Passively Q-switched Diode-Pumped Thulium Laser at 2305 nm

In recent years, there is a growing interest to thulium (Tm) lasers operating at ~2.3 µm according to the 3 H 4 → 3 H 5 transition [1] , [2] . Such short-wavelength infrared emission is of practical importance for sensing of atmospheric species (HF, CO, CH 4 and H 2 CO). Guillemot et al . reported on a continuous-wave (CW) Tm:KY 3 F 10 laser delivering 0.84 W at 2331-2346 nm with a slope efficiency of 53.8% [1] . Canbaz et al . developed a Kerr-lens mode-locked Tm:LiYF 4 laser emitting femtosecond (514 fs) pulses at 2303 nm [2] . However, so far, little attention was paid to passively Q-switched (PQS) Tm lasers at ~2.3 μm. In the present work, we report on a diode-pumped PQS Tm:LiYF 4 laser operating on the 3 H 4 → 3 H 5 transition and delivering stable pulsed output without any colasing at ~1.9 μm.