Статті в журналах: "Pulsed laser radiation"

1

Shemyakin, A. N., M. Yu Rachkov, N. G. Solov’ev та M. Yu Yakimov. "Radiation Power Control of the Industrial CO₂ Laser Excited by а Nonself-Sustained Glow Discharge by Changing the Frequency of Ionization Pulses". Mekhatronika, Avtomatizatsiya, Upravlenie 21, № 4 (11 квітня 2020): 224–31. http://dx.doi.org/10.17587/mau.21.224-231.

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The article describes radiation power control of industrial CO2 lasers of Lantan series excited by а nonself-sustained glow discharge in the automatic mode. These lasers are closed-cycle fast gas-transport lasers excited by a nonself-sustained glow discharge with ionization by periodic-pulsed capacitively coupled auxiliary discharge. In this case, ionization and conductivity are provided by periodic-pulsed capacitively coupled discharge. The energy contribution to molecular oscillations is provided by the passage of the main discharge current through the plasma with electron density given by ionization. This permits easy laser power control, provides excellent optical homogeneity and stability of an active volume together with high laser efficiency. A system of a nonself-sustained glow discharge with ionization by periodic-pulsed capacitively coupled auxiliary discharge, the stages of creation and brief characteristics of the Lantan series lasers is presented. The method of controlling the power of laser radiation by changing the frequency of the ionization pulses is determined. This control method allows operating of the laser in continuous and in pulse-periodic modes with adjustable pulse ratio and pulse duration, and also provides switching from one mode to another. In the continuous mode, the radiation power is controlled by changing the frequency of ionization pulses, which are high voltage pulses with duration of 100 ns, given with the frequency of 1-5 kHz. Pulse-periodic radiation control is performed by modulating ionization pulses that consists of pulses being delivered in batches. The frequency of the pulses in a batch determines the radiation power in a pulse. The frequency of the batches following is the frequency of the pulse mode, and the length of the batch determines the pulses duration. Based on the experimental data, the dependence of the radiation power on the ionization pulses frequency was determined. An experimental system is presented and the measuring accuracy of the laser radiation power and the frequency of ionization pulses is determined. Data acquiring and processing of experimental results were performed using the NI 6008 USB data acquisition device in the LabVIEW programs of National Instruments. To study the dependence of the laser power on Мехатроника, автоматизация, управление, Том 21, № 4, 2020 231 the frequency of the ionization pulses, a regression analysis method was applied. Studies have shown that the dependence of the laser power on the ionization pulses frequency is linear in a wide range of parameters. The equation of the direct regression is calculated. The confidence estimates of the coefficients of the direct regression and the confidence estimates of the deviation of the theoretical direct regression from the empirical one are calculated with a confidence level of 95%.

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2

Glotov, A. N., Yu V. Golubenko, V. A. Desyatskov, and A. V. Stepanov. "Certain Features of Interaction Between Laser Radiation and Metals." Herald of the Bauman Moscow State Technical University. Series Instrument Engineering, no. 1 (130) (February 2020): 15–32. http://dx.doi.org/10.18698/0236-3933-2020-1-15-32.

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The paper presents experimental investigation results concerning the problem of optimising the efficiency of interaction between laser radiation and metals. We used several types of Nd lasers featuring the desired combination of power, temporal and spatial radiation parameters as sources of the radiation required. To pump these lasers, we employed rectangular pulses at a periodicity eliminating effects characteristic of continuous-wave and pulsed laser operation modes. This limits the laser radiation parameters driving the interaction efficiency functions to strictly those parameters that match the single-pulse laser operation mode. Temporal radiation parameter variation involved measurements in the free-running and high-frequency Q-switching modes as well as adjusting pumping (lasing) pulse durations. Power parameter variation was implemented through altering radiation energy density over the irradiated surface. Spatial structure of the ablative radiation was varied by means of optical radiation transfer facilities and different laser emitters. The experimental investigation results allowed us to establish certain patterns concerning the interaction between laser radiation and metals as a function of radiation parameters listed

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3

Александров, В. А., В. В. Бесогонов та Д. Г. Калюжный. "Импульсная проводимость в Ag-Pd-резисторах, индуцированная импульсами лазера". Журнал технической физики 92, № 5 (2022): 738. http://dx.doi.org/10.21883/jtf.2022.05.52379.246-21.

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Pulsed EMF in resistive thick-film Ag - Pd elements is experimentally studied when their surface is irradiated with a laser beam. The dependences of the pulsed EMF on the coordinate of the action of the laser beam on the film surface are obtained. It is shown that applying a constant bias voltage to a thick-film resistive element can significantly increase the amplitude of unipolar EMF pulses induced by laser pulses. It was found that the amplitude and frequency of the EMF signals depend, respectively, on the power and frequency of laser pulses. It is shown that by the value of the pulsed EMF it is possible to control the parameters of the high-power laser radiation incident on the surface in real time. The design of a receiver for recording the parameters of laser radiation based on an Ag - Pd sensitive element has been developed. The sensitivity of the device for measuring the power and pulse repetition rate is estimated.

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4

Khabarov, Kirill, Messan Nouraldeen, Sergei Tikhonov, Anna Lizunova, Alexey Efimov, and Victor Ivanov. "Modification of Aerosol Gold Nanoparticles by Nanosecond Pulsed-Periodic Laser Radiation." Nanomaterials 11, no. 10 (October 13, 2021): 2701. http://dx.doi.org/10.3390/nano11102701.

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This study investigates the processes of interaction of nanosecond pulsed-periodic laser radiation with the flow of aerosol agglomerates of gold nanoparticles synthesized in a spark discharge. Nanoparticles in a gas flow are spatially separated nano-objects whose interaction with each other and with the walls of an experimental cell was insignificant. Therefore, the energy absorbed by nanoparticles was used only for their own heating with further shape and size modification and on heat transfer to the surrounding gas. In the research, we used laser radiation with wavelengths of 527 and 1053 nm at pulse energies up to 900 µJ and pulse repetition rates up to 500 Hz. The dynamics of changes in the nanoparticles size during their sintering process depending on the laser pulses energy is characterized by an S-shaped shrinkage curve. Complete sintering of the initial agglomerates with their transformation into spherical nanoparticles is achieved by a series of impacting laser pulses. The result of nanoparticles’ laser modification is largely determined by the pulse energy and the efficiency of the nanoparticles’ radiation absorption.

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5

Khabarov, Kirill, Messan Nouraldeen, Sergei Tikhonov, Anna Lizunova, Alexey Efimov, and Victor Ivanov. "Modification of Aerosol Gold Nanoparticles by Nanosecond Pulsed-Periodic Laser Radiation." Nanomaterials 11, no. 10 (October 13, 2021): 2701. http://dx.doi.org/10.3390/nano11102701.

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This study investigates the processes of interaction of nanosecond pulsed-periodic laser radiation with the flow of aerosol agglomerates of gold nanoparticles synthesized in a spark discharge. Nanoparticles in a gas flow are spatially separated nano-objects whose interaction with each other and with the walls of an experimental cell was insignificant. Therefore, the energy absorbed by nanoparticles was used only for their own heating with further shape and size modification and on heat transfer to the surrounding gas. In the research, we used laser radiation with wavelengths of 527 and 1053 nm at pulse energies up to 900 µJ and pulse repetition rates up to 500 Hz. The dynamics of changes in the nanoparticles size during their sintering process depending on the laser pulses energy is characterized by an S-shaped shrinkage curve. Complete sintering of the initial agglomerates with their transformation into spherical nanoparticles is achieved by a series of impacting laser pulses. The result of nanoparticles’ laser modification is largely determined by the pulse energy and the efficiency of the nanoparticles’ radiation absorption.

