The luminescence properties of ZBLAN (ZrF4-BaF2-LaF3-AlF3-NaF) fluoride glass doped with Er3+, Yb3+ and Tb3+ ions were investigated. The enhanced of 1.5 mu m luminescence of Er3+ ions under excitation by 940 nm wavelength radiation in ZBLAN:1%Er3++3%Yb3+ composition with additional doping of Tb3+ ions was presented. The optimum value of Tb3+ ion concentration for the most intense emission of 1.5-mu m luminescence was determined. The probabilities of spontaneous emission and luminescence branching coefficients for Er3+ and Tb3+ ions in ZBLAN glass were calculated based on the Judd-Ofelt theory. The compiled theoretical model based on a balance equations taking into account non-resonant transitions allowed to estimate the 4I13/2 and 4I11/2 states populations of Er3+ ions and explain the increasing the population of the 4I13/2 state in three-component alloying.

The work is devoted to the study of the second-harmonic generation (SHG) process as a result of random quasi-phase-matching of thulium laser radiation in ZnSe polycrystals. A linear dependence of the SHG efficiency on the nonlinear medium length has been observed in the experiment. The efficiencies of SHG in ZnSe polycrystals with average grain sizes from 35[Formula: see text][Formula: see text]m to 380[Formula: see text][Formula: see text]m were compared. The obtained results are in good agreement with the theory in the case of a Gaussian grain size distribution.

The current study is dedicated to measuring the Verdet constant of pure and chromium and iron ions doped ZnSe using laser sources in the range from 632.8 to 2430 nm. An increase in the magneto-optical properties of ZnSe as a result of diffusion doping with transition metal ions was experimentally discovered. The results align with the Van Vleck-Hebb theory, which predicts a nearly linear rise in the Verdet constant with increasing of transition element concentration.

A theoretical model for determine the optimal focusing parameter for second harmonic generation (SHG) process in a polycrystalline nonlinear medium has been constructed. Theoretical calculations were confirmed by an experiment to obtain SHG at a wavelength of 968[Formula: see text]nm in a zinc selenide polycrystal using a thulium laser.

Получены новые стекла системы TeO 2 –Na 6 P 6 O 18 . Методом дифференциальной сканирующей калориметрии изучено термическое поведение стекол в области 25–580°C, исследованы температурные зависимости теплоемкости в интервале 25–400°C. Определены характеристики расстеклования и стеклообразного состояния, подобраны аналитические зависимости температур стеклования и термодинамических характеристик стекол от их состава при t = 80°C. Проведен сравнительный анализ полученных зависимостей с аналогичными для изученных ранее бинарных систем на основе TeO 2 . Исследована оптическая прозрачность стекол в УФ-, видимой и ИК-областях спектра. Показана возможность введения в стекла оксидов редкоземельных элементов. Для стекла состава 0.89TeO 2 –0.08Na 6 P 6 O 18 –0.03Nd 2 O 3 изучены люминесцентные характеристики.

— New glasses in the TeO 2 –Na 6 P 6 O 18 system have been prepared, their thermal behavior has been studied by differential scanning calorimetry in the range 25–580°C, and their heat capacity has been determined as a function of temperature in the range 25–400°C. We have evaluated characteristics of the devitrification process and glassy state, obtained analytical representations of the glass transition temperature and the thermodynamic characteristics of the glasses as functions of their composition at 80°C, and carried out a comparative analysis of the results together with those for previously studied TeO 2 -based binary systems. Optical transmission of the glasses has been measured in the UV, visible, and IR spectral regions. We have demonstrated the possibility of doping the glasses with rare-earth oxides and studied luminescence properties of the glass with the composition 0.89TeO 2 –0.08Na 6 P 6 O 18 –0.03Nd 2 O 3 .

TeO 2 –ZnO–Bi 2 O 3 glasses doped with Eu 3+ and Er 3+ ions were prepared and investigated for their physical, optical, and luminescent properties. The optical band gap is calculated for the indirect transition and is within the 3.04–3.10 eV range. The Urbach energy varies from 0.135 to 0.098 eV with the increase in Eu 3+ compound content. Bi 2 Te 2 O 8 and ZnTeO 3 complex oxide phases are generated in the mixture as intermediate compounds in the course of charge thermal processing. The additional doping of TeO 2 –ZnO–Bi 2 O 3 :Er 3+ glass samples with Eu 3+ ions is shown to lead to the appearance of cross-relaxation channels of the Er 3+ ion states and decreases the population of the 4 I 13/2 state of the Er 3+ ions. Simultaneously, the excited 4 I 11/2 state of the Er 3+ ions is also subjected to strong cross-relaxation decay. The Eu 3+ ions are shown to decrease the 4 I 13/2 level population of Er 3+ ions, which may facilitate the attainment of population inversion if the 4 I 13/2 level is at the lower level of the laser transition.

