Calculation of the probability of the 4T2 → 4A2 transition in luminescence spectra of the Mn4+ ion in gadolinium-gallium

The T-4(2) --> (4)A(2) transition of the Mn4+ ion has been observed in the luminescence spectrum of Mn4+:Cd3Ga5O12 upon intense laser pumping. It is shown that an increase in the intensity of the T-4(2) --> (4)A(2) transition with respect to the E-2 --> (4)A(2) transition in these crystals with increasing pumping power relates to the increased role of induced transitions. The intensity of this process is greater in the region where the E-2 --> (4)A(2) and T-4(2) --> (4)A(2) transition bands overlap most, which leads to an increase of the zero-phonon line of the latter transition, peaking at a wavelength of 694 nm. The rates of radiative and nonradiative recombination involving the T-4(2), E-2 and (4)A(2) terms of the Mn4+ ion in gallium-gadolinium garnet (GGG) are calculated using data from luminescence spectra measured at different temperatures. The Mn4+ :GGG crystal is proposed for use as an active element of lasers with continuous frequency tuning. (C) 2003 MAIK "Nauka/Interperiodica".