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6

Афанасьєва, Ольга Валентинівна, Наталія Олексіївна Лалазарова та Олена Георгіївна Попова. "Нові технології лазерної поверхневої обробки". Aerospace technic and technology, № 2 (28 квітня 2021): 59–65. http://dx.doi.org/10.32620/aktt.2021.2.07.

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Subject and purpose. Currently, gas, solid-state, and fiber lasers are used to process materials in the aviation industry. For the thermal treatment of steels, gas CO2 lasers with a capacity of more than 1 kW used, which are reliable in operation but have high cost and low efficiency. There are no results on the use of low-power (up to 20 W) pulsed-mode lasers for surface hardening of steel products. The purpose of this work is to determine the modes of surface hardening of products from carbon and alloy steels using low-power solid-state pulsed YAG lasers. Methodology. For laser hardening, a 5 W solid-state YAG laser was used (diode pumping, radiation wavelength λ = 1,064 μm, pulse mode). The use of a nonlinear crystal made it possible to obtain UV radiation with λ = 0,355 μm (third harmonic). The following modes were investigated: processing with single pulses (duration 0,1...0,4 ms) and multi-pulse processing with short (30...70 ms) pulses. The scanning speed was 8...2 mm/s. The energy in the pulse was determined by the photoelectric method. Thermal hardening was performed on the following steels: У12, P6M5. The possibility of UV radiation hardening was evaluated on steel 20, 45, У12, and ШХ15. Findings. The optimum values of pulse duration for maximum hardness in laser hardening of the investigated steels. With multi-pulse treatment of steels, the pulse duration is shorter than with single-pulse treatment, the hardening intensity is higher, and the quality of the processed surface is better. Single-pulse and multi-pulse processing are accompanied by partial melting of the surface of steel products, which does not allow it to be used in cases where a high quality of the surface is required. Laser hardening of steel by ultraviolet radiation is not accompanied by melting. Conclusion. For surface hardening of products, where partial melting of the surface is possible, low-power lasers in pulse mode can be used. Laser hardening by ultraviolet radiation is a promising direction for thermal hardening of steels, which allows maintaining the original quality of the surface layer. Thermal hardening with low-power lasers can be effective for small-sized areas of the processed parts of the fuel equipment of aircraft engines, friction elements, and, especially, the tool is small.

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7

Ражев, А. М., Е. С. Каргапольцев та И. А. Трунов. "Импульсный индукционный CO-=SUB=-2-=/SUB=--лазер с энергией излучения 1 J и высоким КПД с ВЧ возбуждением". Оптика и спектроскопия 130, № 3 (2022): 400. http://dx.doi.org/10.21883/os.2022.03.52169.2836-21.

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An efficient pulsed gas-discharge inductive CO2-laser with a radiation energy of 1.05 J has been developed for the first time. In this case, the pulse duration of the laser radiation was about 10 msec. The maximum efficiency of 21.1% was obtained at a radiation energy of 340 mJ. RF current pulses propagated along the inductor conductor and, thus, an inductive discharge was formed to create an inverse population at the infrared (IR) transitions of CO2* molecules. The temporal and energy characteristics of the radiation of the inductive CO2-laser depending on the duration of the pump pulse are investigated. The spatial characteristics and spectrum of the radiation of the developed laser are estimated. The divergence of the laser radiation was 0.52 mrad. The cross-sectional dimension of the laser output beam was about 35 mm in diameter.

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8

Пашенцев, В. Н. "Изменение характеристик полупроводниковых структур СВЧ-усилителей под воздействием импульсного лазерного излучения". Журнал технической физики 91, № 11 (2021): 1715. http://dx.doi.org/10.21883/jtf.2021.11.51533.43-21.

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The effect of pulsed laser radiation on the change in the parameters of semiconductor structures of field-effect transistors with a Schottky gate with an operating frequency range of 1.5–8 GHz and integrated amplifiers with an operating frequency range of 0.4–6 GHz is studied. Laser radiation with 25 ns pulse duration, incident on the transistor crystal, creates a pulsed photocurrent. It is shown that the amplitude of the pulsed photocurrent is three times higher than the operating transistor current. The current-voltage characteristics of the field-effect transistor were measured in the mode of pulsed laser radiation. The amplitude dependence of the pulsed photocurrent in semiconductor structures on the power of laser radiation for various wavelengths of 1.06 µm and 0.53 µm is studied. It is shown that as a result of the action of pulsed laser radiation on semiconductor structures, a short disappearance of the amplification of the high-frequency signal at the amplifier output occurs.

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9

Dzyubenko, M., I. Kolenov, V. Pelipenko, N. Dakhov, and A. Degtyarev. "Laser rangefinder of relatively eye-safe wavelength range." RADIOFIZIKA I ELEKTRONIKA 26, no. 1 (2021): 41–48. http://dx.doi.org/10.15407/rej2021.01.041.

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Subject and Purpose. The development and prototype making of a laser rangefinder operating in the 1.50…1.70 μm spectral region is reported. This wavelength region is attractive to both laser producers and laser users for, first of all, relative eye-safety of radiation. Methods and Methodology. The paraxial scheme of rangefinder construction is used, involving a software-controlled power supply of laser radiation with technical arrangements providing its adaptation to varying operating conditions. The alignment of the transceiver channels is provided with laser beam visualization methods. Results. A pulsed laser rangefinder operating at a 1.54 μm wavelength has been developed, a prototype has been made. The rangefinder essentially consists of the transmitting and receiving channels and the visual channel for targeting. The radiation source is a pulsed laser on ytterbium-erbium glass with semiconductor diode pumping and modulated Q-factor. The laser provides a 6 mJ power pulse of 25 ns duration and 5 mrad radiation divergence. A laser light spot of a required aperture is formed using a Galilean telescope system. For the photodetector of the reflected radiation, a pin-photodiode with a photosensitive area diagonal of 0.3 mm and a 2.5 ns time resolution is used. The echo signal processing module has been developed and performed, providing a high-precision registration of a time delay between the starting and reflected pulses. An effective method with the use of a charge-coupled device and an LCD monitor has been proposed and implemented for the alignment of all the three rangefinder channels. The rangefinder can operate in a single-pulse or repetitive-pulse mode with a probing pulse repetition rate of 1 Hz. Conclusion. A pulsed laser rangefinder operating in a relatively eye-safe spectrum region has been developed, a prototype has been made. The field tests have shown that the created rangefinder measures an object distance within 140…7 000 m with a measurement error no worse than 3 m.

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10

ZHANG, DUANMING, DAN LIU, ZHIHUA LI, SIPU HOU, BOMING YU, LI GUAN, XINYU TAN, and LI LI. "EFFECTS OF PLASMA SHIELDING ON PULSED LASER ABLATION." Modern Physics Letters B 20, no. 15 (June 30, 2006): 899–909. http://dx.doi.org/10.1142/s021798490601041x.

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We have developed a theoretical model which studies the characteristics of laser-plasma interaction, the effect of plasma shielding and plasma radiation in the ablation process. The model is used to simulate 25 ns square pulsed laser irradiation on YBa 2 Cu 3 O 7 targets, and pulsed laser with the pulse width of 25 ns (FWHM) irradiation on Ni targets. The evolution of the plasma length and the transmitted intensity are performed. The model shows the variation of ablation depth with energy density. Moreover, we obtain the dependence of the ablation depth on the number of laser pulses. The satisfactorily good agreement between our results and experimental results confirms that plasma shielding plays a relevant role in the ablation process.

