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Materials with high thermo mechanical properties are required as laser media for high-powered lasers. One of such materials is lutetium-aluminum garnet (LuAG) doped with ytterbium. In the present work, we discuss for the first time a full comparative study of 5% Yb-doped LuYAG ceramics with variation Lu/Y ratio. Samples were prepared with addition of B2O3, MgO and SiO2 which were used as sintering aids. Grain sizes, shrinkage curves, lattice constants and transmission spectra were measured for all samples. Thermal conductivity was measured in a wide temperature range for all studied samples. Output power of 12 W and 60% slope efficiency were obtained on the 5% Yb:LuAG disk laser.

The results of experimental studies of the effect of ultraviolet radiation in the UVA wavelength range safe for humans on the β-coronavirus infective properties are presented. Bovine coronavirus not pathogenic for humans is selected as a prototype of the COVID-19 (SARS-CoV-2) pathogenic agent. LEDs with wavelengths of 371 nm and 401 nm are used as a radiation source. It is shown that a dose-dependent decrease in the virus infectious titer is observed for both UVA wavelengths.

Lasing in a solid-state inhomogeneously diode end-pumped Nd : KGW/Cr4+ : YAG laser is obtained at wavelengths of 1067 and 1181 nm (Stokes shift 901 cm−1) under conditions of frequency degeneracy of cavity modes. In this case, the radiation has a characteristic ring spatial structure, which testifies to transverse mode locking of the fundamental and Stokes components. The possibility of controlling the Raman conversion efficiency by changing the position of an undoped KGW crystal additionally installed in the cavity is demonstrated. It is shown that the transverse mode locking is accompanied by the total longitudinal mode locking at λ = 1067 and 1181 nm.

We produce composite ceramic laser elements Nd3+:YAG/Cr4+:YAG using two different methods, i.e., (1) layer-by-layer uniaxial pressing in a metallic mold with sequential addition of appropriate portions of the powder; (2) stacking and pressing of previously uniaxially pressed tablets in a cold isostatic press. In lasers where composite ceramic Nd3+:YAG/Cr4+:YAG elements are used together with longitudinal diode pumping, we obtain the lasing regime for both types of active elements at a wavelength of 1,064 nm in the Q-switch mode. Lasers with ceramic composites produced by stacking and cold isostatic pressing of the previously pressed tablets demonstrate a slope efficiency (~30–33%) even higher than lasers with crystalline saturable absorber (~21%). Lasers based on ceramic composites manufactured by layer-by-layer pressing of powders have an efficiency of ~11–19%. Composites made by stacking and cold isostatic pressing of the previously pressed tablets demonstrate a generation threshold close to those in lasers with crystalline saturable absorbers.

Main properties of ytterbium doped lutetiumyttrium aluminum garnet ceramics with different ratios of lutetium to yttrium substitution (x=0-1) and different levels of ytterbium doping (5-15%) are investigated.

SiO 2 , ZrO 2 , B 2 O 3 and MgO oxides and their combinations were used as sintering aids for preparation of yttrium aluminum garnet (YAG) ceramics doped by Nd 2 O 3. The influence of these additives on optimal sintering temperature, grain growth, volume of residual pores and optical quality of the ceramics were investigated. The best combination of the sintering additives was found and high quality samples of YAG:Nd (1 at.%) ceramics were obtained. The original method of laser optical quality characterization of ceramics was developed and tested. The main laser parameters of YAG:Nd (1 at.%) ceramics samples are measured and compared with the best well known laser ceramics.

A dual-wavelength generation at 1047 and 1053 nm is implemented in a diode-endpumped Nd:YLF laser Q-switched by Cr:YAG. This generation is obtained by the tuning of the cavity length near the regions of the transverse-mode degeneracy.

