We grew several thulium- (Tm-) doped crystals and determined the concentration of the incorporated Tm using proton-induced x-ray emission. Polarized absorption and emission spectra of were investigated, allowing the stimulated-emission cross section to be estimated with the reciprocity method and the Fuchtbauer–Ladenburg equation. We report lifetime measurements of each of the transitions from the to multiplet and relate them to the radiative lifetime. In view of these results we revisit the question of as a prospective laser material for laser emission at 1.8 μm in the presence of losses and determine the pumping threshold and slope efficiency for a typical resonator geometry.
© 1998 Optical Society of America