Birefringent filter tuning and linewidth narrowing in a mode-locked pumped deep-ultraviolet continuous-wave Ce:LiCAF Laser

There is a large variety of applications for tunable ultraviolet (UV) lasers, and their demand is rising continuously. However, many of the available UV laser systems are complex as they are typically based on nonlinear frequency conversion of tunable visible or infrared laser sources. Our approach is to generate tunable deep-UV light directly from a solid-state laser crystal that lases in the ultraviolet. The crystal we are using is cerium doped LiCaAlF6 (Ce:LiCAF), which features a maximum gain at 290 nm and an overall gain bandwidth of 35 nm from 280 nm to 315 nm. With an absorption peak at 260 nm to 270 nm, Ce:LiCAF can be pumped conveniently with the fourth harmonic of Nd doped solid-state lasers (λp = 266 nm). We developed a laser system that can be used to generate short laser pulses with frequencies up to 1.103 GHz when set-up for rational-harmonic mode-locking [1], or continuous-wave (CW) output when pumped asynchronously [1,2]. We now report results for birefringent filter tuning and linewidth narrowing of an asynchronously pumped CW cerium laser.