E M Gavrishchuk

Increasing the radiation energy of ZnSe?:?Fe2+ laser at room temperature

Characteristics of the laser on a polycrystalline ZnSe?:?Fe2+ sample pumped by the radiation of a non-chain electro-discharge HF laser at room temperature are investigated. The radiation spot of the HF laser on a surface of an active element had an elliptical shape with the axes a ? b = 2.8???3.2 ? 8.25???9.5?mm. A maximal generation energy E = 192?mJ was obtained at the efficiency with respect to the energy absorbed in the sample ?abs = 23% at the dimensions of the pumping spot a ? b = 6.8???7.5?mm. In this case, a maximal slope efficiency with respect to the absorbed energy was ?sl = 29%. At the spot dimensions a ? b = 2.8???3.2?mm the slope efficiency was ?sl = 34%. Possibilities of a further increase of the generation energy of a ZnSe?:?Fe2+ laser pumped by radiation of the HF laser at room temperature are discussed.

Spectral and temporal characteristics of a ZnSe:Fe2+ laser pumped by a non-chain HF(DF) laser at room temperature

Spectral and temporal characteristics of a ZnSe:Fe2+ laser with a nonselective resonator pumped at room temperature by the radiation of a pulse-periodical electrodischarge HF(DF) laser are studied. It was established that the spectral distributions of the energy and peak power of ZnSe:Fe2+ laser generation depend on a spectral composition of the pumping radiation. The spectra exhibit a line structure with spectral intervals between neighboring lines δλ ≈ 6.8 ÷ 8.6 nm. The shape of the ZnSe:Fe2+ laser generation pulse is wavelength dependent. In a short-wavelength range, the pulse has the form of a peak with a duration of ~5 ns at half-maximum. At a longer wavelength, the peak is accompanied by a tail. The duration and amplitude of the tail increase with wavelength, in a long-wavelength spectrum range, the peak actually becomes unnoticeable on a background of the tail. The spectral dependence of the ZnSe:Fe2+ laser generation pulses shape affects the positions of the energy and peak power maxima on the wavelength axis. The dynamics of ZnSe:Fe2+ laser generation under the pumping by the pulsed HF(DF) laser is discussed.

Laser on single-crystal ZnSe:Fe2+ with high pulse radiation energy at room temperature

A laser on single-crystal ZnSe:Fe2+ was investigated at room temperature. Pumping of the laser was performed by a pulsed electrodischarge HF laser. In experiments, the spot diameter of HF laser radiation incident to the surface of the crystal varied from 5.6 to 17 mm. Generation energy of ~1.2 J was obtained and the efficiency with respect to the energy arriving at the crystal was η in ≈ 25%. The slope efficiency with respect to the energy absorbed in the crystal at large spot dimensions was η slope = 45%.

High-energy room-temperature Fe2+:ZnS laser

Characteristics of a room temperature laser on polycrystalline ZnS:Fe2+ subjected to diffuse doping from two sides were investigated. The sample was pumped by a non-chain electrodischarge HF laser with the FWHM duration of the radiation pulse of ~140 ns. The diameter of the pumping radiation spot on the surface of the crystal was 3.8 mm. Further increases in the size of the pumping spot were limited by parasitic generation arising due to a high concentration of Fe ions in the near-surface layer of the sample at a relatively small depth of doping (short length of active medium). The generation energy of 25.5 mJ was obtained at a slope efficiency of 12% with respect to the energy incident on the sample. Characteristics of lasers on polycrystalline ZnS:Fe2+ and ZnSe:Fe2+ have been compared in equal pumping conditions. The slope efficiencies of ZnSe:Fe2+ and ZnS:Fe2+ lasers with respect to the absorbed energy were 34% and 20%, respectively. At equal pumping energy absorbed in the samples, the duration of the ZnSe:Fe2+ laser radiation pulse was longer than that of the ZnS:Fe2+ laser. Possibilities of increasing the efficiency of ZnS:Fe2+ laser operation at room temperature by improving the technology of sample manufacturing and reducing the duration of the pumping pulse are discussed in this letter.

