Generation of 90-mW continuous-wave tunable laser light at 280 nm by frequency doubling in a KDP crystal

Laser light at a wavelength of 560 nm from a commercial ring dye laser has been frequency doubled in an external enhancement cavity with a KDP crystal. The cavity employs a new design consisting of only three mirrors, permitting a shorter cavity length as well as compensation for astigmatism and coma. With an input power of ~950 mW of green light, ~90 mW of UV light has been produced. The wavelength of the UV light can be tuned corresponding to +/-3 nm by angle tuning of the crystal, and the optical frequency can be scanned electronically up to +/-10 GHz.