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Abstract: Monoclinic 2at% Eu-doped KY(WO4)2 is grown by top-seeded solution growth method. Polarization-resolved absorption and stimulated-emission cross-section spectra are determined for this crystal. Spectroscopic properties of Eu:KY(WO4)2 are modeled within conventional Judd–Ofelt theory, as well as theory of f–f transition intensities for systems with anomalously strong configuration interaction, yielding absorption oscillator strengths, luminescence branching ratios and radiative lifetime of 5D0 state. The impact of excited-state absorption from this state on possibility of laser operation is discussed. Photoluminescent properties of Eu:KY(WO4)2 are determined. This crystal provides intense red emission with CIE coordinates x=0.670, y=0.329. [Copyright &y& Elsevier]

Abstract: The analytical expressions for thermo-optic coefficients, dn/dT, for “fast” and “slow” light waves propagating along the arbitrary direction in a biaxial crystal are derived. On the basis of these expressions, the all-space analysis of existence of athermal directions is performed for monoclinic and biaxial KY(WO4)2 at 1.03μm. The calculations are performed for an arbitrary light propagation direction and polarization (not restricted to the principal planes). The appearance of directions that can be athermal for both “fast” and “slow” waves is predicted. The dispersion of athermal directions is analyzed for visible and near-IR. The existence of upper and lower dispersion limits for athermal behavior of KY(WO4)2 is shown. It is shown that the optical indicatrix axes can be athermal itself at some light wavelengths. Wavelength- and temperature-dependent position of the optical axes of KY(WO4)2 is also determined. [Copyright &y& Elsevier]

Abstract: Novel oxyfluoride glass doped with YbF3 and Eu2O3 is synthesized in the SiO2–PbO–PbF2–CdF2 system by melt-quenching technique. Its physical properties, as well as the optical absorption of Eu3+ and Yb3+ ions are studied. Spectroscopic properties of Eu3+ ions are modeled within modified Judd–Ofelt theory, yielding absorption oscillator strength, luminescence branching ratios and radiative lifetime of 5D0 state. Intrinsic emission of Eu3+ ions under direct excitation in the UV, as well as up-conversion luminescence under near-IR excitation via cooperative energy transfer, 2Yb3+ →Eu3+, are studied. In the latter case, the glass provides intense reddish-orange emission with CIE coordinates x =0.636, y =0.363. The asymmetry parameter R for Eu3+ emission in the studied glass is about 8. The efficiency of this transfer mechanism is estimated from shortening of 2F5/2(Yb3+) lifetime to be 10±1%. [Copyright &y& Elsevier]

Abstract: Lead sulfide quantum dots (QDs) with average diameter of 3.0–6.5nm were grown in novel SiO2–Al2O3–ZnO–Na2O–K2O–NaF glasses highly-doped with PbO and elemental sulfur by means of single-stage heat-treatment at temperatures slightly lower the vitrification point. Introduction of two alkaline components to the glass system allows us to perform the synthesis without control of sulfur evaporation, while stabilization of PbS crystal nuclei was provided by addition of NaF. Optical absorption and photoluminescence of these PbS-QD-doped glasses were studied in dependence on treatment temperature (480–520°C) and duration (5–130h). The growth rate of QDs was substantially enhanced with the increase of treatment temperature. The position of 1S–1S excitonic absorption peak was tuned from 0.75 to 1.6μm, accompanied by management of peak absorption within 7–45cm−1 range. Intense Gaussian-shaped photoluminescence associated with radiative exciton recombination from 1S–1S state was observed in 1.1–1.6μm spectral range. [Copyright &y& Elsevier]

Absorption and luminescence of nickel-containing ZnO–Al2O3–SiO2 glasses and glass–ceramics nucleated by TiO2 and ZrO2 were investigated for variable NiO content and heat-treatment conditions. Ni2+ ions in the as-cast glasses are predominately five-fold coordinated. Heat-treatment of glasses containing 1–3mol.% NiO at 730–800°C results in precipitation of nickel titanate–zirconate xNiO·yTiO2·zZrO2 nanocrystals with Ni2+ ions entering octahedral sites. Optical absorption of samples treated at 800–1100°C is determined by precipitation of gahnite nanophase with Ni2+ ions entering both octahedral and tetrahedral sites and minor fraction of ions remaining in the residual glass phase. These samples are characterized by strong near-IR luminescence associated with 3T2g(3F)→ 3A2g(3F) transition of [6]Ni2+ ions (FWHM more than 200nm, centered at ~1.2μm) in gahnite nanocrystals. Luminescence intensity increases substantially with the increase of heat-treatment temperature due to increase of volume fraction of gahnite nanophase and size of gahnite nanocrystals (which in turn causes decrease of relative fraction of Ni2+ ions located near the nanocrystal surface and suppresses the non-radiative relaxation path), the second factor is the dominant one. Concentration of NiO has dramatic effect on the luminescence efficiency of glass–ceramics due to a strong temperature and concentration quenching. [ABSTRACT FROM AUTHOR]