Nonlinear Optics in a Diamond Micro- and Nano-Cavities

Resonant recirculation of light in optical microcavities can greatly enhance light-matter interactions. In this work, we demonstrate cavity-enhanced second-harmonic and third-harmonic generation from a single-crystal diamond microdisk. The presence of crystal defects – here nitrogen-vacancy centers – breaks the inversion symmetry of the diamond crystal, allowing for observation of the otherwise forbidden second-harmonic generation. We further show that the photon emission follows a clear dependency with cavity detuning of both the pump and emission modes, a clear indication of a doubly-resonant configuration.