The generation characteristics of a laser with a Fe:CdTe single crystal grown by a modified vertical gradient freeze method and subjected to high-temperature treatment as an active element have been studied. The possibility of efficient pumping using Fe:ZnSe or deuterium fluoride laser has been demonstrated. The broadband generation in the range of 5.3-6.0 $\mu \mathrm{m}$ with a maximum energy of up to 0.35 J per pulse has been obtained.

The diffusion of iron impurities in zinc selenide (ZnSe) during hot isostatic pressing (HIP) in the temperature range T = 1000-1300 degrees C and pressures P = 100-190 MPa has been investigated. The iron concentration and its distribution over the sample volume with a step from 20 to 50 mu m was determined by IR spectroscopy in combination with an IR microscope. The diffusion coefficients of Fe in ZnSe at various temperatures and pressures were determined. The diffusion coefficients of Fe in ZnSe at P = 100 MPa and T = 1000 degrees C were (5.3 +/- 0.6) x10-(10) cm(2)/s, T = 1300 degrees C were (9.4 +/- 0.9)x10(-9) cm(2)/s. It is shown that the temperature dependences are described by the Arrhenius equation, and the isostatic pressure does not affect the value of the diffusion coefficients.

Using two-photon confocal microscopy in the spectral range of 0.44–0.73 μm, the spatial distribution of the luminescent characteristics of CVD-ZnSe doped with chromium using the HIP process was studied. It has been established that as a result of this process, four types of impurity-defect centers are formed in the crystal. It is shown that their formation involves point centers that form in the doping zone and diffuse deep into the crystal. Assumptions are made about the nature of these point centers.

The record value of the output energy of Fe:CdTe laser, as well as the slope and total efficiency in terms of absorbed energy of 350 mJ, 57% and 42%, respectively, were obtained at the room temperature of the active element. An Fe:CdTe single crystal was pumped by a nonchain electric discharge deuterium fluoride laser operated in the spectral range of 3.6–4.06 μ m. The pump pulse full duration at half maximum was 220 ns. The output energy of the Fe:CdTe laser was limited by the development of transverse parasitic oscillations for pump spot diameters on the crystal surface of more than 11 mm. A laser with a non-selective cavity generated in the ranges of 5.5–6.0 μ m and 5.3–5.5 μ m at the output mirror reflectances of 53% and 21%, respectively.

The hot isostatic pressing of zinc sulfide, obtained by chemical vapor deposition technology, are studied to improve its quality characteristics. As a result of the studies carried out in the visible and near IR regions of the spectrum, the transmission of the treated samples was increased by 6-7 times compared to the untreated ones. In the wavelength range of 3-10 μm, the light transmission of the treated samples reached the theoretical limit. Keywords: chalcogenides, zinc sulfide, chemical vapor deposition, hot isostatic pressing.

The hot isostatic pressing of zinc sulfide, obtained by chemical vapor deposition technology, are studied to improve its quality characteristics. As a result of the studies carried out in the visible and near IR regions of the spectrum, the transmission of the treated samples was increased by 6-7 times compared to the untreated ones. In the wavelength range of 3-10 μm, the light transmission of the treated samples reached the theoretical limit.

— The conditions and kinetics of yttrium aluminum garnet (YAG) crystallization from an X-ray amorphous mixture of hydrated yttrium and aluminum compounds (with a stoichiometric yttrium to aluminum ratio) containing various functional groups have been studied by simultaneous thermal analysis, and temperature variations of the composition of conversion products have been monitored by X-ray diffraction. The technique used to analyze nonisothermal differential scanning calorimetry data in order to assess parameters and gain detailed insight into the mechanism of YAG formation can serve as a basis for predicting temperature and time conditions of formation of not only YAG but also other functional crystalline phases in designing modified and novel ceramic and glass-ceramic materials.

The operation at room temperature of a single-crystal Fe:CdTe laser excited by a nonchain electric-discharge DF laser was studied. The output energy of 29 mJ was obtained with a slope efficiency in terms of absorbed energy of 30%. The development of transverse parasitic oscillation at large pump spot sizes on the crystal surface limited the laser output energy. The laser with a nonselective cavity operated in the range of 5.3–5.9 μ m; the total width of the generation spectrum was about 600 nm. Comparison of the Fe:CdTe generation spectra, obtained by pumping the crystal with DF and Fe:ZnSe lasers, confirmed the shift of the generation spectrum to the long wavelength region with increasing pump wavelengths. The maximum generation wavelength of the Fe:CdTe laser with a nonselective resonator excited by the Fe:ZnSe laser was 6.02 μ m with a total width of the generation spectrum of about 370 nm. Ways are discussed for further increasing the room-temperature output energy of a Fe:CdTe laser.

