4 J unstable cavity direct-liquid-cooled disk laser

A quasi-continuous unstable laser resonator with a direct-liquid-cooled method is developed. The refractive index matching liquid and 10 pieces of 45 m m × 18 m m × 2 m m Nd:YLF crystals with different doping levels are used as coolant and gain media, respectively. The stepped transmittance convex and concave mirrors are used as the cavity mirror to construct the unstable resonator. Experimentally, the flow rate of the coolant is 5 m/s and the effective amplification rate of the unstable cavity is 1.3. A quasi-continuous output single-pulse energy of 4 J is obtained with the optical-optical efficiency of 20%, the repetition frequency of 250 Hz, the wavelength of 1047 nm, and the beam quality factor β of 10 approximately. By introducing an adaptive optical (AO) system into the cavity, a higher power and higher beam quality laser is expected to be achieved.