquamous change of a café-au-lait spot in her face. The onset of this change occurred just after her relocation. The café-au-lait spot had been irradiated by laser approximately 20 years ago. Clinically, there was a coin-sized erythema with a slight scale on the pigmented lesion in the left lateral orbital region. Histopathologically, the lesion demonstrated both spongiotic dermatitis and interface dermatitis together with lymphohistiocytic cell infiltration, in addition to moderate acanthosis and elongation of rete ridges with slight basal hyperpigmentation. From these clinical and histopathological findings, the lesion was diagnosed as eczematous dermatitis occurring on the café-au-lait spot after laser radiation. Another interesting histopathological finding was that some parts of a lobule of the sebaceous gland were occupied exclusively by degenerative atrophic sebocytes. From the viewpoint of pathogenesis, the eczematous dermatitis of this patient could have been an accompanying feature of a neurogenic inflammation occurring on the café-au-lait spot after laser radiation, and the atrophic change of a part of the sebaceous lobule might have been induced by a morphogenetic alteration of certain germinative cells of the sebaceous lobule due to laser radiation.

Biophotonics of the interaction of low-intensity laser radiation with blood erythrocytes

NASA Astrophysics Data System (ADS)

Asimov, M. M.; Asimov, R. M.; Batyan, A. N.; Trusevich, M. O.; Rubinov, A. N.

2013-06-01

We have studied experimentally how optical radiation affects the neutralization of the toxic action of heavy metals and harmful chemical compounds (ecotoxicants) on the oxygen-transport function of blood erythrocytes. It has been found that the optical radiation has a stabilizing effect and prevents lowering the erythrocyte concentration in the presence of phenol and heavy metals in blood. We have studied the neutralization efficiency of the toxic action of ecotoxicants in relation to the laser irradiation time. The obtained data on the effect of the laser radiation on the thermal denaturation of hemoglobin and erythrocytes yield the scientific substantiation to the development of the optical method for the use in medicine upon drawing and conserving donor blood. We have shown that the obtained data can be used in medicine for improving the reliability of conditions of conservation and storage of donor blood, as well as for preventing the toxic action of harmful chemical compounds in the environment.

Propagation of intense laser radiation through a diffusion flame of burning oil

NASA Astrophysics Data System (ADS)

Gvozdev, S. V.; Glova, A. F.; Dubrovskii, V. Yu; Durmanov, S. T.; Krasyukov, A. G.; Lysikov, A. Yu; Smirnov, G. V.; Pleshkov, V. M.

2015-06-01

We report the results of measuring the absorption coefficient of radiation from a cw ytterbium fibre single-mode laser with the power up to 1.5 kW by a diffusion flame of oil, burning in the atmosphere air at normal pressure on a free surface. For the constant length (30 mm) and width (30 mm) of the flame and the distance 10 mm between the laser beam axis and the oil surface the dependence of the absorption coefficient, averaged over the flame length, on the mean radiation intensity (varied from 4.5 × 103 to 1.2 × 106 W cm-2) entering the flame is obtained. The qualitative explanation of nonmonotonic behaviour of the absorption coefficient versus the intensity is presented.

EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Thermally induced optical damage to barium-sodium niobate crystals

NASA Astrophysics Data System (ADS)

Baryshev, S. A.; Goncharova, I. F.; Konvisar, P. G.; Kuznetsov, V. A.

1990-06-01

Thermally induced optical damage (TIOD) was observed in undoped barium-sodium niobate (BSN) crystals as a result of changes in their temperature. This damage was deduced from the behavior of YAG:Nd3+ laser radiation when a BSN crystal was inserted in the resonator and also using a helium-neon laser probe beam. The experimental results were satisfactorily explained by the familiar pyroelectric model of TIOD and, in the crystals studied, an inhomogeneity of the conductivity rather than an inhomogeneity of the pyroelectric constant played the main role.

Quantum fluctuations of radiation in a ring Nd : YAG chip laser

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

Lariontsev, E G; Firsov, V V

2015-07-31

We report theoretical and experimental investigation of intensity fluctuations in a travelling-wave ring Nd : YAG chip laser, caused by the noise of spontaneous emission. In accordance with theory and experiment, quantum intensity fluctuations in the laser under study decrease dramatically with increasing pump over the threshold. As a result of the research performed, the factor β is found, which determines the ratio of the rate of spontaneous emission into the generated mode to the total rate of spontaneous emission into all modes. The effect of the relaxation rate from the lower laser level on quantum fluctuations of the radiationmore » intensity is found. (control of radiation parameters)« less

Quasi-monoenergetic protons accelerated by laser radiation pressure and shocks in thin gaseous targets

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

He Minqing; Shao Xi; Liu Chuansheng

Recent experiments and simulations have demonstrated effective CO{sub 2} laser acceleration of quasi-monoenergetic protons from thick gaseous hydrogen target (of thickness tens of laser wavelengths) via hole boring and shock accelerations. We present here an alternative novel acceleration scheme by combining laser radiation pressure acceleration with shock acceleration of protons in a thin gaseous target of thickness several laser wavelengths. The laser pushes the thin gaseous plasma forward while compressing it with protons trapped in it. We demonstrated the combined acceleration with two-dimensional particle-in-cell simulation and obtained quasi-monoenergetic protons {approx}44 MeV in a gas target of thickness twice of themore » laser wavelength irradiated by circularly polarized CO{sub 2} laser with normalized laser amplitude a{sub 0}=10.« less

Microprocessing of human hard tooth tissues surface by mid-infrared erbium lasers radiation

NASA Astrophysics Data System (ADS)

Belikov, Andrey V.; Shatilova, Ksenia V.; Skrypnik, Alexei V.

2015-03-01

A new method of hard tooth tissues laser treatment is described. The method consists in formation of regular microdefects on tissue surface by mid-infrared erbium laser radiation with propagation ratio M2<2 (Er-laser microprocessing). Proposed method was used for preparation of hard tooth tissues surface before filling for improvement of bond strength between tissues surface and restorative materials, microleakage reduction between tissues surface and restorative materials, and for caries prevention as a result of increasing microhardness and acid resistance of tooth enamel.

Computational model of collisional-radiative nonequilibrium plasma in an air-driven type laser propulsion

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

Ogino, Yousuke; Ohnishi, Naofumi

A thrust power of a gas-driven laser-propulsion system is obtained through interaction with a propellant gas heated by a laser energy. Therefore, understanding the nonequilibrium nature of laser-produced plasma is essential for increasing available thrust force and for improving energy conversion efficiency from a laser to a propellant gas. In this work, a time-dependent collisional-radiative model for air plasma has been developed to study the effects of nonequilibrium atomic and molecular processes on population densities for an air-driven type laser propulsion. Many elementary processes are considered in the number density range of 10{sup 12}/cm{sup 3}<=N<=10{sup 19}/cm{sup 3} and the temperaturemore » range of 300 K<=T<=40,000 K. We then compute the unsteady nature of pulsively heated air plasma. When the ionization relaxation time is the same order as the time scale of a heating pulse, the effects of unsteady ionization are important for estimating air plasma states. From parametric computations, we determine the appropriate conditions for the collisional-radiative steady state, local thermodynamic equilibrium, and corona equilibrium models in that density and temperature range.« less

Generation of high power sub millimeter radiation using free electron laser

NASA Astrophysics Data System (ADS)

Panwar, J.; Sharma, S. C.; Malik, P.; Yadav, M.; Sharma, R.

2018-03-01

We have developed an analytical formalism to study the emission of high power radiation lying in the sub millimetre range. A relativistic electron beam (REB) is velocity modulated by the pondermotive force exerted by the laser beams. After passing through the drift space, the beam gets density modulated which further interacts with the strong field wiggler and acquires a transverse velocity that couples with the modulated density of the beam in the presence of ion channel which contribute to the non-linear current density which further leads to the emission of the radiation. The output radiation can be modified by changing the wiggler parameters and the energy of the electron beam. The power of the output radiation is found to increase with the modulation. The obtained radiation can be employed for various applications.

Investigation of the vapour-plasma plume in the welding of titanium by high-power ytterbium fibre laser radiation

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

Bykovskiy, D P; Petrovskii, V N; Uspenskiy, S A

2015-03-31

The vapour-plasma plume produced in the welding of 6-mm thick VT-23 titanium alloy plates by ytterbium fibre laser radiation of up to 10 kW power is studied in the protective Ar gas medium. High-speed video filming of the vapour-plasma plume is used to visualise the processes occurring during laser welding. The coefficient of inverse bremsstrahlung by the welding plasma plume is calculated from the data of the spectrometric study. (interaction of laser radiation with matter)

Visible laser and UV-A radiation impact on a PNP degrading Moraxella strain and its rpoS mutant.

PubMed

Nandakumar, Kanavillil; Keeler, Werden; Schraft, Heidi; Leung, Kam T

2006-07-05

The role of stationary phase sigma factor gene (rpoS) in the stress response of Moraxella strain when exposed to radiation was determined by comparing the stress responses of the wild-type (WT) and its rpoS knockout (KO) mutant. The rpoS was turned on by starving the WT cultures for 24 h in minimal salt medium. Under non-starved condition, both WT and KO planktonic Moraxella cells showed an increase in mortality with the increase in duration of irradiation. In the planktonic non-starved Moraxella, for the power intensity tested, UV radiation caused a substantially higher mortality rate than did by the visible laser light (the mortality rate observed for 15-min laser radiation was 53.4 +/- 10.5 and 48.7 +/- 8.9 for WT and KO, respectively, and 97.6 +/- 0 and 98.5 +/- 0 for 25 s of UV irradiation in WT and KO, respectively). However, the mortality rate decreased significantly in the starved WT when exposed to these two radiations. In comparison, rpoS protected the WT against the visible laser light more effectively than it did for the UV radiation. The WT and KO strains of Moraxella formed distinctly different types of biofilms on stainless steel coupons. The KO strain formed a denser biofilm than did the WT. Visible laser light removed biofilms from the surfaces more effectively than did the UV. This was true when comparing the mortality of bacteria in the biofilms as well. The inability of UV radiation to penetrate biofilms due to greater rates of surface absorption is considered to be the major reason for the weaker removal of biofilms in comparison to that of the visible laser light. This result suggests that high power visible laser light might be an effective tool for the removal of biofilms. (c) 2006 Wiley Periodicals, Inc.

Simulation of radiation in laser produced plasmas

NASA Astrophysics Data System (ADS)

Colombant, D. G.; Klapisch, M.; Deniz, A. V.; Weaver, J.; Schmitt, A.

1999-11-01

The radiation hydrodynamics code FAST1D(J.H.Gardner,A.J.Schmitt,J.P.Dahlburg,C.J.Pawley,S.E.Bodner,S.P.Obenschain,V.Serlin and Y.Aglitskiy,Phys. Plasmas,5,1935(1998)) was used directly (i.e. without postprocessor) to simulate radiation emitted from flat targets irradiated by the Nike laser, from 10^12 W/cm^2 to 10^13W/cm^2. We use enough photon groups to resolve spectral lines. Opacities are obtained from the STA code(A.Bar-Shalom,J.Oreg,M.Klapisch and T.Lehecka,Phys.Rev.E,59,3512(1999)), and non LTE effects are described with the Busquet model(M.Busquet,Phys.Fluids B,5,4191(1993)). Results are compared to transmission grating spectra in the range 100-600eV, and to time-resolved calibrated filtered diodes (spectral windows around 100, 180, 280 and 450 eV).

Hard tooth tissue removal by short and long Er:YAG or Er,Cr:YSGG mid-infrared laser radiation

NASA Astrophysics Data System (ADS)

Jelínková, H.; Dostálová, T.; Remeš, M.; Šulc, J.; Němec, M.; Fibrich, M.

2017-02-01

Hard dental tissue removal by laser radiation is an alternative treatment to conventional dental-drilling procedures. The advantages of this therapy are fast and localized treatment of hard dental tissue and painlessness. The most effective systems for those purposes are Er-lasers generating radiation at wavelengths of around 3 μm. The aim of this study was qualitative and quantitative examination of human dentin and ivory tissue removal by pulsed free-running (FR) and Q-switched (QSW) Er:YAG and Er,Cr:YSGG laser radiations. From the obtained results it follows that generally Er:YAG laser has lower threshold for the tissue removal in both FR and QSW regimes. Furthermore, the FR Er:YAG and Er,Cr:YSGG radiation can be effective for both dentin and ivory ablation and can prepare smooth cavities without side effects. The QSW regime is useful preferably for precise ablation of a starting tooth defect and for the part of the tooth very close to the gum. This regime is excellent for micro-preparation or for tooth treatment of children.

Applications of Light Amplification by Stimulated Emission of Radiation (Lasers) for Restorative Dentistry

PubMed Central

Najeeb, Shariq; Khurshid, Zohaib; Zafar, Muhammad Sohail; Ajlal, Syed

2016-01-01

Light amplification by stimulated emission of radiation (laser) has been used widely in a range of biomedical and dental applications in recent years. In the field of restorative dentistry, various kinds of lasers have been developed for diagnostic (e.g. caries detection) and operative applications (e.g. tooth ablation, cavity preparation, restorations, bleaching). The main benefits for laser applications are patient comfort, pain relief and better results for specific applications. Major concerns for using dental lasers frequently are high cost, need for specialized training and sensitivity of the technique, thereby compromising its usefulness particularly in developing countries. The main aim of this paper is to evaluate and summarize the applications of lasers in restorative dentistry, including a comparison of the applications of lasers for major restorative dental procedures and conventional clinical approaches. A remarkable increase in the use of lasers for dental application is expected in the near future. PMID:26642047

Interaction of cw CO2 laser radiation with plasma near-metallic substrate surface

NASA Astrophysics Data System (ADS)

Azharonok, V. V.; Astapchik, S. A.; Zabelin, Alexandre M.; Golubev, Vladimir S.; Golubev, V. S.; Grezev, A. N.; Filatov, Igor V.; Chubrik, N. I.; Shimanovich, V. D.

2000-07-01

Optical and spectroscopic methods were used in studying near-surface plasma that is formed under the effect CW CO2 laser of (2- 5)x106W/cm2 power density upon stainless steel in He and Ar shielding gases. The variation of plume spatial structure with time has been studied, the outflow of gas-vapor jets from the interaction area has been characterized. The spectra of plasma plume pulsations have been obtained for the frequency range Δf = 0-1 MHz. The temperature and electron concentration of plasma plume have been found under radiation effect upon the target of stainless steel. Consideration has been given to the most probable mechanisms of CW laser radiation-metal non-stationary interaction.

Effects of laser radiation field on energies of hydrogen atom in plasmas

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

Bahar, M. K., E-mail: mussiv58@gmail.com

2015-09-15

In this study, for the first time, the Schrödinger equation with more general exponential cosine screened Coulomb (MGECSC) potential is solved numerically in the presence of laser radiation field within the Ehlotzky approximation using the asymptotic iteration method. The MGECSC potential includes four different potential forms in consideration of different sets of the parameters in the potential. By applying laser field, the total interaction potential of hydrogen atom embedded in plasmas converts to double well-type potential. The plasma screening effects under the influence of laser field as well as confinement effects of laser field on hydrogen atom in Debye andmore » quantum plasmas are investigated by solving the Schrödinger equation with the laser-dressed MGECSC potential. It is resulted that since applying a monochromatic laser field on hydrogen atom embedded in a Debye and quantum plasma causes to shift in the profile of the total interaction potential, the confinement effects of laser field on hydrogen atom in plasmas modeled by the MGECSC potential change localizations of energy states.« less

Influence of Laser Radiation Power Density on the Intensity of Spectral Lines for Main Components in a Clay Laser-Induced Plasma

NASA Astrophysics Data System (ADS)

Anufrik, S. S.; Kurian, N. N.; Znosko, K. F.; Belkov, M. V.

2018-05-01

We have studied the intensity of the spectral lines for the main components in clay: Al I 309.4 nm, Al II 358.7 nm, Mg II 279.6 nm, Ti II 323.6 nm vs. the position of the object relative to the focus of the optical system when the samples are exposed to single laser pulses from a YAG:Nd3+ laser. We have determined the permissible ranges for positioning the object relative to the focus of the optical system (positive and negative defocusing) for which there is practically no change in the reproducibility of the intensity for the spectral lines for red and white clay samples. We show that the position of the object relative to the focus of the optical system should be within the range ΔZ ±1.5 mm for optimal laser pulse energies for the analyte spectral lines. We have calculated the radiation flux density for different laser pulse energies and different distances from the focus to the object. We have shown experimentally that reducing the radiation flux density leads to a decrease in the intensity of the analyte spectral lines.

Theoretical study of the generation of terahertz radiation by the interaction of two laser beams with graphite nanoparticles

NASA Astrophysics Data System (ADS)

Sepehri Javan, N.; Rouhi Erdi, F.

