Here we present the study of spectral and kinetic characteristics of Er3+ ions in the heavily doped BaY1.8Lu0.2F8 mixed crystals, which are homologous to well-known fluoride host BaY2F8 with high value of crystal field splitting. Absorption and luminescence spectra were registered, and the luminescence decay was studied in the IR spectral range for BaY1.8Lu0.2F8 crystals doped with Er3+ ions at concentrations of 20.0 at. % and 30.0 at. %. Based on the Judd-Ofelt theory, the intensity parameters were determined from the absorption spectra with the use of two approaches, the standard theory (J -O), and the intermediate configuration interaction (ICI). It is shown that investigated BaY1.8Lu0.2F8:Er3+ crystals propose the value of stimulated emission cross-section at the wavelength around 2.7 pm higher than that for Er -doped YAG and at the level of Er -doped LiYF4 crystals. In addition, it was shown that for BaY1.8Lu0.2F8 crystals with a high doping level of Er3+ (more than 20.0 at. %), the radiative lifetime of the 4I13/2 state becomes shorter than the lifetime of the 4I11/2 state, which speaks for success on efficient laser oscillation at a wavelength of about 2.7 pm (the 4I11/2 -> 4I13/2 transition).

Herewe present the spectral and kinetic characteristics of $\mathrm{Er}^{3+}$ ions in the heavily doped $\mathrm{BaY}_{1.8} \mathrm{Lu}_{0.2} \mathrm{~F}_{8}$ mixed crystals and evaluate the possibility of continuous laser oscillation at a wavelength of $2.7 \mu \mathrm{m}$.

Stimulated-emission cross-sections for the 4 I 11/2 → 4 I 13/2 and 4 I 13/2 → 4 I 15/2 transitions of Er 3+ ions in three cubic sesquioxides Y 2 O 3 , Lu 2 O 3 and Sc 2 O 3 are revised. The transition probabilities in emission are determined using the Judd-Ofelt theory and lifetime studies.

The oxyfluoride-lead-silicate-germanate glass with composition of 30SiO(2)-10GeO(2)-xPbO-(50-x) PbF2-10CdF(2)-yTm(2)O(3), x = 5, 25, 45, y = 0.01, 0.1, 0.5, 1.0 (mol. %) were prepared by melt-quenching technique and their spectroscopic properties, including parameters calculated by the JO method, were studied. A new approach for calculation of the pump efficiency of the F-3(4) level at excitation of the H-3(4) level by using stationary spectra of luminescence at transitions H-3(4)-> F-3(4) and F-3(4)-> H-3(6) was proposed. For the samples with a high content of Tm2O3, the efficiency reaches the value of 1.8. It was established that the quadrupole-quadrupole interaction between thulium ions dominates in the D-A energy transfer due to the cross-relaxation H-3(4)+H-3(6)-> F-3(4)+F-3(4). On the base of the rate equations, a new fitting procedure was proposed for obtaining the probabilities of donor acceptor, W-DA, and up-conversion, W-UP, energy transfer. It was obtained that W-DA similar to 6 10(5) 1/s and W-UP << W-DA for the samples with 0.5 and 1.0 mol. % of Tm2O3. The laser related properties, the stimulated emission cross sections, gain spectra, of the glass studied, were obtained and discussed.

We study the silica gel-glasses obtained by vitrification in air or in a gas mixture of H 2 :Ar xerogels doped with Sm, Al, and Ba. It is found that during their synthesis it is possible to form impurity hexagonal and tetragonal crystallites of SiO 2 and tetragonal crystallites of SmSi 2 . When the reducing synthesis conditions are applied, the incorporation of samarium in glass simultaneously in two oxidation states (3+ and 2+) takes place. Meanwhile, Sm-Al-containing glasses provide a sufficiently effective sensitization of the luminescence of Sm 2+ ions by Sm 3+ ions, while in Sm-Al-Ва-containing glasses this effect is absent because Sm 2+ ions are localized mainly in the glass sublattice formed with the participation of Ba 2+ ions. Based on the spectra obtained, the positions of the energy states of the Sm 2+ and Sm 3+ ions in such glasses are calculated.

Lasing and spectroscopic properties of an LiY 0.3 Lu 0.7 F 4 :Pr 3+ crystal grown by the Bridgman–Stockbarger method were investigated in detail. Absorption and luminescence spectra were recorded using polarized light. Lifetimes of excited states 3 P J were determined. Absorption and emission transition intensities were calculated according to f–f-transition intensity theory taking into account interconfiguration interaction. Stimulated emission transverse cross sections were determined using the Füchtbauer–Ladenburg method. Pumping by an InGaN laser diode produced continuous-wave laser generation at 522.6 nm ( 3 P 1 → 3 H 5 ) in Pr-doped mixed fluoride crystals with a maximum output power of 0.38 W and a slope efficiency of 19%.

Lasing and spectroscopic properties of an LiY0.3Lu0.7F4:Pr3+ crystal grown by the Bridgman–Stockbarger method were investigated in detail. Absorption and luminescence spectra were recorded using polarized light. Lifetimes of excited states 3PJ were determined. Absorption and emission transition intensities were calculated according to f–f-transition intensity theory taking into account interconfiguration interaction. Stimulated emission transverse cross sections were determined using the Füchtbauer–Ladenburg method. Pumping by an InGaN laser diode produced continuous-wave laser generation at 522.6 nm (3P1 → 3H5) in Pr-doped mixed fluoride crystals with a maximum output power of 0.38 W and a slope efficiency of 19%.

The fifth author's name should read K. N. Nishchev. Figure 3 on page 587 is incorrect.

