Laser Spectroscopy of Some Yag: R-E System

Abstract

Despite the fact that the terminal level has a much longer lifetime than the initial level the heavily-doped YAG:Er crystal proved to be an efficient system for 3 micron laser emission at room temperature. This was tentatively explained as due to a cross-relaxation process which depop ulates the terminal level and repopulates the initial one. Our studies by laser spectroscopy show the effect of this and of several other crossrelaxation processes on the kinetics of deactivation of the levels involved in the laser process. The essential role of energy transfer and cross relaxation in up-conversion of green or red pump light into a blue or violet emission was also put into evidence. A computer simulation of the laser generation was performed with the estimated cross-relazation rates. High-resolution laser spectroscopy at 77K of YAG:Nd shows that in several samples the luminescence spectrum R₁→Z₁ of the transition ⁴F_3/2→⁴I_9/2 contain, besides the normal 11435 cm^-1 line, an additional emission at 11430 cm^-1. The room temperature decay for this transition in a low-resolution measurement for these samples is definitely nonexponential. A possible law to fit the observed data was discussed. For samples which contain parts from “core” of the crystal an additional 11428 cm^-1 emission is observed. This presentation was based on work performed together with S. Georgescu, A. Lupei, C. Jonescu, I. Ursu (Central Institue for Physics, Bucharest), V. Zhekov, T. M. Murina, A. M. Prokhorov (Institute for General Physics, Moscow).