2017-12-01

In this theoretical study, we investigate the generation of terahertz radiation by considering the beating of two similar Gaussian laser beams with different frequencies of ω1 and ω2 in a spatially modulated medium of graphite nanoparticles. The medium is assumed to contain spherical graphite nanoparticles of two different configurations: in the first configuration, the electric fields of the laser beams are parallel to the normal vector of the basal plane of the graphite structure, whereas in the second configuration, the electric fields are perpendicular to the normal vector of the basal plane. The interaction of the electric fields of lasers with the electronic clouds of the nanoparticles generates a ponderomotive force that in turn leads to the creation of a macroscopic electron current in the direction of laser polarizations and at the beat frequency ω1-ω2 , which can generate terahertz radiation. We show that, when the beat frequency lies near the effective plasmon frequency of the nanoparticles and the electric fields are parallel to the basal-plane normal, a resonant interaction of the laser beams causes intense terahertz radiation.

EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Feasibility of generation of picosecond and subpicosecond x-ray pulses in thin films

NASA Astrophysics Data System (ADS)

Gordienko, Vyacheslav M.; Dzhidzhoev, M. S.; Kolchin, V. V.; Magnitskiy, Sergey A.; Platonenko, Viktor T.; Savel'ev, Andrei B.; Tarasevitch, A. P.

1995-02-01

The characteristics of a femtosecond laser plasma, formed by irradiation of a thin freely suspended carbon film, are investigated numerically. It is shown that the use of thin films can increase considerably the electron temperature of a femtosecond laser plasma and make it possible to generate x-rays of shorter wavelengths. This method can also be used to increase the efficiency of conversion of the energy of laser pulses into the radiation emitted by hydrogen-like carbon ions without a significant increase in the duration of x-ray pulses.

Laser therapy and sclerotherapy in the treatment of oral and maxillofacial hemangioma and vascular malformations

NASA Astrophysics Data System (ADS)

Crişan, Bogdan; BǎciuÅ£, Mihaela; BǎciuÅ£, Grigore; Crişan, Liana; Bran, Simion; Rotar, Horatiu; Moldovan, Iuliu; Vǎcǎraş, Sergiu; Mitre, Ileana; Barbur, Ioan; Magdaş, Andreea; Dinu, Cristian

2016-03-01

Hemangioma and vascular malformations in the field of oral and maxillofacial surgery is a pathology more often found in recent years in patients. The aim of this study was to evaluate the efficacy of the laser photocoagulation performed with a diode laser (Ga-Al-As) 980 nm wavelength in the treatment of vascular lesions which are located on the oral and maxillofacial areas, using color Doppler ultrasonography for evaluation of the results. We also made a comparison between laser therapy and sclerotherapy in order to establish treatment protocols and recommendations associated with this pathology. We conducted a controlled study on a group of 92 patients (38 male and 54 female patients, with an average age of 36 years) having low flow hemangioma and vascular malformations. Patients in this trial received one of the methods of treatment for vascular lesions such as hemangioma and vascular malformations: laser therapy or sclerotherapy. After laser therapy we have achieved a reduction in size of hemangioma and vascular malformations treated with such a procedure, and the aesthetic results were favorable. No reperfusion or recanalization of laser treated vascular lesions was observed after an average follow-up of 6 to 12 months. In case of sclerotherapy a reduction in the size of vascular lesions was also obtained. The 980 nm diode laser has been proved to be an effective tool in the treatment of hemangioma and vascular malformations in oral and maxillofacial area. Laser therapy in the treatment of vascular lesions was more effective than the sclerotherapy procedure.

Induction of lambda prophage by 213 nm laser radiation: a quantitative comparison with 193 nm excimer radiation using image analysis.

PubMed

Matchette, L S; Grossman, L W; Hahn, D W; Cooney, C

1996-03-01

We compared the DNA damage produced by radiation from two UV laser wavelengths, 213 nm and 193 nm, with that produced by noncoherent 254 nm radiation. Following irradiation of Escherichia coli BR339, a bacteriophage lambda lysogen containing the lacZ gene, pro-phage induction was measured by assaying for beta-galactosidase. Because of the limited penetration by UV laser wavelengths an agar overlay of the lysogen was used as the irradiation target. Irradiation of 254 nm was performed in buffer suspension followed by transfer of 5 microL spots onto assay plants. Computer image analysis was used to monitor the rate of product formation, observed as an increase in optical density of the irradiated zones on assay plates. We found that the rate of product formation was a more reproducible unit of comparison than the optical density present at the end of the reaction. Although the rate of product formation was not linearly related to enzyme concentration, the data could be fit to a simple logarithmic function. Using this method, we concluded that the DNA damaging ability of 213 nm radiation was 10 times more efficient than 193 nm radiation and about 100 times less efficient than 254 nm noncoherent radiation.

The response of Galileo aft cover components to laser radiation

NASA Technical Reports Server (NTRS)

Metzger, J. W.

1982-01-01

The aft region of the Galileo probe will be subjected to severe heat transfer rates dominated by the radiation contributions. To assess the response of several vehicle aft region components to thermal radiation, tests employing a 10 KW CO2 laser were conducted. The experiments evaluated the annulus/aft cover interface, the umbilical feedthrough assembly and the mortar cover seal assembly. Experimental evidence of the response of the phenolic nylon heatshield and quantitative measures of its effect on gap geometries of several vehicle components were acquired. In addition, qualitative measures of the survivability of the irradiated components were obtained.

Er:YAG and alexandrite laser radiation propagation in the root canal and its effect on bacteria

NASA Astrophysics Data System (ADS)

Jelinkova, Helena; Dostalova, Tatjana; Duskova, Jana; Miyagi, Mitsunobu; Shoji, Shigeru; Sulc, Jan; Nemec, Michal

1999-05-01

The goal of the study was to verify differences between the alexandrite and Er:YAG laser energy distribution in the root canal and in the surrounding dentin and bone tissues. For the experiment, two lasers were prepared: the Er:YAG laser (λ=2.94 μm) with a delivery system fluorocarbon polymer-coated silver hollow glass waveguide ended by a special sapphire tip and the alexandrite laser (λ=0.75 μm) with a silicon fiber. The Er:YAG laser was operated in a free-running mode, the length of the generated pulses was 250 μsec and the output energy ranged from 100 to 350 mJ. The pulse length of the free- running alexandrite laser was 70 μsec and the output energy was ranged from 80 up to 200 mJ. For the experiment prepared root canals of molars were used. It was ascertained that the radiation of the alexandrite laser passes through the root canal and hits the surrounding tissue. Nocardia asteroids, Filaments, Micrococcus albus, Lactobacillus sp and Streptococcus sanguis colonies were treated by the Er:YAG or alexandrite laser radiation. The surface was checked by scanning electron microscopy. From the result it follows that the Er:YAG laser destroyed microbial colonies but the differences is in the depth of the affected area.

Evolution of energy deposition during glass cutting with pulsed femtosecond laser radiation

NASA Astrophysics Data System (ADS)

Kalupka, C.; Großmann, D.; Reininghaus, M.

2017-05-01

We report on investigations of the energy deposition in the volume of thin glass during an ablation cutting process with pulsed femtosecond laser radiation by time-resolved pump-probe shadowgraphy. For a single laser pulse, the temporal evolution of the transient electronic excitation of the glass volume is imaged up to 10 ps after initial excitation. For an increasing number of laser pulses, the spatial excitation of the glass volume significantly changes compared to single pulse irradiation. Sharp spikes are observed, which reduce the transmission of the illuminating probe pulse. This indicates local maxima of the absorption and, therefore, energy deposition of the pump pulse energy in the glass volume. Furthermore, for an increasing number of pulses, different shapes of the surface ablation crater are observed. To study the correlation between the shape of the surface ablation crater and the energy deposition in the glass volume, simulations of the spatial intensity distribution of the pump pulse are executed by means of linear beam propagation method. We show that the transient excitation spikes observed by pump-probe shadowgraphy can be explained by refraction and diffraction of the laser radiation at the surface ablation crater. Our results provide an experimental validation for the physical reason of an ablation stop for an ablation cutting process. Moreover, the simulations allow for the prediction of damage inside the glass volume.

Assessment and Mitigation of Radiation, EMP, Debris & Shrapnel Impacts at Megajoule-Class Laser Facilities

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

Eder, D C; Anderson, R W; Bailey, D S

2009-10-05

The generation of neutron/gamma radiation, electromagnetic pulses (EMP), debris and shrapnel at mega-Joule class laser facilities (NIF and LMJ) impacts experiments conducted at these facilities. The complex 3D numerical codes used to assess these impacts range from an established code that required minor modifications (MCNP - calculates neutron and gamma radiation levels in complex geometries), through a code that required significant modifications to treat new phenomena (EMSolve - calculates EMP from electrons escaping from laser targets), to a new code, ALE-AMR, that is being developed through a joint collaboration between LLNL, CEA, and UC (UCSD, UCLA, and LBL) for debrismore » and shrapnel modelling.« less

An MLC-based linac QA procedure for the characterization of radiation isocenter and room lasers' position.

PubMed

Rosca, Florin; Lorenz, Friedlieb; Hacker, Fred L; Chin, Lee M; Ramakrishna, Naren; Zygmanski, Piotr

2006-06-01

We have designed and implemented a new stereotactic linac QA test with stereotactic precision. The test is used to characterize gantry sag, couch wobble, cone placement, MLC offsets, and room lasers' positions relative to the radiation isocenter. Two MLC star patterns, a cone pattern, and the laser line patterns are recorded on the same imaging medium. Phosphor plates are used as imaging medium due to their sensitivity to red light. The red light of room lasers erases some of the irradiation information stored on the phosphor plates enabling accurate and direct measurements for the position of room lasers and radiation isocenter. Using film instead of the phosphor plate as imaging medium is possible, however, it is less practical. The QA method consists of irradiating four phosphor plates that record the gantry sag between the 0 degrees and 180 degrees gantry angles, the position and stability of couch rotational axis, the sag between the 90 degrees and 270 degrees gantry angles, the accuracy of cone placement on the collimator, the MLC offsets from the collimator rotational axis, and the position of laser lines relative to the radiation isocenter. The estimated accuracy of the method is +/- 0.2 mm. The observed reproducibility of the method is about +/- 0.1 mm. The total irradiation/ illumination time is about 10 min per image. Data analysis, including the phosphor plate scanning, takes less than 5 min for each image. The method characterizes the radiation isocenter geometry with the high accuracy required for the stereotactic radiosurgery. In this respect, it is similar to the standard ball test for stereotactic machines. However, due to the usage of the MLC instead of the cross-hair/ball, it does not depend on the cross-hair/ball placement errors with respect to the lasers and it provides more information on the mechanical integrity of the linac/couch/laser system. Alternatively, it can be used as a highly accurate QA procedure for the nonstereotactic machines

INTERACTION OF LASER RADIATION WITH MATTER. LASER PLASMA: Calculation of mass transfer in the remote cutting of metals by radiation of a high-power repetitively pulsed CO2 laser

NASA Astrophysics Data System (ADS)

Gladush, G. G.; Rodionov, N. B.

2002-01-01

The mechanism of remote cutting of steel plates by radiation of a high-power repetitively pulsed CO2 laser is theoretically studied. The models of melt removal by the gravity force and the recoil pressure of material vapour are proposed and the sufficient conditions for the initiation of cutting are determined. A numerical model of a thermally thin plate was employed to describe the cutting for large focal spots.

The creation of radiation dominated plasmas using laboratory extreme ultra-violet lasers

NASA Astrophysics Data System (ADS)

Tallents, G. J.; Wilson, S.; West, A.; Aslanyan, V.; Lolley, J.; Rossall, A. K.

2017-06-01

Ionization in experiments where solid targets are irradiated by high irradiance extreme ultra-violet (EUV) lasers is examined. Free electron degeneracy effects on ionization in the presence of a high EUV flux of radiation is shown to be important. Overlap of the physics of such plasmas with plasma material under compression in indirect inertial fusion is explored. The design of the focusing optics needed to achieve high irradiance (up to 1014 Wcm-2) using an EUV capillary laser is presented.

Effect of laser UV radiation on the eye scleral tissue in patients with open-angle glaucoma

NASA Astrophysics Data System (ADS)

Razhev, A. M.; Iskakov, I. A.; Churkin, D. S.; Orishich, A. M.; Maslov, N. A.; Tsibul'skaya, E. O.; Lomzov, A. A.; Ermakova, O. V.; Trunov, A. N.; Chernykh, V. V.

2018-05-01

We report the results of an experimental study of the effect of short-pulse laser UV radiation on the eye scleral tissue. As samples, we used isolated flaps of the eye scleral tissue from the patients with open-angle glaucoma of the second and third stages. The impact was implemented using the radiation of an excimer XeCl laser with a wavelength of 308 nm and a laser with a wavelength tunable within from 210 to 355 nm. Depending on the problem to be solved, the energy density on the surface of the irradiated tissue varied from a fraction of mJ cm-2 to 15 J cm-2. For the first time we studied the optical properties of the intraocular fluid in the UV and blue spectral range. The study of the ablation process under the action of radiation with a wavelength of 308 nm showed that the rate of material evaporation can vary within 24%–30% at an energy density above 7 J cm-2, depending on the glaucoma stage and the individual features of a patient. The excitation–emission matrices of laser-induced fluorescence (LIF) of the eye scleral tissue were studied experimentally using a laser with a wavelength tuned in the range 210–355 nm. We found the differences in the LIF spectra caused by the excitation wavelength and the openangle glaucoma stage.

Generation of radicals in hard biological tissues under the action of laser radiation

NASA Astrophysics Data System (ADS)

Sviridov, Alexander P.; Bagratashvili, Victor N.; Sobol, Emil N.; Omelchenko, Alexander I.; Lunina, Elena V.; Zhitnev, Yurii N.; Markaryan, Galina L.; Lunin, Valerii V.

2002-07-01

The formation of radicals upon UV and IR laser irradiation of some biological tissues and their components was studied by the EPR technique. The radical decay kinetics in body tissue specimens after their irradiation with UV light were described by various models. By the spin trapping technique, it was shown that radicals were not produced during IR laser irradiation of cartilaginous tissue. A change in optical absorption spectra and the dynamics of optical density of cartilaginous tissue, fish scale, and a collagen film under exposure to laser radiation in an air, oxygen, and nitrogen atmosphere was studied.

Measurements and Calculations of Halfraum Radiation Drives at the Omega Laser

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

MacLaren, S A; Back, C A; Hammer, J H

2005-01-06

Thin walled gold halfraums are a common choice for producing x-ray drives in experiments at high-power laser facilities. At the Omega Laser, we use 10 kJ of laser energy in a two-pulse sequence to generate halfraum drive temperatures of 160-190 eV for {approx}3ns. This type of drive is well characterized and reproducible, with characterization of the drive radiation temperature typically performed using the Dante diagnostic. Additionally, calibrated Photoconductive Diamond Detectors (PCDs) are used to measure the drive when it is desirable to utilize the Dante elsewhere in the experiment. Measurements of halfraum drives from both Dante and PCDs are comparedmore » with calculations, with good agreement. This agreement lends the calculations a predictive capability in designing further experiments utilizing halfraum drives.« less

Comparison of effects of diode laser and CO2 laser on human teeth and their usefulness in topical fluoridation.

PubMed

González-Rodríguez, Alberto; de Dios López-González, Juan; del Castillo, Juan de Dios Luna; Villalba-Moreno, Juan

2011-05-01

Various authors have reported more effective fluoridation from the use of lasers combined with topical fluoride than from conventional topical fluoridation. Besides the beneficial effect of lasers in reducing the acid solubility of an enamel surface, they can also increase the uptake of fluoride. The study objectives were to compare the action of CO(2) and GaAlAs diode lasers on dental enamel and their effects on pulp temperature and enamel fluoride uptake. Different groups of selected enamel surfaces were treated with amine fluoride and irradiated with CO(2) laser at an energy power of 1 or 2 W or with diode laser at 5 or 7 W for 15 s each and compared to enamel surfaces without treatment or topical fluoridated. Samples were examined by means of environmental scanning electron microscopy (ESEM). Surfaces of all enamel samples were then acid-etched, measuring the amount of fluoride deposited on the enamel by using a selective ion electrode. Other enamel surfaces selected under the same conditions were irradiated as described above, measuring the increase in pulp temperature with a thermocouple wire. Fluorination with CO(2) laser at 1 W and diode laser at 7 W produced a significantly greater fluoride uptake on enamel (89 ± 18 mg/l) and (77 ± 17 mg/l) versus topical fluoridation alone (58 ± 7 mg/l) and no treatment (20 ± 1 mg/l). Diode laser at 5 W produced a lesser alteration of the enamel surface compared to CO(2) laser at 1 W, but greater pulp safety was provided by CO(2) laser (ΔT° 1.60° ± 0.5) than by diode laser (ΔT° 3.16° ± 0.6). Diode laser at 7 W and CO(2) laser at 2 W both caused alterations on enamel surfaces, but great pulp safety was again obtained with CO(2) (ΔT° 4.44° ± 0.60) than with diode (ΔT° 5.25° ± 0.55). Our study demonstrates that CO(2) and diode laser irradiation of the enamel surface can both increase fluoride uptake; however, laser energy parameters must be carefully

Use of near infrared femtosecond lasers as sub-micron radiation microbeam for cell DNA damage and repair studies.

