Transition rates of Tb3+ in TbP5O14, TbLiP4O12, and TbAl3(BO3)4: An evaluation for laser applications

Abstract

The properties of Tb3+ in crystals of three stoichiometric Tb compounds, viz., TbP5O14, TbLiP4O12, and TbAl3(BO3)4 have been studied by spectroscopic absorption and emission methods to evaluate these materials as hosts for Tb3+ laser applications. The absorption spectra between 50000 and 200 cm−1 at 300 °K, the emission spectra between 27000 and 14000 cm−1 at 300 °K, and the fluorescence decay characteristics of 5D4 emission at 300 and 5 °K are given. Because of cross relaxation, the 5D3 and 5G6 emissions in all three materials were concentration-quenched strongly with a similar behavior observed in other hosts. Quenching in the 5D4 states was negligible except for TbAl3(BO3)4 where moderate quenching was observed due to energy transfer to nonradiative traps. Transition rates between various states were calculated by using the Judd–Ofelt approach and a first order wavefunction set, and good fit was obtained between the calculated and experimental parameters. The transition rates were then used to find the emission cross sections of various lines.