Quasi-2D GaN layers inserted in an AlGaN matrix are proposed as a novel active region to develop a high-output-power UV light source. Such a structure is successfully achieved by precise control in molecular beam epitaxy and shows an amazing output power of ≈160 mW at 285 nm with a pulsed electron-beam excitation. This device is promising and competitive in non-line-of-sight communications or the sterilization field.

We report the internal structures and emission properties of GaN/AlN single- and multiple-quantum-well (QW) heterostructures with well widths of dw = 1–4 monolayers (MLs), grown by plasma-assisted molecular-beam epitaxy on c-sapphire at metal-rich conditions and low temperatures (∼700 °C). The formation of plane QWs with abrupt symmetrical interfaces is confirmed by both scanning transmission electron microscopy and X-ray diffraction analysis. Pulse-scanning and continuous-wave output powers of 150 and 28 mW, respectively, at a peak emission wavelength of 235 nm were achieved at 300 K in an electron-beam-pumped deep-ultraviolet (1.5 ML-GaN/5.5 nm-AlN)360 multiple-QW emitter with a maximum efficiency of 0.75%.

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 discuss the synthesis, characterization, and comprehensive study of Ba-122 single crystals with various substitutions and various superconducting transition temperatures. We use five complementary techniques to obtain a self-consistent set of data on the superconducting properties of Ba-122. A major conclusion of our work is the coexistence of two superconducting condensates differing in the electron–boson coupling strength. The two gaps that develop in distinct Fermi surface sheets are nodeless in the kxky plane and exhibit s-wave symmetry; the two-band model suffices for the description of the main parameters of the superconducting state. A moderate interband coupling and a considerable Coulomb repulsion in the description of the two-gap superconducting state of barium pnictides favor the s++ model.

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