Spectroscopic properties and energy transfer parameters of Tm3+ ions in gallium lanthanum sulfide glass

This work presents the spectroscopic characterization of Tm3+ doped gallium lanthanum sulfide (GaLaS) chalcogenide glass through absorption, fluorescence and lifetime measurements-of excited H-3(4) and F-3(4) states, and a study of Tm3+:Tm3+ energy transfer. The cross relaxation H-3(4), H-3(6) --> F-3(4), F-3(4) responsible for the pumping of level F-3(4) and the laser transition at 1800 nm (F-3(4) --> H-3(6)), as well as the energy migration H-3(4), H-3(6) --> H-3(4), H-3(6) processes are studied in terms of the microscopic parameters of energy transfer C-da and C-dd obtained by the Kushida model of multipolar interactions and by a rate equation treatment of the dynamics of levels F-3(4) and H-3(4). From this treatment it was possible to simulate level F-3(4) temporal evolution curves for different Tm3+ concentrations, leading to results that are in excellent agreement with experimental ones. All the samples studied in the work present positive optical gain coefficients for excitation densities higher than 12 kW cm(-2) indicating the potentiality of GaLaS:Tm3+ glass as a mid-infrared laser active medium.