We demonstrate cavity-enhanced second- and third-harmonic generation from a diamond microdisk containing nitrogen-vacancy centers. The photon emission follows a clear dependency with detuning of both the pump and emission modes, indicating a doubly-resonant configuration.
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.
Diamond constitutes a promising material platform for a myriad of photonic applications. In this work, we demonstrate several novel nonlinear optical phenomena in fibre-taper coupled diamond micro and nanocavities. Central to these observations are ensembles of nitrogen-vacancy (NV) centres native to the diamond devices. We first show photoinduced modifications of second-harmonic generation (SHG) from a microdisk, and demonstrate, for the first time, that the strength of the SHG strongly depends on the charge state of the NV centres. Illuminating the microdisk with a green laser quenches the SHG signal. Removing the green laser recovers the original SHG signal, allowing for deterministic optical switching of the device’s χ(2). We next show strong photorefractive blue-shifting of the resonance frequency in a diamond photonic crystal cavity. The total frequency shift exceeds the intrinsic linewidth, corresponding to a fractional change in refractive index of ∼ −10−4.