The generation of tunable coherent uv radiation by sum frequency mixing, in potassium pentaborate, the outputs of two tunable N2 pumped dye lasers has been investigated. Tunable radiation extending from 217 nm to 208 nm has been generated in this manner. A conversion efficiency of 2.5 × 10-4 is observed at input powers of ~2 kW in each laser beam. Improved refractive index data for potassium pentaborate are also presented.
F. B. Dunning and R. E. Stickel,Jr., "Sum frequency mixing in potassium pentaborate as a source of tunable coherent radiation at wavelengths below 217 nm," Appl. Opt. 15, 3131-3134 (1976)