Photoacoustic effect in micro- and nanostructures: numerical simulations of Lagrange equations

The work provides the description of theoretical and numerical modeling techniques of thermomechanical effects that take place in absorbing micro- and nanostructures of different materials under the action of pulsed laser radiation. A proposed technique of the numerical simulation is based on the solution of equations of motion of continuous media in the form of Lagrange for spatially inhomogeneous media. This model allows calculating fields of temperature, pressure, density, and velocity of the medium depending on the parameters of laser pulses and the characteristics of micro- and nanostructures.

Эмиссионные спектры молекулярных газов CHF-=SUB=-3-=/SUB=-, CCl-=SUB=-2-=/SUB=-F-=SUB=-2-=/SUB=-, SF-=SUB=-6-=/SUB=- в диапазоне 3-20 nm при импульсном лазерном возбуждении с использованием различных газовых струй в качестве мишеней

The article considers the results of studies of the emission spectra of CHF3, CCl2F2, SF6 upon excitation by pulsed laser radiation. We used Nd:YAG laser, λ = 1064 nm, τ = 5 ns, and Epulse = 0.8 J. The spectral range of 3-20 nm was studied. We used capillary and supersonic conical nozzles with dcrit = 145 μm, 2α = 12o, L = 5 mm, and dcrit = 450 μm, 2α = 11o, L = 5 mm to form an atomic cluster beam. The emission spectra for various gas targets were obtained, the obtained spectra were deciphered, and the ions emitting in this spectral range were determined. We observed that with increasing particle concentration in the zone of laser spark, the radiation intensity increases. In this case, the intensity of ion lines with high degrees of ionization increases faster.

Method development to secure the stability of the parameters of pulsed and continuous radiation in laser systems with semiconductor pumping

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.

SILICON PLASMA HEATING IN AIR AT THE COMBINED BICHROMATIC LASER RADIATION AT WAVELENGTHS OF 355 and 532 nm

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.

Model of the impurities redistribution in the surface layer of an alloy under the action of pulsed laser radiation

Model of the impurities redistribution in the surface layer of an alloy under the action of pulsed laser radiation

The Effect of using Repetitively Pulsed Laser Radiation in Selective Laser Melting when Creating a Metal Matrix Composite Ti-6Al-4V – B4C.

A metal-matrix composite based on Ti-6Al-4V – B4C with TiB, TiB2 and TiC inclusions was successfully obtained as a result of in-situ synthesis using repetitively pulsed laser radiation. For the first time, the phase composition of the obtained metal-matrix composite was studied using synchrotron radiation. A comparison of the effect of using continuous and pulsed-periodic radiation in selective laser melting on the microstructure and mechanical properties of coatings was made. The use of repetitively pulsed radiation made it possible to form more uniform structures and to improve the mechanical properties of metal-matrix coatings in comparison with the continuous mode of exposure. It has been established that the use of repetitively pulsed radiation and the formation of TiB2, TiB, TiC phases made it possible to increase the wear resistance of the formed composite by a factor of 6 in comparison with the Ti-6Al-4V metal coating.