1,721,005 research outputs found
Luminescence spectroscopy of Er3+-doped and Er3+, Yb3+-codoped LaPO4 single crystals
No full textLaPO4 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 1.5 mu m, that have been found to be similar to important oxide laser crystals doped with Er3+. Efficient visible upconversion has been observed upon excitation at 980 nm in the codoped crystals. This behaviour is attributed to Yb3+-Er3+ energy transfer processes
Optical spectroscopy of Er3+-doped LaVO4 crystal
No full textTransparent single crystals of erbium-doped LaVO4 in form of platelets having an average size 0.5 x 2 x 2 mm(3) 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 970 nm 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. (C) 2009 Elsevier B.V. All rights reserved
Optical Methods in Characterization of HTSC Thin Film Substrates
No full textShort overview of optical methods which proved to be useful in the characterization of HTSC thin film substrates is presented. Preliminary tests in polariscopic arrangements, interferometric measurements, optical absorption and emission spectroscopy reveal macroscopic deficiencies of the crystal. Intentionally introduced impurity ions serve as probes of a local strength and symmetry of the crystal field. Results of optical study of SrLaGaO and SrLaAlO crystals are presented and discussed
Disordered Nd-Doped Crystals for Diode Pumping
No full textSome interest has been directed recently to neodymium doped crystals with strong inhomogeneous broadening of absorption bands which are believed to be better suited for diode pumping than the crystals with ordered lattice. The disordered Nd-doped crystals may be obtained in two ways. The first one is to introduce a structural disorder in ordered lattice by substituting partially one or more cations by cations with different charges. Alternatively, the compounds with inherently disordered structure are synthesized and doped with Nd. We consider two wide families of compounds of general formulae ABCO and ABCO where A stands for Ca, Sr, Ba, B is Y or rare earth and C stands for Ga or Al. Both the families form the crystals with inherently disordered structure and can accept an appreciable amount of Nd. Results of structural and spectroscopic investigations are used to determine material's parameters relevant to laser performance. Comparison of several disordered crystals is made and their suitability for diode pumping is discussed
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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