Watt-level actively Q-switched intracavity frequency-doubled Pr:LiYF ₄ laser at 261 nm

We report on a watt-level nanosecond 261-nm laser from an acousto-optically Q-switched visible Pr:YLF laser through intracavity second-harmonic generation (SHG). By implementing direct water-cooling for thermal management and an intracavity mirror for double-passing nonlinear crystal, a maximum average power of 1.03 W has been achieved at a repetition rate of 40 kHz, which, to the best of our knowledge, is the highest power ever reported from an intracavity-frequency-doubled pulsed, short-wave ultraviolet (UV-C) laser at 261 nm. Decreasing the repetition rate to 20 kHz, a single-pulse energy of 43.4 µJ can be obtained. This approach with a robust and simple structure demonstrates a promising way toward the direct generation of high-power UVC laser pulses.