Room-temperature laser on a ZnSe : Fe2+ polycrystal with undoped faces, excited by an electrodischarge HF laser

Characteristics of a laser on a ZnSe : Fe2+ polycrystalline active element with undoped faces (the concentration of Fe ions was maximal inside the crystal and zero at the faces) were studied. The laser was pumped by a non-chain electrodischarge HF laser at room temperature of the crystal. The active element was fabricated by the method of diffuse doping, which prevented the iron film newly deposited to a ZnSe substrate from interacting with atmospheric air (moisture and oxygen) and hindered the subsequent penetration of oxygen into the ZnSe matrix in the course of the high-temperature annealing of the sample. This method was used instead of those employed earlier for doping polycrystalline samples; it noticeably increased the efficiency and generation energy of a ZnSe : Fe2+ laser at room temperature of the crystal. The generation energy was 298 mJ at the slope efficiency of η slope = 45% and the total efficiency with respect to the absorbed energy of η abs = 40%.

Recrystallization behavior of zinc chalcogenides during hot isostatic pressing

This paper examines the effect of hot isostatic pressing (HIP) on the recrystallization behavior of zinc chalcogenides prepared by chemical vapor deposition (CVD). We discuss the mechanisms of this process in CVD ZnS, ZnSe, and ZnSxSe1 − x at high temperatures and pressures and consider conditions under which secondary recrystallization occurs during HIP and high-temperature annealing.

Room-temperature laser on a ZnS:Fe2+ polycrystal with a pulse radiation energy of 0.6 J

A laser on polycrystalline ZnS:Fe2+ samples pumped at room temperature by a pulsed electrodischarge HF laser was investigated. Samples of zinc sulphide grown by the method of chemical vapour deposition (CVD) were doped with iron ions from two sides by the diffusion method. The doping of the crystals was performed using the process of hot isostatic pressing (HIP treatment) at an argon pressure of 100 MPa and a temperature of 1265 °С. A longer duration of HIP treatment resulted in a greater depth of sample doping and higher slope efficiency of the laser. For a crystal subjected to HIP treatment for 151 h, a generation energy 660 mJ was obtained. The values of the slope and total efficiency of the energy absorbed in an active element were, respectively, η slope = 36% and η abs ≈ 26%. Based on the results obtained, and data from earlier published works, a conclusion has been made that to enhance the generation characteristics of a ZnS:Fe2+ laser it is necessary to increase the temperature of the HIP treatment of CVD ZnS.

Self-propagating high-temperature synthesis of Lu2O3 powders for optical ceramics

A technique has been developed for the self-propagating high-temperature synthesis of lutetium oxide (Lu2O3) powders using citric acid, glycine, and lutetium acetate as fuels. We have carried out thermodynamic analysis of synthesis conditions and examined the effect of the nature of the fuel on the properties of the resultant powders. Using vacuum sintering at a temperature of 1780°C and powders prepared with glycine as a fuel and containing 25 mol % yttrium oxide and 5 mol % lanthanum oxide as sintering aids, we have obtained transparent lutetium oxide-based ceramics.

The energy and spectral characteristics of a room-temperature pulsed laser on a ZnS:Fe2+ polycrystal

The energy and spectral characteristics of a laser on a ZnS:Fe2+ polycrystal operating at room temperature have been studied. The laser was pumped by a non-chain electro-discharge HF laser with a full-width at half-maximum pulse duration of ~140 ns. The diameter of the pumping radiation spot on the crystal surface was 3.8 mm. The two-sided diffuse doping of a polycrystalline CVD-ZnS sample with the surfaces preliminarily coated by high-purity iron films was performed in the process of hot isostatic pressing (HIP) in an argon atmosphere at a pressure of 100 MPa and temperature of 1290 °С. Increasing the duration of the HIP treatment from 54 h to 72 h made it possible to obtain twice the doping depth, and correspondingly, twice the length of active medium. As a result, the slope laser efficiency with respect to the absorbed energy was raised by a factor of 1.75 as compared to the value obtained in our earlier work with a polycrystalline sample. The generation energy was 25 mJ at a slope efficiency of η slope = 35%. It was established that the generation spectra of the laser with a non-selective resonator have a linear structure with intervals between the neighboring lines of δ λ ≈ 6 ÷ 8 nm, which is spurious for solid-state lasers. The spectral structure observed is not related to the elements inside the resonator, which might form Fabry–Perot interferometers.

Effect of the Composition of Starting Yttrium Aluminum Hydroxide Sols on the Properties of Yttrium Aluminum Garnet Powders

A technique has been developed for the synthesis of yttrium aluminum garnet sols aggregationstable in water as a dispersion medium. Depending on the type of precursor used, the temperature of yttrium aluminum garnet formation varies from 900°C to 1100°C. We have obtained yttrium aluminum garnet nanopowders with an average particle size from 40 to 300 nm, depending on the aluminum yttrium hydroxide hydrosol synthesis procedure and annealing temperature.