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11

Tikhomirov, S. A. "Femtosecond System with Pulse Pumping of Seed Laser and Amplifier by Using a Single Power Unit." Devices and Methods of Measurements 12, no. 1 (March 19, 2021): 23–29. http://dx.doi.org/10.21122/2220-9506-2021-12-1-23-29.

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For several decades development of methods for generating ultrashort pulses has been an independent urgent scientific and technical problem. There is a constant improvement both in the methods of such pulses receiving and in methods of their use. The aim of this work was to investigate the possibility of realizing the coordinated operation of two fundamentally different types of pump lasers for the femtosecond oscillator and amplifier based on one single-lamp laser head and to create on this basis a compact high-power femtosecond system with pulsed pumping and one power unit.The practical implementation of two types of pulsed lasers (nano- and picosecond ones operating, respectively, in Q-switch and modelock regime) on a single laser head with two active elements and one pump lamp is carried out. The required synchronization in time the pump pulse femtosecond amplifier formation and quasi-stationary region of generated pulses in the output radiation of a femtosecond Ti:sapphire is obtained.On this basis a compact, pulse pumped monoblock laser system has been developed that can generate femtosecond pulses with a duration of 50–150 fs with an energy up to 1 mJ and a high enough pulse repetition rate (up to 1 kHz which is determined by the type of laser head and pump unit used). In the developed laser system a compact scheme of a stretcher-compressor with a single common diffraction grating is used.Laser systems of this type characterized by a relatively low cost due to the use of a single power supply unit for simultaneous pumping of the amplifier and oscillator, as well as lower requirements for the quality of optical elements and usage conditions due to the pulse mode of operation, are quite practical and can be used both in scientific research in the field of ultra-high-speed kinetic spectroscopy and nonlinear optics, as well as in numerous technical applications, particular in the precision processing of materials, as optical simulators of the action of heavy charged particles in testing the radiation resistance of integrated circuits and electronic modules.

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12

Razhev, Aleksandr, Dmitriy Churkin, and Alexey Zavyalov. "Pulsed Inductive Molecular Hydrogen Laser." Siberian Journal of Physics 4, no. 3 (October 1, 2009): 12–19. http://dx.doi.org/10.54362/1818-7919-2009-4-3-12-19.

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A pulsed inductive discharge molecular H2 laser has been created for the first time. The excitation system of a toroidal pulsed inductive discharge for molecular hydrogen electron levels excitation was developed. Generation at two wavelengths of 0,89 and 1,12 m was obtained. The spectral, temporal and energy parameters of laser emission under various pressures and pumping conditions were investigated. The maximum pulse power of 6,7 kW was achieved. The measured pulse duration was 18 ± 1 ns. In the cross-section, the laser radiation had the ring shape with an external diameter of 33 mm and thickness of 4 mm.

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13

Abdelhalim, Ibrahim, Omnia Hamdy, Aziza Ahmed Hassan, and Salah Hassab Elnaby. "Nd:YAG fourth harmonic (266-nm) generation for corneal reshaping procedure: An ex-vivo experimental study." PLOS ONE 16, no. 11 (November 29, 2021): e0260494. http://dx.doi.org/10.1371/journal.pone.0260494.

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Corneal reshaping is a common medical procedure utilized for the correction of different vision disorders relying on the ablation effect of the UV pulsed lasers, especially excimer lasers (ArF) at 193 nm. This wavelength is preferred in such medical procedures since laser radiation at 193 nm exhibits an optimum absorption by corneal tissue. However, it is also significantly absorbed by the water content of the cornea resulting in an unpredictability in the clinical results, as well as the high service and operation cost of the commercial ArF excimer laser device. Consequently, other types of solid-state UV pulsed lasers have been introduced. The present work investigates the ablation effect of solid-state laser at 266 nm in order to be utilized in corneal reshaping procedures. Different number of pulses has been applied to Polymethyl Methacrylate (PMMA) and ex-vivo rabbit cornea to evaluate the ablation effect of the produced laser radiation. PMMA target experienced ellipse-like ablated areas with a conical shape in the depth. The results revealed an almost constant ablation area regardless the number of laser pulses, which indicates the stability of the produced laser beam, whereas the ablation depth increases only with increasing the number of laser pulses. Examination of the ex-vivo cornea showed a significant tissue undulation, minimal thermal damage, and relatively smooth ablation surfaces. Accordingly, the obtained 266-nm laser specifications provide promising alternative to the traditional 193-nm excimer laser in corneal reshaping procedure.

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14

Al-Juboory, Karim H., David J. Williams, and M. H. Nayfeh. "THE EFFECT OF PULSED EXCIMER LASER RADIATION ON CONTROL OF IN VITRO CULTURE CONTAMINATION AND THE GROWTH OF HEDERA CANARIENSIS." HortScience 25, no. 9 (September 1990): 1150a—1150. http://dx.doi.org/10.21273/hortsci.25.9.1150a.

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This study was initiated to investigate the effect of pulsed XeCL excimer laser radiation (308 nm) at 25 and 50 pulses per second at radiation levels of 0, 100 mJ, 200 mJ, and 300 mJ on microorganism contamination of in vitro cultures of Heder a canariensis. Explants were cultured on Murashige and Skoog (MS) medium supplemented with 8 mg/BA and 0.2 mg/NAA. The medium was adjusted to pH 5.7. The cultures were maintained for 16-hours photoperiods at 25.5°C. One day following transfer the explants were treated with pulsed excimer laser radiation. The percentage of contamination was reduced by laser radiation treatments. The effect of 5 0 pulses of radiation was found to increase the petiole length, leaf blade width, and leaf number of explants.

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15

Minko, D. V. "Influence of parameters of impulse laser impact on the formation of the gradient of the structure of porous titanium powder." Litiyo i Metallurgiya (FOUNDRY PRODUCTION AND METALLURGY), no. 3 (October 5, 2018): 88–94. http://dx.doi.org/10.21122/1683-6065-2018-3-88-94.

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The possibility of selective laser sintering of graded porous and compactly porous structures by surface fusion of powder particles is demonstrated while maintaining a solid core, which leads to the formation of interparticle contacts in the presence of a liquid phase. The interaction of the light flux of the laser pulse with the surface of the powder particles under multiple reflection is considered. It is shown that the effect of single pulses of laser radiation leads to the formation of sintered structural elements of a powder material having a diameter approximately equal to the diameter of the focal spot. Technological regimes of pulsed laser action are established at which steady contact formation of titanium powder particles of the fractional compositions under study occurs. The possibility of obtaining powder materials with a gradient structure by controlling the parameters of pulsed laser action is experimentally demonstrated. It was found that accurate dosing of thermal energy and the number of pulses of laser radiation makes it possible to minimize shrinkage of powder layers in the absence of particle conglomeration, to control the structural characteristics and properties of products, to preserve the microstructure and phase composition of the initial materials.

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16

Stolzenberg, Ulf, Mayka Schmitt Rahner, Björn Pullner, Herbert Legall, Jörn Bonse, Michael Kluge, Andreas Ortner, Bernd Hoppe, and Jörg Krüger. "X-ray Emission Hazards from Ultrashort Pulsed Laser Material Processing in an Industrial Setting." Materials 14, no. 23 (November 24, 2021): 7163. http://dx.doi.org/10.3390/ma14237163.

