Doubly resonant optical parametric oscillator formed by index matching cavity mirrors directly onto an uncoated...

We demonstrate the use of index-matching fluid to contact cavity mirrors directly onto an uncoated LiB(3)O(5) crystal to form a compact, stable resonator for use as an optical parametric oscillator. Specifically, we report on the characteristics of a continuous-wave, doubly resonant, type II phase-matched LiB(3)O(5) optical parametric oscillator formed in this way. Using a single-frequency argon-ion pumping laser operating at 514.5 nm, we measured a pump power threshold of approximately 100 mW and a total external conversion efficiency of approximately 15%. By altering the crystal temperature under noncritical phase matching, we measured coarse frequency tuning over approximately 36 THz, limited only by mirror coating bandwidths. We discuss also the transverse and longitudinal mode properties of the optical parametric oscillator outputs.