The results of the experimental investigation into a nitrogen laser pumped by a longitudinal discharge in which nitrogen is replaced by air are presented. The fabrication of an experimental sample of such a laser is reported. The laser is excited by a pulse generator with voltage inversion in storage capacitors, which charges the discharge capacitor connected to a two-section discharge tube with an inner diameter of 6.7–17 mm and a length of one section of 100–217 mm. It is shown that, at an air pressure of 7–9 mm Hg and its pumping through the discharge tube, the laser can operate with a pulse repetition rate of up to 100 Hz and provide a radiation pulse energy of 0.27–1.9 mJ at a wavelength of 337.1 nm at a duration of 4 to 13.5 ns.

This study investigates the modifications induced in the microstructure, phase composition, and chemical state of TiNi alloy and AISI 316 L stainless steel surfaces by 266-nm UV laser treatment, revealing a correlation between these changes and the resulting wettability of laser-treated surfaces. The results demonstrate that UV laser treatment at a fluence of 0.2 J/cm2 significantly enhances the hydrophilicity of both TiNi alloy and steel without altering their surface topography at scanning speeds ≥1200 μm/s. The water contact angle decreases from ≈75° to <15°, reaching a minimum of ≈10° for the TiNi alloy and ≈13° for the stainless steel. This change correlates with a substantial increase in surface free energy, driven primarily by a rise in the polar component. Data from X-ray photoelectron spectroscopy, X-ray diffraction, and atomic force microscopy reveal that the enhanced hydrophilicity is predominantly attributable to the formation of an oxide layer on the surface of both materials, rather than to topographic effects. Additionally, UV laser treatment effectively removes adsorbed organic contaminants from the surfaces of both materials. For the TiNi alloy, laser-induced modification leads to the formation of titanium oxides (primarily TiO2). For the stainless steel, the laser-induced oxide layer exhibits an increased Cr2O3/CrO3 ratio and is dominated by iron oxides. Long-term storage experiments in ambient air show that the laser-treated surfaces undergo a moderate increase in contact angle over 7–35 days, stabilizing at 50–60°, which remains significantly below the untreated value, and this degradation is consistent with organic contamination of the oxide surface.

This paper presents a numerical analysis of the behavior of non-uniform KrF laser pump discharges excited by high-power current pulses (~10 MW/cm3). It was shown that, for same electrodes roughness, the density of plasma spots on the cathode surface increases with increasing excitation pulse power. In some modes, a localized increase in pump power density in a non-uniform active medium allows for higher output energy compared to a uniform discharge.

The effect of UV laser treatment (λ = 266 nm) on the wettability, phase and chemical composition of TiNi alloy and AISI 316L stainless steel was studied. Laser treatment resulted in a 2.5–7.5-fold decrease in the water contact angle and an increase in the polar component of the surface energy. Analysis of the experimental data revealed that this effect is primarily due to chemical modification: the formation of surface oxide layers on both materials.

The microstructure and surface functional characteristics of Ti-6Al-4V titanium alloy were investigated following treatment with nanosecond ultraviolet (UV) laser irradiation. UV laser treatment led to the formation of titanium oxide phases (TiO2, TiO) and an increase in surface oxygen content (up to 12–20%). This resulted in enhanced nanohardness (by 25– 30%), increased roughness, and a significant increase in hydrophilicity – the water contact angle decreased from 80° to 9– 13°. The changes are attributed to surface oxidation and an increase in the polar component of surface free energy.

We examined the influence of pulsed ultraviolet (UV) laser radiation on the microstructure, phase composition, and functional characteristics of surface layers of Ti–6Al–4V alloy. Laser treatment leads to significant changes in the phase composition of the alloy surface, where newly formed oxide phases (TiO2, TiO) are detected in addition to the main initial α- and β-phases of Ti. It is shown that UV laser treatment leads to an increase of nanohardness by 25–30

Highly coherent radiation smoothly tunable in a specified wavelength range is required for efficient operation of lidar systems. This work experimentally studies generation of coherent radiation in a compound dispersion cavity of an alexandrite laser with various spectral and spatial selectors located in the external and fundamental-wave cavities, respectively. The mode structure of the output radiation is analyzed depending on the selective properties of the used cavity. Compound cavity operating conditions necessary for generation of narrow-band tunable radiation in the self-injection mode are considered. Improved characteristics of alexandrite laser output radiation are to ensure efficient radiation conversion into higher harmonics, thus expanding the scope of application of these lasers in lidar systems.

The surface laser treatment of TiNi alloy by a Nd:YAG laser operating at a wavelength of 266 nm with different parameters (laser fluence 0.05–0.1 J/cm2, number of laser pulses 600-6000) is presented. Different analyses, including the study of surface morphology, free energy, roughness changes, phase composition, and surface chemistry are evaluated in relation to the wettability control of TiNi alloy. The results reveal a remarkable enhancement in hydrophilicity, evidenced by a sharp decrease in the water contact angle from 75.0 ± 5.1° to 11.4 ± 5.1°. This wettability improvement is positively correlated with the increased laser fluence and the number of laser pulses. The main contribution to the wettability alterations after laser treatment belongs to the surface saturation with oxygen and a subsequent formation of an oxide layer. This oxide layer significantly increases the polar component of the surface energy, thereby enhancing the hydrophilic properties of the TiNi alloy.

The results of investigating N2 lasers pumped by a pulsed longitudinal discharge are presented. Conditions have been defined for stable burning of a volume discharge of 40 ns duration at a current density up to 5 kA/cm2 and a specific pump power up to 10 MW/cm3. A generation energy of 3.5 mJ and a pulse full width at half maximum up to 24 ns are obtained. The temporal and spatial behavior of laser radiation is investigated. The ability of the laser to operate in pulse-periodic mode with a pulse repetition rate up to 100 Hz is shown.