The values of the Verdet constant at a wavelength of 632.8 nm in Cr: ZnSe and undoped ZnSe were obtained. It was shown that the Verdet constant in undoped zinc selenide does not depend on the crystallite size. The experimentally determined maximum value of the Verdet constant for Cr: ZnSe was 226.5 rad/(T·m), which is more than two times higher than the corresponding value for ZnSe.

Random lasing was obtained on micropowders of zinc selenide activated by divalent chromium ions by pumping with laser radiation at a wavelength of 1.94 $\mu\mathrm{m}$ . The dependences of the spectral composition and shape of the emission spectra of powders with various morphologies on the exciting radiation power density are studied.

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.

The conversion of infrared radiation of a Tm3+:YAP laser at a wavelength of 1.93 mu m into visible light in [(ZrF4)(0.4)-(BiF3)(0.6)](100-x)-(HoF3)(x) (x = 1.5 or 5 wt%) ceramic samples was investigated. The emission bands at wavelengths of 650 nm, 900 nm and 1100 nm corresponding to transitions from F-5(5), I-5(5) and I-5(6) levels to the ground state I-5(8) were observed in upconversion luminescence spectra. From the experimental data, an estimate of the crossrelaxation coefficient from S-5(2) was obtained. It was K-cr approximate to 1 x 10(-16) cm(3) s(-1). The threshold power density of Tm3+:YAP laser, at which a luminescence was observed on the ceramic samples, was about 0.85 W cm(-2).

In this study, a method is proposed to measure the spatial properties of laser emissions in the range of 2.0 mu m. The infrared emission spectrum is first converted into a spectrum in the visible range using a fluorozirconate ZBLAN:Ho3+ glass sample. Subsequently, the converted emission is detected using a Pulnix TM-7CN CCD camera and the laser beam image is numerically processed using a specialized software package in the Lab VIEW environment. This enables the measurement of intensity distribution over the beam cross-section of the diode-pumped CWYAP:Tm3+ laser emitting at 1.94 mu m. The beam quality factor, M-2 , is also evaluated. (C) 2020 Optical Society of America

An approach of self-propagating high-temperature synthesis of ytterbium doped mixed yttria, scandia and lutetia powders Yb-0.1(RE1(x)RE2(1-x))(1.9)O-3 (RE1 and RE2 =Sc, Y, Lu, x = 0, 0.25, 0.5, 0.75, 1) was developed. A comparative study of the structural properties of the powders obtained by XRD analysis and Raman spectroscopy was carried out. The formation of rare earth oxides solid solutions throughout the studied compositional range was confirmed. The presence of residual hydroxyl groups in the resulting powders, most notable for scandia, was demonstrated. The broadening of Yb3+ ions luminescence bands in the matrices of structurally disordered mixed oxides was ascertained in comparison with individual rare earth oxides from 16 nm for Yb:Sc2O3 up to 25 nm for Yb-0.1(Y0.75Sc0.25)(1.9)O-3. (C) 2018 Elsevier B.V. All rights reserved.

Показано преобразование ИК излучения Tm : YAP-лазера с длиной волны 1930 nm в видимый свет керамикой состава LiY (1-x-y) Hox , Yby , где x = 1-5 mol.% и y = 0-15 mol.%.Показано, что величина пороговой плотности мощности визуализации ИК излучения снижается при увеличении концентрации ионов Ho 3+ , а дополнительное легирование образцов керамики ионами Yb 3+ изменяет спектр антистоксовой люминесценции.Величина пороговой плотности мощности визуализации излучения Tm : YAP-лазера при увеличении содержания ионов гольмия снижалась и в

Cr2+:ZnSe polycrystalline active elements with different distribution profiles of Cr2+ ions concentration over their thicknesses were fabricated. Dependences of the output laser powers on the incident pump power of Tm3+-laser in continuous and pulse modes were obtained. There was found to be a correlation between the generation slope efficiency and the shape of the concentration profile. There was proposed a numerical model to explain the experimental results by the influence of thermo-optical distortions caused by uneven heating of the active elements due to the pumping process.

