K₃Sr₃Li₂Al₄B₆O20F: a competitive nonlinear optical crystal for generation of a 266 nm laser

The fourth harmonic generation (FHG) of a Nd:YAG laser using NLO crystals is an effective method to achieve a high-power UV laser at 266 nm. Based on practical application, the growth and application evaluation of K3Sr3Li2Al4B6O20F are systematically performed. The crystals were successfully grown and the wafer and right angle prism were obtained. By using the minimum deviation technique, the refractive index dispersion was accurately measured and fit well with the shortest type I phase-matching wavelength of about 237 nm. Its laser damage threshold is higher than that of BBO. Furthermore, for the first time, the Nd:YAG direct fourth-harmonic laser (266 nm) was successfully output via the wafer of K3Sr3Li2Al4B6O20F. Owing to its excellent comprehensive properties, including non-deliquescence, moderate birefringence, sufficiently large SHG, small walk-off angle, the ability of FHG and higher laser damage threshold, K3Sr3Li2Al4B6O20F is expected to be a promising competitive UV NLO crystal for the generation of a 266 nm laser.