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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.

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Characteristics of a laser on a ZnSe : Fe 2+ 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 nonchain 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 hightemperature 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 : Fe 2+ 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%.

The characteristics of an Fe 2+ :ZnSe laser at room temperature and its active elements with undoped faces were studied. Polycrystalline elements with one or two diffusion-doped internal layers were obtained by the solid-state diffusion bonding technique applied to chemical vapor deposition grown ZnSe plates preliminary doped with Fe 2+ ions in the process of hot isostatic pressing. A non-chain electric-discharge HF laser was used to pump the crystals. It was demonstrated that increasing the number of doped layers allows increasing the maximum diameter of the pump radiation spot and the pump energy without the appearance of transversal parasitic oscillation. For the two-layer-doped active element with a diameter of 20 mm an output energy of 480 mJ was achieved with 37% total efficiency with respect to the absorbed energy. The obtained results demonstrate the potential of the developed technology for fabrication of active elements by the solid-state diffusion bonding technique combined with the hot isostatic pressing treatment for efficient IR lasers based on chalcogenides doped with transition metal ions.