Visualization of IR radiation of a Tm:YLF laser with a wavelength of 1908 nm in 53ZrF4–20BaF2–3LaF3–1HoF3–3AlF3–20NaF (mol %) ceramic samples is studied. The luminescence spectra of Но3+-doped ZBLAN ceramics exhibit bands in the regions of 540, 650, and 900 nm, which correspond to the 5S2 → 5I8, 5F5 → 5I8, and 5I5 → 5I8 transitions, the red band (650 nm) being most intense. The population of the upper levels of these transitions can be explained using the cascade excitation mechanism. A visualization model is developed based on balance equations for populations of the upper energy states of Но3+ ions. The population distributions are numerically estimated as functions of the excitation intensity. The obtained time dependences of the populations of the 5S2 and 5F5 states correlate with the experimental time dependences of the luminescence intensity at the 5S2 → 5I8 and 5F5 → 5I8 transitions upon pulsed excitation. The threshold power density of a Tm:YLF laser at which luminescence of the ceramic samples was observed was ~2 W/cm2.

Исследована визуализация ИК излучения Tm : YLF-лазера на длине волны 1908 nm в образцах керамики 53ZrF 4 -20BaF 2 -3LaF 3 -1HoF 3 -3AlF 3 -20NaF (mol%).В спектрах люминесценции легированных Но 3+ ZBLAN-керамик наблюдались полосы в областях длин волн 540, 650 и 900 nm, соответствующих переходам 5 S 2 → 5 I 8 , 5 F5 → 5 I 8 , 5 I5 → 5 I 8 с максимальной интенсивностью красной полосы (650 nm).Заселение верхних уровней этих переходов может быть объяснено с помощью механизма каскадного возбуждения.На основе системы балансных уравнений для населенностей энергетических состояний ионов Но 3+ создана модель визуализатора.Сделаны численные оценки распределения населенностей в зависимости от интенсивности возбуждения.Полученные временные зависимости населенностей состояний 5 S 2 и 5 F5 коррелируют с экспериментальными зависимостями изменения интенсивности люминесценции на переходах 5 S 2 → 5 I 8 и 5 F5 → 5 I 8 при импульсном возбуждении.Пороговая плотность мощности излучения Tm : YLF-лазера, при которой на керамическом образце наблюдалось свечение, составила ∼ 2 W/cm 2 .

Cr2+:ZnSe polycrystalline active elements were fabricated, with different distribution profiles of Cr ions concentration over their thicknesses and an equal absorption at a pump wavelength of 1.9 mu m. The lasing characteristics of the obtained samples in short cavity schemes were determined, using a CW Tm3+-doped fiber laser and a Tm3+:YLF pulsed laser as the sources of pumping. There was found to be a correlation between the generation slope efficiency and the shape of the concentration profile. It was determined that bilateral doping samples achieved better laser performance. The maximum values of the slope efficiencies with respect to the absorbed power were eta = 73% in the pulse-periodic mode, and eta = 37% in the continuous-wave mode.

This paper describes a comparative study of structural and luminescent properties of 5% Yb-doped yttrium, scandium, and lutetium oxides (Yb:RE2O3) powders and ceramics fabricated by self-propagating high-temperature synthesis. According to X-ray diffractometry and electron microscopy the chosen method ensures preparation of low-agglomerated cubic C-type crystal structured powders at one step. No crucial differences in luminescence spectra were found the Yb:RE2O3 powders and ceramics. It was shown that the emission lifetimes of the Yb: RE2O3 powders are lowered by crystal structure defects, while its values for ceramics samples are compared to that of monocrystals and more influenced by rare earth impurities.

Cr2+:CdSe single-crystal laser with four-mirror cavity design pumped by a pulse-periodic Tm3+:YAP laser has been developed. The average power of 420 mW at the pulse duration of 200 ns and the repetition rate of 2 kHz was achieved in a non-selective cavity. Continuous wavelength tuning in the range 2.42–3.05 µm was carried out using a golden diffraction grating as a selective mirror.