The fluorescence of nitric oxide excited molecules NO A(2)Sigma occurring through two-color laser action on nitrogen dioxide NO2 has been studied. The NO2 pre-photofragmentation stage was carried out by a 355 nm ns laser pulse to obtain vibrationally excited NO X-2 Pi, nu''(1) molecules. Subsequent femtosecond 472 nm laser pulse at an intensity of similar to 300 GW/cm(2) led to the induced fluorescence of NO A(2)Sigma, nu '(0) as a result of two-photon resonance absorption by the NO A(2)Sigma-X-2 Pi, nu'nu'' (0,1) band.

Development of laser technologies increases requirements for lasers being developed which generate narrow-band radiation at different wavelengths. In view of this, the importance of wavelength-tunable diode and vibronic lasers with broadband amplification circuits increases. A possibility of generating highly coherent radiation in a solid-state alexandrite laser using an original composite cavity which includes an additional external dispersive cavity is confirmed. Conditions for narrow-band (less than 20 pm) radiation generation in this cavity with a possibility of smooth tuning the lasing wavelength in the spectral range 740–780 nm are experimentally studied. Narrow-band lasing in an alexandrite laser with a radiation energy of 30 mJ and a pulse duration of 35 ns is shown. The created compact narrow-band alexandrite laser can be an effective alternative to parametric oscillators (OPO) and Ti:Sapphire lasers in lidar systems operating in the spectral range 700–850 nm.

The results of experimental and theoretical studies of the operation of an electric-discharge KrCl laser (λ = 222 nm) at pump power densities of 10 MW/cm3 are presented. The radiation energy obtained experimentally was 55 mJ for a mixture with He as a buffer gas and 120 mJ for a mixture with Ne at a pump pulse duration of 30 ns. A numerical model of a KrCl laser using a He/Ne/Kr/HCl gas mixture with a uniform pump discharge is described. It is shown numerically that the dependence of the optimal (from the point of view of obtaining maximum radiation energy) pump power density on the partial pressures of the buffer gas and HCl is close to linear.

An original technique is suggested for pumping a pulsed CO2 laser by a longitudinal discharge in an alternating magnetic field. A small CO2 laser with active medium ∼200 mm long, pulse energy of ∼30 mJ, and efficiency of 3.4

This paper presents the study results of the single-frequency interaction of KrCl laser broadband radiation with nitro compound vapors in the atmosphere. The optical method of a substance spectroscopic analysis including photofragmentation of a complex R-NO2 molecule followed by laser-induced fluorescence of vibrationally excited fragments of NO X2 & pi;, v">0 (PF-LIF) was studied in the experiments. It has been shown that R-NO2 molecules exposed to & lambda; = 222 nm FWHM 0.3 nm KrCl laser broadband radiation undergo photofragmentation followed by resonant excitation of several electronic-vibrational levels of NO X2 & pi;, v" (2,4). At the same time, the concentration of fragmented NO X2 & pi;, v" (2,4) increases due to the secondary PF-LIF NO2 process during the nanosecond laser pulse.

The paper presents results of experimental study of the dynamics of laser-induced fragmentation of nitrobenzene molecules. It has been shown that when two laser pulses interacting with nitrocompound molecules and their decay products (NO fragments) are time delayed, it is possible to increase the sensitivity of the method of laser fragmentation/laser-induced fluorescence by approximately an order of magnitude for an optimal time delay between the pulses.

An algorithm for numerical simulation of time-frequency energy distribution of chirped Gaussian laser beams during amplification is proposed. The algorithm is based on a time-frequency description of laser radiation by the Wigner distribution function and the concept of a physical spectrum, which allows one to use the photon transfer equation for modeling the evolution of space, energy, and spectra characteristics of laser radiation. A comparison of the numerical simulation results and experimental measurements of laser radiation characteristics in a XeF(C-A) gas amplifier of a THL-100 hybrid laser system confirmed the applicability of the proposed model.

The process of broadband KrCl laser λ rad = 222 nm interaction with nitrogen dioxide in the atmosphere is considered. During the laser pulse, photofragmentation of NO 2 occurs, followed by resonant excitation of several electronic vibrational levels of NO A 2 Ʃ – X 2 П, ν'ν''(2,2) and NO С 2 П – X 2 П, ν'ν''(0,4). The fluorescence intensity of NO A 2 Σ increases with increasing nitrogen pressure due to intermolecular nonradiative energy transfer from the metastable level of N 2 A 3 Σ to the electronic level of NO A 2 Σ.

We report the results of experimental and numerical investigations of a discharge KrF laser with specific pump power of 3.5 and 7 MW/cm3; generation is obtained with specific radiation pulse energy of about 6 and 9.5 J/L for an internal energy efficiency of about 4%. Time dependences of the formation of charged and excited particles in a dense excimer plasma with an electron concentration of ~1016 cm–3 are obtained. The conditions for effective operation of the laser are proposed, which will ensure a further increase in the specific radiation energy by more than two times with preserved high internal laser efficiency relative to the energy input into the discharge.

Results of numerical and experimental studies on monitoring and control for optical elements of an electric discharge KrF laser by the method of density-based spatial clustering of applications with noises (DBSCAN) are presented. Different methods of processing digital signals obtained using a position-sensitive detector controlling the position of the optical axis of the laser system are considered. A numerical model of optical system stability is developed based on the DBSCAN method with an additional inclusion of digital signal processing with the use of the cumulative moving average. A technique for correction of controlled mirrors with an accuracy of 60 ± 10 µrad for their return to normal position is proposed and implemented; the alignment time does not exceed 5 min.