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Interactions between ultrashort laser pulses with intensities larger than 1013 W/cm2 and solids during material processing can lead to the emission of X-rays with photon energies above 5 keV, causing radiation hazards to operators. A framework for inspecting X-ray emission hazards during laser material processing has yet to be developed. One requirement for conducting radiation protection inspections is using a reference scenario, i.e., laser settings and process parameters that will lead to an almost constant and high level of X-ray emissions. To study the feasibility of setting up a reference scenario in practice, ambient dose rates and photon energies were measured using traceable measurement equipment in an industrial setting at SCHOTT AG. Ultrashort pulsed (USP) lasers with a maximum average power of 220 W provided the opportunity to measure X-ray emissions at laser peak intensities of up to 3.3 × 1015 W/cm2 at pulse durations of ~1 ps. The results indicate that increasing the laser peak intensity is insufficient to generate high dose rates. The investigations were affected by various constraints which prevented measuring high ambient dose rates. In this work, a list of issues which may be encountered when performing measurements at USP-laser machines in industrial settings is identified.

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17

Ivanenko, A. V., B. N. Nyushkov, and S. V. Smirnov. "Generation of high-energy single pulses and pulse clusters in ytterbium fibre lasers with quasi-synchronous modulation of the pump power." Quantum Electronics 51, no. 12 (December 1, 2021): 1061–67. http://dx.doi.org/10.1070/qel17653.

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Abstract Additional capabilities of the method of quasi-synchronous pump power modulation developed by the authors for nanosecond high-energy pulsed oscillation of fibre lasers with a long-lived (about 1 ms) upper laser level are investigated. Using an Yb fibre laser as an example, it is shown that quasi-synchronous pump power modulation makes it possible to generate not only a periodic sequence of single nanosecond pulses, but also regular pulse clusters with a controlled number of nanosecond subpulses that make up a cluster. In addition, the feasibility of scaling the energy of laser pulses obtained by the method of quasi-synchronous modulation of the pump power is studied when proceeding to the use of active double-clad fibres and higher-power multimode pump sources. Pulses with energies up to 430 nJ are obtained in a laser configuration maintaining linear polarisation of radiation. The results obtained significantly expand the possibilities of applying the method of quasi-synchronous modulation of the pump power in conventional fibre lasers based on stimulated emission.

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18

Pakula, R., and R. Sigel. "Generation of Intense Black-Body Radiation in a Cavity by a Laboratory Pulsed Power Source." Zeitschrift für Naturforschung A 41, no. 3 (March 1, 1986): 463–67. http://dx.doi.org/10.1515/zna-1986-0301.

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Pulsed laser and particle beams afford possibilities of generating intense black-body radiation in small cavities of high-Z material. The radiation confinement in the cavity is investigated on the basis of the non-stationary hydrodynamic equations including radiative heat transfer. It is estimated that with a pulse energy of 1012 erg a temperature of about 5 x 106 K may be obtainable.

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19

Metzner, Daniel, Markus Olbrich, Peter Lickschat, Alexander Horn, and Steffen Weißmantel. "Experimental and Theoretical Determination of the Effective Penetration Depth of Ultrafast Laser Radiation in Stainless Steel." Lasers in Manufacturing and Materials Processing 7, no. 4 (October 14, 2020): 478–95. http://dx.doi.org/10.1007/s40516-020-00129-9.

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AbstractThis study intends to present a simple two-temperature model (TTM) for the fast calculation of the ablation depth as well as the corresponding effective penetration depth for stainless steel by considering temperature-dependent material parameters. The model is validated by a comparison of the calculated to the experimentally determined ablation depth and the corresponding effective penetration depth in dependence on the pulse duration (200 fs up to 10 ps) and the fluence. The TTM enables to consider the interaction of pulsed laser radiation with the electron system and the subsequent interaction of the electrons with the phonon system. The theoretical results fit very well to the experimental results and enable the understanding of the dependence of the ablation depth and of the effective penetration depth on the pulse duration. Laser radiation with a pulse duration in the femtosecond regime results in larger ablation depths compared to longer-pulsed laser radiation in the picosecond regime. Analogously to the ablation depth, larger effective penetration depths are observed due to considerably higher electron temperatures for laser radiation with pulse durations in the femtosecond regime.

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20

Abdurakhmanova, S. R., G. D. Bukharov, Z. S. Gheisser, V. V. Davydov, and V. Yu Rud. "Method development to secure the stability of the parameters of pulsed and continuous radiation in laser systems with semiconductor pumping." Journal of Physics: Conference Series 2086, no. 1 (December 1, 2021): 012126. http://dx.doi.org/10.1088/1742-6596/2086/1/012126.

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Abstract The necessity of increasing the stability of the parameters of pulsed and cw laser radiation when operating at peak powers is substantiated. Particular attention is paid to the parameters of pulsed laser radiation in systems with semiconductor pumping. The main requirement in this case is the repeatability of the parameters of the output pulses with high accuracy. This condition is ensured by the stability of the diode supply drivers, especially at peak powers, which are required for scientific research. It was found that even a short-term excess (about 1 ms) of the upper range of the permissible current leads to damage to the laser diode, which instantly degrades the parameters of laser radiation. The developed technique can significantly reduce the likelihood of these phenomena and increase the reliability of the laser.

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21

Batenin, V. M., V. T. Karpukhin, M. M. Malikov, A. S. Averyushkin, M. A. Kazaryan, N. A. Lyabin, and R. A. Zakharyan. "The induction pumping of Coaxial Lasers on Self-Terminating Transitions." Alternative Energy and Ecology (ISJAEE), no. 16-18 (September 11, 2018): 98–112. http://dx.doi.org/10.15518/isjaee.2018.16-18.098-112.

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The paper presents the results of the numerical simulations of pumping a copper vapour laser by a repetitively pulsed induction (electrodeless) discharge. We have investigated the version of the laser with an annular discharge volume formed by two coaxial cylinders. Such coaxial chamber is shown to be more appropriate for the induction pumping than the conventional cylindrical chamber. In the first case, higher coupling factors in the transformercoupled circuit of the induction discharge as well as rather high curl electric field are achieved. Moreover, from the ecological point of view, the coaxial chamber appears to be safer for the surrounding personnel in terms of their exposure to electromagnetic radiation. The present work briefly presents the physical model of the laser which describes the dynamics of the plasma parameters, the kinetics of the inverse population of the working levels for the laser on self terminating transitions as well as the development of the induction radiation. The paper also presents the electrical equations describing the simplest source of electrical pump pulses. The thermal characteristics of the working medium are estimated and the design calculations of the chamber are performed. The numerical experiments have found that, in contrast to the case of a conventional copper vapour laser with aperiodic discharge, in the regarded versions of the copper vapour laser the pump pulse is realized as a train of high-frequency damped oscillations. The analysis of the physical processes occurring in the plasma of the high-frequency discharge is carried out. The pulsed behaviour of the Joule heat power is shown to release results in pronounced pulsations of the electron temperature. This fact, however, does not significantly affect the operation of the laser on self-terminating transitions. In the optimal pumping regimes, subtle oscillations are merely observed for the inverse population of the copper atom working levels and for the intensity in the radiation pulse. High output laser characteristics achieved in the numerical simulations demonstrate the potential for efficient pumping of the copper vapour laser using the inductive method which is new for such lasers.

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22

Semyonov, A. P., I. V. Shuba, I. V. Krivtsun, and V. F. Demchenko. "Modeling of weld pool behaviour in spot welding by pulsed laser radiation." Paton Welding Journal 2014, no. 4 (April 28, 2014): 17–21. http://dx.doi.org/10.15407/tpwj2014.04.02.