A technology for obtaining high-quality single-crystal active elements for a Fe:CdTe laser was described, which includes growing a single crystal from a melt using a modified vertical gradient freeze method followed by high -temperature treatment to remove free charge carriers. The room-temperature lasing and luminescence charac-teristics of a Fe:CdTe single crystal with a Fe2+ ions concentration of 6.1 x 1018 cm-3 were studied. The upper laser level lifetime, the output energy and a slope efficiency with respect to absorbed energy of the Fe:CdTe laser excited by the Fe:ZnSe laser were 340 ns, 13.5 mJ and 32%, respectively. The lasing spectrum of the Fe:CdTe laser with a nonselective cavity was located within the range 5.63-6.02 mu m. It was noted the possibility to control the lasing spectrum by changing the pump laser spectrum (shifting the Fe:ZnSe laser spectrum to the short-or long-wavelength region by changing the quality factor of the cavity). Ways are discussed for further increasing the output energy of a Fe:CdTe laser at room temperature of the active element, in particular, by using a non -chain electric-discharge DF laser for pumping.

The paper describes a method of fabrication of Cr2+:CdSe active elements by high-temperature diffusion. On test samples, repetitively pulsed laser generation was obtained at a wavelength of about 2.65 mu m with an efficiency of up to 69% in terms of absorbed power.

The authors have developed procedures of mechanical, chemical mechanical, and magnetorheological polishing that allow obtaining surfaces of optical elements of high optical quality on the basis of high-purity polycrystalline zinc selenide doped by ions of transition metals (Cr 2+ :ZnSe).

The current study is dedicated to measuring the laser-induced damage threshold of chemical vapor-deposited ZnSe and ZnSe:Cr flat optical elements, which were subjected to chemical–mechanical polishing and polishing using magnetorheological fluids. Research was carried out using a Q-switched 1064 nm Nd:YAG laser with 12-ns pulse duration at a repetition rate of 5 Hz. It was shown that as a result of the magnetorheological finishing, the surface roughness is significantly reduced and the damage threshold for the surfaces of chalcogenide optical elements is significantly increased.

Исследуется влияние атмосферы отжигов CVD-ZnSe, проводимых в режимах, близких к процедуре их легирования железом, на люминесцентные характеристики этих кристаллов. Обнаружено, что отжиги в атмосфере аргона и селена приводят к качественному изменению примесно-дефектного состава и к сложному пространственному распределению люминесцентных характеристик CVD-ZnSe, особенно в области кристалла на расстоянии до 400 мкм от поверхности. В случае отжига цинка его люминесцентные характеристики более однородны, за исключением приповерхностной зоны шириной ~100 мкм, имеющей высокую интенсивность люминесценции во всем исследуемом спектральном диапазоне (0.44-0.72 мкм). Полученные результаты интерпретируются на основе предположения об испарении цинка при отжиге в аргоне и селене. На основе анализа пространственного распределения люминесценции делаются предположения о природе наблюдаемых примесно-дефектных центров. Ключевые слова: двухфотонная конфокальная микроскопия, CVD-ZnSe, примесно-дефектный состав, высокотемпературный отжиг.

A technique was presented for obtaining laser media based on polycrystalline zinc selenide doped with iron from spray pyrolysis deposited films in the solid-phase diffusion process. The effect of the ligature film composition and the high-temperature treatment conditions on the lasing characteristics of Fe:(In):ZnSe active elements was investigated. Lasing with an energy of 100 mJ at a differential absorbed energy efficiency of 42% was obtained on 20 mm disk Fe:ZnSe element pumped by a pulsed electric-discharge HF laser.

Изучены спектры фотолюминесценции поликристаллического CVD (chemical vapour deposition) ZnSe, выращенного с большим избытком селена и содержащего комплексы \O*Se-Cu+i\ на дефектах упаковки. Измерено поглощение, дополняющее эти данные. Рассмотрены особенности спектров фотолюминесценции по сравнению с катодолюминесценцией. Показано, что идентичные полосы фотолюминесценции наблюдаются как несколько более коротковолновые, чем полосы катодолюминесценции. Для исследованных кристаллов представлена зонная модель согласно результатам, полученным в данной работе. Длинноволновое смещение спектров фотолюминесценции при уменьшении энергии возбуждения соответствует сдвигу по энергетической шкале зонной модели с соответствующим изменением типа излучательных переходов. Внесены изменения, определяющие природу группы эквидистантных полос 477-490 нм, характерных для образцов ZnSe с избытком кислорода и Se. Результаты могут быть полезны для более полного изучения структуры многофононных экситонных спектров фото- и катодолюминесценции кристаллов АIIВVI. Ключевые слова: зонная модель, узколинейчатые многофононные спектры, экситонное излучение, дефекты упаковки, изоэлектронная примесь кислорода, несущая эффективный отрицательный заряд.