PubMed

Botchway, S W; Reynolds, P; Parker, A W; O'Neill, P

2010-01-01

Laser induced radiation microbeam technology for radiobiology research is undergoing rapid growth because of the increased availability and ease of use of femtosecond laser sources. The main processes involved are multiphoton absorption and/or plasma formation. The high peak powers these lasers generate make them ideal tools for depositing sub-micrometer size radiant energy within a region of a living cell nucleus to activate ionising and/or photochemically driven processes. The technique allows questions relating to the effects of low doses of radiation, the propagation and treatment of deoxyribonucleic acid (DNA) damage and repair in individual live cells as well as non-targeted cell to cell effects to be addressed. This mini-review focuses on the use of near infrared (NIR) ca. 800nm radiation to induce damage that is radically different from the early and subsequent ultraviolet microbeam techniques. Ultrafast pulsed NIR instrumentation has many benefits including the ability to eliminate issues of unspecific UV absorption by the many materials prevalent within cells. The multiphoton interaction volume also permits energy deposition beyond the diffraction limit. Work has established that the fundamental process of the damage induced by the ultrashort laser pulses is different to those induced from continuous wave light sources. Pioneering work has demonstrated that NIR laser microbeam radiation can mimic ionising radiation via multiphoton absorption within the 3D femtolitre volume of the highly focused Gaussian beam. This light-matter interaction phenomenon provides a novel optical microbeam probe for mimicking both complex ionising and UV radiation-type cell damage including double strand breaks (DSBs) and base damage. A further advantage of the pulsed laser technique is that it provides further scope for time-resolved experiments. Recently the NIR laser microbeam technique has been used to investigate the recruitment of repair proteins to the sub

Effects of low level laser therapy (LLLT) on pressured human osteoblasts: A histomorphologic and quantitative study

NASA Astrophysics Data System (ADS)

Pyo, S. J.; Song, W. W.; Kim, I. R.; Park, B. S.; Kim, C. H.; Kim, S. S.; Chung, I. K.; Kim, Y. D.

2012-03-01

Previous research has investigated the effects of LLLT during titanium implantation, tooth movement and bone graft using deproteinized bovine bone and recognized that these circumstances were nothing more than intentional controlled overpressure against static cells since this controlled trauma could affect cell function/malfunction, or cell recovery/apoptosis. The present preliminary study was conducted to prove if LLL would influence cell viability and cell function after excessive damage, which is enough to diminish cell numbers and distort the features of cells. Our aim is to evaluate whether low level laser irradiation (LLLi) could be helpful in the recovery of traumatized osteoblasts (pressure damaged cells) by observing the morphology and the survival rate of those cells. This model used bone cell cultures which were traumatized by a pressure with 250 G of centripetal force and observed their response to such trauma and low level laser irradiation. In this experiment, a Ga-Al-As diode LLL (IMPRA-ORT, NDLux, Seoul, KOREA) was used with a wavelength of 808 nm, a focus of 14 × 24 mm, which was wide enough to cover the whole dish surface or well within at least 2 times radiation, and an output of 100 mW. Statistical analysis showed a higher recovery rate of damaged osteoblasts in the radiation group than the non-radiation group ( p < 0.05). The nonradiation group had a very poor proliferation rate in comparison to the control group ( p < 0.05) in every time period. In the control group, actin filaments showed a random orientation and cell process branched variously around each cell. In contrast, compressed cells, these patterns were turned into thicker and shorter cytoskeletons. As time progressed, every living cell recovered from the severe stress and recovered both form and function. In summary, the present study showed the capacity of LLLT to aid the recovery of the cell skeleton and affect cell viability on overpressured osteoblasts. These results may

Temperature and pressure dependence of dichloro-difluoromethane (CF2C12) absorption coefficients for CO2 waveguide laser radiation

NASA Technical Reports Server (NTRS)

Harward, C. N.

1977-01-01

Measurements were performed to determine the pressure and temperature dependence of CFM-12 absorption coefficients for CO2 waveguide laser radiation. The absorption coefficients of CFM-12 for CO2 waveguide laser radiation were found to have no spectral structure within small spectral bandwidths around the CO2 waveguide laser lines in the CO2 spectral band for pressures above 20 torr. All of the absorption coefficients for the CO2 laser lines studied are independent of pressure above 100 torr, except for the P(36) laser CO2 spectral band. The absorption coefficients associated with the P(42) line in the same band showed the greatest change with temperature, and it also has the largest value of all the lines studied.

Dynamically controlled deposition of colloidal nanoparticle suspension in evaporating drops using laser radiation.

PubMed

Ta, V D; Carter, R M; Esenturk, E; Connaughton, C; Wasley, T J; Li, J; Kay, R W; Stringer, J; Smith, P J; Shephard, J D

2016-05-18

Dynamic control of the distribution of polystyrene suspended nanoparticles in evaporating droplets is investigated using a 2.9 μm high power laser. Under laser radiation a droplet is locally heated and fluid flows are induced that overcome the capillary flow, and thus a reversal of the coffee-stain effect is observed. Suspension particles are accumulated in a localised area, one order of magnitude smaller than the original droplet size. By scanning the laser beam over the droplet, particles can be deposited in an arbitrary pattern. This finding raises the possibility for direct laser writing of suspended particles through a liquid layer. Furthermore, a highly uniform coating is possible by manipulating the laser beam diameter and exposure time. The effect is expected to be universally applicable to aqueous solutions independent of solutes (either particles or molecules) and deposited substrates.

Removal of a glowing spot from an image tube using laser radiation.

NASA Technical Reports Server (NTRS)

Gurski, T. R.

1972-01-01

A troublesome problem with the Kron electronograph has been the presence of a white glowing spot on the glass wall of the tube adjacent to the focus electrode. The procedure followed to eliminate the spot was to operate in the dark and apply voltage only to the focused electrode. Ruby laser radiation was unfocused, and its position was shifted on the electrode between laser shots until an effect was observed. This technique for removing the glowing spot should be applicable to other electronic image tubes.

INTERACTION OF LASER RADIATION WITH MATTER. LASER PLASMA: The mechanism of the drilling of holes in vertical metallic plates by cw CO2 laser radiation

NASA Astrophysics Data System (ADS)

Likhanskii, V. V.; Loboiko, A. I.; Antonova, G. F.; Krasyukov, A. G.; Sayapin, V. P.

1999-02-01

The possibility of making a hole in a vertical plate with the aid of laser radiation at a surface temperature not exceeding the boiling point is analysed neglecting the vapour pressure. The mechanism of the degradation of the liquid layer involving a reduction of its thickness, as a result of the redistribution of the molten mass owing to the operation of the force of gravity and of thermocapillary convection, is examined. The theoretical dependence of the critical size of the molten zone on the plate thickness is obtained and a comparison is made with experimental data.

Low-level laser therapy to treat fibromyalgia.

PubMed

Ruaro, J A; Fréz, A R; Ruaro, M B; Nicolau, R A

2014-11-01

Several clinical treatments have been proposed to manage symptoms of fibromyalgia. Low-level laser therapy (LLLT) may be a useful tool to treat this dysfunction. The aim of this study was to evaluate the effects of LLLT in patients with fibromyalgia. A placebo-controlled, randomized clinical trial was carried out with 20 patients divided randomly into either an LLLT group (n = 10) or a placebo group (n = 10). The LLLT group was treated with a GaAlAs laser (670 nm, 4 J/cm(2) on 18 tender points) three times a week over 4 weeks. Before and after treatment, patients were evaluated with the Fibromyalgia Impact Questionnaire (FIQ), McGill Pain Questionnaire, and visual analog scale (VAS). Data from the FIQ and McGill questionnaire for the treated and control groups were analyzed by paired t tests, and Wilcoxon tests were used to analyze data from the VAS. After LLLT or sham treatment, the number of tender points was significantly reduced in both groups (LLLT, p < 0.0001; placebo, p = 0.0001). However, all other fibromyalgia symptoms showed significant improvements after LLLT compared to placebo (FIQ, p = 0.0003; McGill, p = 0.0078; and VAS, p = 0.0020). LLLT provided relief from fibromyalgia symptoms in patients and should be further investigated as a therapeutic tool for management in fibromyalgia.

INTERACTION OF LASER RADIATION WITH MATTER. LASER PLASMA: Spectroscopic investigation of thermodynamic parameters of a plasma plume formed by the action of cw CO2 laser radiation on a metal substrate

NASA Astrophysics Data System (ADS)

Vasil'chenko, Zh V.; Azharonok, V. V.; Filatova, I. I.; Shimanovich, V. D.; Golubev, V. S.; Zabelin, A. M.

1996-09-01

Emission spectroscopy methods were used in an investigation of thermodynamic parameters of a surface plasma formed by the action of cw CO2 laser radiation of (2-5)×106 W cm-2 intensity on stainless steel in a protective He or Ar atmosphere. The spatiotemporal structure and pulsation characteristics of the plasma plume were used to determine the fields of the plasma electron density and temperature.

Laser Materials and Laser Spectroscopy - A Satellite Meeting of IQEC '88

NASA Astrophysics Data System (ADS)

Wang, Zhijiang; Zhang, Zhiming

1989-03-01

The Table of Contents for the book is as follows: * Laser Materials * Laser Site Spectroscopy of Transition Metal Ions in Glass * Spectroscopy of Chromium Doped Tunable Laser Materials * Spectroscopic Properties of Nd3+ Ions in LaMgAl11O19 Crystal * Spectral Study and 2.938 μm Laser Emission of Er3+ in the Y3Al5O12 Crystal * Raman-infrared Spectra and Radiationless Relaxation of Laser Crystal NdAl3(BO3)4 * A Study on HB and FLN in BaFCl0.5Br0.5:Sm2+ at 77K * Pair-pumped Upconversion Solid State Lasers * CW Upconversion Laser Action in Neodymium and Erbium doped Solids * Ultra-high Sensitive Upconversion Fluorescence of YbF3 Doped with Trace Tm3+ and Er3+ * The Growth and Properties of NYAB and EYAB Multifunctional Crystal * Study on Fluorescence and Laser Light of Er3+ in Glass * Growth and Properties of Single Crystal Fibers for Laser Materials * A Study on the Quality of Sapphire, Ruby and Ti3+ Doped Sapphire Grown by Temperature Gradient Technique (TGT) and Czochralski Technique (CZ) * The Measurement of Output Property of Ti3+ Al2O3 Laser Crystal * An Xα Study of the Laser Crystal MgF2 : V2+ * Q-switched NAB Laser * Miniature YAG Lasers * Study of High Efficiency {LiF}:{F}^-_2 Color Center Crystals * Study on the Formation Conditions and Optical Properties of (F2+)H Color Center in NaCl:OH- Crystals * Novel Spectroscopic Properties of {LiF}:{F}^+_3 - {F}_2 Mixed Color Centers Laser Crystals * Terraced Substrate Visible GaAlAs Semiconductor Lasers with a Large Optical Cavity * The Temperature Dependence of Gain Spectra, Threshold Current and Auger Recombination in InGaAsP-InP Double Heterojunction Laser diode * Time-resolved Photoluminescence and Energy Transfer of Bound Excitons in GaP:N Crystals * Optical Limiting with Semiconductors * A Critical Review of High-efficiency Crystals for Tunable Lasers * Parametric Scattering in β - BaB2O4 Crystal Induced by Picosecond Pulses * Generation of Picosecond Pulses at 193 nm by Frequency Mixing in β - BaB2O4

Laser-driven beam lines for delivering intensity modulated radiation therapy with particle beams

PubMed Central

Hofmann, Kerstin M; Schell, Stefan; Wilkens, Jan J

2012-01-01

Abstract Laser-accelerated particles are a promising option for radiation therapy of cancer by potentially combining a compact, cost-efficient treatment unit with the physical advantages of charged particle beams. To design such a treatment unit we consider different dose delivery schemes and analyze the necessary devices in the required particle beam line for each case. Furthermore, we point out that laser-driven treatment units may be ideal tools for motion adaptation during radiotherapy. Reasons for this are the potential of a flexible gantry and the time structure of the beam with high particle numbers in ultrashort bunches. One challenge that needs to be addressed is the secondary radiation produced in several beam line elements. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) PMID:22930653

The accumulation of femtosecond laser radiation energy in crystals of lithium fluoride

NASA Astrophysics Data System (ADS)

Dresvyanskiy, V. P.; Glazunov, D. S.; Alekseev, S. V.; Losev, V. F.; Chadraa, B.; Bukhtsooj, O.; Baasankhuu, N.; Zandan, B.; Martynovich, E. F.

2015-12-01

We present the results of studies of energy accumulation during the non-destructive interaction of extremely intense near infrared laser radiation with model wide band gap dielectric crystals of lithium fluoride, when the intensity of pulses is sufficient for effective highly nonlinear absorption of light and for the excitation of the electron subsystem of matter and the energy of pulses is still not sufficient for significant heating, evaporation, laser breakdown or other destruction to occur. We studied the emission of energy in the form of light sum of thermally stimulated luminescence accumulated under conditions of self-focusing and multiple filamentation of femtosecond laser radiation. It was established that it's the F2 and F3+ color centers and supplementary to them centers of interstitial type which accumulate energy under the action of a single femtosecond laser pulses. When irradiated by series of pulses the F3, F3- and F4 centers additionally appear. F2 centers are the main centers of emission in the process of thermally stimulated luminescence of accumulated energy. The interstitial fluoride ions (I-centers) are the kinetic particles. They split off from the X3- centers in the result of thermal decomposition of latter on the I-centers and molecules X20. I-centers recombine with F3+ centers and form F2 centers in excited state. The latter produce the characteristic emission spectrum emitted in the form of thermally stimulated luminescence.

Low-level laser therapy for Peyronie's disease

NASA Astrophysics Data System (ADS)

Johnson, Douglas E.; Bertini, John E. J.; Harris, James M.; Hawkins, Janet H.

1995-05-01

We are reporting the preliminary results of a nonrandomized trial using a low-level gallium- aluminum-arsenide (GaAlAs) laser at a wavelength of 830 nm (Microlight 830, Lasermedics, Inc., Stafford, TX) to treat patients with symptomatic Peyronie's disease. All patients entered into the study had disease consisting of a well-defined fibrous plaque causing pain and/or curvature of the penile shaft on erection that interfered with satisfactory sexual intercourse. Treatment has consisted of 30 mW administered over a duty cycle of 100 seconds (3 J) beginning at the base of the penis and extending to the coronal sulcus over the dorsum of the penis at 0.5 cm intervals. An additional duty cycle of 100 seconds was delivered to each 0.5 cm of palpable plaque. The ability of the therapy to reduce the size of the fibrous plaque, the severity of the penile curvature, and the severity of pain associated with penile erection and the treatment's effect on the patient's quality of life were assessed for each patient at completion of therapy and 6 weeks later.

Physical Approaches to Designing a Two-Cascade Terahertz Laser Generating Difference-Frequency Radiation in a Nonlinear Optical ZnGeP2 Crystal

NASA Astrophysics Data System (ADS)

Gribenyukov, A. I.; Dyomin, V. V.; Polovtsev, I. G.; Yudin, N. N.

2018-03-01

An optical layout of a two-cascade frequency converter of the mid-IR laser radiation into the terahertz (THz) radiation is proposed. In the first stage it is assumed to convert the Tm:YLF-laser frequency in a Cr+2:ZnSe polycrystal into the radiation with the wavelength 2-3 μm. The second cascade can be presented as a parametric conversion of the frequencies of two laser sources operating in the 2-3 μm range into the THz radiation via the difference-frequency mixing in a nonlinear optical ZnGeP2 crystal. The estimates of the terahertz output signal are reported.

EFFECTS OF LASER RADIATION ON MATTER: Simulation of photon acceleration upon irradiation of a mylar target by femtosecond laser pulses

NASA Astrophysics Data System (ADS)

Andreev, Stepan N.; Rukhadze, Anri A.; Tarakanov, V. P.; Yakutov, B. P.

2010-01-01

Acceleration of protons is simulated by the particle-in-cell (PIC) method upon irradiation of mylar targets of different thicknesses by femtosecond plane-polarised pulsed laser radiation and at different angles of radiation incidence on the target. The comparison of the results of calculations with the experimental data obtained in recent experiments shows their good agreement. The optimal angle of incidence (458) at which the proton energy achieves its absolute maximum is obtained.

