We report laser related polarized spectroscopy and continuous-wave (CW) laser operation of Yb3+:Gd2-xYxSiO5 (& khcy; = 0.385) (Yb:GYSO) crystal under a single-mode fiber-coupled laser diode pumping at the wavelength of about 976 nm. The absorption and stimulated emission cross-section spectra were determined for light polarized to the principal optical axes ( N p , Nm, Ng) of the crystal. The radiative lifetime of the upper manifold 2F5/2 of Yb3+ ions was estimated to be 885 mu s. In CW mode of laser operation the maximal output power reached up to 382 mW and maximal optical-to-optical efficiency was about 71 %. The widest tunability range of 116 nm was obtained for the E//Np polarization.

Тhe efficiency and the performance of membrane electrode assemblies (MEAs) of the anion exchange membrane (AEM) water electrolyzer is determined to a significant degree by the properties of the materials used as porous transport layers (PTLs). Due to the high surface roughness, porosity, and pore size, the direct use of Ni foam as an electrode material is difficult, and its preliminary compression is required, which irreversibly affects the electrode structure. In the presented work, the effect of Ni foam compression on the structure of an electrode based on it, as well as on the AEM water electrolyzer MEA is considered, including the distribution of voltage losses. The effect of the compression degree on the Ni-foam electrode structure and the performance of the AEM water electrolyzer MEA is considered. The optimal electrode compression provides a significant decrease in the loss of microporous layer particles and catalyst layer nanoparticles in deep surface voids of the PTL, and the development of an interface between the nanostructured catalyst layer and the electrode.

A new type of separation materials for alkaline water electrolyzers has been obtained: a diaphragm synthesized by the phase inversion method and a multilayer microfilm membrane with zirconium hydroxide hydrogel as a hydrophilic filler. Experimental data on their porosity, electrical conductivity, and gas density, as well as the results of their tests as part of an alkaline electrolyzer battery are presented in comparison with a porous diaphragm based on polysulfone with a hydrophilic filler (TiO2), synthesized by the traditional phase inversion method. The advantages and disadvantages of new materials are assessed, and ways for further research and development are determined.

Using the method of polysulfone chloromethylation followed by quaternization, an anion-exchange membrane is synthesized for water electrolyzers with alkaline electrolyte. The characteristics of this membrane such as porosity, electrical conductivity, and gas-tightness are determined. A comparative analysis of characteristics of this membrane as compared with a porous diaphragm (analog of ZifronPerl) is carried out. The results of tests of the membrane within an alkaline electrolyzer battery are compared with the results for the porous diaphragm based on unmodified polysulfone with a hydrophilic filler (TiO2) and synthesized by phase inversion. The possible mechanism of the degradation of the main chain in quaternized polysulfone is presented. The ways are proposed for the further development of the technology of anion-exchange membranes based on polysulfone.

By the method of chloromethylation and further quaternization of polysulfone, the synthesis of an anion-exchange membrane for electrolyzers of water with an alkaline electrolyte was carried out. The characteristics of the resulting membrane are determined: porosity, electrical conductivity, gas density. A comparative analysis of the characteristics of the membrane and the porous diaphragm (analog of ZifronPerl) is given, the results of tests in the composition of an alkaline electrolyzer battery in comparison with a porous diaphragm based on unmodified polysulfone with hydrophilic filler (TiO2) synthesized by phase inversion are presented. A possible mechanism of degradation of the main chain of quaternized polysulfone is described. The ways of further development of the technology of anion-exchange membranes based on polysulfone are proposed.

We demonstrate continuous wave and passively Q-switched Er,Yb:GdMgB5O10 microchip lasers emitting in the spectral range of 1.5-1.6 mu m. A maximal output power of 220 mW was obtained at 1568 nm at an absorbed pump power of 2.3 W with a slope efficiency of 18%. By using an MBE-grown Cr:ZnS thin layer as a saturable absorber laser pulse with a duration of 24 ns and an energy of 3 mu J at a repetition rate of 50 kHz were obtained at a wavelength of 1568 nm.

