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Modification of ABS wetting properties by ultrashort and short pulse lasers
摘要： Wetting is an important property of solid surfaces, where the surface roughness has a meaningful influence on it. This study focuses on the wetting behavior of micro-textures fabricated on acrylonitrile butadiene styrene (ABS) thermoplastic polymer to provide it anti-fingerprint properties. The structuring process was performed by ultrashort (picosecond) and short (nanosecond) pulses based on square pillars. Wetting behavior was assessed by water and oleic acid static and dynamic (hysteresis) contact angles. Both sort of micro-textures displayed a water contact angle tailored from 90. Apparent color changes induced by laser were assessed to get information about the aesthetical appearance.
关键词： ultrashort pulses,polymers,wettability,short pulses.,laser radiation,contact angle
更新于2025-09-12 10:27:22
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The processes underlying the laser photochromic effect in colloidal plasmonic nanoparticle aggregates
摘要： We have studied the dynamic and static processes occurring in disordered multiparticle colloidal Ag aggregates with natural structure and affecting their plasmonic absorption spectra under pico- and nanosecond pulsed laser radiation, as well as the physical origin responsible for these processes. We have shown that depending on the duration of the laser pulse, the mechanisms of laser modification of such aggregates can be associated both with changes in the resonant properties of particles due to their heating and melting (picosecond irradiation mode) and with the particle shifts in resonant domains of aggregates (nanosecond pulses) which depend on the wavelength, intensity and polarization of the radiation. These mechanisms results in formation of a narrow dip in the plasmonic absorption spectrum of aggregates near the laser radiation wavelength and affect the shape and position of the dip. The effect of polydispersity of nanoparticle aggregates on laser photochromic reaction has been studied.
关键词： Nanoparticle,surface plasmon resonance,photochromic process,pulsed laser radiation
更新于2025-09-12 10:27:22
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The Radioprotective Effects of Low-Intensity Laser Radiation on Rat Peripheral Blood Cells
摘要： The radioprotective effect of low-intensity laser radiation on blood cells was studied on Wistar rats. The following procedures was carried out: single total body γ-radiation (dose of 3 Gy) of rats; over-vein irradiation with continuous laser radiation (λ = 670 nm); and combined γ- and laser irradiation, which varied among different series of experiments according to the number of procedures and the energy density of the laser radiation (2.5 J/cm2, 1.25 J/cm2). The influence of γ- and laser radiation on the number of peripheral blood cells in rats, the activity of antioxidant defense enzymes (superoxide dismutase and catalase), and on the blood absorption spectra in regions sensitive to its oxygenation were studied. On the 4th day after γ-irradiation, the radioprotective effect of low-intensity laser radiation was manifested as an increase in the average number of leukocytes (up to 1.4 times) and lymphocytes (up to 1.8 times) in comparison with reduced γ-irradiation, in an increase in the relative lymphocyte proportion in the leukocyte population (up to 1.5 times), and in an increase in the activities of catalase and superoxide dismutase, which were decreased by the γ-irradiation. It was found that the changes in the number of erythrocytes, leukocytes, lymphocytes, and superoxide dismutase activity initiated by γ-radiation alone and by combined laser and γ-radiation differed in individual rats and depended on individual initial values. The molecular mechanisms of the observed photo-radiobiological effects are discussed.
关键词： low-intensity laser radiation,blood absorption spectra,γ-radiation,blood cells,antioxidant defense enzymes
更新于2025-09-11 14:15:04
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Increasing efficiency of the laser action to materials
摘要： The processes of interaction of laser radiation with the surface layer of the metal during laser action are considered. An effective method of laser hardening of the surface layer due to the total effect of laser radiation and a cooler in the treatment area is proposed.
关键词： Hardening,Laser radiation,Laser,Metallography,Cryogenic treatment
更新于2025-09-11 14:15:04
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Electrical Parameters of a Laser Beam Channel in the Atmosphere. II
摘要： Results of measurements of the conductivity and electric field strength in the laser radiation propagation channel and near it are presented. An experimental setup and measurement scheme are described. The data have been obtained in the prebreakdown regime. The dependences of the laser-induced field strength on the laser radiation power and the optical characteristics of the propagation channel are investigated. The feasibility of ionization channel diagnostics using the electro-optical effects in the atmosphere is shown.
关键词： laser radiation,propagation channel,electrical parameters,optical breakdown
更新于2025-09-11 14:15:04
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The Influence of Solar Illumination on the Sensitivity of Passive Lidar for Reception of The Scattered Laser Radiation
摘要： We solve the problem of determining the power of the received scattered optical radiation from external laser beams, which propagate in the Earth’s atmosphere, by passive lidar in a weakly turbid transparent atmosphere and also determine the lidar operation radius. Under the night conditions without solar illumination, the lidar operation radius can exceed 2300 km when detecting the beams with powers is about 100 kW. In the presence of solar illumination, the operation radius decreases by an order of magnitude. For a small power of the external beam, the experimental and theoretical data are in good agreement, which makes it possible to extrapolate the obtained theoretical results to larger powers of the external beams with allowance for the radiation loss because of the secondary Rayleigh scattering.
