Resonantly pumped 2.118 μm Ho : YAP laser Q-switched by a Cr2+: ZnS as a saturable absorber

A passively Q-switched Ho : YAP laser operating at room temperature with a Cr²⁺ : ZnS saturable absorber pumped with a continuous wave Tm : YAP laser was demonstrated. A comparative analysis of laser performances with different output couplers was first carried out. Using Cr²⁺ : ZnS as the saturable absorber, the maximum average output power 6.1 W was obtained at the pump power of 32.1 W, with a pulse repetition frequency of 7.5 kHz and a pulse width of 93.6 ns. The output central wavelength of the passively Q-switched laser shifted to 2111.7 nm from a continuous wave operation of 2118.7 nm. The beam quality factor M ² was 1.4 on the x-axis and 1.6 on the y-axis with diffraction limited beam quality.