The influence of the excited configurations with the charge transfer on the Stark structure of the multiplets of Eu3+ ion in the elpasolites was investigated with the help of the modified crystal field Hamiltonian. Cs2NaYCl6:Eu3+ and Cs2NaEuCl6 crystal systems were chosen as the subjects of our research. The modified Hamiltonian of the crystal field was for the first time applied to the crystal systems activated by Eu3+ ions and its use has allowed to reduce considerably the root-mean-square deviation and to define the covalence parameters from optical spectra. The convenient algorithm for determination of errors of the modified Hamiltonian parameters is offered.

We present the analysis of wave functions and the effect of configuration interaction on the intensity of absorption bands for Pr 3+ , Tm 3+ , and Er 3+ ions. It is shown that due to the strong spin–orbit interaction the wave functions of rare-earth ions are multicomponent superpositions of ″pure″ 2S+1 L J multiplets with different values of S and L and the same values of the angular momentum J. For this reason, the effect of configurational interaction depends not only on the energy gap up to excited configurations, but also on the presence of high-energy 2S+1 L J components. The presence of such components yields a strong influence on the configuration interaction even at the deep layers. Another consequence of the multicomponent composition of the wave functions is the formation of groups of strongly interrelated states. When the configuration interaction is not fully taken into account, the error in describing the oscillator strengths is distributed among all the states of the group, and the low overall accuracy of the description is not perceived as a contradiction to the theory. To confirm the proposed assumptions, the oscillator strengths of the absorption transitions of laser materials activated by Pr 3+ , Tm 3+ , and Er 3+ ions are described using the modified Judd–Ofelt theory.

A Sm3+:KY(WO4)2 crystal was grown by the modified Czochralski technique. Polarized absorption and fluorescence spectra, as well as a fluorescence decay curve, were recorded at room temperature. Radiative properties such as emission probabilities, branching ratios and radiative lifetimes were investigated within the framework of the Judd-Ofelt theory as well as the theory of f-f transition intensities which takes into account the influence of the excited configurations. Emission cross section spectra were determined. 4G5/2 fluorescence decay was analyzed within the framework of the Inokuti-Hirayama model. The spectroscopic properties of Sm:KYW crystal were compared with those of other Sm3+-doped materials.

In this work we report the spectroscopic properties of Tm3+:NaBi(MoO4)(2) crystals with the dopant concentrations of 0.7 at.% and 3 at.%. The energy levels of the Tm3+ in the NaBi(MoO4)(2) host were determined from polarized optical absorption and photoluminescence spectra measured at 77.4 K. Radiative properties of the crystals were calculated in context of Judd-Ofelt theory. Raman spectra of the crystal were studied. The concentration dependences of emission decay times of H-3(4) and F-3(4) levels were analyzed. The potential of the crystal for building tunable and ultrafast pulse lasers is shown on the base of cross sections and gain coefficient in the range of 1.9 mu m.

We present the analysis of wave functions and the effect of configuration interaction on the intensity of absorption bands for Pr 3 + , Tm 3 + , and Er 3 + ions. It is shown that due to the strong spin-orbit interaction the wave functions of rare-earth ions are multicomponent superpositions of “pure” 2S + 1 L J multiplets with different values of S and L and the same values of the angular momentum J. For this reason, the effect of configurational interaction depends not only on the energy gap up to excited configurations, but also on the presence of high-energy 2S + 1 L J components. The presence of such components wields a strong influence on the configuration interaction even at the deep layers. Another consequence of the multicomponent composition of the wave functions is the formation of groups of strongly interrelated states. When the configuration interaction is not fully taken into account, the error in describing the oscillator strengths is distributed among all the states of the group, and the low overall accuracy of the description is not perceived as a contradiction to the theory. To confirm the proposed assumptions, the oscillator strengths of the absorption transitions of laser materials activated by Pr 3 + , Tm 3+ , and Er 3 + ions are described using the modified Judd-Ofelt theory.

We report on a detailed spectroscopic study of Eu3+ ions in the monoclinic KYb(WO4)2 crystal. The polarized room and low-temperature absorption spectra are measured. The maximum σabs corresponding to the 7F1 → 5D1 transition is 1.32×10–20cm2 at 534.2nm with a bandwidth of 0.7nm (for E||Nm). The Stark sub-levels of the excited mulitplets are determined. A Judd-Ofelt analysis is applied to the Eu3+:KYb(WO4)2 crystal to determine the probability of spontaneous transitions, radiative lifetimes and luminescence branching ratios. Within the strong configuration interaction (SCI) approximation, the intensity parameters are Ω2=4.757, Ω4=2.295, Ω6=1.644 [10–20cm2] and Δf=50160cm–1. The radiative lifetime of the 5D0 state is 351 µs. The maximum stimulated-emission cross-section corresponding to the 7F1 → 5D1 transition is 1.44×10–20cm2 at 703.2nm (for E||Nm). Under UV excitation, the Eu3+:KYb(WO4)2 crystal provides intense red photoluminescence with CIE coordinates, x=0.675, y=0.325.

Ca9Nd(VO4)(7) single crystal was grown by the Czochralski method in inert atmosphere. The crystal structure and chemical composition were studied. Polarized absorption and luminescence spectra were investigated in details. It was found that the Ca9Nd(VO4)(7) crystals belongs to self-activated laser materials with a weak concentration quenching of luminescence. Judd-Ofelt analysis was performed. The emission cross-sections spectra for (4)F3/2 -> (4)I9/2, (4)I11/2, (4)I13/2 transitions were determined. For the first time Raman spectra of the Ca9Nd(VO4)(7) single crystal were recorded and interpreted. (C) 2016 Elsevier B.V. All rights reserved.