The effect of sintering aids of SiO2, ZrO2, B2O3, and MgO oxides on the optimum sintering temperature, ceramics grain growth, total volume of residual pores, and optical quality of obtained ceramics is studied. The best combinations of sintering aids are found; as a result, YAG:Nd (1 at%) samples of ceramics of high optical quality are obtained. An original method for characterizing laser properties of ceramics is developed. Comparative measurements of main laser characteristics of the obtained ceramics and ceramics of the Konoshima Chemical Corp. Ltd wellknown in the world practice, are performed.

Transverse mode locking of the Stokes component generated in the mode of stimulated Raman scattering self-conversion by a pulsed diode end-pumped Nd:YVO4/Cr:YAG laser is implemented for the first time under conditions of frequency degeneracy of cavity modes.

Prospects of active media based on nano- and microparticles of laser crystals and glasses are discussed. Study on laser beams propagation over the index-matched mixtures of solid microparticles with liquids and results of experiments on pumping and lasing in active media with microparticles of Nd-doped glasses and fluoride crystals will be reported.

Transparent Cr4+:YAG ceramics with high optical quality was fabricated using solid state reactive sintering. The effect of CaO/MgO ratio on Cr3+ →Cr4+ conversion efficiency was studied. In samples with fixed total amount of divalent ions, Cr4+ conversion efficiency is growing with increasing of Ca2+/Mg2+ ratio. Samples were fully transparent after sintering at 1840 °C for 8 h and annealing in air at 1400 °C for 10 h. Some rather specific defects were observed, their nature investigated and model of forming proposed. Most probable nature of these defects is tungsten inclusions in ceramics sourced by tungsten vapors inside the vacuum furnace. This is far more pronounced with high calcium oxide presence in ceramic samples. The main saturable absorber characteristics were systematically measured.

The influence of the resonator configuration on the temporal characteristics of Nd: YLF crystals laser generation in the region of frequency degeneracy of the transverse modes of a resonator operating in the Q-Switch mode is studied. It is shown that in the degeneracy regions, the pulse duration stretches, while the peak pulse amplitude and the pulse repetition period decrease.

We describe a compact dual-wavelength (1.047 and 1.053 μm) diode end-pumped Q-switched Nd:YLE laser source which has a number of applications in demand. In order to achieve its dual-wavelength operation it is suggested for the first time to use essentially nonmonotonous dependences of the threshold pump powers at these wavelengths on the cavity length in the region of the cavity semiconfocal configuration under a radius of the pump beam smaller than the radius of the zero Gaussian mode. Here we demonstrate one of the most interesting applications for this laser: difference frequency generation in a GaSe crystal at a frequency of 1.64 THz. A superconducting hot-electron bolometer is used to detect the THz power generated and to measure its pulse characteristics.

SiO2, ZrO2, B2O3 and MgO oxides and their combinations were used as sintering aids for preparation of yttrium aluminum garnet (YAG) ceramics doped by Nd2O3, Er2O3, Ho2O3, Tm2O3 and Yb2O3. The influence of these additives on optimal sintering temperature, grain growth, volume of residual pores and optical quality of the ceramics were investigated. The best combination of the sintering additives was found and high quality samples of YAG:Nd (1 at.%) ceramics were obtained. The original method of laser optical quality characterization of ceramics was developed and tested. The main laser parameters of YAG:Nd (1 at.%) ceramics samples are measured and compared with the best well known laser ceramics. The samples of YAG:RE (RE- Er2O3, Ho2O3, Tm2O3 and Yb2O3) ceramics are obtained, and their optical transmittance spectra are measured. Composite structures of YAG:Yb (5 at.%) - YAG were obtained by the simplest method of successive joint compaction of different composition layers.

The influence of transverse mode locking in critical cavity configurations on the threshold pump power of diode end-pumped solid-state lasers was investigated both theoretically and experimentally for the large portion of the cavity stability region. An experimental study was performed for lasers based on Nd:YLF, Nd:YVO4, Nd:GdVO4 and Nd:KGW crystals.