The influence of the atmosphere of CVD-ZnSe annealing carried out in modes close to the procedure of their doping with iron on the luminescent characteristics of these crystals is investigated. It was found that annealing in the atmosphere of argon and selenium leads to a qualitative change in the impurity-defect composition and to a complex spatial distribution of the luminescent characteristics of CVD-ZnSe, especially in the crystal region at a distance of up to 400 microns from the surface. In the case of annealing in zinc, the luminescent characteristics are more uniform, with the exception of the near-surface zone with a width of about 100 microns, which has a high luminescence intensity in the entire spectral range under study (0.44-0.72 microns). The obtained results are interpreted on the basis of the assumption about the evaporation of zinc during annealing in argon and selenium. Based on the analysis of the spatial distribution of luminescence, assumptions are made about the nature of the observed impurity-defect centers. Keywords: two-photon confocal microscopy, CVD-ZnSe, impurity-defect composition, high temperature annealing.

In this Letter, a multi-pass amplifier based on polycrystalline Fe:ZnSe element grown by the chemical vapor deposition (CVD) method and doped through diffusion technique is realized with output energy of more than 3 mJ at 4.5 mu m. The crystal used in the experiment has external doping layers with peak Fe ions concentration of (1-2).1019 m(-3) located on the surface and Fe ions diffusion depth of hundreds of microns. The crystal demonstrates small-signal gain per pass of 5.7 (corresponding to effective gain of 7.1 cm(-1) taking into account 8 mm total length of the crystal) for short pump pulse (40-ns) under the optimal pump fluence of around 0.8 J/cm(2) and upper-level lifetime of 670 +/- 10 ns under moderate cooling to 7-8 degrees C, which makes such a crystal very attractive for mid-IR femtosecond multi-pass amplifiers and generators. Moreover, properties of the polycrystalline Fe:ZnSe elements grown by CVD and doped through diffusion and CVD methods with higher Fe ions concentration are also studied at different temperatures and compared with a single crystal element.

The diffusion of chromium impurities in zinc chalcogenides (ZnS, ZnSe) during hot isostatic pressing (HIP) in the temperature range T = 1000-1330 degrees C and pressures P = 100-190 MPa has been investigated. The chromium concentration and its distribution over the sample volume with a step from 5 to 50 mu m was determined by FTIR spectroscopy in combination with an IR microscope. The diffusion coefficients of Cr in ZnS and ZnSe at various temperatures and pressures were determined. The diffusion coefficients of Cr at 1300 degrees C were (7.0 +/- 0.3) x 10(-8) cm2/s in ZnSe and (3.4 +/- 0.4) x 10(-8) cm(2)/s in ZnS. It is shown that the temperature dependences are described by the Arrhenius equation, and the isostatic pressure does not affect the value of the diffusion coefficients.

Spatial distribution of luminescence characteristics of CVD-ZnSe doped with Aluminum and both Aluminum and Iron by thermal diffusion were studied. The diffusion method leads to formation of two areas in crystal volume: (1) area with high aluminum concentration in which the luminescence of defective-impurity centers (DICs) dominates and exciton luminescence is absent and (2) area with low aluminum concentration in which exciton luminescence dominates. The border of two areas recognized on luminescence map is sharp that not corresponded to diffusion nature. The result is explained by assuming the anomalous nature of aluminum diffusion, leading to a sharp change in the aluminum concentration at a certain distance from the doping surface. Method of aluminum doping process applied in present paper leaded to weakens of well-known luminescence suppression effect by iron ions in ZnSe.

A laser-quality anisotropic ZnS:Cr2+ element was obtained using prolonged hot isostatic pressing at high temperature. Lasing centered at a wavelength of 2.45 µm was obtained with longitudinal pumping at a wavelength of 1.94 µm. The short-cavity laser slope efficiency with respect to the absorbed power was about 78%. The lasing wavelength was continuously tuned in the range of 2.35-2.52 µm by rotating the Brewster active element around the normal to its surface.