UV laser radiation alters the embryonic protein profile of adrenal-kidney-gonadal complex and gonadal differentiation in the lizard, Calotes Versicolor.

PubMed

Khodnapur, Bharati S; Inamdar, Laxmi S; Nindi, Robertraj S; Math, Shivkumar A; Mulimani, B G; Inamdar, Sanjeev R

2015-02-01

To examine the impact of ultraviolet (UV) laser radiation on the embryos of Calotes versicolor in terms of its effects on the protein profile of the adrenal-kidney-gonadal complex (AKG), sex determination and differentiation, embryonic development and hatching synchrony. The eggs of C. versicolor, during thermo-sensitive period (TSP), were exposed to third harmonic laser pulses at 355 nm from a Q-switched Nd:YAG laser for 180 sec. Subsequent to the exposure they were incubated at the male-producing temperature (MPT) of 25.5 ± 0.5°C. The AKG of hatchlings was subjected to protein analysis by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and to histology. The UV laser radiation altered the expression of the protein banding pattern in the AKG complex of hatchlings and it also affected the gonadal sex differentiation. SDS-PAGE of AKG of one-day-old hatchlings revealed a total of nine protein bands in the control group whereas UV laser irradiated hatchlings expressed a total of seven protein bands only one of which had the same Rf as a control band. The UV laser treated hatchlings have an ovotestes kind of gonad exhibiting a tendency towards femaleness instead of the typical testes. It is inferred that 355 nm UV laser radiation during TSP induces changes in the expression of proteins as well as their secretions. UV laser radiation had an impact on the gonadal differentiation pathway but no morphological anomalies were noticed.

Dependence of optimal initial density on laser parameters for multi-keV x-ray radiators generated by nanosecond laser-produced underdense plasma

NASA Astrophysics Data System (ADS)

Tu, Shao-yong; Yuan, Yong-teng; Hu, Guang-yue; Miao, Wen-yong; Zhao, Bin; Zheng, Jian; Jiang, Shao-en; Ding, Yong-kun

2016-01-01

Efficient multi-keV x-ray sources can be produced using nanosecond laser pulse-heated middle-Z underdense plasmas generated using gas or foam. Previous experimental results show that an optimal initial target density exists for efficient multi-keV x-ray emission at which the laser ionization wave is supersonic. Here we explore the influence of the laser intensity and the pulse duration on this optimal initial target density via a one-dimensional radiation hydrodynamic simulation. The simulation shows that the optimal initial density is sensitive to both the laser intensity and the pulse duration. However, the speed of the supersonic ionization wave at the end of the laser irradiation is always maintained at 1.5 to 1.7 times that of the ion acoustic wave under the optimal initial density conditions.

Laser surgery: using the carbon dioxide laser.

PubMed Central

Wright, V. C.

1982-01-01

In 1917 Einstein theorized tha through an atomic process a unique kind of electromagnetic radiation could be produced by stimulated emission. When such radiation is in the optical or infrared spectrum it is termed laser (light amplification by stimulated emission of radiation) light. A laser, a high-intensity light source, emits a nearly parallel electromagnetic beam of energy at a given wavelength that can be captured by a lens and concentrated in the focal spot. The wavelength determines how the laser will be used. The carbon dioxide laser is now successfully employed for some surgical procedures in gynecology, otorhinolaryngology, neurosurgery, and plastic and general surgery. The CO2 laser beam is directed through the viewing system of an operating microscope or through a hand-held laser component. Its basic action in tissue is thermal vaporization; it causes minimal damage to adjacent tissues. Surgeons require special training in the basic methods and techniques of laser surgery, as well as in the safety standards that must be observed. Images FIG. 5 PMID:7074503

Laser Desorption Postionization Mass Spectrometry of Antibiotic-Treated Bacterial Biofilms using Tunable Vacuum Ultraviolet Radiation

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

Gasper, Gerald L; Takahashi, Lynelle K; Zhou, Jia

2010-08-04

Laser desorption postionization mass spectrometry (LDPI-MS) with 8.0 ? 12.5 eV vacuum ultraviolet synchrotron radiation is used to single photon ionize antibiotics andextracellular neutrals that are laser desorbed both neat and from intact bacterial biofilms. Neat antibiotics are optimally detected using 10.5 eV LDPI-MS, but can be ionized using 8.0 eV radiation, in agreement with prior work using 7.87 eV LDPI-MS. Tunable vacuum ultraviolet radiation also postionizes laser desorbed neutrals of antibiotics and extracellular material from within intact bacterial biofilms. Different extracellular material is observed by LDPI-MS in response to rifampicin or trimethoprim antibiotic treatment. Once again, 10.5 eV LDPI-MSmore » displays the optimum trade-off between improved sensitivity and minimum fragmentation. Higher energy photons at 12.5 eV produce significant parent ion signal, but fragment intensity and other low mass ions are also enhanced. No matrix is added to enhance desorption, which is performed at peak power densities insufficient to directly produce ions, thus allowing observation of true VUV postionization mass spectra of antibiotic treated biofilms.« less

An Improved Measurement Method for the Strength of Radiation of Reflective Beam in an Industrial Optical Sensor Based on Laser Displacement Meter.

PubMed

Bae, Youngchul

2016-05-23

An optical sensor such as a laser range finder (LRF) or laser displacement meter (LDM) uses reflected and returned laser beam from a target. The optical sensor has been mainly used to measure the distance between a launch position and the target. However, optical sensor based LRF and LDM have numerous and various errors such as statistical errors, drift errors, cyclic errors, alignment errors and slope errors. Among these errors, an alignment error that contains measurement error for the strength of radiation of returned laser beam from the target is the most serious error in industrial optical sensors. It is caused by the dependence of the measurement offset upon the strength of radiation of returned beam incident upon the focusing lens from the target. In this paper, in order to solve these problems, we propose a novel method for the measurement of the output of direct current (DC) voltage that is proportional to the strength of radiation of returned laser beam in the received avalanche photo diode (APD) circuit. We implemented a measuring circuit that is able to provide an exact measurement of reflected laser beam. By using the proposed method, we can measure the intensity or strength of radiation of laser beam in real time and with a high degree of precision.

An Improved Measurement Method for the Strength of Radiation of Reflective Beam in an Industrial Optical Sensor Based on Laser Displacement Meter

PubMed Central

Bae, Youngchul

2016-01-01

An optical sensor such as a laser range finder (LRF) or laser displacement meter (LDM) uses reflected and returned laser beam from a target. The optical sensor has been mainly used to measure the distance between a launch position and the target. However, optical sensor based LRF and LDM have numerous and various errors such as statistical errors, drift errors, cyclic errors, alignment errors and slope errors. Among these errors, an alignment error that contains measurement error for the strength of radiation of returned laser beam from the target is the most serious error in industrial optical sensors. It is caused by the dependence of the measurement offset upon the strength of radiation of returned beam incident upon the focusing lens from the target. In this paper, in order to solve these problems, we propose a novel method for the measurement of the output of direct current (DC) voltage that is proportional to the strength of radiation of returned laser beam in the received avalanche photo diode (APD) circuit. We implemented a measuring circuit that is able to provide an exact measurement of reflected laser beam. By using the proposed method, we can measure the intensity or strength of radiation of laser beam in real time and with a high degree of precision. PMID:27223291

Local thermodynamic equilibrium in a laser-induced plasma evidenced by blackbody radiation

NASA Astrophysics Data System (ADS)

Hermann, Jörg; Grojo, David; Axente, Emanuel; Craciun, Valentin

2018-06-01

We show that the plasma produced by laser ablation of solid materials in specific conditions has an emission spectrum that is characterized by the saturation of the most intense spectral lines at the blackbody radiance. The blackbody temperature equals the excitation temperature of atoms and ions, proving directly and unambiguously a plasma in local thermodynamic equilibrium. The present investigations take benefit from the very rich and intense emission spectrum generated by ablation of a nickel-chromium-molybdenum alloy. This alternative and direct proof of the plasma equilibrium state re-opens the perspectives of quantitative material analyses via calibration-free laser-induced breakdown spectroscopy. Moreover, the unique properties of this laser-produced plasma promote its use as radiation standard for intensity calibration of spectroscopic instruments.

EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Selective metallisation of diamonds with the aid of laser radiation

NASA Astrophysics Data System (ADS)

Shafeev, Georgii A.; Pimenov, S. M.; Lubnin, Evgenii N.; Smolin, A. A.; Konov, Vitalii I.; Laptev, V. A.

1995-02-01

An experimental investigation was made of laser activation of diamond surfaces (single crystals and polycrystalline diamond films) prior to electroless before catalytic deposition of metals from solutions. The activation was carried out by a copper vapour laser or a KrF excimer laser in two ways: decomposition of a thin film of palladium acetylacetonate and local laser stimulated modification of the diamond surface by laser evaporation. An ohmic contact (Cu or Ni) with an adhesive strength of 3 N mm-2 was formed and the spatial resolution achieved was 10 μm.

Influence of low-level laser radiation on kidney functions

NASA Astrophysics Data System (ADS)

Koultchavenia, Ekaterina V.

1998-12-01

Most of all renal diseases are accompanied by lowering of kidney functions. That makes the quality of the treatment worse. On an example 69 patients receiving Low-Level Laser Therapy (LLLT), the influence of the laser radiation on a contracting system of blood, on current of an active and inactive tubercular inflammation and on partial functions of kidneys were investigated. Is established, that LLLT does not render influence to a contracting system; promotes stopping of unspecific and moderate peaking of a specific inflammation of kidneys. Is proved, that after a rate of laserotherapy the improving of a blood micricirculation in kidney occurs in 57.9% of patients; a secretion - in 63.1% of the patients; a stimulation of urodynamic is fixed in 79% of cases. Magnification of diuresis, improving filtration and concentration functions of kidneys also is marked.

LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Control of the angular distribution of the radiation emitted by phase-locked laser arrays

NASA Astrophysics Data System (ADS)

Kachurin, O. R.; Lebedev, F. V.; Napartovich, M. A.; Khlynov, M. E.

1991-03-01

A numerical investigation was made of the influence of the number and packing density of a linear array of periodically arranged coherent sources on the efficiency of redistributing the radiation power from the side lobes to the main lobe of the angular distribution of the emitted radiation by using a binary phase corrector mounted in the image-doubling plane. The results are given of experimental investigations of a new device for improving the radiation pattern of phase-locked laser arrays.

Dynamics of laser-induced channel formation in water and influence of pulse duration on the ablation of biotissue under water with pulsed erbium-laser radiation

NASA Astrophysics Data System (ADS)

Ith, M.; Pratisto, H.; Altermatt, H. J.; Frenz, M.; Weber, H. P.

1994-12-01

The ability to use fiber-delivered erbium-laser radiation for non-contact arthroscopic meniscectomy in a liquid environment was studied. The laser radiation is transmitted through a water-vapor channel created by the leading part of the laser pulse. The dynamics of the channel formation around a submerged fiber tip was investigated with time-resolved flash photography. Strong pressure transients with amplitudes up to a few hundreds of bars measured with a needle hydrophone were found to accompany the channel formation process. Additional pressure transients in the range of kbars were observed after the laser pulse associated with the collapse of the vapor channel. Transmission measurements revealed that the duration the laser-induced channel stays open, and therefore the energy transmittable through it, is substantially determined by the laser pulse duration. The optimum pulse duration was found to be in the range between 250 and 350 µS. This was confirmed by histological evaluations of the laser incisions in meniscus: Increasing the pulse duration from 300 to 800 µs leads to a decrease in the crater depth from 1600 to 300 µm. A comparison of the histological examination after laser treatment through air and through water gave information on the influence of the vapor channel on the ablation efficiency, the cutting quality and the induced thermal damage in the adjacent tissue. The study shows that the erbium laser combined with an adequate fiber delivery system represents an effective surgical instrument liable to become increasingly accepted in orthopedic surgery.

Maculopathy following exposure to visible and infrared radiation from a laser pointer: a clinical case study.

PubMed

Hanson, James V M; Sromicki, Julian; Mangold, Mario; Golling, Matthias; Gerth-Kahlert, Christina

2016-04-01

Laser pointer devices have become increasingly available in recent years, and their misuse has caused a number of ocular injuries. Online distribution channels permit trade in devices which may not conform to international standards in terms of their output power and spectral content. We present a case study of ocular injury caused by one such device. The patient was examined approximately 9 months following laser exposure using full-field and multifocal electroretinography (ERG and MF-ERG), electrooculography (EOG), and optical coherence tomography (OCT), in addition to a full ophthalmological examination. MF-ERG, OCT, and the ophthalmological examination were repeated 7 months after the first examination. The output of the laser pointer was measured. Despite severe focal damage to the central retina visible fundoscopically and with OCT, all electrophysiological examinations were quantitatively normal; however, qualitatively the central responses of the MF-ERG appeared slightly reduced. When the MF-ERG was repeated 7 months later, all findings were normal. The laser pointer was found to emit both visible and infrared radiation in dangerous amounts. Loss of retinal function following laser pointer injury may not always be detectable using standard electrophysiological tests. Exposure to non-visible radiation should be considered as a possible aggravating factor when assessing cases of alleged laser pointer injury.

Laser-heated thruster

NASA Technical Reports Server (NTRS)

Kemp, N. H.; Lewis, P. F.

1980-01-01

The development of a computer program for the design of the thrust chamber for a CW laser heated thruster was examined. Hydrodgen was employed as the propellant gas and high temperature absorber. The laser absorption coefficient of the mixture/laser radiation combination is given in temperature and species densities. Radiative and absorptive properties are given to determine radiation from such gas mixtures. A computer code for calculating the axisymmetric channel flow of a gas mixture in chemical equilibrium, and laser energy absorption and convective and radiative heating is described. It is concluded that: (1) small amounts of cesium seed substantially increase the absorption coefficient of hydrogen; (2) cesium is a strong radiator and contributes greatly to radiation of cesium seeded hydrogen; (3) water vapor is a poor absorber; and (4) for 5.3mcm radiation, both H2O/CO and NO/CO seeded hydrogen mixtures are good absorbers.

Report on the Study of Radiation Damage in Calcium Fluoride and Magnesium Fluoride Crystals for use in Excimer Laser Applications

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

None, None

1999-10-04

A study was performed to investigate the effects of radiation damage in calcium fluoride and magnesium fluoride crystals caused by gamma rays and UV photons from excimer lasers. The purpose was to study and correlate the damage caused by these two different mechanisms in various types of material used for fabricating optical elements in high power excimer lasers and lens systems of lithography tools. These optical systems are easily damaged by the laser itself, and it is necessary to use only the most radiation resistant materials for certain key elements. It was found that a clear correlation exists between the,more » radiation induced damage caused by high energy gamma rays and that produced by UV photons from the excimer laser. This correlation allows a simple procedure to be developed to select the most radiation resistant material at the ingot level, which would be later used to fabricate various components of the optical system. This avoids incurring the additional cost of fabricating actual optical elements with material that would later be damaged under prolonged use. The result of this screening procedure can result in a considerable savings in the overall cost of the lens and laser system.« less

Microhardness of demineralized enamel following home bleaching and laser-assisted in office bleaching

PubMed Central

Ghanbarzadeh, Majid; Akbari, Majid; Hamzei, Haniye

2015-01-01

Background There is little data regarding the effect of tooth whitening on microhardness of white spot lesions. This study was conducted to investigate the effect of home-bleaching and laser-assisted in-office bleaching on microhardness of demineralized enamel. Material and Methods Forty bovine incisors were selected and immersed in a demineralizing solution for 12 weeks to induce white spot lesions. Enamel blocks were prepared and randomly assigned to two groups of 20 each. The first group underwent home bleaching with 15% carbamide peroxide which was applied for 8 hours a day over a period of 15 days. In the second group, in-office bleaching was performed by 40% hydrogen peroxide and powered by irradiation from an 810 nm gallium-aluminum-arsenide (GaAlAs) diode laser (CW, 2W). This process was performed for 3 sessions every seven days, in 15 days. The specimens were stored in Fusayama Meyer artificial saliva during the experiment. Surface microhardness was assessed before and after the bleaching therapies in both groups. Results Microhardness decreased significantly following both home bleaching and laser-assisted in-office bleaching (p<0.05). There were no significant differences in hardness values among the two groups either before (p=0.131) or after (p=0.182) the bleaching procedures. Conclusions Tooth whitening through home bleaching or laser-assisted in-office bleaching can result in a significant reduction in microhardness of white spot lesions. Therefore, it is suggested to take protective measures on bleached demineralized enamel. Key words:White spot lesion, bleaching, laser, microhardness, demineralized enamel, home bleaching, in-office bleaching. PMID:26330939

Processes of interaction of laser radiation with porous transparent materials during their ablation

NASA Astrophysics Data System (ADS)

Osipov, V. V.; Lisenkov, V. V.; Platonov, V. V.; Tikhonov, E. V.