关键词： Rayleigh scattering,scattered laser radiation,detection radius,passive lidar,solar illumination
更新于2025-09-11 14:15:04
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Fiber Fuse Effect in Hollow Core Optical Fibers
摘要： Fiber fuse effect (FFE) is one of phenomena restricting the high power/intensity/pulse energy laser radiation transport through optical fibers. FFE (alternatively, optical discharge (OD) propagation through fiber core) was initially observed in solid state silica fibers [1], and later in fibers of various materials and constructions, including microstructured fibers. Hollow core fibers developed in recent decades can transport high power laser radiation. However, it was recently discovered that FFE is present in such fibers as well [2]. In this work OD propagation through hollow-core revolver fibers (RFs) was investigated. Reflecting cladding of RFs consists of only one layer of capillaries [3]. The cross section pictures of two RFs used in experiments are shown in Fig.1(a,b: RF1 and RF2). All our RFs had transparency bands at laser radiation wavelength 1.06 m. The Q-switched mode-locked Nd:YAG solid state laser was used in our experiments to reach a high enough radiation intensity in the fiber core. The laser radiation consisted of nanosecond trains of picosecond pulses (PPs): the train duration was 130 ns, duration of PP was 100 ps at repetition rate 76 MHz. The average output power of the laser was 3 W. The laser radiation was launched into and passed the ~50 cm RF without any significant disturbances. However, touching of the output end of the fiber with a metal plate gave rise to OD propagation with an average velocity Vav of ~1m/s. In the case of RF1 the silica structure of the fiber was completely destroyed after the OD passage, and its fragments were held together only by the polymer cladding. In the case of RF2 having a twice as thick support tube the fiber can be inspected after OD passage as a whole. It turned out that Vav depends essentially on the fact whether RF was during the experiment covered by polymer or not. In the last case Vav was ~3 times higher (~3 m/s) than for coated fiber (Fig.1, e). Each PP left in the RF2 fingerprint in the form of capillary destruction region of ~100 m length, and these regions were separated from each other by ~100 m regions of undamaged capillaries (Fig.1,c). And in the case of uncoated RF2 (Fig.1,d) the fingerprints of PP trains are separated by ~1 mm from each other contributing to the Vav increase.
关键词： Fiber fuse effect,laser radiation,revolver fibers,optical discharge,hollow core optical fibers
更新于2025-09-11 14:15:04
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Study of Grain Boundary Character || Control the Metal Grain Boundary Recrystallization Evolution by the Laser Radiation Electric Field Strength Direction Under Cyclic Thermal Loading
摘要： The spatial grating formation at metal surface under the linear polarized laser radiation action is briefly considered. The spatial grating periods are well described in framework of universal polariton model (UPM) and are well-defined physical quantities. The production of new-type gratings (quasi-gratings) at laser power densities lower than the metal melting threshold with power-dependent typical spatial scale and polarization-dependent orientation are discovered. The regularities of quasi-grating production are experimentally studied. The physical model of quasi-grating formation explaining the anisotropic character of metal recrystallization is suggested. The anisotropy is caused by the directed electron flux interaction with grain boundaries. The electron flux results from the drag effect of electrons by surface plasmon polaritons (SPPs). SPPs are excited by incident laser radiation on the surface irregularities including the grain boundaries. The volume analog of considered effect is the electroplastic one, and some of its regularities are considered.
关键词： grain boundary movement,laser radiation,electrons drag by surface plasmon polaritons,metal,electroplastic effect,surface plasmon polaritons,linear polarization,anisotropic recrystallization
更新于2025-09-11 14:15:04
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Growth, spectroscopic, diode-pumped mid-infrared laser properties of Er:GSAG crystal
摘要： A great potential mid-infrared laser crystal of heavily Er3+ doped GSAG crystal with high optical quality is successfully grown by Cz method. The crystal quality of Er:GSAG crystal is determined by XRC. The structure parameters of Er:GSAG crystal are obtained by the X-ray Rietveld refinement method (a=b=c=12.3196?). The absorption cross section at 961nm and 967 nm are 0.381 × 10-21 cm2 and 0.414 × 10-21 cm2, respectively. The 962 nm laser diode end-pumped Er:GSAG laser operated at 2828 nm is demonstrated for the first time. The performance of Er:GSAG laser is investigated in great detail. A maximum output power of Er:GSAG laser is 410 mW when pumped by 962 nm LD at 300 Hz and 0.5 ms. Simulating results display the highest temperatures of Er:GSAG laser spot is 345.8 K, indicating a small thermal lensing effect of Er:GSAG crystal. Besides, the laser performance of Er:GSAG crystals which irradiate by different doses of gamma-ray are used to investigated its potential for working in the radiation resistance environment. The results show the relatively minor differences on the Er:GSAG lasers performance, indicating a great potential of Er:GSAG crystal in radiant environment application.
关键词： Er:GSAG,Mid-infrared laser,Radiation resistant,Crystal structure,Absorption spectrum
更新于2025-09-11 14:15:04
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Theoretical Investigation of the Shubnikov-de Haas Magnetoresistance Oscillations in a Quantum well under the Influence of Confined Acoustic Phonons
摘要： The Shubnikov – de Haas magnetoresistance oscillations in the Quantum well (QW) under the influence of confined acoustic phonons, The theoretical results show that the conductivity tensor, the complex magnetic impedance of the magnetic field, the frequency, the amplitude of the laser radiation, the QW width, the temperature of the system and especially the quantum index m characterizes the confinement of the phonon. The amplitude of the oscillations of the Shubnikov-de Haas impedance decreases with the increase of the influence of the confined acoustic phonons. The results for bulk phonons in a QW could be achieved, when m goes to zero. We has been compared with other studies when perform the numerical calculations are also achieved for the GaAs/AlGaAs in the QW. Results show that The Shubnikov – de Haas magnetoresistance oscillations amplitude decrease when phonon confinement effect increasing and when width L of the QW increases to a certain value, The Shubnikov – de Haas magnetoresistance oscillations amplitude completely disappears can not be observed.
关键词： Quantum well and width L of quantum well,Confined acoustic phonons,Quantum kinetic equation,Laser radiation,Shubnikov–de Haas magnetoresistance oscillations
更新于2025-09-10 09:29:36