Effect of temperature on excited state relaxation dynamics and up-conversion phenomena in La3Ga5.5Ta0.5O14:Er3+ single crystals

• Published in: Journal of alloys and compounds Vol. 610; pp. 451 - 455
• Main Authors: Lisiecki, Radosław, Ryba-Romanowski, Witold, Komar, Jarosław, Berkowski, Marek
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier B.V 15-10-2014; Elsevier
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Exact sciences and technology; Laser properties; LGT:Er single crystal; Luminescence; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Photoluminescence; Physics; Up-conversion; Laser properties; LGT:Er single crystal; Up-conversion; Luminescence; Impurity density; Thermalization; Doping; Photoluminescence; Frequency conversion; Czochralski method; Excited states; Energy-level transitions; Multi-phonon processes; Absorption spectra; Erbium additions
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2014.05.016

•LGT:Er single crystals obtained by Czochralski method.•Analysis of absorption and emission spectra as well as decay curves of luminescence.•Influence of the temperature on the LGT:Er spectroscopic properties.•Spectroscopic evaluation of the LGT:Er potential laser qualities.
The La3Ga5.5Ta0.5O14 (LGT) single crystals nominally doped with 5at.% and 1at.% of Er3+ were grown by the Czochralski method in an atmosphere of nitrogen containing small amount of oxygen. Examination of the grown crystals employing a coupled plasma emission spectroscopy (ICP ES) revealed that actual concentrations of Er3+ ions amount to 3.8at.% and 0.27at.%, respectively. Absorption and emission spectra as well as relaxation of excited states of Er3+ ions in the LGT host were investigated as a function of temperature in the 300–700K temperature region. The main attention was focused on spectroscopic properties of the LGT:Er crystal that are relevant to a potential laser operation associated with the 4I13/2→4I15/2 transition of Er3+ near 1.6μm and to up-conversion of infrared radiation into green luminescence originated in the 2H11/2, 4S3/2 levels. It was found that the increase of temperature affects weakly spectral features of inhomogeneously broadened absorption bands related to the 4I15/2→4I11/2 and 4I15/2→4I13/2 transitions. Observed decrease of the 4I11/2 lifetime is consistent with calculated dependence assuming the contribution of multiphonon relaxation process that involves emission of 5 phonons with energy of 660cm−1. Decrease of lifetime for the 2H11/2, 4S3/2 group of levels with increasing temperature, calculated assuming thermalization effects and the contribution of multiphonon relaxation, is slightly slower than experimental dependence, however. Integrated intensity of up-converted green emission excited at 980nm diminishes quickly with increasing temperature and becomes hardly visible already at 670K. It is supposed that this is due to simultaneous decrease of quantum efficiencies of both the intermediate 4I11/2 level and luminescent 2H11/2, 4S3/2 group of levels.