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The Influence of X-ray and UV Laser Radiation on the Optical Properties of Alkali-Containing Silicate Glasses
摘要： The results of complex action of X-ray and nanosecond UV laser radiation on alkali-containing silicate glasses are presented. It is shown that X-ray irradiation of glasses forms luminescent color centers in them, which is related to increasing concentration of structural defects in glass network. Laser radiation destroys these defects, which is accompanied by bleaching of glasses and disappearance of luminescence in irradiated regions. The dynamics of glass bleaching under action of laser radiation and the influence of alkali-metal (Li, Na, K) ions on this process are studied. Mechanisms of destruction of color centers by laser radiation are proposed.
关键词： color centers,laser radiation,absorption,luminescence,silicate glass,X-ray radiation
更新于2025-09-16 10:30:52
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Semiconductor Plasma Antennas Formed by Laser Radiation
摘要： Efficiency of the transmission of high-frequency signals by semiconductor plasma antennas based on Ge and Si single crystals with surface nonequilibrium electron-hole plasma generated by laser diode radiation has been experimentally studied. Dependences of the amplitude of a radiated 6- to 7.5-GHz microwave signal on the laser power and size of the laser-irradiated region on the semiconductor transmitting dipole antenna are determined. It is shown that a more than tenfold increase can be achieved in the efficiency of useful signal transmission by the plasma antenna formed in Ge crystals.
关键词： laser radiation,plasma antenna,silicon,germanium,microwave radiation,semiconductor,electron-hole plasma
更新于2025-09-16 10:30:52
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Structure and Phase Composition of Ti-6Al-4V Samples Produced by Direct Laser Deposition
摘要： In this article had been carried out X-ray phase analysis of the samples obtained using direct laser deposition. Two groups of samples were studied: the first one was obtained with oscillation of laser radiation, the second one – without. The investigations have shown that in the process of direct laser deposition, the α+β phase is formed from a Ti-6Al-4V titanium alloy with oscillation of laser radiation.
关键词： high-speed direct laser deposition,titanium alloys,X-ray analysis,oscillations of laser radiation,Ti-6Al-4V alloy,microstructure
更新于2025-09-16 10:30:52
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Influence of Surface Modification of Granules of Powder Material on the Dynamics of Selective Laser Melting
摘要： The method for increasing the efficiency of layer-by-layer laser melting of aluminum powders is proposed in this paper. The analysis of the starting material (powder distribution by size and morphology of the granule surface) is carried out. The possibility of changing the absorbing capacity of a powder composition using highly absorbent materials has been studied. Conclusions were made about the effectiveness of the method for modifying particles of a powder composition based on the data obtained. On the expressed effect of the morphology of the powder material and on the presence of absorbing coatings on the surface of the granules upon absorption of laser radiation energy, data are obtained.
关键词： absorption of laser radiation,particle modification,carbon additives,laser fusion
更新于2025-09-16 10:30:52
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Selective rear-side ablation of aluminum thin layers with ultrashort-pulsed laser radiation
摘要： In recent years, several applications for laser ablation of thin metal layers from the fused silica substrate side have been studied. The rear-side ablation is a highly effective ablation method for thin layer structuring and reveals a high structuring quality. Therefore, the present work dealt with the selective rear-side ablation of thin aluminum layers (10–50 nm) on fused silica with ultrashort-pulsed laser radiation (λ = 1028 nm, ??H = 0.2–10 ps and w0,86 = 15.2 μm). The influences of pulse duration and layer thickness on the ablation thresholds as well as the incubation coefficients were determined. For layer thicknesses of 30 and 50 nm, a decrease of the ablation threshold with increasing pulse duration was determined. Whereas, the ablation threshold remained constant for layer thicknesses of 10 and 20 nm. Different morphologies were observed depending on the process parameters. The rear-side ablation of aluminum proceeded over the melting phase and no lift-off process had taken place. In addition to experimental investigations, calculations were carried out to determine the theoretical threshold fluences. The theoretical values were compared to experimental data. With the help of these investigations, the quality of the structuring of aluminum layers can be improved.
