2.0 μm emission properties and energy transfer of Tm 3+ /Ho 3+ -codoped tellurite glass

This paper reports on spectroscopic properties and energy transfer of Tm 3+ /Ho 3+ -codoped ZnO-WO 3 -TeO 2 glass upon excitation of 808nm diode laser. The J-O strength parameters， spontaneous emission probability and radiative lifetime of Ho 3+ were calculated using Judd-Ofelt theory. The absorption cross-section and stimulated emission cross-section were also investigated. Our result indicates that the highest gain of 2.0 μm emission, which comes from 5 I 7 to 5 I 8 transition of Ho 3+ , might be achieved from the glass at the rare-earth ion concentration of 0.5 mol% of Tm 2 O 3 and 0.15 mol% of Ho 2 O 3 . It is found that coefficients of the forward Tm 3+ →Ho 3+ energy transfer is about 18 times that for the backward Tm 3+ ←Ho 3+ energy transfer. The calculated fluorescence lifetime of the 5 I 7 level of Ho 3+ is 3.9 ms and the emission cross section of the 5 I 7 → 5 I 8 transition of Ho 3+ exhibits a maximum of 9.15×10 -21 cm 2 at 2027 nm. We also found that Tm 3+ /Ho 3+ -codoped tellurite glass is a promising host material for potential 2.0 μm laser by comparing the quantum efficiencies, the values of σ e × τ m and gain coefficients of fluoride and heavy metal oxide glasses respectively.