2018-03-01

The effect of ytterbium fibre laser radiation with λ = 1.07 μm on the pressed micropowders of transparent oxides and fluorides (CaF2, Y2O3, Al2O3, YSZ, etc.) having low absorption coefficients is theoretically studied. Using the numerical modelling, it is established that the radiation scattering in the medium of particles 0.5–4.6 μm in diameter leads to the concentration of radiation in the local regions of the medium, with the intensity level exceeding the intensity of the incident radiation (0.46 MW cm-2) by many times. It is shown that with the growth of the refractive index n of the material from 1.38 (MgF2) to 2.12 (YSZ) the intensity of radiation in the region of the strongest local maximum increases from 3.8 to 31 MW cm-2. In our opinion, this factor can be dominant in determining the possibility of achieving the ablation of such a medium by means of the radiation having an intensity of no greater than 1 MW cm-2. This hypothesis is experimentally checked by the example of preparing a nanopowder of CaF2 (n = 1.43) and 1% Nd : Y2O3 (n = 1.91) by evaporating the pressed target with the porosity 50% by the continuous-wave radiation of the ytterbium fibre laser with the power 600 W and the intensity 0.4 MW cm-2. Inside the CaF2 target, the scattered radiation intensity is smaller than the optical breakdown threshold, and the target is not evaporated. Under the same conditions, the target made of higher-melting 1% Nd : Y2O3 evaporates well, and the efficiency of the nanopowder production amounts to 23 g h-1.

A path to practical Solar Pumped Lasers via Radiative Energy Transfer.

PubMed

Reusswig, Philip D; Nechayev, Sergey; Scherer, Jennifer M; Hwang, Gyu Weon; Bawendi, Moungi G; Baldo, Marc A; Rotschild, Carmel

2015-10-05

The optical conversion of incoherent solar radiation into a bright, coherent laser beam enables the application of nonlinear optics to solar energy conversion and storage. Here, we present an architecture for solar pumped lasers that uses a luminescent solar concentrator to decouple the conventional trade-off between solar absorption efficiency and the mode volume of the optical gain material. We report a 750-μm-thick Nd(3+)-doped YAG planar waveguide sensitized by a luminescent CdSe/CdZnS (core/shell) colloidal nanocrystal, yielding a peak cascade energy transfer of 14%, a broad spectral response in the visible portion of the solar spectrum, and an equivalent quasi-CW solar lasing threshold of 23 W-cm(-2), or approximately 230 suns. The efficient coupling of incoherent, spectrally broad sunlight in small gain volumes should allow the generation of coherent laser light from intensities of less than 100 suns.

High Energy Ion Acceleration by Extreme Laser Radiation Pressure

DTIC Science & Technology

2017-03-14

and was published in Nuclear Instruments and Methods A [11]. For similar targets, it was found that by monitoring the divergence of a low- energy ...AFRL-AFOSR-UK-TR-2017-0015 High energy ion acceleration by extreme laser radiation pressure Paul McKenna UNIVERSITY OF STRATHCLYDE VIZ ROYAL COLLEGE...MM-YYYY)   14-03-2017 2. REPORT TYPE  Final 3. DATES COVERED (From - To)  01 May 2013 to 31 Dec 2016 4. TITLE AND SUBTITLE High energy ion acceleration

Voice quality after treatment of early vocal cord cancer: a randomized trial comparing laser surgery with radiation therapy.

PubMed

Aaltonen, Leena-Maija; Rautiainen, Noora; Sellman, Jaana; Saarilahti, Kauko; Mäkitie, Antti; Rihkanen, Heikki; Laranne, Jussi; Kleemola, Leenamaija; Wigren, Tuija; Sala, Eeva; Lindholm, Paula; Grenman, Reidar; Joensuu, Heikki

2014-10-01

Early laryngeal cancer is usually treated with either transoral laser surgery or radiation therapy. The quality of voice achieved with these treatments has not been compared in a randomized trial. Male patients with carcinoma limited to 1 mobile vocal cord (T1aN0M0) were randomly assigned to receive either laser surgery (n=32) or external beam radiation therapy (n=28). Surgery consisted of tumor excision with a CO2 laser with the patient under general anaesthesia. External beam radiation therapy to the larynx was delivered to a cumulative dose of 66 Gy in 2-Gy daily fractions over 6.5 weeks. Voice quality was assessed at baseline and 6 and 24 months after treatment. The main outcome measures were expert-rated voice quality on a grade, roughness, breathiness, asthenia, and strain (GRBAS) scale, videolaryngostroboscopic findings, and the patients' self-rated voice quality and its impact on activities of daily living. Overall voice quality between the groups was rated similar, but voice was more breathy and the glottal gap was wider in patients treated with laser surgery than in those who received radiation therapy. Patients treated with radiation therapy reported less hoarseness-related inconvenience in daily living 2 years after treatment. Three patients in each group had local cancer recurrence within 2 years from randomization. Radiation therapy may be the treatment of choice for patients whose requirements for voice quality are demanding. Overall voice quality was similar in both treatment groups, however, indicating a need for careful consideration of patient-related factors in the choice of a treatment option. Copyright © 2014 Elsevier Inc. All rights reserved.

Voice Quality After Treatment of Early Vocal Cord Cancer: A Randomized Trial Comparing Laser Surgery With Radiation Therapy

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

Aaltonen, Leena-Maija, E-mail: leena-maija.aaltonen@hus.fi; Rautiainen, Noora; Sellman, Jaana

Objective: Early laryngeal cancer is usually treated with either transoral laser surgery or radiation therapy. The quality of voice achieved with these treatments has not been compared in a randomized trial. Methods and Materials: Male patients with carcinoma limited to 1 mobile vocal cord (T1aN0M0) were randomly assigned to receive either laser surgery (n=32) or external beam radiation therapy (n=28). Surgery consisted of tumor excision with a CO{sub 2} laser with the patient under general anaesthesia. External beam radiation therapy to the larynx was delivered to a cumulative dose of 66 Gy in 2-Gy daily fractions over 6.5 weeks. Voice quality wasmore » assessed at baseline and 6 and 24 months after treatment. The main outcome measures were expert-rated voice quality on a grade, roughness, breathiness, asthenia, and strain (GRBAS) scale, videolaryngostroboscopic findings, and the patients' self-rated voice quality and its impact on activities of daily living. Results: Overall voice quality between the groups was rated similar, but voice was more breathy and the glottal gap was wider in patients treated with laser surgery than in those who received radiation therapy. Patients treated with radiation therapy reported less hoarseness-related inconvenience in daily living 2 years after treatment. Three patients in each group had local cancer recurrence within 2 years from randomization. Conclusions: Radiation therapy may be the treatment of choice for patients whose requirements for voice quality are demanding. Overall voice quality was similar in both treatment groups, however, indicating a need for careful consideration of patient-related factors in the choice of a treatment option.« less

Nonlinear frequency conversion of radiation from a copper-vapor laser

NASA Astrophysics Data System (ADS)

Polunin, Iu. P.; Troitskii, V. O.

1987-11-01

The nonlinear frequency conversion of copper-vapor laser radiation in a KDP crystal was studied experimentally. Output powers of 600 mW and 120 mW were obtained at wavelengths of 271 nm (the sum frequency) and 289 nm (the second harmonic of the yellow line), respectively. The conversion efficiency in both cases was about 3 percent; when selector losses were taken into accounted, the efficiency amounted to 5 percent.

Stable room-temperature LiF:F2+* tunable color-center laser for the 830-1060-nm spectral range pumped by second-harmonic radiation from a neodymium laser

NASA Astrophysics Data System (ADS)

Ter-Mikirtychev, V. V.

1995-09-01

Simultaneous photostability and thermostability of a room-temperature LiF:F2+ * tunable color-center laser, with an operating range over 830-1060 nm, pumped by second-harmonic radiation of a YAG:Nd3+ laser with a 532-nm wavelength has been achieved. The main lasing characteristics of the obtained LiF:F2+* laser have been measured. Twenty-five percent real efficiency in a nonselective resonator cavity and 15% real efficiency in a selective resonator cavity have been obtained. The stable LiF:F2 +* laser operates at a 1-100-Hz pulse-repetition rate with a 15-ns pulse duration, a 1-1.5-cm-1 narrow-band oscillation bandwidth, and divergency of better than 6 \\times 10-4. Doubling the fundamental frequencies of F2+ * oscillation made it possible to obtain stable blue-green tunable radiation over the 415-530-nm range.

Effect of photobiomodulation (670 nm) associated with vitamin A on the inflammatory phase of wound healing.

PubMed

Otterço, A N; Brassolatti, P; Andrade, A L M; Avó, L R S; Bossini, P S; Parizotto, N A E

2018-05-22

Wound healing is a complex biological process with specific phases. Photobiomodulation (PBM) decreases the inflammatory infiltrate, stimulating fibroblast proliferation and angiogenesis, and therefore, is indicated for wound healing. Vitamin A is used to reverse the inhibitory effects on wound healing and accelerate the healthy granulation tissue. The study aimed to evaluate the effect of topical vitamin A and PBM (GaAlAs) in inflammatory phase of cutaneous wounds. Forty Wistar male rats were separated into four groups: (1) control (CG); (2) laser group (LG) GaAlAs, 670 nm, 30 mW, energy per point of 0.9 J, radiating by 1 point in 30 s; (3) vitamin A group (VitAG); and (4) laser group plus vitamin A (LG + VitAG). Wounds were surgically made by a punch biopsy with 10 mm of diameter on the back of the animals and all treatments were started according to the experiment. The treatments were administered for four consecutive days and biopsy was performed on day 4. We performed both H&E and immunohistochemistry analysis. The results were compared between groups by one-way analysis of variance ANOVA test with post hoc Tukey (p < 0.05). Inflammatory infiltrate increased significantly in LG compared to CG and VitAG (p < 0.05). Regarding angiogenesis, VEGF expression was increased significantly in LG and LG + VitAG groups, p < 0.01. The results indicate that proposed treatments were effective on the healing process improved by LG and LG + VitAG. We show that laser plus vitamin A enhances healing by reducing the wound area and may have potential application for clinical management of cutaneous wounds.

Enhanced THz radiation generation by photo-mixing of tophat lasers in rippled density plasma with a planar magnetostatic wiggler and s-parameter

NASA Astrophysics Data System (ADS)

Abedi-Varaki, M.

2018-02-01

In this paper, the effects of planar magnetostatic wiggler and s-parameter on the terahertz (THz) radiation generation through rippled plasma have been investigated. Efficient THz radiation generation by photo-mixing of tophat lasers for rippled density plasma in the presence of the wiggler field has been presented. Fundamental equations for the analysis of the non-linear current density and THz radiation generation by wiggler magnetostatic field have been derived. It is shown that for the higher order of the tophat lasers, the values of THz amplitude are greater. In fact, the higher order of the tophat lasers has a sharp gradient in the intensity of lasers, which leads to a stronger nonlinear ponderomotive force and, consequently, a stronger current density. In addition, it is seen that by increasing s-parameter, the normalized transverse profile becomes more focused near the axis of y. Furthermore, it is observed that the normalized laser efficiency has a decreasing trend with increasing normalized THz frequency for different values of the wiggler field. Also, it is shown that by employing a greater order of the tophat lasers and a stronger wiggler field, the efficiency of order of 30% can be achieved. Moreover, it is found that we can control focus and intensity of THz radiation emitted in rippled plasma by choosing the appropriate order of the tophat lasers and tuning of the wiggler field.

FIBER OPTICS. ACOUSTOOPTICS: Amplification of semiconductor laser radiation in the wavelength range 1.24-1.3 μm by stimulated Raman scattering in an optical fiber

NASA Astrophysics Data System (ADS)

Belotitskiĭ, V. I.; Kuzin, E. A.; Ovsyannikov, D. V.; Petrov, Mikhail P.

1990-07-01

An investigation was made of the influence of weak semiconductor laser radiation on the spectrum of stimulated Raman scattering in a single-mode optical waveguide pumped by a YAG:Nd3+ laser emitting at 1.06 μm. The scattered radiation power increased by a factor exceeding 10 at the semiconductor laser wavelength. A small-signal dynamic gain reached 47 dB. Simultaneous amplification was observed of several modes of multimode semiconductor laser radiation with an intermode spectral interval of 1.3 nm.

Generation of continuous-wave single-frequency 1.5 W 378 nm radiation by frequency doubling of a Ti:sapphire laser.

PubMed

Cha, Yong-Ho; Ko, Kwang-Hoon; Lim, Gwon; Han, Jae-Min; Park, Hyun-Min; Kim, Taek-Soo; Jeong, Do-Young

2010-03-20

We have generated continuous-wave single-frequency 1.5 W 378 nm radiation by frequency doubling a high-power Ti:sapphire laser in an external enhancement cavity. An LBO crystal that is Brewster-cut and antireflection coated on both ends is used for a long-term stable frequency doubling. By optimizing the input coupler's reflectivity, we could generate 1.5 W 378 nm radiation from a 5 W 756 nm Ti:sapphire laser. According to our knowledge, this is the highest CW frequency-doubled power of a Ti:sapphire laser.

Laser radiation wavefront conjugation in fiber optic lightguides

NASA Astrophysics Data System (ADS)

Chertkov, A. A.

1986-02-01

Wavefront conjugation precision during stimulated brillouin scattering is investigated in a monofiber with spatially homogeneous and inhomogeneous beams at lambda = 106 micrometer. A Q-modulated YAG:Nd sup 3+ laser with initial transmission of 25% was employed as the radiation source. The energy of the incident and reflected radiation was measured by means of F-28 photoelements outputting their signals to an S8-12 oscilloscope. The behavior of the coefficient of reflection from the stimulated Brillouin scattering mirror as a function of the amount by which the pumping energy exceeded the threshold was found to be the same for all types of fibers, and to be independent of astigmatism and angular beam divergence. The wavefront conjugation quality as a function of the energy level was also the same for all of the lightguides employed: quartz, silicate and silicate-quartz. The good wavefront conjugation observed for astigmatic and spatially inhomogeneous beams make it possible to compensate satisfactorily for inhomogeneities in the distorting wavefront of the beam.

Enhanced betatron radiation by steering a laser-driven plasma wakefield with a tilted shock front

NASA Astrophysics Data System (ADS)

Yu, Changhai; Liu, Jiansheng; Wang, Wentao; Li, Wentao; Qi, Rong; Zhang, Zhijun; Qin, Zhiyong; Liu, Jiaqi; Fang, Ming; Feng, Ke; Wu, Ying; Ke, Lintong; Chen, Yu; Wang, Cheng; Xu, Yi; Leng, Yuxin; Xia, Changquan; Li, Ruxin; Xu, Zhizhan

2018-03-01

We have experimentally realized a scheme to enhance betatron radiation by manipulating transverse oscillation of electrons in a laser-driven plasma wakefield with a tilted shock front (TSF). Very brilliant betatron x-rays have been produced with significant enhancement both in photon yield and peak energy but almost maintain the e-beam energy spread and charge. Particle-in-cell simulations indicate that the accelerated electron beam (e beam) can acquire a very large transverse oscillation amplitude with an increase in more than 10-fold, after being steered into the deflected wakefield due to the refraction of the driving laser at the TSF. Spectral broadening of betatron radiation can be suppressed owing to the small variation in the peak energy of the low-energy-spread e beam in a plasma wiggler regime. It is demonstrated that the e-beam generation, refracting, and wiggling can act as a whole to realize the concurrence of monoenergetic e beams and bright x-rays in a compact laser-wakefield accelerator.

Statistical properties of radiation from VUV and X-ray free electron laser

NASA Astrophysics Data System (ADS)

Saldin, E. L.; Schneidmiller, E. A.; Yurkov, M. V.

1998-03-01

The paper presents a comprehensive analysis of the statistical properties of the radiation from a self-amplified spontaneous emission (SASE) free electron laser operating in linear and nonlinear mode. The investigation has been performed in a one-dimensional approximation assuming the electron pulse length to be much larger than a coherence length of the radiation. The following statistical properties of the SASE FEL radiation have been studied in detail: time and spectral field correlations, distribution of the fluctuations of the instantaneous radiation power, distribution of the energy in the electron bunch, distribution of the radiation energy after the monochromator installed at the FEL amplifier exit and radiation spectrum. The linear high gain limit is studied analytically. It is shown that the radiation from a SASE FEL operating in the linear regime possesses all the features corresponding to completely chaotic polarized radiation. A detailed study of statistical properties of the radiation from a SASE FEL operating in linear and nonlinear regime has been performed by means of time-dependent simulation codes. All numerical results presented in the paper have been calculated for the 70 nm SASE FEL at the TESLA Test Facility being under construction at DESY.