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23

Smirnov, Ivan V., and Yuri V. Sudenkov. "Influence of High Pressure Torsion on Thermoelastic and Thermoelectric Response of Pure Copper and Aluminum under Pulsed Laser Radiation." Defect and Diffusion Forum 385 (July 2018): 296–301. http://dx.doi.org/10.4028/www.scientific.net/ddf.385.296.

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This work presents experimental studying the effect of processing by severe plastic deformation (SPD) on the thermoelastic and thermoelectric properties of pure aluminum and copper under pulsed laser radiation. The studies were carried out on technical aluminum AD1 (99.3%) and pure copper M1 (99.9%). High pressure torsion (HPT) was used for processing by SPD. After the HPT processing, the materials samples in the form of a plane disk were subjected to pulsed laser radiation focused on the disk center. Pulsed lasers with a wavelength of 1.06 micron and operating in the free laser oscillation mode with pulse duration of 100 microseconds or in the mode of a single pulse with duration of about 10 nanoseconds were used. The thermoelastic and thermoelectric responses of the materials were determined by measuring acoustic waves and the thermoelectric power. The disks with the initial coarse-grained material state were considered as a reference sample, and the disks of the materials after SPD processing were considered as a controlled object. The results demonstrated a very high sensitivity of the parameters of thermoelastic and thermoelectric response to structural changes in the materials. For example, the used HPT mode led to a reduction in the maximum thermoelectric power value for aluminum by 40% and for copper by 35%.

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24

Levytskyi, S. M. "Influence of laser radiation on optical transparent dielectrics." Physics and Chemistry of Solid State 21, no. 2 (June 15, 2020): 279–83. http://dx.doi.org/10.15330/pcss.21.2.279-283.

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This paper deals with the main characteristics of the influence of pulsed laser radiation and its application for the labeling of transparent dielectrics. On the basis of the analysis of the literature data and the study of the possibilities of using laser radiation for marking different materials, it is proposed to investigate the effect of the radiation wavelength on the size of the received defect inside the material. Experimentally shown that the pulse laser processing of samples with laser irradiation energy below 3.4 mJ/cm2 visual tags in the sample are not formed. Thus, you can control the geometric dimensions of the mark.

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25

Kuisat, Florian, Fernando Lasagni, and Andrés Fabián Lasagni. "Smoothing additive manufactured parts using ns-pulsed laser radiation." Progress in Additive Manufacturing 6, no. 2 (February 9, 2021): 297–306. http://dx.doi.org/10.1007/s40964-021-00168-4.

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AbstractIt is well known that the surface topography of a part can affect its mechanical performance, which is typical in additive manufacturing. In this context, we report about the surface modification of additive manufactured components made of Titanium 64 (Ti64) and Scalmalloy®, using a pulsed laser, with the aim of reducing their surface roughness. In our experiments, a nanosecond-pulsed infrared laser source with variable pulse durations between 8 and 200 ns was applied. The impact of varying a large number of parameters on the surface quality of the smoothed areas was investigated. The results demonstrated a reduction of surface roughness Sa by more than 80% for Titanium 64 and by 65% for Scalmalloy® samples. This allows to extend the applicability of additive manufactured components beyond the current state of the art and break new ground for the application in various industrial applications such as in aerospace.

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26

Schille, Joerg, Sebastian Kraft, Theo Pflug, Christian Scholz, Maurice Clair, Alexander Horn, and Udo Loeschner. "Study on X-ray Emission Using Ultrashort Pulsed Lasers in Materials Processing." Materials 14, no. 16 (August 12, 2021): 4537. http://dx.doi.org/10.3390/ma14164537.

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The interaction of ultrashort pulsed laser radiation with intensities of 1013 W cm−2 and above with materials often results in an unexpected high X-ray photon flux. It has been shown so far, on the one hand, that X-ray photon emissions increase proportionally with higher laser power and the accumulated X-ray dose rates can cause serious health risks for the laser operators. On the other hand, there is clear evidence that little variations of the operational conditions can considerably affect the spectral X-ray photon flux and X-ray emissions dose. In order to enhance the knowledge in this field, four ultrashort pulse laser systems for providing different complementary beam characteristics were employed in this study on laser-induced X-ray emissions, including peak intensities between 8 × 1012 W∙cm−2 < I0 < 5.2 × 1016 W∙cm−2, up to 72.2 W average laser power as well as burst/bi-burst processing mode. By the example of AISI 304 stainless steel, it was verified that X-ray emission dose rates as high as H˙′ (0.07) > 45 mSv h−1 can be produced when low-intensity ultrashort pulses irradiate at a small 1 µm intra-line pulse distance during laser beam scanning and megahertz pulse repetition frequencies. For burst and bi-burst pulses, the second intra-burst pulse was found to significantly enhance the X-ray emission potentially induced by laser pulse and plasma interaction.

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27

FEDENEV, A. V., S. B. ALEKSEEV, I. M. GONCHARENKO, N. N. KOVAL', E. I. LIPATOV, V. M. ORLOVSKII, M. A. SHULEPOV, and V. F. TARASENKO. "UV and IR laser radiation's interaction with metal film and teflon surfaces." Laser and Particle Beams 21, no. 2 (April 2003): 265–72. http://dx.doi.org/10.1017/s0263034603212155.

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The interaction of Xe (λ ∼ 1.73 μm) and XeCl (0.308 μm) 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 (λ ∼ 10.6 μm), and Xe (λ ∼ 1.73 μm) 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.

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28

Al-Juboory, Karim H. "PULSED EXCIMER LASER RADIATION AND SELECTED GROWTH REGULATORS INFLUENCE THE GROWTH AND DEVELOPMENT OF POTHOS (EPIPREMNUM AUREUM L.) IN VITRO CULTURE." HortScience 26, no. 6 (June 1991): 757B—757. http://dx.doi.org/10.21273/hortsci.26.6.757b.

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Shoots of greenhouse-grown Pothos were surface disinfested and explanted on modified Murashige and Skoog (MS) medium. Later they were treated with pulsed XeCl excimer laser radiation for 30 sec. Cultures treated with 12 or 25 pulses of excimer laser radiation showed only 23% and 10% contamination, respectively, versus 75% control. Inaddition, we demonstrated that pulsed XeCl excimer laser radiation affected the subsequent growth and regenerability of in vitro plants. The reason for this increased growth needs further investigation. Both BA and TDZ were important for increasing the number of shoots generated from a microshoot as well as inducing shoot organogenesis from Pothos callus. Of the 50 rooted ex vitro plants from this experiment only 30% were variegated like parental clone. The others were either pure green or albino, suggesting chimeral segregation.

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29

Kot, V. A. "Integral method of solving heat-conduction problems with the second-kind boundary condition. 3. Pulsed laser heating." Proceedings of the National Academy of Sciences of Belarus, Physical-Technical Series 64, no. 1 (March 28, 2019): 69–80. http://dx.doi.org/10.29235/1561-8358-2019-64-1-69-80.

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Exact and approximate solutions to the non-stationary problem on the heat conduction in a semi-bounded body exposed to a pulsed laser radiation flow have been obtained. The action of rectangular, triangular and parabolic laser radiation pulses on this body was investigated. Polynomial relations have been constructed on the basis of the boundary-characteristic method with introduction into consideration of the temperature-disturbance front, and they made it possible to obtain practically exact solutions for the temperature function and its time derivative at both the stages of heating and cooling of the body. It is shown by some examples that the success in solving problems on the pulsed plasma heating of bodies is associated in many respects with the necessity of definition of the time law of movement of the temperature-disturbance front with the use of the Pade diagonal approximation, which excludes, practically completely, the divergence of the power series defining the law of movement of this front, in particular, in small time intervals. The approach proposed for solving heat-conduction problems with the second-kind boundary condition allows one to simply and effectively find solutions for isotherms and lines of equal heating and cooling. Analysis of the results obtained allows the conclusion that the effectiveness of solving various technological problems, based on the use of pulsed laser radiation, is determined by the success in solving the problems on control of the time shape of a laser pulse and determination of the temperature fields in the body on the basis of polynomial representations.

