Judd–Ofelt analysis and luminescence property of Tm3+ in Ga2S3–GeS2–La2S3 glasses

Glasses with the compositions of 60GaS3/2 · 10GeS2 · 27LaS3/2 · 3TmS3/2 and 60GaS3/2 · 10GeS2 · 29.7LaS3/2 · 0.3TmS3/2 in mol% were prepared and their luminescence properties were measured. Judd–Ofelt analysis was performed for the 3 mol% Tm3+-doped glass. The Ω2 parameter was larger than those of fluoride glasses, while the Ω4 and Ω6 were comparable with those of oxide and fluoride glasses. Radiative transition rates of excited levels and branching ratios were calculated using the Ω parameters and reduced matrix elements. The radiative transition rates were about 10 times larger than those of oxide and fluoride glasses because of the larger refractive index of the sulfide glass. Decay curves of the emissions from 3F3(+3F2) (695 nm) and 3H4 (798 nm) levels were measured for the 0.3 mol% Tm3+-doped glass. Emission quantum efficiencies were 13±1% and 93±7% for the 3F3 and the 3H4 levels, respectively. Emission spectra in the wavelength range of 1000–1700 nm were also observed by the excitation of the 3F3 and 3H4 levels.