Efficient ultraviolet beam generation at 294.5 nm by frequency-quadrupling a LD-pumped actively Q-switched Nd:YAG/SrWO4 Raman laser

An efficient all-solid-state ultraviolet laser at 294.5 nm is demonstrated based on the stimulated Raman scattering and two stages of second-harmonic generation. With a three-mirror cavity, a 2.63 W laser at 589.6 nm with a pulse width of ∼8.5ns and a pulse repetition frequency of 20 kHz is obtained. Employing a BBO crystal as the frequency-doubled medium, a 332 mW UV beam at 294.5 nm with a pulse width of ∼5.8ns is obtained under an incident pump power of 14.12 W; the corresponding conversion efficiency is 2.4% from 808 to 294.5 nm.