Stimulated and spontaneous emission probabilities of Tm3+ in TeO2-CdCl2 glass: the role of the local structure

Abstract

We present the results of a study which uses experimental and theoretical methods to investigate the characteristics of the 1450- and 1800-nm luminescence bands of Tm3+-doped TeO2-CdCl2 glasses as a function of the CdCl2 fraction. These glasses are potentially important in the design of fiber-optic amplifiers and fiber lasers. In the experiments, the glass samples were prepared by fusing a mixture of their respective reagent grade powders in a platinum crucible at 750degreesC for 30 min. The spectroscopic properties were then investigated by measuring the absorption, fluorescence intensities, and the fluorescence lifetimes at room temperature by using diode and Ti:sapphire pump lasers operating around 800 nm. In the theoretical calculations, Judd-Ofelt analysis was used to assess the effect of the glass composition on the radiative transition probabilities, quantum luminescence efficiencies, and the stimulated emission cross-sections. The results indicate that the luminescence quantum efficiency, while remaining approximately constant around 10% for the 1450-nm band, increases with increasing CdCl2 concentration for the 1800-nm emission. Furthermore, the stimulated emission cross-sections for the 1450- and 1800-nm transitions were found to be largest for the sample with 30 mol% CdCl2.