The fluorophosphate glasses with composition of Ba(PO3)2 - AlF3-CaF2 - MgF2-BaF2 - SrF2-YbF3 - ErF3 were synthesized and their spectroscopic properties were studied. The main attention here was paid to studying the luminescence kinetics Yb3+ (1040 nm) and Er3+ (1550 nm, 655 nm and 540 nm). It has been found that the population of the 4I13/2 (Er3+) level and the relaxation of the 2F5/2 (Yb3+), 4F9/2, and 2H11/2+4S3/2 (Er3+) levels are close to exponential and the probabilities of these processes are well approximated by linear functions with respect to the ytterbium concentration. All this led to the conclusion that the migration-accelerated energy transfer makes a significant contribution to the population and deactivation of these energy levels. A scheme of the main energy transfer channels in an ensemble of ytterbium and erbium ions and the corresponding system of rate equations are proposed. On the basis of these equations, mathematical modeling of the luminescence kinetics of ytterbium and erbium ions was carried out and the energy transfer parameters were estimated.

Методом Бриджмена выращены монокристаллы YAlO3-Er (YAP:Er) из расплавов с разным соотношением Y/Al. Сравниваются структурные дефекты и центры окраски при Y/Al = 1 и Y/Al > 1, а также образующиеся в кристаллах в результате гамма-облучения и термообработки. На основе полученных данных определены условия выращивания кристаллов YAP:Er, свободных от центров окраски и двойников. Исследованы спектрально-люминесцентные свойства кристаллов: зарегистрированы спектры поглощения и люминесценции в поляризованном свете, исследована кинетика люминесценции и определено время жизни уровня 4I13/2 иона Er3+. YAlO3-Er (YAP:Er) միաբյուրեղները աճեցվել են Բրիջմենի եղանակով հալույթներից տարբեր Y/Al հարաբերակցությամբ: Համեմատվել է բյուրեղներում կառուցվածքային արատների և գունավորման կենտրոնների ձևավորումը Y/Al = 1 և Y/Al > 1 համար, ինչպես նաև գամմա- ճառագայթման և ջերմային մշակման դեպքում: Ստացված արդյունքների հիման վրա որոշվել են գունավորման կենտրոններից և կրկնակներից զերծ YAP:Er բյուրեղների աճեցման պայմանները: Հետազոտվել են բյուրեղների սպեկտրալ-լյումինեսցենտային հատկությունները՝ գրանցվել են բևեռացած լույսում կլանման և լյումինեսցենցիայի սպեկտրերը, հետազոտվել է լյումինեսցենցիայի կինետիկան և որոշվել է Er3+ իոնի 4I13/2 մակարդակի կյանքի տևողությունը: Single crystals of YAlO3-Er (YAP:Er) are grown by the Bridgman method from melts with different Y/Al ratio. The structural defects and color centers are compared for Y/Al = 1 и Y/Al > 1, as well as formed in the processes of gamma-irradiation and thermal treatment. Based on the obtained data, growth conditions of YAP:Er crystals free of color centers and twins are determined. Spectral-luminescent properties of crystals are investigated, i.e., the polarized absorption and luminescent spectra are registered, the luminescence kinetics is investigated and the lifetime of the 4I13/2 level of Er3+ ion is determined.

Alkaline water electrolysers are widespread in many industries, including systems with hydrogen cycle of energy storage. One of the problems of modern alkaline water electrolysers is insufficient purity of generated electrolysis gases relative to electrolysis systems with solid-polymer electrolyte. In this regard, work on modification of existing porous diaphragms is actively carried out. One new area of research is the impregnation of new hydrophilic fillers into the composition of existing diaphragms and the transition to ion-solvate membranes. In this work the synthesis of zirconium hydroxide hydrogel inside a porous diaphragm with the hydrophilic filler TiO2 was carried out. This synthesis makes it possible to obtain a membrane with anion-exchange properties. A possible mechanism of OH- hydroxyl ion transfer by immobilized K+ ion was also proposed. The obtained results demonstrated the resistance of the membrane to concentrated alkaline solutions.

The article is devoted to the creation of a new generation element base for aqueous alkaline electrolyzers with anion-exchange membranes. As a result of the research, two new membranes and various types of electrodes have been proposed, which significantly increase the purity of the generated electrolysis gases and the operating outlet pressure directly at the outlet of the electrolysis module while maintaining low values of specific energy consumption. In this case, the electrolysis module consists entirely of electrode-membrane blocks. Their composition includes components tested in industrial alkaline electrolysis, which distinguishes them from known analogues in chemical resistance. Various types of catalysts that can be used as part of membrane-electrode blocks are considered separately. The results of express tests of electrodes made of stainless steel 12X18H10T are presented, the oxidation process of chromium, which is part of the alloy, is shown, which leads to a decrease in its corrosion resistance. When testing electrodes based on a steel mesh coated with a protective layer of nickel, extensive pitting corrosion was detected on the anode during its operation at high current densities. As an alternative, electrodes made of nickel mesh are proposed. These samples showed excellent corrosion resistance and high adhesion to electrodeposited catalysts. Catalytic coatings consisting of nickel or nickel-cobalt powder with additionally chemically precipitated phosphorus were investigated as catalysts.

