Abstract

There has been considerable recent progress in the operation of tunable uv solid-state lasers based on trivalent cerium doped fluoride crystals^1-2, most notably Ce.LiCAF, Ce:LiSAF and Ce:LiLuF. To date most reported operation has been restricted to below 10 Hz pulse repetition frequency (PRF), partly due to restrictions in the operating PRF of the pump laser (KrF excimer or frequency quadrupled Nd:YAG). Frequency doubled copper vapour lasers³ (CVLs) operate al kilohertz PRFs (4-24 kHz) and can produce three uv wavelengths namely: 255 nm (second harmonic of the CVL green). 289 nm (second harmonic of the yellow) and 271nm (sum-frequency). These uv wavelengths efficiently access the pump bands for Ce³⁺ doped fluoride crystals, in particular 271 nm corresponds to the peak of the σ-polariscd absorption in the LiCAF and LiSAF hosts, and 289 nm matches the absorption peak for LiLuF. In all cases, these pump wavelengths are longer than those employed to date for cerium doped solid stale lasers, thus potentially minimising the formation of transient and permanent colour centres that often limit performance at high PRF. As well as high PRF operation and uv wavelength flexibility, the frequency doubled CVL also offers high beam quality tor efficient longitudinal pumping geometries.

© 1996 IEEE