Coaxially end-pumped passively Q-switched orthogonally-polarized dual-crystal Tm,Ho:LLF laser at 2050 nm and 2052 nm

A coaxially end-pumped passively Q-switched orthogonally-polarized dual-wavelength laser at 2 µm with dual Tm,Ho:LuLiF₄ (LLF) laser crystals as the gain media and a Cr:ZnS crystal as the saturable absorber is reported for the first time, as far as we know. The maximum average output powers of 63.4 mW at 2050nm in P-polarization direction and 43.6 mW at 2052nm in S-polarization direction were obtained at the absorbed pump power of 2.21 W, and the corresponding pulse widths, single energies and peak powers of the P-polarization state and S-polarization state were 54.6 ns, 6.1 µJ, 111.8 W and 50.9 ns, 4.3 µJ, 83.9 W, respectively. The pulse repetition frequencies of the P-polarization state and S-polarization state maintained equality and changed from 2.61 kHz to 10.22 kHz with increasing the absorbed pump power from 0.67 W to 2.21 W. The present results provide a method of achieving passively Q-switched orthogonally-polarized dual-wavelength laser at 2 µm by adopting dual Tm,Ho:LLF laser crystals.