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Abstract: Praseodymium and cerium co-doped yttrium silicate (Pr,Ce:YSO) crystal with high optical quality was grown by the Czochralski method. The segregation coefficient of Pr3+ and Ce3+ is measured to be 0.547 and 0.136, respectively. The polarized absorption bands centered at 268nm, 299nm and 356nm were assigned to 4f (2F5/2)→5d inter-configuration transitions of Ce3+, while bands centered at 220nm and 250nm were assigned to 4fn–4fn−15d transitions of Pr3+. The VUV–UV excitation spectra for monitoring Pr3+ emissions centered at 610nm (1D2→3H4) and 489nm (3P0→3H4), as well as Ce3+ emission centered at 450nm were recorded at T=8K in the range of 100nm–320nm. Polarized excitation spectra for Ce3+ emission centered at 424nm and Pr3+ emission centered at 611nm were recorded at T=300K. Polarized emission spectra were obtained upon excitation at 365nm and 456nm at T=300K. Lifetimes were estimated to be 170μs for Pr3+ (1D2), 3μs for Pr3+ (3P0) and 39ns for Ce3+ (5d1). [Copyright &y& Elsevier]

Abstract: The KGd2F7:Tb and KGd2F7:Tb,Eu samples were obtained using a solid state reaction. Excitation spectra and emission spectra are reported and analyzed within the VUV–UV–vis spectral range. The intense green luminescence is observed in the KGd2F7:Tb while the combined emission of terbium and europium in the KGd2F7:Tb,Eu covers substantially the region of white light. The materials under study can be effectively excited making use of intense f–d transitions of Tb3+ in the VUV–UV region. Experimental lifetimes of luminescent levels have been measured and discussed. It was found that the considerable energy transfer from Tb3+ to Eu3+ occurs. [Copyright &y& Elsevier]

Abstract: Transparent single crystals of erbium-doped LaVO4 in form of platelets having an average size 0.5×2×2mm3 were obtained by the flux method using Pb2V2O7 as the solvent. Inductively coupled plasma (ICP) measurement revealed that the actual Er/La=0.3% molar ratio in the crystals is lower than Er/La=1% nominal molar ratio due to significant difference of ionic radii of La and Er. Luminescence spectra and luminescence decay curves for Er3+ transitions in the visible and near infrared region were recorded. Unpolarized Raman spectrum of undoped LaVO4 crystal was acquired, too. Up-converted green emission following excitation at 808 and 970nm was observed and dependence of its intensity on incident excitation power was determined. Based on experimental data gathered the relaxation dynamics of excited states of Er3+ was analyzed and mechanisms involved in the up-conversion phenomena were discussed. [Copyright &y& Elsevier]

Abstract: LaPO4 single crystals lightly doped with Er3+, and codoped with Er3+ and Yb3+ have been grown by spontaneous nucleation in a lead phosphate flux. Absorption and luminescence spectra have been measured in the visible and near-IR regions and the excited state dynamics has been studied upon pulsed laser excitation. The obtained results have allowed the evaluation of the effective emission cross-sections around 1.5μm, that have been found to be similar to important oxide laser crystals doped with Er3+. Efficient visible upconversion has been observed upon excitation at 980nm in the codoped crystals. This behaviour is attributed to Yb3+–Er3+ energy transfer processes. [Copyright &y& Elsevier]

Abstract: Good optical quality U3+-doped PbCl2 single crystals of the composition Pb0.99U0.01Cl2 have been obtained by the Bridgman–Stockbarger method. Luminescence spectra of the crystals were recorded in a wide spectral range at room and liquid nitrogen temperatures, and are discussed. Strong infrared emission was observed under 514nm laser pumping to the 5f26d1 bands. The lifetimes of the emitting levels in the visible and near infrared region are given. [Copyright &y& Elsevier]

Abstract: Illumination of single crystal samples of erbium-doped YVO4 and LuVO4 by infrared femtosecond pulses brings about an intense green luminescence assigned to the 4S3/2 - 4I15/2 transition of Er3+ ions. When lowering the sample temperature an additional broad band in the blue related to the VO4 3− emission appears and next grows steadily. It has been observed that the variation of wavelength of incident infrared femtosecond pulses in the region 800nm–1600nm affects weakly the intensity of both the blue and green luminescence bands. Analysis of luminescence dynamics made it possible to reveal that upon infrared excitation the rise time of the 4S3/2 luminescence is longer by a factor of four, roughly as compared to that recorded upon direct excitation into high energy levels of Er3+. Observed temperature dependence of up-converted blue and green luminescence implies that the energy transfer from vanadate groups cannot be considered as a main mechanism involved in the excitation erbium ions. It has been supposed that erbium ions are likely to be excited by energy transfer from free electrons created in the conduction band of the host by multiphoton excitation and /or by non-resonant multi-step ETU process involving absorption of infrared light in multiphonon side bands of electronic transitions. Creation of free electrons has been corroborated by changes of electrical conductivity of crystals induced by an illumination with infrared femtosecond pulses. [Copyright &y& Elsevier]