Dispersion engineering of crystalline resonators via microstructuring

Record quality factors and large selection of materials make optical crystalline resonators attractive for emerging areas of research. While basic parameters of a resonator are important, fine-tuning of its mode frequencies can dramatically improve efficiency of nonlinear optical interactions. However, dispersion engineering of high-quality crystalline resonators has not been reported due to limitations of existing methods. Moreover, spectral and dispersion engineering often cannot be effectively combined in demonstrated approaches. Here, we show by numerical modeling that dispersion can be engineered by microstructuring the light-guiding boundary of a resonator that is built around an axially symmetric substrate. We experimentally demonstrate ultrahigh-quality-factor (1 x 10(8)) crystalline resonators capable of generating Kerr combs with expanded bandwidth. The new approach enables spectral and dispersion engineering flexibility in any resonator with axial symmetry that can support a photonic belt structure. (C) 2015 Optical Society of America