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30

Gaković, B., M. Trtica, S. Petrović, P. Panjan, M. Čekada, and Z. Samardžija. "Surface Structures Formed on AISI 420 Stainless Steel by Pulsed Laser Irradiation." Materials Science Forum 494 (September 2005): 309–14. http://dx.doi.org/10.4028/www.scientific.net/msf.494.309.

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The effects of TEA CO2 laser radiation on AISI 420 stainless steel and formed surface structures are studied. The laser energy density of 45.0 J/cm2 has modified the target surface. Qualitatively, the modifications of AISI 420 steel can be summarized as follows: change of color after action of one laser pulse; central zone of interaction in crater like form and periphery zone of interaction (for more than 10 laser pulses); appearance of grainy features and ablation rate of near 4 nm per laser pulse (action of 400 laser pulses); hydrodynamical effects like resolidified rim and droplets.

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31

Michaelis, M. M., P. F. Cunningham, R. S. Cazalet, J. A. Waltham, and M. Notcutt. "Gas lens applications." Laser and Particle Beams 9, no. 2 (June 1991): 641–51. http://dx.doi.org/10.1017/s0263034600003645.

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Various gas lenses are briefly reviewed, together with their imperfections. We discuss the applicability of these lenses as objectives for telescopes and as the final focusing element of high-power laser systems: cw lasers in industry and pulsed lasers for plasma research. A novel phase conjugate experiment employing a gas lens is described. Pulsed gas lenses are proposed as a solution to the problems of high laser fluence and radiation damage in post-break-even fusion experiments.

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32

Kansaku, Rei, Naoki Sakakibara, Atsushi Amano, Hisako Endo, Takashi Shimabukuro, and Michiaki Sueishi. "Histological difference between pulsed wave laser and continuous wave laser in endovenous laser ablation." Phlebology: The Journal of Venous Disease 30, no. 6 (May 30, 2014): 429–34. http://dx.doi.org/10.1177/0268355514538248.

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Background Endovenous laser ablation to saphenous veins has been popular as a minimally invasive treatment for chronic venous insufficiency. However, adverse effects after endovenous laser ablation using continuous wave laser still remain. Pulsed wave with enough short pulse duration and sufficiently long thermal relaxation time may avoid the excess energy delivery, which leads to the perforation of the vein wall. Method (1) Free radiation: Laser is radiated in blood for 10 s. (2) Endovenous laser ablation: Veins were filled with blood and placed in saline. Endovenous laser ablations were performed. Results (1) There were clots on the fiber tips with continuous wave laser while no clots with pulsed wave laser. (2) In 980-nm continuous wave, four of 15 specimens had ulcers and 11 of 15 had perforation. In 1470-nm continuous wave with 120 J/cm of linear endovenous energy density, two of three presented ulcers and one of three showed perforation. In 1470-nm continuous wave with 60 J/cm of linear endovenous energy density, two of four had ulcers and two of four had perforation. In 1320-nm pulsed wave, there were neither ulcers nor perforation in the specimens. Conclusions While endovenous laser ablation using continuous wave results in perforation in many cases, pulsed wave does not lead to perforation.

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33

Senatsky, Y. V., N. E. Bykovsky, S. M. Pershin, and A. A. Samokhin. "Transmittance in a thin aluminum layer at nanosecond pulsed laser ablation." Laser and Particle Beams 35, no. 1 (February 13, 2017): 177–81. http://dx.doi.org/10.1017/s0263034617000064.

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AbstractSince the beginning of the 1960s and up to the present time, laser ablation from metal surfaces under the action of short light pulses has been the topic of many researches. One of the first objects in the early ablation experiments presented thin metal films evaporated by radiation, which were used in lasers with nanosecond pulses as optical gates for Q-switching in resonators or for decoupling in amplifiers. Bleaching of the gates based on metal layers with a time constant τt ≈ 10−8 s observed in a number of experiments, was usually considered as a result of a simple evaporation of matter. We analyze the data of the experiments with a mylar tape [≈0.05 µm aluminum (Al) layer on ≈20 µm lavsan substrate] used as a gate for optical isolation in one of the first Nd: glass laser facilities with a power of ≈1 GW. That gate was irradiated by pulses of Q-switched oscillators: pulse duration 10−7–10−8 s, intensity 107–108 W/cm2. A jump in the transmittance of the expanding Al layer was registered (from ≈0.1 to 50% at τt ≈ 10−9 s). The present study shows that one should consider the metal–insulator phase transition in a superheated liquid metal layer as the mechanism of the fast (up to 10–10–10–11 s) increase in the transmittance of the Al film gate at nanosecond-pulsed laser ablation.

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34

Olofson, Frans, and Leif Holmlid. "Intense ionizing radiation from laser-induced processes in ultra-dense deuterium D(-1)." International Journal of Modern Physics E 23, no. 09 (September 2014): 1450050. http://dx.doi.org/10.1142/s0218301314500505.

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Nuclear fusion in ultra-dense deuterium D(-1) has been reported from our laboratory in a few studies using pulsed lasers with energy < 0.2 J. The direct observation of massive particles with energy 1–20 MeV u-1 is conclusive proof for fusion processes, either as a cause or as a result. Continuing the step-wise approach necessary for untangling a complex problem, the high-energy photons from the laser-induced plasma are now studied. The focus is here on the photoelectrons formed. The photons penetrating a copper foil have energy > 80 keV. The total charge created is up to 2 μC or 1 × 1013 photoelectrons per laser shot at 0.13 J pulse energy, assuming isotropic photon emission. The variation of the photoelectron current with laser intensity is faster than linear for some systems, which indicates rapid approach to volume ignition. On a permanent magnet at approximately 1 T, a laser pulse-energy threshold exists for the laser-induced processes probably due to the floating of most clusters of D(-1) in the magnetic field. This Meissner effect was reported previously.

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35

Gabdrakhmanov, Azat T., Irek H. Israphilov, and Lenar N. Shafigullin. "Research of Laser Welding of Thin-Sheet Structural Steels by Pulsed Laser Radiation." Materials Science Forum 946 (February 2019): 901–5. http://dx.doi.org/10.4028/www.scientific.net/msf.946.901.

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Specific features of the formation of welded metals under the pulsed action of laser radiation are described. It is shown that the quality of the technological process of welding depends on the energy characteristics of the laser technological complex, the temperature of the surface layer. The results of experimental studies on the effect of pulsed laser radiation on steel 08YU with the possibility of obtaining a welded seam with the required quality indices are presented.

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36

Allen, Ralph G., Scott J. Thomas, Robert F. Harrison, Joseph A. Zuclich, and Michael F. Blankenstein. "Ocular Effects of Pulsed Nd Laser Radiation." Health Physics 49, no. 5 (November 1985): 685–92. http://dx.doi.org/10.1097/00004032-198511000-00001.

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37

Weingarten, Christian, Emrah Uluz, Andreas Schmickler, Karsten Braun, Edgar Willenborg, André Temmler, and Sebastian Heidrich. "Glass processing with pulsed CO_2 laser radiation." Applied Optics 56, no. 4 (January 24, 2017): 777. http://dx.doi.org/10.1364/ao.56.000777.

