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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,

Graphene is a promising building block material for developing novel photonic and optoelectronic devices. Here, we report a comprehensive experimental study of chemical-vapor deposited (CVD) monolayer graphene’s optical properties on three different substrates for ultraviolet, visible, and near-infrared spectral ranges (from 240 to 1000 nm). Importantly, our ellipsometric measurements are free from the assumptions of additional nanometer-thick layers of water or other media. This issue is critical for practical applications since otherwise, these additional layers must be included in the design models of various graphene photonic, plasmonic, and optoelectronic devices. We observe a slight difference (not exceeding 5%) in the optical constants of graphene on different substrates. Further, the optical constants reported here are very close to those of graphite, which hints on their applicability to multilayer graphene structures. This work provides reliable data on monolayer graphene’s optical properties, which should be useful for modeling and designing photonic devices with graphene.

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)

Efflcient room-temperature lasing is obtained in a Fe ^: ZnSe crystal pumped by 2.9364-цт giant pulses from an Er: YAG laser. The slope efficiency of a Fe ^ : ZnSe laser with respect to the absorbed pump energy is 13 %. The laser with a dispersion resonator can be continuously tuned from 3.95 to 5.05 цт. The luminescence lifetime of the T2 level of the Fe ^ ion in a ZnSe matrix at room temperature is measured to be 355 ± 15 ns.