关键词： ultrashort-pulsed laser radiation,incubation coefficients,aluminum thin layers,laser ablation,rear-side ablation
更新于2025-09-16 10:30:52
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Contribution of Mechanical Stresses to the Surface Relief Formation Under Laser Irradiation of Semiconductors
摘要： The paper considers the effect of elastic stresses arising under pulsed laser irradiation of epitaxial layers of CdxHg1–xTe solid solutions on the formation of a periodic surface relief as a result of recrystallization of material melted by radiation.
关键词： semiconductor solid solution,pulsed laser radiation,surface recrystallization,thermoelastic stresses
更新于2025-09-16 10:30:52
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A Complex for Diagnostics of Laser Radiation of Semiconductor Targets Excited by a High-Frequency-Modulated Electron Beam
摘要： A complex of equipment for diagnosing the parameters of laser radiation of semiconductor targets, which are excited by high-frequency-modulated electron-beam pulses, is described. The ability to control the shape and duration of laser radiation in the picosecond range via high-frequency modulation of an accelerating-voltage pulse was demonstrated experimentally. A train of laser-radiation pulses with a maximum intensity of up to 2 × 107 W/cm2 was obtained on a cadmium sulfide target (λ = 525 nm).
关键词： picosecond range,cadmium sulfide,semiconductor targets,high-frequency-modulated electron-beam pulses,laser radiation
更新于2025-09-16 10:30:52
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Capacitive Characteristics of High-Speed Photovoltaic Converters at Combined Lighting
摘要： p–i–n GaAs photovoltaic converters of modulated laser radiation (810–830 nm) transferring both energy (laser power) and information signal were developed. The capacitance and frequency characteristics of the photovoltaic converters at a constant 0.2–1 W and variable 16 mW laser power were studied. The dependences of the heterostructures capacitance on the voltage at the p–i–n junction were obtained; it has been found out that the charge accumulated in the i-layer plays the dominant role. As a result, the decrease in the thickness of the undoped region improves the frequency characteristics. This paper shows that at the voltage in the DC circuit of 0.8 V and the laser power of 0.6 W, the efficiency of 39% can be achieved with the 450 MHz transmission band in case of the 20 mV AC signal amplitude at the load of 2.5 Ω. For the voltage in the DC circuit of 1 V in similar modes of continuous laser radiation, the efficiency was 48.6%, and the transmission band was 135 MHz. Increasing the laser power to 1 W reduced the efficiency by about 1% and the bandwidth by 30 MHz. The achieved characteristics of the studied photovoltaic converters would make it possible to use them for providing autonomous power supply for devices with low power consumption at the data rate of 100 Mbit/s and above.
关键词： modulated laser radiation,capacitance,p–i–n structure,photovoltaic converters
更新于2025-09-16 10:30:52
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Sharp Small-Scale Perturbations of Fringes at the Interference of Dispersed Broad-Spectrum Laser Beams
摘要： The interference of two dispersed laser speckle-?elds with a great spectrum width has been studied by numerical modeling. Local small-scale perturbations of interference fringes with an abrupt drop of contrast in the interference picture have been revealed. It has been shown that these perturbations occur in the region of a large phase gradient and a small module of the mutual coherence function of coinciding interfering ?elds. The analytical description of small-scale perturbations is given, and the probability of their appearance is estimated.
关键词： dispersed beams,phase singularity,broadband laser radiation,interference,speckle ?elds
更新于2025-09-16 10:30:52
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Research of the Treatment Parameters Effects on the Layer Formation during Wire-Feed Laser-TIG Deposition with Aluminum Alloy
摘要： The paper presents the results of an investigation of the influence parameters of laser radiation on the formation of the deposition layer during laser-TIG direct deposition of aluminum wire. Experimental studies have focused on the determination the dependence shape of layer on the laser power, the distance between axis of laser beam and axis of arc, arc parameters. High-speed video recording of the process was carried out. The metallographic analysis of cross-sections of the samples was performed.
关键词： additive technologies,aluminum wire,formation of layer,laser radiation
更新于2025-09-16 10:30:52