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Optical matching of a multimode gradient fibre and single-mode stepped-index fibre in a photopolymerizable composition
摘要： The opportunity to optically match waveguides characterized by an essentially different field structure in a photopolymerizable medium is investigated. The example of a multimode gradient fibre (core diameter 50 μm) and a single-mode stepped-index fibre SMF-28 (core diameter 8.2 μm) shows that the efficiency of radiation transmission from the wide fibre into the narrow one can reach 60% at a distance between their end faces of about 900 μm.
关键词： nonlinear optics,photopolymer,optical matching of fibres,fibre optics,laser radiation
更新于2025-09-23 15:22:29
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Influence of Focused Pulsed Laser Radiation on the Properties of Amorphous FeSi6B16 Metal Alloy
摘要： The effect of focused pulsed laser radiation (number of pulses and power density) on an amorphous FeSi6B16 metal film is studied. The states of the alloy before and after laser irradiation are analyzed using methods of atomic force microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and microhardness measurements. Focused laser radiation in any exposure mode is established to cause high-temperature heating of the surface of an amorphous alloy in the irradiation zone. The result of such heating is melting of the material surface and propagation of the heat wave front from the strongly heated surface to its inner layers, which induces the redistribution of elements in the Fe–Si–B system, a change in the structure, and an increase in the microhardness.
关键词： microhardness,nonequilibrium state,X-ray photoelectron spectroscopy,atomic-force microscopy,surface,laser radiation,amorphous alloys
更新于2025-09-23 15:21:01
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Control of Multiple Filamentation of Femtosecond Laser Pulses in Air
摘要： The results are presented of experiments on controlling the characteristics of the multiple filamentation domain of femtosecond laser pulses along atmospheric paths via variations in the initial spatial focusing, beam radius, and pulse energy, as well as the optical field structure at the initial beam aperture.
关键词： filamentation,femtosecond pulse,bimorph deformable mirror,laser radiation,postfilamentation light channel,self-focusing
更新于2025-09-23 15:21:01
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Arrays of Carbon Nanotubes in a Field of Continuous Laser Radiation
摘要： A numerical analysis of the phase-matching conditions during the incidence of one or two counterpropagating laser beams on an ordered array of single-walled carbon nanotubes (CNTs) is performed. The conditions for the generation of slow surface plasmon waves of the terahertz (THz) and far infrared range propagating along the nanotubes of the irradiated array are determined. It is shown that the plasmon frequency can be controlled by changing the angle of incidence of laser radiation on the structure under study. Thus, it is possible to fulfill the condition of longitudinal resonance, in which each array nanotube is a dipole antenna radiating at the plasmon frequency. In this case, the array forms a system of a large number of in-phase emitters, which allows increasing the efficiency of conversion of laser radiation into THz radiation in comparison with a single nanoantenna.
关键词： phase-matching conditions,terahertz radiation,carbon nanotubes,laser radiation,plasmon waves
更新于2025-09-23 15:19:57
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A Synergy of Strain Loading and Laser Radiation in Determining the High-Performing Electrical Transports in the Single Cu-Doped SnSe Microbelt
摘要： Semiconducting microbelts are key components of the thermoelectric micro-devices, and their electrical transport properties play significant roles in determining the thermoelectric performance. Here, we report heavily Cu-doped single-crystal SnSe microbelts as potential candidates employed in thermoelectric micro-devices, fabricated by a facile solvothermal route. The considerable Cu-doping concentration of ~11.8 % up to the solubility contributes to a high electrical conductivity of ~416.6 S m-1 at room temperature, improved by one order of magnitude compared with pure SnSe (38.0 S m-1). Meanwhile, after loading ~1 % compressive strain and laser radiation, the electrical conductivity can be further improved to ~601.9 S m-1 and ~589.2 S m-1, respectively, indicating great potentials for applying to thermoelectric micro-devices. Comprehensive structural and compositional characterizations indicate that the Cu+ doping state provides more hole carriers into the system, contributing to the outstanding electrical conductivity. Calculations based on first-principle density functional theory reveal that the heavily doped Cu lowers the Fermi level down into the valence bands, generating holes, and the 1 % strain can further reduce the bandgap, strengthening the ability to release holes, and, in turn, leading to such an excellent electrical transport performance. This study fills the gaps of finding novel materials as potential candidates employed in the thermoelectric micro-devices and provides new ideas for micro/nanoscale thermoelectric material design.
