Development of infrared fiber lasers at 1555 nm and at Er-doped zinc-tellurite glass fiber

We manufactured and characterized a low-loss gain fiber based on high-purity TeO2 -ZnO-La2O3-Na2O undoped glass for 100-mu m cladding and TeO2 -ZnO-La2O3-Na2O glass for 10-mu m core doped with 0.24 mol% Er2O3. To confirm that the produced fiber is a promising active element for the infrared range, we demonstrated experimentally broadband laser amplification and CW generation at the I-4(13/2) -> I-4(15/2) transition at 1555 nm with a single-mode diode pump at 975 nm at the I-4(15/2) -> I-4(11/2) transition. We developed a numerical model calibrated to the experimental data for prediction and optimization of laser characteristics in schemes with different parameters. The model describes single- wavelength lasing as well as dual-wavelength cascade lasing at 1555 nm and 2800 nm. It was shown numerically that for the optimized parameters, the maximum slope efficiency at 2800 nm at the I-4(11/2) -> I-4(13/2) transition can reach similar to 20%. The maximum calculated efficiency at 1555 nm exceeds 30%.