Broadly tunable continuous wave 2.3-µm Tm 3+ :tellurite bulk glass laser

We report, for the first time to the best of our knowledge, a continuous wave trivalent thulium ion (Tm 3+ )-doped bulk glass near 2.3 µm. In the experiments, a bulk Tm 3+ -doped tellurite glass with the stoichiometric composition of 74TeO 2 –12ZnO–4La 2 O 3 –10Na 2 O (Tm 3+ :TZLN) was used. Lasing operation was achieved by using an x-fold cavity at the free-running wavelength of 2303 nm. The maximum slope efficiency of 6.2% was obtained with respect to the absorbed pump power with a 1% transmitting output coupler. In this case, as high as 100-mW output power was generated with 2.2 W of absorbed pump power. Continuous, broad tuning was achieved from 2233 nm to 2400 nm. The excitation spectrum of the laser was also investigated and 2.3-µm lasing was obtained by varying the pump wavelength over the 773–809-nm range. The absorption cross section was determined to be 4.4 × 10 −21 cm 2 , based on open-aperture z-scan measurement. By using the laser efficiency data, the emission cross section of the Tm 3+ :TZLN glass was further determined to be 1.3 × 10 −20 cm 2 at 2.3 µm.