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We have found that BiB3O6:Tm3+ glass nanoparticles (NP) incorporated into the polymethylmethacrylate (PMMA) and polycarbonate (PC) polymer matrices additionally treated by dc-electric field (at electric strength about 8 kV/cm) at temperatures above the glassing temperature of the polymers show promising values of electrooptics coefficients (up to 10 pm/V at λ = 633 nm). It was established that only during incorporation into the highly polarized PC matrices one could observe an enhancement of the electroopitcs effect (EOE) coefficient with increasing time of the dc-electric treatment. The main increase was observed for all the samples at times higher than 80 min of dc-electric field treatment at temperature above the glassing temperatures of the corresponding polymers. The most striking feature is the achievement of effective electrooptics coefficient value below than 10 pm/V (λ = 633 nm) for the 4% content of the Tm doped BiBO glass nanoparticle (NP) embedded in the PC matrix. In the case of the bulk glasses the thermal poling unambiguously shows that the achieved maximal values of the electrooptics coefficient did not exceed 3.2 pm/V for 0.5% Tm+3 concentration. [ABSTRACT FROM AUTHOR]

The defect structure of YVO4 single crystals doped with Er3+, Ho3+ and Ca2+ were studied by X-ray diffraction topographic methods, using laboratory and synchrotron radiation sources. Variously developed block structure was the dominating imperfection of the investigated crystals observed both in conventional Lang and synchrotron topographs. The evaluation of block misorientation was realised by means of superimposed projection and section white beam synchrotron radiation topographs. More possibilities of following the mutual rotation of blocks were provided by means of white beam synchrotron radiation WBSR projection topographs exposed through the fine mesh. [ABSTRACT FROM AUTHOR]

The present work is devoted to investigation of optical absorption in pure and neodymium-doped YAlO3 (YAP) single crystals in the spectral range 0.2-1.1 μm induced by the influence of 12C ions irradiation with energy 4.50 MeV/u (MeV per nucleon) and a fluence 2×109 cm-2 or of 235U ion irradiation with energy 9.35 MeV/u and a fluence 5×1011 cm-2. The induced absorption in the case of 12C ions irradiation is caused by recharging of point growth defects and impurities under the radiation influence. After irradiation by 235U ions with fluence 5×1011 cm-2 the strong absorption rise is probably caused by contribution of the lattice destruction as a result of heavy ion bombardment. [ABSTRACT FROM AUTHOR]

Abstract: Praseodymium-aluminum (PrAlO3) perovskite crystals have been grown by the Czochralski method for the first time, to our knowledge. An almost periodic microtwin structure has been observed in the as-grown crystals, and a three-dimensional texturing of the polished surfaces has been observed. Optical absorption and emission spectra have been investigated at room temperature for crystals containing only Pr3+ ions as well as for crystals containing a mixture of Pr3+/Pr4+ ions. The observed broad emission band for the as-grown crystals could lead to a future potential application as a tunable laser for the whole visible range. [Copyright &y& Elsevier]

The up-conversion of infrared radiation at 808 nm, emitted by a diode laser, into blue emission centered at 480 nm in 1 at.% Tm, 5 at.% Yb: YVO4; 1 at.% Tm, 8 at.% Yb: YVO4 and 2 at.% Tm, 5 at.% Yb: YVO4 has been studied. The highest intensity of blue emission is found for the 1 at.% Tm, 8 at.%Yb: YVO4 system. The power dependence of up-converted emission upon continuous-wave excitation as well as the time evolution of its intensity upon short-pulse excitation were found to be consistent with a two-step excitation mechanism in which the forward Tm3+–Yb3+ energy transfer is followed by the back Yb3+–Tm3+ energy transfer. The effect of dopant concentrations on the up-conversion process is interpreted taking into account dynamics of the excited states involved. [ABSTRACT FROM AUTHOR]

We have discovered a photoinduced linear electrooptic effect (EOE) in the GdCOB doped by the rare-earth ions of the Tm3+ and Sm3+. We have found that doping by Tm3+ is essentially more efficient for increasing EOE compared with the Sm3+ ones. Moreover, increasing Sm3+ content diminishes the values of the r23 electrooptics coefficient. For comparison, the corresponding values for the pure GdCOB are nonsensitive to UV-pumping power and maximal EOE is less than 0.3 pm/V. [Copyright &y& Elsevier]

We have discovered a photoinduced linear electrooptics effect (EOE) in the GdCOB doped by the rare earth ions of Tm3+ and Sm3+. We have found that doping by Tm3+ is essentially more efficient for increasing EOE compared with the Sm3+ ones. Moreover, increasing the Sm3+ content diminishes the values of the r23 electrooptics coefficient. For comparison, the corresponding values for the pure GdCOB are non-sensitive to UV pumping power and maximal EOE is less than 0.3 pm/V. [Copyright &y& Elsevier]

