All-solid-state, continuous-wave, 195 nm light generation in β-BaB2O4

We demonstrated, for the first time, an all-solid-state, continuous-wave laser operating at less than 200 nm. It was based on the doubly-resonant sum-frequencymixing of a frequency-quadrupled Nd:YAG laser at 266 nm with a Ti:Sapphire laser at 745 nm. A Brewster-cut, Czochralski-grown, beta-barium-borate (BBO) crystal was employed to construct low loss resonators. Generated power inside BBO crystal was 3 mW, which is to our knowledge the highest power of continuous wave light below 200 nm. Bandwidth of 0.84 pm at about 195 nm is suited for high-resolution microscope. Environmental contamination control will be necessary for long term operation.