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38

Berik, E., and V. Davidenko. "Statistical properties of pulsed dye laser radiation." Optics Communications 67, no. 2 (June 1988): 129–32. http://dx.doi.org/10.1016/0030-4018(88)90318-5.

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39

Khayrullina, L. R., and F. K. Smorodin. "Processing of products with pulsed laser radiation." Journal of Physics: Conference Series 1870, no. 1 (April 1, 2021): 012001. http://dx.doi.org/10.1088/1742-6596/1870/1/012001.

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40

Kostrubiec, F., and M. Walczak. "Microhardness of the Surface Layer of Tungsten and Molybdenum After Recrystallization With Laser Radiation." Journal of Engineering Materials and Technology 113, no. 1 (January 1, 1991): 130–34. http://dx.doi.org/10.1115/1.2903368.

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We present results of microhardness measurements in melted local regions in molybdenum and tungsten. Microhardness has been measured by the Vickers method. Melted regions have been produced by pulsed Nd-glass laser. The emphasis is on correlation between conditions of recrystallization (energy of laser beam and method of irradiation-single pulse or multiple pulse) and the microhardness value.

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41

Chumakov, A. N., and V. V. Lychkoskyi. "SILICON PLASMA HEATING IN AIR AT THE COMBINED BICHROMATIC LASER RADIATION AT WAVELENGTHS OF 355 and 532 nm." Journal of Applied Spectroscopy 88, no. 6 (November 24, 2021): 900–906. http://dx.doi.org/10.47612/0514-7506-2021-88-6-900-906.

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The formation and heating of laser plasma under the irradiation of silicon in ambient air by pulsed laser radiation with wavelengths of 355 and 532 nm at radiation power density up to 5 GW/cm2 has been experimentally investigated. An increased efficiency of the formation and heating of ablation plasma under bichromatic irradiation of silicon with advanced action of nanosecond pulses with a wavelength of 355 nm has been established.

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42

Maksimovsky, Sergey Nikoloaevich, and Aleksey Urievich Stavtsev. "Nucleation under the impact of pulsed laser radiation." Nexo Revista Científica 34, no. 06 (December 31, 2021): 1785–92. http://dx.doi.org/10.5377/nexo.v34i06.13158.

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The article shows theoretical calculations of nucleation in nonequilibrium conditions under the impact of high-power laser radiation, and their experimental confirmation. The phase transition during homogeneous nucleation without seed in the gas phase has long been studied by various scientists in the developed countries of the world. Several nucleation theories have been developed, however, they are difficult or impossible to apply to fast-flowing crystallization processes occurring at high pressures and temperatures that take place when using high-power laser radiation in the gas phase. In this article, an extended model of nucleation in the gas phase is developed using traditional thermodynamic concepts, as well as the influence of the process conditions on the equilibrium concentration and the formed particle size within the range from 100 nm to 1 micron is predicted. The article describes experiments on growing structures on plastic substrates containing inside optical inhomogeneities in the form of diffraction gratings. The calculation of the sublimation evaporation pressures of aluminum is conducted depending on different laser radiation power densities. The authors obtained images of nascent structures by electron microscopy and demonstrated the possibility of observing the nucleation phases in situ by changing the power of laser radiation of the sample.

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43

Slipchenko, S. O., A. A. Podoskin, D. A. Veselov, L. S. Efremov, V. V. Zolotarev, A. E. Kazakova, P. S. Kop’ev та N. A. Pikhtin. "Vertical stacks of pulsed (100 ns) mesa-stripe semiconductor lasers with an ultra-wide (800 μm) aperture emitting kilowatt-level peak power at a wavelength of 1060 nm". Quantum Electronics 52, № 2 (1 лютого 2022): 171–73. http://dx.doi.org/10.1070/qel17985.

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Abstract A pulsed source of radiation in the spectral region of 1060 nm with a kilowatt level peak output power is developed based on a vertical stack of microbars of stripe semiconductor lasers with an ultra-wide (800 μm) aperture. The laser stack contains three microbars with three emitters each, which ensures an emitting area of 2.6 × 0.4 mm. The highest radiative efficiency of the stack is 2.48 W A−1. The maximum achieved peak power reached 1400 W under pumping by current pulses with an amplitude of 650 A and a duration of 100 ns and is limited by the current source capacity.

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44

Звонков, Б. Н., О. В. Вихрова, Ю. А. Данилов, П. Б. Демина, М. В. Дорохин, М. Н. Дроздов, Д. А. Здоровейщев та ін. "Импульсное лазерное облучение светоизлучающих структур со слоем (Ga,Mn)As". Физика твердого тела 63, № 9 (2021): 1245. http://dx.doi.org/10.21883/ftt.2021.09.51247.01h.

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InGaAs/GaAs heteronanostructures with a (Ga,Mn)As layer on the surface were fabricated by MOCVD epitaxy and pulsed laser deposition, and the effect of a pulsed excimer laser (wavelength 248 nm, pulse duration ~ 30 ns) on their radiative, structural and galvanomagnetic properties was studied. The radiation energy density was varied in the range from 200 to 360 mJ/cm2. In the studies, photoluminescence spectroscopy was used, which makes it possible to analyze the polarization characteristics of the radiation of the structures. The crystalline perfection of the initial and laser-irradiated samples was studied using Raman spectroscopy. The elemental composition of the structures and its depth distribution were studied by secondary ion mass spectrometry. The effect of pulsed laser annealing on the ferromagnetic properties of heteronanostructures was characterized by the behavior of the magnetic field dependences of the Hall resistance and magnetoresistance at temperatures of 10–300 K in the range of magnetic fields ± 3600 Oe. At room temperature, the study was carried out in magnetic fields reaching values of ± 28000 Oe. To obtain the calculated temperature distributions along the sample thickness and in time using a model of the laser annealing process based on solving the problem of heat propagation in a one-dimensional GaAs system taking into account the (Ga,Mn)As layer on the surface, we used the original data on the thermal conductivity coefficient of structures with a layer (Ga,Mn)As obtained using a modified frequency separation technique (3ω-method).

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45

Heinricht, F. "High-Speed Reflection Electron Microscopy of Laser-Induced Surface Transitions." Proceedings, annual meeting, Electron Microscopy Society of America 48, no. 1 (August 12, 1990): 312–13. http://dx.doi.org/10.1017/s0424820100180318.

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Micropatterning of bulk material by pulsed laser radiation is a promising technique for many applications, e.g. drilling and data storage. Due to the fact that laser radiation can be applied very localized, high power densities in a small volume of the treated specimen can be realized. As a result of rapid heat-up and cool-down processes, unusual phases and microstructures can be generated.Time-resolving methods, especially imaging with short exposures times are quite useful in order to understand the physics standing behind. As a diagnostic tool electrons are superior to other probes, e.g. light optics, due to their sensitivity to topography, material composition and structure. Unfortunately , the SEM - one of the most common microscopes for surface analysis - cannot be used for investigations in the the nanoseconds time domain due to its far to slow scan time. On the other hand, the reflection electron microscope (REM) is one of the very few instruments, which is capable to image all points of the treated surface simultanously.In order to achieve electron optical images of laser pulse induced processes on surfaces with exposures times of a few nanoseconds, a high-speed REM was developed. This new instrument is based on a conventional TEM, additionally equipped with the following units:- a laser pulsed thermal electron gun, which delivers high-brightness electron pulses with duration of 20ns.

