Generation of coherent cw radiation tunable from 211 nm to 216 nm.

Many spectroscopic studies require a source of coherent cw radiation tunable in the uv. Continuous wave radiation in the 257-360-nm range has been generated by sum frequency mixing, in potassium dihydrogen phosphate (KDP) and its isomorphs, selected output lines from an argon or krypton ion laser with the output of a cw dye laser. Recent studies of mixing in potassium pentaborate (KB5) using pulsed laser systems however suggested that cw radiation at wavelengths considerably shorter than 257 nm could be generated by mixing, in an angle-tuned KB5 crystal, with the uv output lines of an ion laser. The input wavelengths required to produce phase matched sum frequency mixing with the uv lines of an argon ion laser, calculated by use of the data obtained using pulsed laser systems, are shown in Fig. 1, as a function of the angle between the direction of propagation of the interacting beams and the b axis of the crystal, for angle tuning in both the ab and bc planes. It is evident from Fig. 1 that, with input wavelengths readily available from cw dye laser systems, tunable uv radiation can be generated over a considerable wavelength range which extends below that obtainable by direct second harmonic generation. The present Letter reports the generation of tunable cw radiation in the 211-216-nm range by mixing in KB5.