[Mid-infrared emission and multiphonon relaxation in Tm3+-doped Ge-Ga-Se glasses]

A series of chalcogenide glasses based on the composition Ge30 Ga5 Se65 (at. %) doped with the different Tm3+ ions were synthesized by melt-quenching technique. The refractive indexes, Raman spectra, absorption spectra, near-and mid-infrared fluorescence, and lifetimes of glass samples under 800 nm laser excitation were measured. The intensity parameters omega(i) (i = 2, 4, 6), transition probabilities, branching ratios and radiative lifetimes have been predicted for Tm3+ ions in samples by using the Judd-Ofelt theory. The near-infrared emission spectra at 1.23, 1.48 and 1.8 microm were observed and their quantum efficiencies were evaluated respectively in glass doped with 1 Wt% Tm(3+)-ions under 800 nm excitation. The mid-infrared fluorescence spectra were investigated with the different Tm3+ ion concentration under 800 nm excitation. The multiphonon relaxation rate of Tm3+ : 3 H5 --> 3F4 by the measured and calculated lifetimes, and the relative parameters of W(0) and a in Ge30 Ga5 Se65 glass were evaluated. Results show that the multiphonon relaxation rates were significantly lower than other glasses due to the lower maximum phonon energy, so the selenide glasses are promising as host materials for doping by rare earth ions and for preparation of mid-infrared optical elements.