Home – Home – Jornals – Atmospheric and Oceanic Optics 2020 number 3

XIV International Conference on pulsed lasers and their applications (AMPL) was held in Tomsk in September 15-20, 2019. The Conference was traditionally devoted to results of theoretical and experimental studies of physical and chemical processes in laser active media; the newest active media and pumping methods; new laser technologies; fundamental topics of laser physics; application of lasers in science, engineering, medicine and other spheres; discussion of problems and difficulties in development of laser-based equipment; new optical technologies.

The results of experimental studies of the influence of pumping conditions on the spectral and temporal characteristics of IR Ar I laser radiation upon excitation of the active medium by a pulsed inductive longitudinal discharge are presented. The lasing was obtained at transitions of neutral argon atoms at wavelengths of 1213, 1240, 1270, 1694, and 1791 nm in pure argon and its mixtures with helium and neon. The optical pulses length was (5 ± 1) ns (FWHM); the radiation energy attained 0.1 mJ.

An IR laser, which operates in the region 900-2050 nm at transitions of Xe I atoms and is pumped by pulsed inductive cylindrical discharge, has been created. Xenon and its mixtures with helium and argon were used as active media. The influence of the composition of the active gas medium on the intensity of Xe I atom radiation was experimentally studied. The lasing spectrum consisted of three lines with wavelengths of 904.5, 1733, and 2026 nm. The intensity ratio strongly depended on the composition of the active medium. The duration of the optical radiation pulses attained 8 ± 1 ns (FWHM).

When the Ne + Tl gas-vapor mixture was excited by an electron beam, laser generation was obtained and investigated with excitation of the upper levels in the charge exchange reaction at ion lines with λ = 1,922; 1,385; 0,595; 0,695 and 0,707 mm; the lasing at the first two lines was obtained for the first time. In the studied range of pump parameters, a linear dependence of the lasing power on the pumping power was revealed, indicating the efficiency of electron-beam excitation. An average radiation power of 44 mW was reached at λ = 595 nm at a pulse repetition frequency of 1 kHz with an efficiency of ~ 0,06%. A numerical simulation of the laser energy characteristics was carried out.

A transverse-pumped sodium vapor active element has been developed. A possibility of lasing at resonant transitions upon active medium excitation using nanosecond pulses of various energies and spectral conditions has been experimentally investigated. The medium was pumped using a dye laser and a CuBr laser. Radiation was detected on sodium D lines when pumping with CuBr laser yellow emission line.

Lasing energy of 10 mJ was obtained for the first time under nitrogen pumping by a pulsed inductive discharge with a pulsed power higher than 1 MW. The lasing pulse length of the inductive nitrogen laser created was (8.5 ± 0.5) ns (FWHM). The lasing was obtained at two wavelengths of 337.1 and 357.7 nm. The lasing beam had a ring cross section with a diameter of about 33 mm and a width of about 2 mm.

The conditions for the formation of THz radiation in ZnGeP₂ single crystals when generating a difference frequency are considered. It is shown that two-frequency laser pumping sources with lasing pulse duration of ~ 1 ns are required to implement effective THz radiation. It is suggested to use a “generator - amplifier” system of a strontium vapor laser (at the Sr I transitions in the region 3 mm and Sr II in the region 1 mm) as such a source of IR radiation. The conditions of population inversion are considered, under which the lasing pulse duration is ~ 1 ns in the active medium of the strontium vapor laser. It is shown that the use of the “generator -amplifier” system can increase the average lasing power of the strontium vapor laser in proportion to the increase in the volume of active medium of the amplifier.

A laboratory prototype of a complex for high-speed visual-optical diagnostics of plasma-chemical synthesis in powder mixtures is described. The processes are initiated by microwave radiation of a gyrotron. The laboratory prototype allows imaging processes in the reactor and spectra of the resulting radiation. The prototype includes video cameras, spectrometers, and a synchronization system and suggests a possibility of installing an active filtration system based on metal vapor active media. The resulted images of the process of synthesis of various ceramic micro- and nanoparticles are presented. It is shown that the use of temporal filtering of optical images does not completely suppress the background radiation impact.

The results of laboratory experiments on recording the backscattered IR laser radiation from aerosol particles containing organic impurities are presented. The studies were performed at the laboratory test bench according to the lidar sensing scheme along a controlled optical path. Aqueous aerosol and aqueous solutions were used as model media. Aerosol and solutions contained organic impurities: tryptophan, isopropyl alcohol, glycerin, and nicotinamide adenine dinucleotide (NADH). For research in the IR range, the experimental complex was modified. The UV laser was replaced with an IR laser during this upgrade. A liquid-nitrogen-cooled mercury-cadmium-telluride based IR detector was used to record backscatter signals. A possibility of using IR lasers with scanning the radiation frequency for remote sensing of atmospheric organic aerosols is shown.

The results of lidar probing of tropospheric aerosols in Kaliningrad, Russia (54°N, 20°E) are presented. The observations used a two-wave atmospheric lidar (with wavelengths of 532 and 1064 nm), which allows investigation of properties of troposphere up to altitudes of 10-12 km. The measurements carried out in the period 2011-2018 made it possible to determine the features of the vertical structure and the dynamics of aerosol particles. The analysis of the observations revealed intensification of the waves in the range of acoustic-gravity waves in the troposphere during the passage of a solar terminator.

The paper presents an experimental setup, experiments on measuring and calculation of light pressure on structural materials for different angles of incidence of light. This calculation is necessary to determine the materials lighting properties and the total forces moment of solar pressure. As a construction material, industrial metal fiber (net-textile) was used. Net-textile is the material of large-diameter spacecraft antennas. More than 4 000 experimental measurements of the transmittance and reflection coefficients of net-textile were carried out for the calculation.

Based on the numerical simulations in ANSYS software the design of the monomorph (unimorph) deformable mirror has been developed. The control electrodes pattern, which allows reproducing aberrations up to 5th order (the first 21 Zernike modes) on the light aperture with high fidelity, was chosen. All important characteristics of the monomorph mirror were calculated: electrodes influence functions, reproduction errors of the given aberrations, gravitational sag of the mirror, mirror surface deformation due to ambient temperature changing, thermal deformations and thermal field due to the incident laser beam, and natural frequencies of the mirror. The results show a possibility of the effective use of this mirror as an element of adaptive optics systems.

It was shown that heating of the volcanic material taken on the Etna volcano (Italy) by apokampic discharge reduces the voltage at which a positive streamer, the apokamp, starts from the discharge channel and increases its propagation speed. The luminescence spectra show that these processes are accompanied by the emission of easily ionizable K and Na, which is consistent with data on the elemental composition of Etna samples. Based on the data obtained, a hypothesis is proposed that in places of increased volcanic activity at altitudes of 10-18 km (at the level of the troposphere), the appearance probability of blue jets and starters increases.

The chemical properties of pentalene and its isomers, as well as their cations, are considered. Pentalene is a chemically active compound that plays an important role in the formation and destruction of polyaromatic hydrocarbons (PAHs), which are the main components of soot microparticles. They arise during the combustion of fossil fuels and are considered as the most dangerous for human health anthropogenic aerosol atmospheric pollutants. The phenomenon of shift of aromatic/anti-aromatic properties of pentalene and its derivatives upon ionization (changes in the number of p-electrons) is also discussed.