Spectroscopy of thulium-doped tantalum pentoxide waveguides on silicon

The spectroscopic properties and laser operation of thulium-doped tantalum pentoxide (Tm:Ta2O5) waveguides are reported in this paper. Fluorescence ranging from 1600 nm to 2200 nm, corresponding to the 3F4 → 3H6 transition was observed from 3 wt% Tm:Ta2O5 waveguides pumped at a wavelength of 795 nm. Measurements of excited-state lifetime, the emission and absorption spectra, with subsequent calculation of the cross-sections for the deposited films, reveal its potential as a gain medium. Laser operation at a wavelength of 1865 nm was obtained with feedback from the polished end faces alone, demonstrating gain of >9 dB/cm.