Er:YAG and CTH:YAG laser radiation: contact versus non-contact enamel ablation and sonic-activated bulk composite placement

NASA Astrophysics Data System (ADS)

Buckova, M.; Kasparova, M.; Dostalova, T.; Jelinkova, H.; Sulc, J.; Nemec, M.; Fibrich, M.; Bradna, P.; Miyagi, M.

2013-05-01

Laser radiation can be used for effective caries removal and cavity preparation without significant thermal effects, collateral damage of tooth structure, or patient discomfort. The aim of this study was to compare the quality of tissue after contact or non-contact Er:YAG and CTH:YAG laser radiation ablation. The second goal was to increase the sealing ability of hard dental tissues using sonic-activated bulk filling material with change in viscosity during processing. The artificial caries was prepared in intact teeth to simulate a demineralized surface and then the Er:YAG or CTH:YAG laser radiation was applied. The enamel artificial caries was gently removed by the laser radiation and sonic-activated composite fillings were inserted. A stereomicroscope and then a scanning electron microscope were used to evaluate the enamel surface. Er:YAG contact mode ablation in enamel was quick and precise; the cavity was smooth with a keyhole shaped prism and rod relief arrangement without a smear layer. The sonic-activated filling material was consistently regularly distributed; no cracks or microleakage in the enamel were observed. CTH:YAG irradiation was able to clean but not ablate the enamel surface; in contact and also in non-contact mode there was evidence of melting and fusing of the enamel.

Formation of an optical pulsed discharge in a supersonic air flow by radiation of a repetitively pulsed CO{sub 2} laser

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

Malov, Aleksei N; Orishich, Anatolii M

Results of optimisation of repetitively pulsed CO{sub 2}-laser generation are presented for finding physical conditions of forming stable burning of an optical pulsed discharge (OPD) in a supersonic air flow and for studying the influence of pulse parameters on the energy absorption efficiency of laser radiation in plasma. The optical discharge in a supersonic air flow was formed by radiation of a repetitively pulsed CO{sub 2} laser with mechanical Q-switching excited by a discharge with a convective cooling of the working gas. For the first time the influence of radiation pulse parameters on the ignition conditions and stable burning ofmore » the OPD in a supersonic air flow was investigated and the efficiency of laser radiation absorption in plasma was studied. The influence of the air flow velocity on stability of plasma production was investigated. It was shown that stable burning of the OPD in a supersonic flow is realised at a high pulse repetition rate where the interval between radiation pulses is shorter than the time of plasma blowing-off. Study of the instantaneous value of the absorption coefficient shows that after a breakdown in a time lapse of 100 - 150 ns, a quasi-stationary 'absorption phase' is formed with the duration of {approx}1.5 ms, which exists independently of air flow and radiation pulse repetition rate. This phase of strong absorption is, seemingly, related to evolution of the ionisation wave. (laser applications and other topics in quantum electronics)« less

Radiative Reverse Shock Laser Experiments Relevant to Accretion Processes in Cataclysmic Variables

NASA Astrophysics Data System (ADS)

Krauland, Christine

2012-10-01

We present results from experiments that explore radiative reverse shock waves and their contribution to the evolving dynamics of the cataclysmic variable (CV) system in which they reside. CVs are close binary star systems containing a white dwarf (WD) that accretes matter from its late-type main sequence companion star. In the process of accretion, a reverse shock forms when the supersonic infalling plasma is impeded. It provides the main source of radiation in the binary systems. In the case of a non-magnetic CV, the impact on an accretion disk produces this ``hot spot,'' where the flow obliquely strikes the rotating accretion disk. This collision region has many ambiguities as a radiation hydrodynamic system, but shock development in the infalling flow can be modeled [1]. We discuss the production of radiative reverse shocks in experiments at the Omega-60 laser facility. The ability of this high-intensity laser to create large energy densities in targets having millimeter-scale volumes makes it feasible to create supersonic plasma flows. Obtaining a radiative reverse shock in the laboratory requires a sufficiently fast flow (> 60 km/s) within a material whose opacity is large enough to produce energetically significant emission from experimentally achievable layers. We will show the radiographic and emission data from three campaigns on Omega-60 with accompanying CRASH [2] simulations, and will discuss the implications in the context of the CV system. [4pt] [1] Armitage, P. J. and Livio, M., ApJ, 493, 898 (1998).[0pt] [2] van der Holst, B., Toth, G., Sokolov, I.V., et al., ApJS, 194, 23 (2011).

Modification in oxidative processes in muscle tissues exposed to laser- and light-emitting diode radiation.

PubMed

Monich, Victor A; Bavrina, Anna P; Malinovskaya, Svetlana L

2018-01-01

Exposure of living tissues to high-intensity red or near-infrared light can produce the oxidative stress effects both in the target zone and adjacent ones. The protein oxidative modification (POM) products can be used as reliable and early markers of oxidative stress. The contents of modified proteins in the investigated specimens can be evaluated by the 2,4-dinitrophenylhydrazine assay (the DNPH assay). Low-intensity red light is able to decrease the activity of oxidative processes and the DNPH assay data about the POM products in the biological tissues could show both an oxidative stress level and an efficiency of physical agent protection against the oxidative processes. Two control groups of white rats were irradiated by laser light, the first control group by red light and the second one by near-infrared radiation (NIR).Two experimental groups were consequently treated with laser and red low-level light-emitting diode radiation (LED). One of them was exposed to red laser light + LED and the other to NIR + LED. The fifth group was intact. Each group included ten animals. The effect of laser light was studied by methods of protein oxidative modifications. We measured levels of both induced and spontaneous POM products by the DNPH assay. The dramatic increase in levels of POM products in the control group samples when compared with the intact group data as well as the sharp decrease in the POM products in the experimental groups treated with LED low-level light were statistically significant (p ≤ 0.05). Exposure of skeletal muscles to high-intensity red and near-infrared laser light causes oxidative stress that continues not less than 3 days. The method of measurement of POM product contents by the DNPH assay is a reliable test of an oxidative process rate. Red low-intensity LED radiation can provide rehabilitation of skeletal muscle tissues treated with high-intensity laser light.

Saturation of the laser-induced narrowband coherent synchrotron radiation process: Experimental observation at a storage ring

NASA Astrophysics Data System (ADS)

Hosaka, M.; Yamamoto, N.; Takashima, Y.; Szwaj, C.; Le Parquier, M.; Evain, C.; Bielawski, S.; Adachi, M.; Zen, H.; Tanikawa, T.; Kimura, S.; Katoh, M.; Shimada, M.; Takahashi, T.

2013-02-01

We study the efficiency limitation affecting laser-induced coherent synchrotron radiation (CSR) at high laser power. Experiments are made on the UVSOR-II storage ring in conditions of narrowband terahertz CSR emission. While, at moderate power, CSR power increases quadratically with laser power, a noticeable decrease in efficiency and eventually a decrease in CSR power is observed experimentally at high power. Details of the underlying process are analyzed numerically. As the saturation effect depends almost instantaneously on the laser intensity, the saturation occurs locally in longitudinal space. This has important consequences on the modulation pattern induced on the electron bunch.

Development of a solar-powered infrared injection laser microminiature transmitting system

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

Falter, D.D.; Alley, G.T.; Falter, K.G.

1989-01-01

A solar-powered infrared microminiature transmitting system is being developed to provide scientists with a tool to continuously track and study Africanized bees. Present tracking methods have limited ranges and lack the capability of continuously tracking individual insects. Preliminary field tests of a stationary prototypic transmitter have demonstrated a range of 1.1 km. The basic design consists of an array of nine 1-mm{sup 2} solar cells, which collect energy for storage in a 1.0-{mu}F tantalum chip capacitor. When the capacitor has been charged to a sufficient level, the circuitry that monitors the capacitor voltage level wakes up'' and fires a 5-{mu}smore » pulse through an 840-nm GaAlAs injection laser diode. The process is then repeated, making the signal frequency (which ranges from 50 to 300 Hz) dependent on solar luminance. The solar cells, capacitor, and laser diode are mounted in hybrid microcircuit fashion directly on the silicon substrate containing the CMOS control and driver circuitry. The transmitter measures {approximately}4 {times} 6 mm and weighs {approximately}65 mg. The receiving system is based on an 8-in. telescope and a Si PIN diode detector. 8 refs., 10 figs.« less

Solar Pumped, Alkali Vapor Laser.

DTIC Science & Technology

1987-09-04

convert the solar radiation to electricity or longer wavelength blackbody radiation which is then used to power the laser. A directly pumped solar laser...wavelength blackbody radiation which is then used to power the laser. A directly pumped solar laser would utilize a portion of the solar spectrum to directly...sodium dimer (near the upper laser state) and a second body. *, I will review the method we used for measuring these rates and present preliminary

SU-F-T-525: Monitordeep-Inspiratory Breathhold with a Laser Sensor for Radiation Therapy of Left Breast Cancer

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

Tai, A; Currey, A; Li, X Allen

2016-06-15

Purpose: Radiation therapy (RT) of left sided breast cancers with deep-inspiratory breathhold (DIBH) can reduce the dose to heart. The purpose of this study is to develop and test a new laser-based tool to improve ease of RT delivery using DIBH. Methods: A laser sensor together with breathing monitor device (Anzai Inc., Japan) was used to record the surface breathing motion of phantom/volunteers. The device projects a laser beam to the chestwall and the reflected light creates a focal spot on a light detecting element. The position change of the focal spot correlates with the patient’s breathing motion and ismore » measured through the change of current in the light detecting element. The signal is amplified and displayed on a computer screen, which is used to trigger radiation gating. The laser sensor can be easily mounted to the simulation/treatment couch with a fixing plate and a magnet base, and has a sensitivity range of 10 to 40 cm from the patient. The correlation of breathing signals detected by laser sensor and visionRT is also investigated. Results: It is found that the measured breathing signal from the laser sensor is stable and reproducible and has no noticeable delay. It correlates well with the VisionRT surface imaging system. The DIBH reference level does not change with movement of the couch because the laser sensor and couch move together. Conclusion: The Anzai laser sensor provides a cost-effective way to improve beam gating with DIBH for treating left breast cancer. It can be used alone or together with VisionRT to determine the correct DIBH level during the radiation treatment of left breast cancer with DIBH.« less

Enhanced laser absorption from radiation pressure in intense laser plasma interactions

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

Dollar, F.; Zulick, C.; Raymond, A.

The reflectivity of a short-pulse laser at intensities of 2 x 10 21Wcm -2 with ultra-high contrast (10 -15) on sub-micrometer silicon nitride foilswas studied experimentally using varying polarizations and target thicknesses. Furthermore, the reflected intensity and beam quality were found to be relatively constant with respect to intensity for bulk targets. For submicron targets, the measured reflectivity drops substantially without a corresponding increase in transmission, indicating increased conversion of fundamental to other wavelengths and particle heating. The experimental results and trends we observed in 3D particle-in-cell simulations emphasize the critical role of ion motion due to radiation pressure onmore » the absorption process. Ion motion during ultra-short pulses enhances the electron heating, which subsequently transfers more energy to the ions.« less

Enhanced laser absorption from radiation pressure in intense laser plasma interactions

DOE PAGES

Dollar, F.; Zulick, C.; Raymond, A.; ...

2017-06-06

The reflectivity of a short-pulse laser at intensities of 2 x 10 21Wcm -2 with ultra-high contrast (10 -15) on sub-micrometer silicon nitride foilswas studied experimentally using varying polarizations and target thicknesses. Furthermore, the reflected intensity and beam quality were found to be relatively constant with respect to intensity for bulk targets. For submicron targets, the measured reflectivity drops substantially without a corresponding increase in transmission, indicating increased conversion of fundamental to other wavelengths and particle heating. The experimental results and trends we observed in 3D particle-in-cell simulations emphasize the critical role of ion motion due to radiation pressure onmore » the absorption process. Ion motion during ultra-short pulses enhances the electron heating, which subsequently transfers more energy to the ions.« less

Influence of femtosecond laser radiation on cells of the transplantable tumour Krebs-2

NASA Astrophysics Data System (ADS)

Meshalkin, Yu P.; Popova, N. A.; Nikolin, V. P.; Kaledin, V. I.; Kirpichnikov, A. V.; Pestryakov, Efim V.

2012-06-01

The influence of femtosecond radiation of a titaniumsapphire laser on cells of the transplantable ascitic tumour Krebs-2 was studied. After in vitro irradiation by the pulsed fundamentalharmonic radiation with the wavelength 800 nm, pulse duration 30 fs, repetition rate 1 kHz, mean power 100 and 300 mW and exposure time 3 min, as well as by the second-harmonic radiation (40 nm, 50 fs, 120 mW), all cells were diffusely stained by the vital stain trypan blue, which may be an evidence of their death or abnormalities of membrane permeability. However, implantation of such cells to experimental animals led to formation of tumours at the transplantation site with the kinetics slightly different from the control one. In the group of mice to which the cells were inoculated after irradiation with second harmonic pulses of titanium-sapphire laser the inhibition of tumour growth was observed due to partial death of cells under the action of UV spectral components. To explain the mechanism of the observed phenomenon the possibility of pore formation (photoporation) in the cell membrane, described earlier in the papers on foreign DNA transfection into cells, is considered.

Flexible waveguides for IR laser radiation and surgery applications.

PubMed

Gannot, I; Dror, J; Calderon, S; Kaplan, I; Croitoru, N

1994-01-01

Flexible plastic waveguides were developed to deliver IR radiation, especially at 10.6 microns, which is the CO2 laser radiation wavelength. The waveguide is made from teflon tube with the inner wall coated with a metal layer and a dielectric overlayer. The internal diameter (ID) is 1.0 mm, length 1.0-1.2 m, and the distal tip decreases moderately to ID approximately 0.6 mm. The distal part on the last 10 centimeters is coated externally with a metal layer. Maximum power that can be delivered at the outlet is approximately 30 W and 10.6 x 10(3) W/cm2. This type of waveguide was used in several medical operations to evaluate its cutting characteristics and the resistances to heat reflection from the tissue while operating in orifices containing liquid substances.

A path to practical Solar Pumped Lasers via Radiative Energy Transfer

DOE PAGES

Reusswig, Philip D.; Nechayev, Sergey; Scherer, Jennifer M.; ...

2015-10-05

The optical conversion of incoherent solar radiation into a bright, coherent laser beam enables the application of nonlinear optics to solar energy conversion and storage. Here, we present an architecture for solar pumped lasers that uses a luminescent solar concentrator to decouple the conventional trade-off between solar absorption efficiency and the mode volume of the optical gain material. We report a 750-μm-thick Nd 3+ -doped YAG planar waveguide sensitized by a luminescent CdSe/CdZnS (core/shell) colloidal nanocrystal, yielding a peak cascade energy transfer of 14%, a broad spectral response in the visible portion of the solar spectrum, and an equivalent quasi-CWmore » solar lasing threshold of 23 W-cm -2, or approximately 230 suns. The efficient coupling of incoherent, spectrally broad sunlight in small gain volumes should allow the generation of coherent laser light from intensities of less than 100 suns.« less

A path to practical Solar Pumped Lasers via Radiative Energy Transfer

PubMed Central

Reusswig, Philip D.; Nechayev, Sergey; Scherer, Jennifer M.; Hwang, Gyu Weon; Bawendi, Moungi G.; Baldo, Marc. A.; Rotschild, Carmel

2015-01-01

The optical conversion of incoherent solar radiation into a bright, coherent laser beam enables the application of nonlinear optics to solar energy conversion and storage. Here, we present an architecture for solar pumped lasers that uses a luminescent solar concentrator to decouple the conventional trade-off between solar absorption efficiency and the mode volume of the optical gain material. We report a 750-μm-thick Nd3+-doped YAG planar waveguide sensitized by a luminescent CdSe/CdZnS (core/shell) colloidal nanocrystal, yielding a peak cascade energy transfer of 14%, a broad spectral response in the visible portion of the solar spectrum, and an equivalent quasi-CW solar lasing threshold of 23 W-cm−2, or approximately 230 suns. The efficient coupling of incoherent, spectrally broad sunlight in small gain volumes should allow the generation of coherent laser light from intensities of less than 100 suns. PMID:26434400

Influence of laser radiation on the growth and development of seeds of agricultural plants

NASA Astrophysics Data System (ADS)

Grishkanich, Alexander; Zhevlakov, Alexander; Polyakov, Vadim; Kascheev, Sergey; Sidorov, Igor; Ruzankina, Julia; Yakovlev, Alexey; Mak, Andrey

2016-04-01

The experimental results presented in this study focused on the study of biological processes caused by exposure to the coating layers of the laser green light seed (λ = 532 nm) range for the larch, violet (λ = 405 nm) and red (λ = 640 nm) for spruce. Spend a series of experiments to study the dependence of crop seed quality (spruce and larch from the pine family) from exposure to laser radiation under different conditions. In all the analyzed groups studied seed germination and growth of seedlings exposed to laser exposure, compared with the control group. The results showed that the higher percentage of germination than seeds of the control group.

