Mode-selective toroidal mirrors for unstable resonator planar waveguide and thin slab solid-state lasers

In this paper, two new fabrication methods are developed for highly curved toroidal laser resonator mirrors based on laser micromachining of cylindrical substrates that already have the large lateral curvature R_T provided by conventional polishing. These mirrors are produced by a two-step CO₂ laser machining process with high resolution ablative laser cutting and then laser polishing, or by vaporization of silica in the CO₂ laser smoothing process at higher than usual power. The produced mirrors are with R_T = 32 mm and 15 mm radius of curvature and 14 mm lateral length for use with the 200 mum core height Nd:YAG and a 150 mum core Yb:YAG planar waveguide laser respectively.