The effect of La2O3 in Tm31-doped germanate-tellurite glasses for,2 mm

A germanate-tellurite glass (GeO2-TeO2-K2O-Nb2O5-La2O3) with thulium doping has been investigated for application as a laser material around 2.0 mm regions. Under the 808 nm laser diode pumped, intense 1.8 mm emission is obtained. Based on the absorption spectra, radiative properties are predicted using Judd-Ofelt theory. The maximum value of emission cross-section of Tm31 around 1.8 mm can reach 1.463 10220 cm2, which indicated that the germanate-tellurite glass may provide high gain as a good medium for efficient 1.8 mm laser system. R ecently, Tm31 doped glass has been widely investigated for mid-infrared fiber lasers around 2.0 mm since the transitions of Tm31:3F4R 3H6. Themid-infrared fiber lasers in the 2.0 mmhave generated great interest for its potential applications in several fields, such as medical surgery, remote sensing, eye-safe laser radar, military, and atmospheric pollutionmonitoring in the last decades1–4. Rare–earth thulium ions are often chosen to produce laser radiation at 1.8 mm through the transitions of Tm31:3F4 R 3H6. In this paper, Tm31 has been selected as active ions because the ground state of Tm31:3H6 can be pumped directly by 808 nm commercial laser diodes. Laser emission at 1.8 mm strongly dependents on the efficiency of the energy transfer process among Tm31 ions. In order to obtain high-power infrared emissions from Tm31, the host glass plays an important role