Photomechanical model of tooth enamel ablation by Er-laser radiation

NASA Astrophysics Data System (ADS)

Belikov, A. V.; Shatilova, K. V.; Skrypnik, A. V.; Vostryakov, R. G.; Maykapar, N. O.

2012-03-01

The photomechanical model of ablation of human tooth enamel is described in this work. It takes into account the structural peculiarities of enamel: free water in the enamel pores or cracks. We consider the photomechanical destruction of the enamel rods of hydroxyapatite by the pressure of water contained in the enamel pores and heated by laser radiation. This model takes into account attenuation by the Lambert-Beer law when radiation passes through the tissue and the fact that the tissue removal occurs when a unit volume of water was heated to the critical temperature. Decreasing logarithmic dependence of the enamel removal efficiency on the energy density was obtained as a result of the calculations. The shape of this function follows the shape of the experimental curve.

Comparison of survival between radiation therapy and trans-oral laser microsurgery for early glottic cancer patients; a retrospective cohort study.

PubMed

De Santis, R J; Poon, I; Lee, J; Karam, I; Enepekides, D J; Higgins, K M

2016-08-02

The literature reports various treatment methodologies, such as trans-oral laser microsurgery, radiation therapy, total/partial laryngectomies, and concurrent radiation chemotherapy for patients with early larynx cancer. However, at the forefront of early glottis treatment is trans-oral laser microsurgery and radiation therapy, likely due to better functional and survival outcomes. Here we conduct the largest Canadian head-to-head comparison of consecutive patients treated with either radiation therapy or trans-oral laser microsurgery. Additionally, we compare these two treatments and their 5-year survival rates post treatment to add to the existing literature. Charts of patients who were diagnosed with early glottic cancer between 2006 and 2013 were reviewed. Seventy-five patients were identified, and split into 2 groups based on their primary treatment, trans-oral laser microsurgery and radiation therapy. Kaplan-Meier survival curves, life-tables, and the log-rank statistic were reported to determine if there was a difference between the two treatment groups and their disease-specific survival, disease-free survival, and total laryngectomy-free survival. Additionally, each different survival analysis was stratified by potential confounding variables, to help conclude which treatment is more efficacious in this population. The 5-year disease-specific survival rate is 93.3 % σ = 0.063 and 90.8 % σ = 0.056 for patients treated with trans-oral laser microsurgery and radiation therapy, respectively (χ (2) < 0.001, p = 0.983). The disease free survival rate is 60.0 % (σ =0.121) for patients treated with trans-oral laser microsurgery, and 67.2 % (σ = 0.074) for those who received RT (χ (2) = 0.19, p = 0.663). Additionally, the total laryngectomy-free survival rate is 84.1 % (σ = 0.1) and 79.1 % (σ = 0.072) for patients' early glottic cancer treated by trans-oral laser microsurgery and radiation therapy, respectively (�

Isotopic imaging via nuclear resonance fluorescence with laser-based Thomson radiation

DOEpatents

Barty, Christopher P. J. [Hayward, CA; Hartemann, Frederic V [San Ramon, CA; McNabb, Dennis P [Alameda, CA; Pruet, Jason A [Brentwood, CA

2009-07-21

The present invention utilizes novel laser-based, high-brightness, high-spatial-resolution, pencil-beam sources of spectrally pure hard x-ray and gamma-ray radiation to induce resonant scattering in specific nuclei, i.e., nuclear resonance fluorescence. By monitoring such fluorescence as a function of beam position, it is possible to image in either two dimensions or three dimensions, the position and concentration of individual isotopes in a specific material configuration. Such methods of the present invention material identification, spatial resolution of material location and ability to locate and identify materials shielded by other materials, such as, for example, behind a lead wall. The foundation of the present invention is the generation of quasimonochromatic high-energy x-ray (100's of keV) and gamma-ray (greater than about 1 MeV) radiation via the collision of intense laser pulses from relativistic electrons. Such a process as utilized herein, i.e., Thomson scattering or inverse-Compton scattering, produces beams having diameters from about 1 micron to about 100 microns of high-energy photons with a bandwidth of .DELTA.E/E of approximately 10E.sup.-3.

Theory and simulations of radiation friction induced enhancement of laser-driven longitudinal fields

NASA Astrophysics Data System (ADS)

Gelfer, E. G.; Fedotov, A. M.; Weber, S.

2018-06-01

We consider the generation of a quasistatic longitudinal electric field by intense laser pulses propagating in a transparent plasma with radiation friction (RF) taken into account. For both circular and linear polarization of the driving pulse we develop a 1D analytical model of the process, which is valid in a wide range of laser and plasma parameters. We define the parameter region where RF results in an essential enhancement of the longitudinal field. The amplitude and the period of the generated longitudinal wave are estimated and optimized. Our theoretical predictions are confirmed by 1D and 2D PIC simulations. We also demonstrate numerically that RF should substantially enhance the longitudinal field generated in a plasma by a 10 PW laser such as ELI Beamlines.

Potentialities of a new sigma(+)-sigma(-)laser configuration for radiative cooling and trapping

NASA Astrophysics Data System (ADS)

Dalibard, J.; Reynaud, S.; Cohen-Tannoudji, C.

1984-11-01

In the process of cooling and trapping neutral atoms, a new laser configuration is investigated which consists of two counterpropagating laser beams with orthogonal sigma(+) and sigma(-)polarizations. It is shown that such a configuration looks more promising than an ordinary standing wave (where the two counterpropagating waves have the same polarization), and this result is explained as being due to angular momentum conservation which prevents any coherent redistribution of photons between the two waves. The present conclusions are based on a quantitative calculation of the various parameters (potential depth, friction coefficient, diffusion coefficient) describing the mean value and the fluctuations of the radiative forces experienced, in such a laser configuration, by an atom with a J = 0 ground state and a J = 1 excited state.

Comparative morphological investigation on the rabbit's auricle after exposure to CO2- and Nd:YAG-laser radiation.

PubMed

Wandhöfer, A; Bally, G; Kauffmann, G; Karduck, A

1977-10-31

By comparing the effects of CO2- and Nd:YAG-laser radiation (mainly differing in wave-length by a factor of 10), a surgical instrument suitable for Otorhinolaryngology had to be found. The studies were performed on the rabbit's auricle in order to examine the effect of the laser irradiation mainly on the cartilage. The CO2-laser was found to be more efficient in cutting and caused less extended tissue damage than the Nd:YAG-laser. The latter seems to be more suitable for soft tissue surgery.

EFFECTS OF LASER RADIATION ON MATTER: Role of the external photoelectric effect in surface microprocessing

NASA Astrophysics Data System (ADS)

Ageev, Vladimir P.; Konov, Vitalii I.; Krechetov, A. I.

1990-08-01

An analysis is made of the photoemission of electrons in gases when the surface of a solid is subjected to high-intensity ultraviolet laser radiation which does not cause surface heating. Various situations are considered in which generation of high local electric fields and of a dense cloud of charged particles near the surface may alter and even determine the mechanism of laser-stimulated processes on surfaces of solids.

Isolated few-cycle radiation from chirped-pulse compression of a superradiant free-electron laser

DOE PAGES

Huang, Yen -Chieh; Zhang, Zhen; Chen, Chia -Hsiang; ...

2015-08-31

When a short electron bunch traverses an undulator to radiate a wavelength longer than the bunch length, intense superradiance from the electron bunch can quickly deplete the electron’s kinetic energy and lead to generation of an isolated chirped radiation pulse. Here, we develop a theory to describe this novel chirped pulse radiation in a superradiant free-electron laser and show the opportunity to generate isolated few-cycle high-power radiation through chirped-pulse compression after the undulator. The theory is completely characterized by how fast the electron energy is depleted for a given length of an undulator. We further present two design examples atmore » the THz and extreme-ultraviolet wavelengths and numerically generate isolated three- and nine-cycle radiation pulses, respectively.« less

Experimental Validation of Thermal Retinal Models of Damage from Laser Radiation

DTIC Science & Technology

1979-08-01

for measuring relative intensity profile with a thermocouple or fiber-optic sensor .............................................. 72 B-2 Calculated...relative intensity profiles meas- ured by 5- and 10-pm-radius sensors of a Gaussian beam, with standard deviation of 10 Pm...the Air Force de - veloped a model for the mathematical prediction of thermal ef- fects of laser radiation on the eye (8). Given the characteris- tics

A Study of the Influence of Low Intensity Laser Therapy on Painful Temporomandibular Disorder Patients

PubMed Central

Sattayut, S.; Bradley, P.

2012-01-01

A double-blind clinical trial was conducted on 30 female Temporomandibular Disorders (TMD) patients who had pain as a chief complaint. The patients were randomly allocated into three groups based on Low Intensity Laser (LILT) regimes namely 820 nm Gallium Aluminium Arsenide (GaAlAs) laser at energy densities of 21.4J/cm2, 107 J/cm2 and placebo laser. Each patient had three LILT treatments in a week. The pressure pain threshold (PPT) of trigger points in masticatory muscles, unassisted maximum mouth opening without pain (MOSP) and symptom severity index (SSI) were recorded as baseline data and monitored after every treatment. Jaw kinesiology, electromyography (EMG) and pain rating index from McGill pain questionnaire were also recorded as baseline and final results. The analysis of covariance and further analysis showed that the higher energy density laser group had significant increases in PPT and EMG amplitude recorded from voluntary clenching (cEMG) compared with the placebo group at P values 0.0001 and 0.022 respectively. A significantly greater number of patients recovered from myofascial pain and TMJ arthralgia as assessed clinically in the higher energy group compared with the placebo (P value = 0.02 and 0.006 respectively). There was no statistically significant difference in the other parameters of assessment among the groups at a P value 0.05. At a period of 2 to 4 weeks review after LILT, there was an average 52% reduction of pain as assessed by SSI. PMID:24511188

Infrared radiation and inversion population of CO2 laser levels in Venusian and Martian atmospheres

NASA Technical Reports Server (NTRS)

Gordiyets, B. F.; Panchenko, V. Y.

1983-01-01

Formation mechanisms of nonequilibrium 10 micron CO2 molecule radiation and the possible existence of a natural laser effect in the upper atmospheres of Venus and Mars are theoretically studied. An analysis is made of the excitation process of CO2 molecule vibrational-band levels (with natural isotropic content) induced by direct solar radiation in bands 10.6, 9.4, 4.3, 2.7 and 2.0 microns. The model of partial vibrational-band temperatures was used in the case. The problem of IR radiation transfer in vibrational-rotational bands was solved in the radiation escape approximation.

The optical pumping of alkali atoms using coherent radiation from semi-conductor injection lasers and incoherent radiation from resonance lamps

NASA Technical Reports Server (NTRS)

Singh, G.

1973-01-01

An experimental study for creating population differences in the ground states of alkali atoms (Cesium 133) is presented. Studies made on GaAs-junction lasers and the achievement of population inversions among the hyperfine levels in the ground state of Cs 133 by optically pumping it with radiation from a GaAs diode laser. Laser output was used to monitor the populations in the ground state hyperfine levels as well as to perform the hyperfine pumping. A GaAs laser operated at about 77 K was used to scan the 8521 A line of Cs 133. Experiments were performed both with neon-filled and with paraflint-coated cells containing the cesium vapor. Investigations were also made for the development of the triple resonance coherent pulse technique and for the detection of microwave induced hyperfine trasistions by destroying the phase relationships produced by a radio frequency pulse. A pulsed cesium resonance lamp developed, and the lamp showed clean and reproducible switching characteristics.

The study of theoretical and experimental feasibilities of the rocket fuel components ignition by laser radiation

NASA Astrophysics Data System (ADS)

Belyaev, Vadim S.; Guterman, Vitaly Y.; Ivanov, Anatoly V.

2004-06-01

The report presents the theoretical and experimental results obtained during the first year of the ISTC project No. 1926. The energy and temporal characteristics of the laser radiation necessary to ignite the working components mixture in a rocket engine combustion chamber have been predicted. Two approaches have been studied: the optical gas fuel laser-induced breakdown; the laser-initiated plasma torch on target surface. The possibilities and conditions of the rocket fuel components ignition by a laser beam in the differently designed combustion chambers have been estimated and studied. The comparative analysis shows that both the optical spark and light focusing on target techniques can ignite the mixture.

Luminescent light source for laser pumping and laser system containing same

DOEpatents

Hamil, Roy A.; Ashley, Carol S.; Brinker, C. Jeffrey; Reed, Scott; Walko, Robert J.

1994-01-01

The invention relates to a pumping lamp for use with lasers comprising a porous substrate loaded with a component capable of emitting light upon interaction of the component with exciting radiation and a source of exciting radiation. Preferably, the pumping lamp comprises a source of exciting radiation, such as an electron beam, and an aerogel or xerogel substrate loaded with a component capable of interacting with the exciting radiation, e.g., a phosphor, to produce light, e.g., visible light, of a suitable band width and of a sufficient intensity to generate a laser beam from a laser material.

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

PubMed

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

1991-06-01

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

Laser ablation of dental tissues with picosecond pulses of 1.06-microm radiation transmitted through a hollow-core photonic-crystal fiber.

PubMed

Konorov, Stanislav O; Mitrokhin, Vladimir P; Fedotov, Andrei B; Sidorov-Biryukov, Dmitrii A; Beloglazov, Valentin I; Skibina, Nina B; Shcherbakov, Andrei V; Wintner, Ernst; Scalora, Michael; Zheltikov, Aleksei M

2004-04-10

Sequences of picosecond pulses of 1.06-microm Nd:YAG laser radiation with a total energy of approximately 2 mJ are transmitted through a hollow-core photonic-crystal fiber with a core diameter of approximately 14 microm and are focused onto a tooth's surface in vitro to ablate dental tissue. The hollow-core photonic-crystal fiber is shown to support the single-fundamental-mode regime for 1.06-microm laser radiation, serving as a spatial filter and allowing the laser beam's quality to be substantially improved. The same fiber is used to transmit emission from plasmas produced by laser pulses onto the tooth's surface in the backward direction for detection and optical diagnostics.

Development of a fiber-guided laser ultrasonic system resilient to high temperature and gamma radiation for nuclear power plant pipe monitoring

NASA Astrophysics Data System (ADS)

Yang, Jinyeol; Lee, Hyeonseok; Lim, Hyung Jin; Kim, Nakhyeon; Yeo, Hwasoo; Sohn, Hoon

2013-08-01

This study develops an embeddable optical fiber-guided laser ultrasonic system for structural health monitoring (SHM) of pipelines exposed to high temperature and gamma radiation inside nuclear power plants (NPPs). Recently, noncontact laser ultrasonics is gaining popularity among the SHM community because of its advantageous characteristics such as (a) scanning capability, (b) immunity against electromagnetic interference (EMI) and (c) applicability to high-temperature surfaces. However, its application to NPP pipelines has been hampered because pipes inside NPPs are often covered by insulators and/or target surfaces are not easily accessible. To overcome this problem, this study designs embeddable optical fibers and fixtures so that laser beams used for ultrasonic inspection can be transmitted between the laser sources and the target pipe. For guided-wave generation, an Nd:Yag pulsed laser coupled with an optical fiber is used. A high-power pulsed laser beam is guided through the optical fiber onto a target structure. Based on the principle of laser interferometry, the corresponding response is measured using a different type of laser beam guided by another optical fiber. All devices are especially designed to sustain high temperature and gamma radiation. The robustness/resilience of the proposed measurement system installed on a stainless steel pipe specimen has been experimentally verified by exposing the specimen to high temperature of up to 350 °C and optical fibers to gamma radiation of up to 125 kGy (20 kGy h-1).

LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Change in the optical properties of hyaline cartilage heated by the near-IR laser radiation

NASA Astrophysics Data System (ADS)

Bagratashvili, Viktor N.; Bagratashvili, N. V.; Gapontsev, V. P.; Makhmutova, G. Sh; Minaev, V. P.; Omel'chenko, A. I.; Samartsev, I. E.; Sviridov, A. P.; Sobol', E. N.; Tsypina, S. I.

2001-06-01

The in vitro dynamics of the change in optical properties of hyaline cartilage heated by fibre lasers at wavelengths 0.97 and 1.56 μm is studied. The laser-induced bleaching (at 1.56 μm) and darkening (at 0.97 μm) of the cartilage, caused by the heating and transport of water as well as by a change in the cartilage matrix, were observed and studied. These effects should be taken into account while estimating the depth of heating of the tissue. The investigated dynamics of light scattering in the cartilage allows one to choose the optimum radiation dose for laser plastic surgery of cartilage tissues.

