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Abstract: We report random laser action in ground powders of Nd x Y1− x Al3(BO3)4 (x =0.5–1) laser crystals under nanosecond pulse excitation at 802nm. The dependence of the random laser threshold energy on the neodymium concentration and focusing conditions is investigated. The slope efficiency of the output random laser emission is determined as a function of Nd3+ concentration. [Copyright &y& Elsevier]

Abstract: In this work we report the near infrared to visible upconversion luminescence of Er3+ ions in CaZrO3/CaSZ eutectic crystals with ordered lamellar microstructure. The microstructure consists of alternating 2-μm-thick lamellae of calcia-stabilized zirconia (CaSZ) and calcium zirconate (CaZrO3) single crystals. Er3+ ions enter both phases but at a higher concentration in CaSZ. Wavelength selective excitation along the 4I15/2→4I9/2 absorption band allows to distinguish the upconverted emission from Er3+ sites in the two eutectic phases. In the CaZrO3 phase the upconversion emission spectrum is dominated by an intense green emission characterized by sharp (2H11/2,4S3/2) levels together with a more weak red emission from 4F9/2 level. In the CaSZ phase, a broad green and red emissions occur with an enhancement of the red emission from level 4F9/2. These upconverted emissions are attributed to a two photon process. The excitation wavelength dependence of the upconverted luminescence together with its time evolution after infrared pulsed excitation suggest that energy transfer upconversion processes are responsible for the upconversion luminescence. [Copyright &y& Elsevier]

In this paper, we present the preliminary results of the combined effect of high pressure (up to 7.5 GPa) and strong external magnetic fields (up to 28.5 T) on the photoluminescence (PL) properties of Er3+-Yb3+ co-doped single-crystal thin films of well-oriented KY(WO4)2 at low temperatures. Measurements were carried out under pulsed magnetic field, exciting the Er3+ ions via upconversion mechanisms by a Ti:sapphire laser with the external magnetic field applied along the crystallographic b axis. The detailed study of the green 4S3/2→4I15/2 Er3+ PL after infrared excitation around 1 μm as a function of pressure and external magnetic field reveals the potential applicability of this system as sensor of high magnetic fields, high pressure and low temperature, simultaneously. [ABSTRACT FROM AUTHOR]

Abstract: Upconversion luminescence of Er3+ ions in chalcohalide glass and in transparent glass–ceramic samples under continuous wave and pulsed laser excitation in the 4I9/2 level has been studied. Green and red emissions corresponding to (2H11/2, 4S3/2)→ 4I15/2 and 4F9/2 → 4I15/2 transitions, respectively, have been observed and attributed to a two photon upconversion process. A significant increase of upconversion luminescence has been observed in the transparent glass–ceramics if compared with the one from the base glass. Moreover, the red emission corresponding to the 4F9/2 → 4I15/2 transition is enhanced in the glass–ceramics as compared to the green luminescence from (2H11/2, 4S3/2) levels probably due to an increase of the energy transfer processes populating the 4F9/2 level. The possible excitation mechanisms responsible for this upconversion luminescence are discussed. [Copyright &y& Elsevier]

Abstract: Eu2+-doped CsCdBr3 single crystals are studied by polarized variable-temperature optical absorption and luminescence spectroscopy for different excitation wavelengths. Whereas the low-energy absorption band is assigned to f→d transitions within Eu2+ electronic configuration, the high-energy absorption bands are assigned to Eu-trapped exciton due to the proximity of the high-energy d levels to the conduction band. [Copyright &y& Elsevier]

The growth of undoped and Mn6+-doped molybdates and tungstates of alkali-earth metals and BaSO4 has been investigated. Single crystals were grown by the flux method within the temperature range of 600–475 °C, using the ternary NaCl–KCl–CsCl solvent. Sizes of undoped crystals increase within the series tungstates2+≈Sr2+2+. The Mn6+ ion tends to be reduced to Mn5+/Mn4+ with time in the chloride solution, but can be partly stabilized by the addition of alkali-metal carbonates or hydroxides. The incorporation of Mn6+ is governed by the coordination of the MnO42- tetrahedron in the crystal. No significant doping was found for Ca and Sr compounds and only small amounts of Mn6+ were incorporated into BaMoO4 and BaWO4. Crystals with orthorhombic space group Pnma such as BaSO4 exhibit significantly higher doping levels. The Mn6+ distribution in each crystal varies due to manganese reduction with growth time. Temperature-, time-, and concentration-dependent spectroscopy of BaSO4:Mn6+ was performed. [ABSTRACT FROM AUTHOR]

Crystalline KY(WO4)2 thin layers doped with different rare-earth ions were grown on b-oriented, undoped KY(WO4)2 substrates by liquid-phase epitaxy employing a low-temperature flux. The ternary chloride mixture of NaCl, KCl, and CsCl with a melting point of 480°C was used as a solvent. X-ray diffraction, differential-interference contrast microscopy, and profilometry confirmed that the layers were oriented in [0 1 0] direction with a thickness of 5–10 μm. Tb3+, Dy3+, or Yb3+ ions were incorporated into the KY(WO4)2 host, and their distribution coefficients were estimated by electron-probe microanalysis. The layers were crack-free and solvent inclusions could not be found, although the presence of secondary phases in the solution has been observed. The high optical quality of the layers was confirmed by the demonstration of passive and active planar waveguiding. [Copyright &y& Elsevier]

The growth of undoped and Mn6+-doped molybdates and tungstates of alkali-earth metals and BaSO4 has been investigated. Single crystals were grown by the flux method within the temperature range of 600–475 °C, using the ternary NaCl–KCl–CsCl solvent. Sizes of undoped crystals increase within the series tungstates

A new theoretical approach for random lasing of Nd 3+ doped powders is presented. The model's singularity lies in the fact that it proposes a probability distribution of the stimulated photon paths lengths in the sample, as well as a population inversion shared by different photon paths. The model's predictions satisfactorily compare with the results of laser threshold and absolute input/output energy slope of a real Random Laser. The main novel issue is that the best fit to the experimental results requires considering a high level of shared population inversion among different paths. The model simulation of local and spatially integrated Random Laser emissions, as well as their time evolution, is in accordance with the experimental behavior. These results also provide a new method of measuring the stimulated emission cross-section in this kind of random laser materials.