Continuous tuning of double resonance-enhanced second harmonic generation in a dispersive dielectric resonator.

We report a method for continuous tuning of ultraviolet (UV) radiation of second harmonic generation in a dispersive beta barium borate (BBO) whispering gallery mode resonator. The doubly resonant enhancement in a high quality factor resonator leads to high conversion efficiency but the resonator dispersion severely limits practical tuning range. By simultaneously varying the temperature of the resonator and the mechanical stress on the disk, we were able to experimentally demonstrate a continuous tuning range of 70 GHz of 317 nm laser light at 0.74%/mW conversion efficiency. The achieved tuning range is at least 35 times wider than that by either mechanical or temperature tuning alone.