Research of LD-pumped passively Q-switched Yb:YAG thin disk laser

Using 940 nm diode laser as pumping source, a passively Q-switched Yb:YAG thin disk laser by Cr⁴⁺:YAG was realized. The Yb:YAG disk with 500 μm thickness was employed, the Yb³⁺ atom fraction is 10%. The distribution of temperature in Yb:YAG disk with direct water cooling and SiC cooling with different thickness was theoretically simulated, respectively. The maximum output power of 2.8 W at 1030 nm was obtained with 800 μm SiC cooling, the output power has increased by 40% than that obtained with direct water cooling. The initial transmission of Cr⁴⁺:YAG crystal and the output coupling rate were optimized by Degnan's theory. With the initial transmission of Cr⁴⁺:YAG crystal of 93% and the output coupling rate of 10%, a stable pulse train of 1.95 W averaged output power with a pulse energy of 1.2 mJ and pulse width of 74 ns were obtained with 800 μm SiC cooling. The repetition rate is 1.6 kHz, the slope efficiency is 18.1%, and the beam quality M_x²=1.622, M_y²=1.616.