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,

A modified vapour phase contact‐free method to grow homogeneous single crystals of II‐VI compounds doped by transition metals is presented. Single crystals of ZnSe:Cr, ZnSe:Fe, ZnSe:Co, ZnSe:Ni, CdSe:Cr, ZnTe:Cr, ZnS:Fe and ZnS:Mn with doping level up to 1019 cm–3 have been grown. Efficient lasing at about 2.5 and 4 µm with ZnSe:Cr and ZnSe:Fe crystals respectively has been achieved. Dependence of Fe2+:ZnSe laser characteristics on temperature is presented in more detail. A possibility of using Cr2+:ZnSe laser in intracavity laser spectroscopy is demonstrated. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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We report spectroscopic characteristics and laser properties of the mid-infrared active laser medium Cr2+:CdS. Temperature-dependent absorption, luminescence and lifetime measurements of the 5E exited state allow determination of peak emission cross section value of 1.35 × 10−18 cm2 in σ-polarization at room temperature. Lifetime values vary from 7.6 µs at 8 K to 0.48 µs at 320 K, corresponding to 22 % quantum yield at 285 K. Under Tm-fiber laser pumping, the continuous-wave output reached 1.8 W at 2.5 μm with 35.5 % slope efficiency. With a single CaF2 prism, the CW Cr2+:CdS laser could be tuned from 2.240 to 3.285 µm.

For the first time, an experimentally measured seed pulse gain of about 2 cm−1 allows possibilities in the scaling power of such a femtosecond laser system in terawatts. The concept of a subterawatt power level hybrid femtosecond mid-IR (4–5 μm) laser system, based on a weak pulse from an optical parametric mid-IR seeder that is amplified in chalcogenide monocrystalline Fe2+:ZnSe, to gain medium has been proposed and designed. The method and approach for optimizing the choice of nonlinear medium, its length, and the required light intensity for the efficient non-linear self-compression of an ultrashort pulse has also been proposed and considered.