关键词： Cu-doping,tin selenide,electrical transport performance,laser radiation,strain loading
更新于2025-09-23 15:19:57
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Direct-indirect GeSn band structure formation by laser Radiation: The enhancement of Sn solubility in Ge
摘要： Low equilibrium solid solubility of Sn atoms in Ge (less than 1%) leads to limitations in application of this material for IR detectors and emitters. Providing of non-equilibrium conditions by powerful pulsed laser radiation can be successfully applied for enhancement of solubility of impurity atoms in the host material. Here we present laser-induced monotonous redistribution of Sn atoms in Ge, based on the thermogradient effect aiming overcoming equilibrium limitations in the solubility. We applied pulsed nanosecond laser radiation to epitaxial Ge0.96Sn0.04 layer grown on Si substrate to increase Sn atomic concentration up to 14% at the surface layer. As a result, indirect-direct graded bandgap GeSn structure was formed. The TEM/EDS cross-section analysis, X-ray photoelectron spectroscopy, Raman and UV reflection spectra confirmed the increase of Sn atomic content at the surface by order of magnitude. SEM and AFM imaging provided evident microstructure changes, while carrier lifetime changes, determined by differential transmittivity, were not observed, indicating that laser irradiation does not generate defects which reduce electronic quality of the material.
关键词： Laser radiation,Thermogradient effect,Solid solution,Carrier recombination,GeSn
更新于2025-09-23 15:19:57
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Simulation of femtosecond interferometry when studying the effect of intense laser irradiation of a transparent medium
摘要： A method for comparing experimental and simulation results obtained when transmitting a femtosecond laser pulse through a material is proposed. This method is based on computer reproduction of photographs recorded using femtosecond interferometry. A numerical analysis of the spatial and temporal evolution of an intense (~1013 W cm–2) pulse propagating in the bulk of yttrium aluminium garnet is presented.
关键词： fast processes in solids,femtosecond interferometry,femtosecond laser radiation
更新于2025-09-23 15:19:57
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Comments on the 2013 ICNIRP Laser Guidelines
摘要： IN 2013, the International Commission on Non-Ionizing Radiation Protection (ICNIRP) published guidelines on exposure limits for laser radiation of wavelengths between 180 nm and 1,000 mm (ICNIRP 2013a). Since then, the application of the limits has shown that some additional guidance is needed for complex exposure cases. This statement refers primarily to extended laser sources as opposed to the more common point sources. Questions received about the application of exposure limits for retinal thermal hazards from extended sources subtending more than 5 mrad made it clear that clarifications were needed regarding the description of angular subtense and repetitive-pulse correction factors. It is also confirmed that the exposure limit to protect the cornea in the far infrared wavelength range is not based on aversion responses. Also, this statement provides clarification on symbols used in the tables.
关键词： repetitive-pulse correction factors,angular subtense,ICNIRP guidelines,laser radiation,retinal thermal hazards,exposure limits
更新于2025-09-23 15:19:57
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[IEEE 2019 IEEE 8th International Conference on Advanced Optoelectronics and Lasers (CAOL) - Sozopol, Bulgaria (2019.9.6-2019.9.8)] 2019 IEEE 8th International Conference on Advanced Optoelectronics and Lasers (CAOL) - Generation of particles during laser treating of metal in external electric field
摘要： It is shown that in the course of laser processing with radiation flux density ～106 W/cm–2 in the external electric field with different polarity varying from 0 to 106 V/m-1 the change in the evolution features of the plasma torch at the surface of some metals (Cu, Al, Pb) at early stages is quantitative rather than qualitative. At the same time the characteristic size of the target material droplets carried out from the irradiated zone, becomes by several times smaller as the amplitude of the external electric field strength grows, independently of its polarity.
关键词： laser radiation,electric field,gravitycapillary waves,plasma formation
更新于2025-09-23 15:19:57
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Viscous Motion of Spherical Nanoparticles that Scatter Laser Radiation in the Rayleigh Regime
摘要： The mechanism of transverse radiation viscosity for nanospheres moving in laser ?eld is analyzed. It is demonstrated that in the process of light scattering by these particles besides the force Fs accelerating them in the direction of radiation propagation and the gradient force Fg that is due to the spatial inhomogeneity of the light ?eld, there are forces Fvisc that slow down the movement of particles in the transverse directions. These light viscosity forces are due to the Doppler shift in frequency of scattered radiation. The general expressions for these forces acting on particles that scatter radiation in the Rayleigh regime are derived and applied to estimate their e?ect on levitated nanospheres and also on slow electrons moving in the laser and magnetic ?elds. The possible experiments for observation the e?ects of light viscosity are discussed.
关键词： laser radiation,viscous motion,spherical nanoparticles,light viscosity forces,Rayleigh regime
更新于2025-09-23 15:19:57