Single crystals of YAlO 3 -Er (YAP:Er) are grown by the Bridgman method from melts with different Y/Al ratio. The structural defects and color centers are compared for Y/Al = 1 and Y/Al > 1, as well as formed in the processes of gamma-irradiation and thermal treatment. Based on the obtained data, the growth conditions of YAP:Er crystals free of color centers and twins are determined. Spectral-luminescent properties of crystals are investigated: the absorption and luminescent spectra are registered in the polarized light, the luminescence kinetics is investigated and the lifetime of the 4 I 13/2 level of Er 3+ ion is determined.

The article is devoted to the development of a new-generation elemental base for aqueous alkaline electrolyzers with anion-exchange membranes. Two new membranes and various types of electrodes are proposed, which significantly increase the purity of the generated electrolysis gases and the operating outlet pressure directly at the outlet of the electrolysis module, while maintaining low specific energy consumption. The electrolysis module consists entirely of membrane–electrode assemblies. Their composition includes components tested in the industrial alkaline electrolysis; they stand out from the known analogues in their chemical resistance. Various types of catalysts that can be used as part of membrane–electrode assemblies are considered. The results of express tests of the 12Kh18N10T-stainless-steel electrodes revealed the oxidation process of chromium, a part of the alloy, which is shown to lower its corrosion resistance. When testing electrodes based on a steel mesh coated with a protective nickel layer, an extensive anode pitting corrosion was detected during its operating at high current densities. As an alternative, nickel-mesh electrodes are proposed. They showed excellent corrosion resistance and high adhesion of the electrodeposited catalysts. Catalytic coatings consisting of nickel or nickel–cobalt powder with chemically deposited phosphorus are investigated as catalysts.

We report on the generation of few-ns pulses with kW peak power in the red and orange spectral range obtained from a passively Q-switched Pr3+:YLF laser. A compact resonator and thorough investigation of the Co:MgAl2O4 saturable absorber’s initial transmission enables peak powers in excess of 1.1 kW at pulse durations of 2.4 ns and 5.3 ns at 640 nm and 607 nm, respectively. These are the shortest pulse durations among any Q-switched Pr3+ laser and make this system a suitable front-end for efficient frequency doubling into the ultraviolet range.

In this conribution we describe the technological process of transparent Er 3+ :Y 2 O 3 ceramic synthesis, a prospective medium for future laser applications. Hot isostatic pressing (HIP) was used to improve the optical quality of the final product. As the results of our efforts the material with an optical transmission of 0.78-0.80 was obtained, that is close to the theoretical maximum value of 0.83. The main spectral and luminescent properties of the created Er 3+ :Y 2 O 3 optical ceramics in the spectral range of 1.4-1.65 microns was determined and is reported in this work.

In this paper, Er:Y2O3 optical ceramics were fabricated and details of the synthesis were presented. The spectral–luminescent properties of Er3+:Y2O3 optical ceramics were investigated. The absorption and emission cross-section spectra were determined. The luminescence kinetics at near 1.6 µm was single exponential and the lifetime of erbium 4I13/2 energy level was determined. In the frame of the conventional Judd–Ofelt theory, the emission properties of the energy levels of erbium 4I13/2 and 4I11/2 involved in laser operation at near 1.6 µm were calculated. The gain coefficient curves for typical values of the relative population of the upper laser level 4I13/2 were presented. The composition and structure were studied using the SEM, XRD, FTIR spectroscopy, and X-ray computer tomography techniques.