[The laser therapy of rheumatoid arthritis].

PubMed

Soroka, N F

1989-01-01

About 300 patients with rheumatoid arthritis (RA) underwent multimodality treatment including laser radiation of varying wavelengths. Use was made of helium-neon, infrared, argon and helium-cadmium lasers. A new method of combined laser therapy by radiation of helium-cadmium and helium-neon lasers is described. A scheme of optimal parameters and types of laser radiation recommended for the treatment of different clinical varieties of RA is provided.

Visible and near-infrared laser radiation in a biological tissue. A forward model for medical imaging by optical tomography.

PubMed

Trabelsi, H; Gantri, M; Sediki, E

2010-01-01

We present a numerical model for the study of a general, two-dimensional, time-dependent, laser radiation transfer problem in a biological tissue. The model is suitable for many situations, especially when the external laser source is pulsed or continuous. We used a control volume discrete-ordinate method associated with an implicit, three-level, second-order, time-differencing scheme. In medical imaging by laser techniques, this could be an optical tomography forward model. We considered a very thin rectangular biological tissue-like medium submitted to a visible or a near-infrared laser source. Different cases were treated numerically. The source was assumed to be monochromatic and collimated. We used either a continuous source or a short-pulsed source. The transmitted radiance was computed in detector points on the boundaries. Also, the distribution of the internal radiation intensity for different instants is presented. According to the source type, we examined either the steady-state response or the transient response of the medium. First, our model was validated by experimental results from the literature for a homogeneous biological tissue. The space and angular grid independency of our results is shown. Next, the proposed model was used to study changes in transmitted radiation for a homogeneous background medium in which were imbedded two heterogeneous objects. As a last investigation, we studied a multilayered biological tissue. We simulated near-infrared radiation in human skin, fat and muscle. Some results concerning the effects of fat thickness and positions of the detector source on the reflected radiation are presented.

Change in the optical properties of hyaline cartilage heated by the near-IR laser radiation

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

Bagratashvili, Viktor N; Bagratashvili, N V; Omel'chenko, A I

2001-06-30

The in vitro dynamics of the change in optical properties of hyaline cartilage heated by fibre lasers at wavelengths 0.97 and 1.56 {mu}m is studied. The laser-induced bleaching (at 1.56 {mu}m) and darkening (at 0.97 {mu}m) of the cartilage, caused by the heating and transport of water as well as by a change in the cartilage matrix, were observed and studied. These effects should be taken into account while estimating the depth of heating of the tissue. The investigated dynamics of light scattering in the cartilage allows one to choose the optimum radiation dose for laser plastic surgery of cartilagemore » tissues. (laser applications and other topics in quantum electronics)« less

Collisionless dissociation and isotopic enrichment of SF6 using high-powered CO2 laser radiation

NASA Technical Reports Server (NTRS)

Gower, M. C.; Billman, K. W.

1977-01-01

Dissociation of S-32F6 and the resultant isotopic enrichment of S-34F6 using high-powered CO2 laser radiation has been studied with higher experimental sensitivity than previously reported. Enrichment factors have been measured as a function of laser pulse number, wavelength, energy and time duration. A geometry independent dissociation cross section is introduced and measured values are presented. Threshold energy densities, below which no dissociation was observed, were also determined.

Observation of Betatron X-Ray Radiation in a Self-Modulated Laser Wakefield Accelerator Driven with Picosecond Laser Pulses

DOE PAGES

Albert, F.; Lemos, N.; Shaw, J. L.; ...

2017-03-31

We investigate a new regime for betatron x-ray emission that utilizes kilojoule-class picosecond lasers to drive wakes in plasmas. When such laser pulses with intensities of ~ 5 × 1 0 18 W / cm 2 are focused into plasmas with electron densities of ~ 1 × 1 0 19 cm - 3 , they undergo self-modulation and channeling, which accelerates electrons up to 200 MeV energies and causes those electrons to emit x rays. The measured x-ray spectra are fit with a synchrotron spectrum with a critical energy of 10–20 keV, and 2D particle-in-cell simulations were used to modelmore » the acceleration and radiation of the electrons in our experimental conditions« less

On the possibility of using the dynamic Franz - Keldysh effect to detect the parameters of high-power IR laser radiation

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

Grigor'ev, A M

2011-05-31

The increase in the absorption of light by a semiconductor (when the light photon energy is somewhat smaller than the semiconductor bandgap or equals it) in the presence of a strong light wave (for which the semiconductor is transparent) has been investigated. The possibility of designing novel light detectors for measuring the energy parameters and spatial and temporal characteristics of high-power IR laser radiation is demonstrated. (measurement of laser radiation parameters)

Laser readable thermoluminescent radiation dosimeters and methods for producing thereof

DOEpatents

Braunlich, Peter F.; Tetzlaff, Wolfgang

1989-01-01

Thin layer thermoluminescent radiation dosimeters for use in laser readable dosimetry systems, and methods of fabricating such thin layer dosimeters. The thin layer thermoluminescent radiation dosimeters include a thin substrate made from glass or other inorganic materials capable of withstanding high temperatures and high heating rates. A thin layer of a thermoluminescent phoshphor material is heat bonded to the substrate using an inorganic binder such as glass. The dosimeters can be mounted in frames and cases for ease in handling. Methods of the invention include mixing a suitable phosphor composition and binder, both being in particulate or granular form. The mixture is then deposited onto a substrate such as by using mask printing techniques. The dosimeters are thereafter heated to fuse and bond the binder and phosphor to the substrate.

Laser readable thermoluminescent radiation dosimeters and methods for producing thereof

DOEpatents

Braunlich, P.F.; Tetzlaff, W.

1989-04-25

Thin layer thermoluminescent radiation dosimeters for use in laser readable dosimetry systems, and methods of fabricating such thin layer dosimeters are disclosed. The thin layer thermoluminescent radiation dosimeters include a thin substrate made from glass or other inorganic materials capable of withstanding high temperatures and high heating rates. A thin layer of a thermoluminescent phosphor material is heat bonded to the substrate using an inorganic binder such as glass. The dosimeters can be mounted in frames and cases for ease in handling. Methods of the invention include mixing a suitable phosphor composition and binder, both being in particulate or granular form. The mixture is then deposited onto a substrate such as by using mask printing techniques. The dosimeters are thereafter heated to fuse and bond the binder and phosphor to the substrate. 34 figs.

LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Laser-induced extreme UV radiation sources for manufacturing next-generation integrated circuits

NASA Astrophysics Data System (ADS)

Borisov, V. M.; Vinokhodov, A. Yu; Ivanov, A. S.; Kiryukhin, Yu B.; Mishchenko, V. A.; Prokof'ev, A. V.; Khristoforov, O. B.

2009-10-01

The development of high-power discharge sources emitting in the 13.5±0.135-nm spectral band is of current interest because they are promising for applications in industrial EUV (extreme ultraviolet) lithography for manufacturing integrated circuits according to technological precision standards of 22 nm and smaller. The parameters of EUV sources based on a laser-induced discharge in tin vapours between rotating disc electrodes are investigated. The properties of the discharge initiation by laser radiation at different wavelengths are established and the laser pulse parameters providing the maximum energy characteristics of the EUV source are determined. The EUV source developed in the study emits an average power of 276 W in the 13.5±0.135-nm spectral band on conversion to the solid angle 2π sr in the stationary regime at a pulse repetition rate of 3000 Hz.

EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Dynamics of a plasma formed by a surface optical-discharge in a metal vapour interacting with a cw CO2 laser beam

NASA Astrophysics Data System (ADS)

Zaikin, A. E.; Levin, A. V.; Petrov, A. L.

1995-02-01

A surface optical-discharge plasma was formed in a metal vapour under normal conditions by steady-state irradiation with a cw CO2 laser delivering radiation of moderate (2-4.5 MW cm-2) intensity. This plasma strongly screened the irradiated surface. Under the selected experimental conditions the optical discharge was not a continuous (steady-state) process. The plasma cloud was displaced along the beam out of the waist to a region where the laser radiation intensity was almost an order of magnitude less than the threshold for excitation of the optical-discharge plasma in the vapour. A strong screening of the metal surface, which could even completely stop evaporation of the metal, was observed. Self-oscillations of the optical-discharge plasma were observed for the first time in a vapour interacting with cw CO2 radiation: this was attributed to screening of the target surface. Within one period of the self-oscillations there were additional hf plasma pulsations which led to stratification of the plasma cloud. The results obtained were interpreted.

A Novel Approach for the Treatment of Radiation-Induced Hemorrhagic Cystitis with the GreenLight™ XPS Laser

PubMed Central

Martinez, Daniel Roberto; Ercole, Cesar E; Lopez, Juan Gabriel; Parker, Justin; Hall, Mary K

2015-01-01

ABSTRACT Introduction: The treatment of pelvic malignancies with radiotherapy can develop severe sequelae, especially radiation-induced hemorrhagic cystitis. It is a progressive disease that can lead to the need for blood transfusion, hospitalizations, and surgical interventions. This tends to affect the quality of life of these patients, and management can at times be difficult. We have evaluated the GreenLight Xcelerated Performance System (XPS) with TruCoag, although primarily used for management of benign prostatic hypertrophy (BPH), for the treatment of radiation-induced hemorrhagic cystitis. Materials and Methods: After International Review Board (IRB) approval, a retrospective chart review was performed in addition to a literature search. A series of four male patients, mean age of 81 years, with radiation-induced hemorrhagic cystitis secondary to radiotherapy for pelvic malignancies (3 prostate cancer, 1 rectal cancer) were successfully treated with the GreenLight laser after unsuccessful treatment with current therapies described in the literature. Results: All four patients treated with the GreenLight laser had resolution of their hematuria after one treatment and were discharge from the hospital with clear urine. Conclusion: The GreenLight XPS laser shows promising results for the treatment of patients with radiation-induced hemorrhagic cystitis, and deserves further evaluation and validation, especially since there is limited data available in the literature regarding the use of this technology for the treatment of this devastating condition. PMID:26200555

Improved Characteristics of Laser Source of Ions Using a Frequency Mode Laser

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

Khaydarov, R. T.

2008-04-07

We used a mass-spectrometric method to investigate the characteristics of laser-produced plasma ions depending on the nature of the target and on the parameters of the laser radiation. Experiments are carried out on porous Y{sub 2}O{sub 3} targets with different densities {rho}, subjected to a laser radiation, where the laser works in a frequency mode (v = l-12 Hz). We found that the laser frequency has a significant effect on the parameters of plasma ions: with increasing the frequency of the laser the charge, energy and intensity of ions increase for a given parameters of the target. This effect ismore » more pronounced for small densities of the target. We related these two effects to a non-linear ionization process in the plasma due to the formation of dense plasma volume inside the sample absorbing the laser radiation and to the change of the focusing conditions in the case of the frequency mode laser.« less

"Low-intensity laser therapy effect on the recovery of traumatic spinal cord injury".

PubMed

Paula, Alecsandra Araujo; Nicolau, Renata Amadei; Lima, Mario de Oliveira; Salgado, Miguel Angel Castillo; Cogo, José Carlos

2014-11-01

Scientific advances have been made to optimize the healing process in spinal cord injury. Studies have been developed to obtain effective treatments in controlling the secondary injury that occurs after spinal cord injury, which substantially changes the prognosis. Low-intensity laser therapy (LILT) has been applied in neuroscience due to its anti-inflammatory effects on biological tissue in the repairing process. Few studies have been made associating LILT to the spinal cord injury. The objective of this study was to investigate the effect of the LILT (GaAlAs laser-780 nm) on the locomotor functional recovery, histomorphometric, and histopathological changes of the spinal cord after moderate traumatic injury in rats (spinal cord injury at T9 and T10). Thirty-one adult Wistar rats were used, which were divided into seven groups: control without surgery (n = 3), control surgery (n = 3), laser 6 h after surgery (n = 5), laser 48 h after surgery (n = 5), medullar lesion (n = 5) without phototherapy, medullar lesion + laser 6 h after surgery (n = 5), and medullar lesion + laser 48 h after surgery (n = 5). The assessment of the motor function was performed using Basso, Beattie, and Bresnahan (BBB) scale and adapted Sciatic Functional Index (aSFI). The assessment of urinary dysfunction was clinically performed. After 21 days postoperative, the animals were euthanized for histological and histomorphometric analysis of the spinal cord. The results showed faster motor evolution in rats with spinal contusion treated with LILT, maintenance of the effectiveness of the urinary system, and preservation of nerve tissue in the lesion area, with a notorious inflammation control and increased number of nerve cells and connections. In conclusion, positive effects on spinal cord recovery after moderate traumatic spinal cord injury were shown after LILT.

Influence of High-Power Pulsed IR Laser Radiation on the Electrophysical Properties of Cd x Hg1- x Те Heteroepitaxial Layers

NASA Astrophysics Data System (ADS)

Talipov, N. Kh.

2013-05-01

Results of investigations into the electrophysical properties of p- and n-type Cd x Hg1- x Te heteroepitaxial layers grown by molecular beam and liquid phase epitaxy methods after exposure to high-power pulsed IR radiation of solid-state Nd3+:YAG and chemical DF lasers at wavelengths of 1.06 and 3.8-4.2 μm, respectively, are presented. It is demonstrated that the main types of defects resulting from pulsed irradiation are mercury vacancies that play the role of acceptors in this material. The spatial distribution of generated mercury vacancies depends on the intensity and wavelength of laser radiation: the defects generated by pulses of the Nd3+:YAG laser are concentrated only near the surface, whereas DF-laser radiation creates defects in the entire volume of the heteroepitaxial structures. It is established that irradiation with the Nd3+:YAG laser of the p-Cd x Hg1- x Te heteroepitaxial layers implanted by boron ions leads to the activation of implanted boron atoms as a result of melting and recrystallization of the irradiated surface layer.

Growth, spectroscopy, and laser performance of a 2.79 μm Cr,Er,Pr:GYSGG radiation-resistant crystal.

PubMed

Luo, Jianqiao; Sun, Dunlu; Zhang, Huili; Guo, Qiang; Fang, Zhongqing; Zhao, Xuyao; Cheng, Maojie; Zhang, Qingli; Yin, Shaotang

2015-09-15

We demonstrate the growth, spectroscopy, and laser performance of a 2.79 μm Cr,Er,Pr:GYSGG radiation-resistant crystal. The lifetimes for the upper laser level (4)I(11/2) and lower laser level (4)I(13/2) are 0.59 and 0.84 ms, respectively, which are due to the doping of the Pr(3+) ions. A maximum pulse energy of 278 mJ operated at 10 Hz and 2.79 μm is obtained when pumped with a flash lamp, which corresponds to the electrical-to-optical efficiency of 0.6% and a slope efficiency of 0.7%. A maximum average power of 2.9 W at 60 Hz is achieved, which corresponds to the electrical-to-optical efficiency of 0.4% and slope efficiency of 0.8%. Compared with a Cr,Er:YSGG crystal, the Cr,Er,Pr:GYSGG crystal can be operated at a higher pulse repetition rate. These results suggest that doping deactivator Pr(3+) ions can effectively decrease the lower laser level lifetime and improve the laser repetition rate. Therefore, the application fields and range of the Cr,Er,Pr:GYSGG laser can be extended greatly due to its properties of radiation resistance and high repetition frequency.

[Modification of radiation damage to biological objects by lasers].

PubMed

Voskanian, K Sh; Vorozhzova, S V; Abrosimova, A N; Mitsyn, G V; Gaevskiĭ, V N

2012-01-01

A series of experiments had the purpose to study effects of gamma-rays 60Co (5 Gy) and the combined effects of laser 650 nm (1 mJ/cm2) and gamma-rays 60Co (5 Gy) on survivability, body mass, integument and mitotic index of marrow cells (MC) of young mice C57BL/6. Laser was applied to the mouse hairy back only. Ten months of gamma-irradiation brought death to 50% of mice; the combined irradiation killed only 30%. Starting on month six after gamma-irradiation, body mass was less in comparison with mice exposed to the combined irradiation. In addition, all mice lost body mass sharply before death. All gamma-irradiated mice were touched with grey over the period of 30 days; in 40 days, 10 of 20 mice had incipient local radiation alopecia on the back that passed fully within next month. However, all mice developed radiation ulcers on the fourth month since irradiation. Two mice formed also neck tumors. In 5 months tails fell off in 2 mice. Some grey streaks appeared on mice exposed to the combined irradiation 3 months later only; three mice remained black throughout the follow-up. Alopecia was found in three survivors in 5 months after irradiation. Mitotic activity of marrow cells obtained from mice on day 15 since exposure to lasing and combined irradiation was higher in comparison with cells from intact mice. In a year, the MC mitotic index was higher in mice exposed to the combined irradiation as compared with the gamma-irradiated mice.