Tunable continuous-wave laser operation of Tm³⁺ ion doped tellurite glass near 2 μm

We provide an experimental investigation of the absorption saturation and 1.9-μm lasing characteristics of a bulk Tm³⁺:TZLN glass with the host composition of 74TeO₂–12ZnO–4La₂O₃–10Na₂O. By using a z-scan saturation measurement, the absorption cross section at 794 nm was determined to be 5×10⁻²¹cm², in reasonable agreement with the value of 6×10⁻²¹cm² obtained from small-signal transmission measurement. In lasing experiments, double pumping was employed at 794 nm and the bulk Tm³⁺:TZLN glass laser operated at the free running wavelength of 1926 nm. As high as 15.4 mW of continuous-wave output power was obtained with a 2.15% transmitting output coupler at the absorbed pump power of 284 mW. The slope efficiency with respect to the absorbed pump power was 7.1%. By using the threshold and power efficiency data, the stimulated emission cross section was further determined to be 6.8×10⁻²¹cm²at 1926 nm. Finally, continuous tuning of the laser output was demonstrated between 1845 and 1973 nm by using a quartz birefringent plate.