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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.

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.

Experiments on lasing in slurry-like active media based on dense mixtures of laser crystal or glass microparticles with immersion liquids are reported.

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.

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.

The results of investigation of the spectral, luminescent and lasing properties of Tm : Y2O3 ceramics are presented. Lasing in Y2O3 ceramics is obtained at wavelengths of 1.95 and 2.05 μm. The maximum output laser power at these wavelengths was 2.4 and 0.3 W, respectively.

Active media based on particles of solid-state laser materials distributed in liquid or gas may provide a new solution to the problem of heat removal from laser media. We propose active media based on particles of LiF crystal with F2 color centers, as well as of Nd3+-doped crystals and glasses. Mixtures of index-matched liquids with glass and crystal particles, methods of their preparation, and their optical characteristics are considered. The laser characteristics of the active media under excitation by nanosecond laser pulses are compared. A “slurry laser” based on a dense mixture of LiF:F2 microparticles with an index-matched liquid is demonstrated. Lasing was obtained in small neodymium pentaphosphate crystals (NdP5O14) and unpolished bulk pieces of concentrated neodymium phosphate glass in immersion liquids.

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.

Undoped and Nd- or Yb-doped laser-grade yttrium aluminum garnet and (Y,La)2O3 ceramics with a transmittance above 80% in the 1-μm lasing region have been prepared by solid-state reactions using nonagglomerated Y2O3 and Al2O3 nanopowders. The Y2O3 nanopowders were prepared via laser evaporation, chemical precipitation from urea solutions, and grinding of commercially available Y2O3 in a purposedesigned laboratory-scale attritor at stirrer rotation rates of up to 1500 rpm. The YAG ceramics were prepared using commercially available Al2O3. After grinding, all of the powders had a particle size on the order of a hundred nanometers. Green compacts produced from the nanopowders were sintered in a vacuum furnace between 1615 and 1750°C to give highly transparent ceramic samples.

High-quality YAG:RE (Yb, Nd, Cr) ceramics with CaO and MgO as sintering aids were manufactured by solid state reactive sintering method in vacuum. Influence of annealing temperature on optical properties was studied. This combination of sintering aids requires annealing temperatures at least 1300∘C to fully eliminate oxygen vacancies and at least 1400∘C to convert Cr3+ to Cr4+. It was found that annealing in oxidizing atmosphere creates strong changes in short wavelength transmittance. Keywords: laser ceramics, Yttrium aluminium garnet, sintering aids

Tm:Y2O3 , Ho:Y2O3 and Yb:Y2O3 ceramic samples were fabricated using different heat treatments modes. La2O3 (0.5 mol.%) and ZrO2 (1.5 mol.%) were used as sintering additives. Based on the investigation of structural properties of obtained samples, annealing mode was adjusted, and another set of samples with better optical quality was fabricated. In-line transmittance of the latter samples is 70% at 400nm and 75.6% at 600nm. Keywords: Y2O3 , laser ceramics

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.