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Seeded free growth method with physical transport was used for preparation of large-size II-VI single crystals uniformly doped by transition metals directly during the growth. The grown crystals possess small intrinsic losses. Based on these crystals new results on development of mid-IR lasers were achieved. With the CdSe:Cr crystal pumped at the room temperature (RT) by a continuous wave (CW) 1.908-mm thulium fiber laser, output laser power at 2.6 mm was increased up to 1.7 W. CW lasing from the ZnSe:Fe crystal was achieved using the 1 Introduction The market need of effective solidstate broadly tunable mid-infrared lasers for 2-5 mm spectral range is well known. This range stays difficult for quantum cascade lasers in spite of the last great results. The most popular laser now is an optical parametric oscillator. However it works only in pulse periodic mode because it utilizes nonlinear effect. The II-VI compounds doped by transition metals are certainly interesting as active materials for mid-infrared lasers [1,2]. The advantages of these lasers include broad tuning of lasing wavelength, room temperature (RT) operation, high efficiency, and capability to produce the high quality laser beam of 1-10 W output power.Most of transition-metal doped II-VI compound crystals were prepared either by Bridgman method or a solid-state diffusion method. The latter includes growth of a pure crystal preferably from vapor phase and doping of it by thermal diffusion of transition metal through the crystal surface. The crystals prepared in this way are characterized by great intrinsic losses due to the high concentration of background defects. To overtop these intrinsic losses they need to use highly doped crystals. But the higher doping concentration,

We report the results of a study of a pulsed Fe:ZnSe laser for temperatures ranging from 85 to 295 K. With a free-running Er:YAG laser, operating at 2.94 µm, as a pump source, a maximum output energy of 2.1 J at 85 K was produced at a wavelength of 4.1 µm. The optical-to-optical efficiency of the laser was 35% at maximum energy while the maximum absorbed energy slope efficiency was as high as 51%. By operating at 245 K (a temperature which can be easily reached using thermoelectric coolers) we achieved 1.3 J of output energy from an Fe:ZnSe laser, with a slope efficiency of 29% (23% optical-to-optical efficiency). The maximum output energy reached 42 mJ at room temperature (295 K). The temperature dependence of the lifetime of the 5 T 2 energy level of Fe 2+ in ZnSe was studied in the 275-365 K temperature range. The activation energy for nonradiative relaxation was found to be 2235 cm −1 .

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