High power Q-switched Tm3+, Ho3+-codoped 2 µm fiber laser and application for direct OPO pumping

A bidirectional 793 nm diode-pumped actively Q-switched Tm3+, Ho3+-codoped silica polarization maintaining (PM) double-clad (DC) fiber laser is reported. An average output power of 55 W with 100 ns pulse width, 200 kHz repetition rate and 2.09 μm wavelength is obtained with this fiber laser. To the best of our knowledge, this is the highest ever demonstrated average output power emitted from a Q-switched single oscillator 2 μm fiber laser. Thanks to end-caps fusion-spliced on both fiber tips, this fiber laser source is presenting good beam quality factors (M² < 1.7) and no thermal-induced damaging is observed at 55 W average output power. Further power scaling of the laser is only pumppower- limited in the range of the total available pump power in this setup (180 W). Direct OPO ZnGeP2 (ZGP) pumping with this fiber laser has been performed for optical nonlinear conversion in the mid-IR regime. More than 8 W of average output power has been generated in the 3-5 μm band.