Visible lasers are sought for in a variety of applications. They are required in fields as diverse as medicine, materials processing, display and entertainment technology and many others. Moreover, in contrast to infrared lasers, they enable very simple and efficient access to the UV spectral range by a single frequency doubling step. Currently, the choice of direct visibly emitting lasers is limited: The ‘green gap’ prohibits the development of semiconductor lasers with emission in the green and yellow spectral range and only few laser active ions allow for efficient visible lasing. In particular trivalent praseodymium (Pr3+) and terbium (Tb3+) ions have been shown to be the most successful candidates for efficient high power visible solid-state lasers. Compared to semiconductor lasers, solid-state lasers also provide other advantages, e.g., in terms of energy storage in Q-switched operation as well as beam quality at high output power. In recent years, visibly emitting solid-state lasers have seen a revival enabled by the increasing commercial availability of GaN-based blue emitting pump diodes and an ever-increasing number of publications evidences the vivid research activities in this field. Still, due to the relatively short history of diode-pumped visible solid-state lasers, these are still in an early stage of their development and up to now only few direct visibly emitting solid-state lasers with comparably low output power are commercially available. However, we are convinced that visibly emitting solid-state lasers based on Pr3+ and Tb3+ have the potential for 100-W-class continuous wave output power levels as well as sub-ns pulse durations in Q-switched and sub-ps-pulse durations in mode-locked operation, which would qualify them to fulfil the requirements of most of the applications named above. In this work, we review the state of the art of continuous wave and pulsed visibly emitting solid-state lasers and amplifiers based on Pr3+ and Tb3+ as the active ion. After an introduction, we briefly review the spectroscopic properties of these two ions and their particularities for laser operation as well as the requirements for suitable host materials. In the third chapter, we present the state of the art in the field of continuous wave Pr3+-lasers emitting in the cyan-blue, green, orange, red, and deep-red spectral range based on fluoride, glass, and oxide host materials and discuss prospects for further power scaling. The fourth chapter is devoted to the current state of Tb3+-based continuous wave green and yellow emitting solid-state lasers. In the fifth and sixth chapter we give an overview over existing pulsed visibly emitting solid-state lasers in Q-switched and mode-locked operation mode, respectively. Finally, the seventh chapter is devoted to pulse amplifiers for ultrafast visible lasers before this review closes with a short conclusion.

This work is devoted to the problem of improving the spectral and luminescent properties of optical ceramics based on Y 2 O 3 sesquioxide doped with $\text{Er}^{3+}$ ions. A technology for processing ceramics by hot isostatic pressing has been proposed. SEM-images of Er: Y 2 O 3 samples subjected to the HIP treatment are shown.

Reduced energy consumption is one of the main requirements for application of water electrolyzers with alkaline electrolyte for small-scale power industry. The energy consumption can be reduced, among other things, by changing the assembling of electrodes and diaphragm material. The phase inversion method, which is used for fabricating the polymer-based porous diaphragms for alkaline water electrolyzers, enabled us to develop an electrode–diaphragm assembly in which the electrodes with the catalytic layers and the diaphragm material comprise a single unit. The electrolysis cells with the electrode–diaphragm assemblies of various compositions and the cells of conventional “zero-gap” design are studied.

Solid-state erbium lasers, emitting in the spectral range of 1.5–1.6 µm, are of great interest for several industrial applications. Nowadays the Er:glass is the most widespread laser material for obtaining laser radiation at the wavelength near 1.5 µm. However, the maximal output powers of such lasers are restricted by hundreds of milliwatts because low thermal characteristics of the glass host. By this reason the search for new crystalline hosts doped with erbium ions is the actual task.In this article the investigation results of spectroscopic properties of Er3+,Yb3+:YGdSiO5 (YGSO) crystals are reported. Polarized absorption and luminescence spectra were measured. The lifetimes of energy levels were determined. The excited state absorption spectra were measured. It was shown that excited state absorption band does not overlap with gain band in the range 1.5–1.6 µm. The energy transfer efficiency from ytterbium to erbium ions was estimated. The stimulated emission and gain cross-section spectra for Er3+ ions in YGSO were calculated.

A transparent Yb:YMgB5O10 single crystal with dimensions up to 25 × 23 × 25 mm and weight 10.337 g was grown using a high-temperature solution growth on dipped seeds technique with a K2Mo3O10 solvent. The Yb3+ concentration was calculated to be 4.7 at.% (NYb = 3.71 × 1020 atoms/cm3) with a distribution coefficient Kd of 0.59. The grown crystal was characterized by means of PXRD, TGA-DSC and ATR-FTIR techniques. The spectroscopic characteristics of the Yb:YMgB5O10 crystal were demonstrated. Absorption cross-section spectra were produced. The luminescence spectra of the Yb:YMgB5O10 crystal were measured in the spectral range of 950–1100 nm. The luminescence kinetics of the 2F5/2 energy level were investigated and the lifetime was determined.