A new candidate single crystal (La,Sr)(Al,Ta)O3 (LSAT) as a substrate for GaN epitaxial growth was found. Mixed-perovskite (1 1 1) oriented crystals were successfully grown by conventional Czochralski method. Excellent lattice matching with gallium nitride makes this material specially promising. Determination of the lattice parameters and the phase identification obtained crystals by X-ray diffraction analysis was carried out. Thermal expansion, thermal conductivity and electrical conductivity were measured. GaN epitaxial layers have been grown on (1 1 1) LSAT substrate and the results are presented. [Copyright &y& Elsevier]

Czochralski growth of Ca4GdO(BO3)3 (GdCOB) single crystals, pure and doped with several rare earth ions (Nd3+, Pr3+, Tm3+, and Sm3+), has been carried out. As-grown single crystals free from inclusions, bubbles and cracks were 20 mm in diameter and up to 60 mm in length. Optical absorption spectra of 6 at% thulium and samarium doped calcium gadolinium oxoborate were measured and presented. It was found that introduction of Pr3+ and Tm3+ ions leads to an increase of second-order photoinduced effects in GdCOB. The second harmonic generation shows an increase of at least 35% under the influence of photoinducing nitrogen laser (λ=377 nm) power. [Copyright &y& Elsevier]

Crystals of YVO[sub4]:Ho were grown by the Czochralski method. The structure of the low-energy levels of Ho&sup3+; has been estimated experimentally. Intensity parameters, radiative lifetimes, and branching ratios have been calculated in the framework of the Judd-Ofelt theory. The influence of temperature on luminescence lifetimes has been investigated. The calculated nonradiative transition rate was compared with the energy-gap law. The potential laser gain for the &sup5;I[sub7]-&sup5;I[sub8] transition has been estimated. [ABSTRACT FROM AUTHOR]

Abstract. Laser oscillation around 1.6 micro m was realised at room temperature for low-doped Er:YVO[sub 4] crystals (0.5 at % and 1 at %) as well as for Er(1 at %), Yb(5 at %):YVO[sub 4] crystal in continuous-wave mode. The maximum slope of the input-output curve was about 19% (vs. absorbed power) for Er(0.5 at %):YVO[sub 4]. The laser oscillation was discretely tunable in the spectral range between 1531 and 1604 nm. [ABSTRACT FROM AUTHOR]

The work is devoted to investigation of stable coloration induced by gamma radiation from 60Co (1.25 MeV) in pure and neodymium doped Ca0.28Ba0.72Nb2O6 single crystals. Nature of the induced absorption is discussed. This absorption is due to charge change of native defects or ions forming of crystals (vacancy, niobium ions, etc.). The nature of color centers responsible for induced absorption is discussed. [ABSTRACT FROM AUTHOR]

The present work is devoted to investigation of optical absorption in pure Ca4GdO(BO3)3 single crystals in the spectral range 0.2-1.1 μm induced under influence of the gamma quanta irradiation with absorbed dose 2×103 Gy. The effect of heating in air on the absorption spectrum of irradiated sample is also studied. [ABSTRACT FROM AUTHOR]

Abstract: Acoustically induced two-photon absorption (AITPA) and optical Kerr effect (AIOKE) in Pr and Tm doped calcium gadolinium oxyborate Ca4GdO(BO3)3 (CGOB) nanocrystallites (with sizes below 60nm) prepared by sol–gel method and embedded into the PMMA matrices were studied. The source of the acoustical field generated the frequency equal to about 1.2MHz and achieved maximal acoustical power density equal to about 6W/cm2. The AITPA was measured at fundamental Er:glass laser wavelength (1.54μm) and was observed only during applying of the prolonged acoustical field. The AITPA effect was substantially higher for the Tm3+ doped composites than for the Pr3+ doped ones. With increasing acoustical power, the AITPA increases achieving its maximal value at acoustical power density equal to about 4.70W/cm2. Temperature dependences have demonstrated the maximal values of the AITPA at temperatures equal to about 310K corresponding to the AITPA value equal to about 3.4cm/GW. At the same time at acoustical power density about 3.8W/cm2 the AIOKE achieves its minimum for the Pr doped CGOB nanocomposites. So one can expect that these two effects have different signs of contribution caused by the acoustical field. [Copyright &y& Elsevier]

Yb-doped Sr3Y(BO3)3 nanocrystallites incorporated into polymethyl methacrylate matrices (4.5% by weight) were optically treated by coherent picosecond laser pulses at 1.34 and 0.67 μm. This composite exhibits a large effective electro-optic coefficient (up to 6.2 pm/V at 1040 nm wavelength). Decrease of the nanocrystallite size and increase of the Yb content lead to substantial enhancement of the effective electro-optic coefficient. For nanocrystallite sizes equal to about 5 nm, the coefficient increases from 2.2 pm/V (8% of Yb) up to 6.2 pm/V (20% of Yb). This material appears thus promising in application for the optically operated modulators. [ABSTRACT FROM AUTHOR]