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46

Kopyeva, Mariya S., Serafima A. Filatova, Vladimir A. Kamynin, Anton I. Trikshev, Elizaveta I. Kozlikina, Vadim V. Astashov, Victor B. Loschenov та Vladimir B. Tsvetkov. "Ex Vivo Exposure to Soft Biological Tissues by the 2-μm All-Fiber Ultrafast Holmium Laser System". Applied Sciences 12, № 8 (10 квітня 2022): 3825. http://dx.doi.org/10.3390/app12083825.

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We present the results of ex vivo exposure by an ultrafast all-fiber Holmium laser system to porcine longissimus muscle tissues. A simple Ho-doped laser system generated ultrashort pulsed radiation with less than 1 ps pulse width and a repetition rate of 20 MHz at a central wavelength of 2.06 μm. Single-spot ex vivo experiments were performed at an average power of 0.3 W and different exposure times of 5, 30 and 60 s, varying the total applied energy in the range of 1.5–18 J. Evaluation of laser radiation exposure was performed according to the depth and diameter of coagulation zones, ablation craters and thermal damage zones during the morphological study. Exposure by ultrashort pulsed radiation with an average power of 0.3 W showed destructive changes in the muscle tissue after 5 s and nucleation of an ablative crater. The maximum ablation efficiency was about 28% at the ablation depth and diameter of 180 μm and 500 μm, respectively. The continuous-wave radiation impact at the same parameters resulted only in heating of the near-muscular tissue, without ablation and coagulation traces. Exposure to tissue with an average power at 0.3 W of ultrashort pulsed radiation led, within 30 and 60 s, to similar results as caused by 0.5 W of continuous-wave radiation, although with less carbonization formation.

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47

Oliveira, V., and R. Vilar. "Modification of Polyimide Wettability by KrF Pulsed Laser Ablation." Microscopy and Microanalysis 14, S3 (September 2008): 73–76. http://dx.doi.org/10.1017/s1431927608089435.

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Laser ablation has been extensively studied in polymers because of their considerable utility in diverse fields such as medicine, microelectronics, photonics, etc. As a result, laser ablation of polymers has generated considerable interest in research during the past two decades. Among the many aspects of laser ablation of polymers, several authors have reported the formation and growth of conical structures during laser processing with UV laser radiation. Although this aspect of laser ablation has been investigated since the 1980s, only a few applications of these structures have been reported. In the present paper, we study the development of conical structures on polyimide treated with KrF laser radiation as a function of the radiation fluence, and its effect on the wettability of the polymer.

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48

Bredikhin, Vladimir I., and Viacheslav V. Kazakov. "The Excitation of Ultrasound by Laser Radiation in Water Using an Optical Fiber Laser Converter with a 2D Colloidal Crystalline Coating." Coatings 9, no. 12 (December 14, 2019): 857. http://dx.doi.org/10.3390/coatings9120857.

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The technology of applying a colloidal single-layer coating of transparent polystyrene (PS) Ø 1 μm spheres at the tip face of a quartz fiber has been proposed and tested. Such a coating plays, in a light absorbing liquid, the role of a converter of pulsed laser radiation into acoustic radiation. The generation of ultrasound in water using a converter based on a quartz fiber 1 mm in diameter with a 2D colloidal crystalline coating consisted of polystyrene spheres with a diameter of ~1 μm at the fiber end was investigated. When excited by laser radiation (λ = 1.064 µm), coating of polystyrene spheres created in the liquid a laser thermal microstructure with a characteristic size of fractions of ~λ and a maximum temperature up to 10−2 degree at an energy in a short laser pulse of ~0.005 J. This short-lived thermal microstructure generated sound pulses in the liquid in the approximately 0.2–4 MHz range. The results of the experimental study of this effect are reported. The proposed laser radiation converter with colloidal coating of the optical fiber distal tip by a single layer of transparent spheres can be used for the development of new laser microtools for studying, processing of various objects in microsurgery, microstructuring of the surface, spot cleaning and restoration of objects of art and history.

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49

Kulikova, Nataliya Gennadievna, Zaur Gidovich Zhilokov, Albina Sergeevna Tkachenko, and Tinatin Chkheidze. "On the use of laser therapy in dentistry." Fizioterapevt (Physiotherapist), no. 01 (January 13, 2022): 33–40. http://dx.doi.org/10.33920/med-14-2202-04.

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The aim of the research: to optimize the prevention of dental complications by using electromagnetic low-intensity laser radiation (LILR) techniques on dental and periodontal tissues. Research methods. In 138 dental patients, a clinical and functional assessment of the dental apparatus was carried out, dental indices were studied, the results of vascular endothelial parameters (VEGF-A, sVEGF-R1, sVEGF-R2) and immune parameters (FNF, TNF, IFN-γ, neutrophils) of blood serum (solid-phase enzyme immunoassay with a standard set), as well as VAS pain syndrome parameters were analyzed before/after laser therapy of different wavelength, mode and range (red, infrared). Results. The study made it possible to assess the effectiveness of treatment with LILR with one wavelength and in combination of different lengths of laser radiation as independent factors of preventive exposure in dentistry patients. After applying the techniques of transcanal treatment, dental periapical tissues were treated with laser radiation, including root canals (difficult teeth roots), using the C11 attachment from the «Lazmik-01» device. The study used a modulated red spectrum of LILR in continuous and pulsed mode (l = 635 nm) and an infrared pulsed spectrum (l = 904 nm) in a continuous mode with a sequential exposure to red (l = 635 nm) pulsed and infrared continuous laser radiation (l = 904 nm). Emphasis was placed on pain syndrome, vascular endothelial and immune shifts in dental and periodontal tissues before/after using laser therapy in dental patients. Conclusion. The combination of the red spectrum of LILR in pulsed mode (l = 635 nm) with a sequential exposure to infrared laser radiation (l = 904 nm) in continuous mode provides high vascular endothelial responses in the dental and periodontal tissues of the dental apparatus, and the use of red-spectrum laser radiation in continuous mode (l = 635 nm) in dental patients provides antimicrobial and sanitizing effects, including at the level of the root canals, which is more significant than after the use of infrared laser radiation in pulsed mode, when analgesic results are higher.

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50

Cousins, Lisa M., and Stephen R. Leone. "Production of 0.1–3 eV reactive molecules by laser vaporization of condensed molecular films: A potential source for beam-surface interactions." Journal of Materials Research 3, no. 6 (December 1988): 1158–68. http://dx.doi.org/10.1557/jmr.1988.1158.

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A versatile, repetitively pulsed source of translationally fast, reactive molecules is described that is suitable for materials processing experiments. The pulsed beams are generated by excimer laser vaporization of cryogenic molecular films that are continuously condensed on transparent substrates. The generation of fast, energy variable pulsed molecular sources of Cl2 and NO is demonstrated. The most probable translational energies of Cl2 and NO molecules can be reproducibly varied monotonically by adjusting the laser fluence or film thickness. Here, the most probable translational energy is quoted as the energy corresponding to the maximum of the time-of-flight trace. Using laser fluences of 2–25 mJ cm−2 from a 193 nm excimer laser, the most probable translational energies of Cl2 are 0.4–2 eV. Significant fractions of molecules with translational energies greater than 3 eV are observed at the leading edges of the distributions. Very similar results are obtained by vaporizing Cl2 with 248 and 351 nm radiation. Pulses of translationally fast NO molecules are generated in a similar manner; most probable energies from 0.1–0.4 eV, with the fastest molecules up to 0.8 eV, are obtained using laser fluences of 1–11 mJ cm−2 at 193 nm. Approximately 1013−1014 molecules per cm2 of the film are vaporized per laser pulse, depending on film thickness and laser fluence.

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