Optimization of resonant ring cavity for fourth-harmonic generation of a Nd:YLF laser

Summary form only given. We have constructed a single ring to resonantly double an 18-W Nd:YLF mode-locked laser and re-double the stored green beam to produce a nearly-diffraction-limited ultraviolet (UV) beam of 4.2 W at 263 nm. The IR output of the pump laser is coupled to the slave cavity via a mode-matching telescope, which produces a waist inside the first doubling crystal, a 15-mm-long non-critically phased matched lithium triborate (LBO) crystal. The ring consists of six mirrors, with two 25-cm radius of curvature mirrors enclosing each nonlinear crystal, and two plane mirrors, which fold the ring. The second SHG crystal is a type I critically phased-matched /spl beta/-barium borate (BBO) crystal that converts the 526-nm beam into 263-nm light, which exits the cavity through one of the 25-cm ROC mirrors. The unconverted 526-nm light is re-circulated back to the LBO crystal where it is coherently enhanced by the next input IR pulse.