High-power waveguide resonator second harmonic device with external conversion efficiency up to 75%

We report on a highly efficient waveguide resonator device for the production of 775 nm light using a titanium indiffused LiNbO₃ waveguide resonator. When scanning the resonance, the device produces up to 110 mW of second harmonic power with 140 mW incident on the device—an external conversion efficiency of 75%. The cavity length is also locked, using a Pound–Drever–Hall type locking scheme, involving feedback to either the cavity temperature or the laser frequency. With laser frequency feedback, a stable output power of approximately 28 mW from a 52 mW pump is seen over one hour. (paper)