Energy transfer and 1.48 μm emission properties in chalcohalide glasses doped with Tm3+and Tb3+

Emission characteristics and energy transfer in chalcohalide glasses doped with Tm3+ and Tb3+ were investigated and their potential as S-band fiber-optic amplifiers was evaluated. Upon the addition of CsBr into sulfide glass, intensity of the 1.48 μm emission (3H4 → 3F4 transition) from Tm3+ increased. At the same time, the lifetime of the 3H4 level increased to 1.2 ms, approximately eight times longer than the value obtained from sulfide glass. Quantum efficiency of the transition also increased to approximately 90%. Cross relaxation between the 3H4 and 3F4 levels was significant when Tm3+ ion concentration exceeded 0.2 mol%. Population density of the 3F4 level in Tm3+ decreased upon the addition of Tb3+ due to the Tm3+:3F4 → Tb3+:7F0,1,2 energy transfer. Population inversion became possible when Tb3+ concentration reached 0.11 mol%.