High-repetition-rate passively Q-switched Nd:GdTaO₄ 1066 nm laser under 879 nm pumping

We report an 879 nm laser diode directly pumped passively Q-switched Nd:GdTaO₄ laser at 1066 nm. The continuous-wave output power at 1066 nm reaches 5.6 W under an incident pump power of 12.8 W, corresponding to an optical-to-optical efficiency of 43.8% and a slope efficiency of 48.0%. By using Cr⁴⁺:YAG as the saturable absorber, passively Q-switched laser operation is conducted, yielding a highest pulse repetition frequency of 185 kHz and a maximum average power of 3.6 W. The shortest pulse width of 15.2 ns is achieved with a peak power of 2.34 kW at 33.7 kHz. The beam quality factors at the maximum average output power is measured to be M_x ² = 2.2, M_y ² = 1.5 by using knife-edge method. The thermal focal length and internal loss for Nd:GdTaO₄ crystal is also investigated.