Ultrahigh-Q microcavities in diamond-based photonic crystal slabs

We design extremely flexible, ultrahigh-Q, diamond-based double-heterostructure photonic crystal slab cavities by modifying the refractive index of the diamond. The refractive index changes needed for ultrahigh-Q cavities with Q ~ 10⁷, are well within what can be achieved (Deltan ~ 0.02). The Q is around 30 times larger than previously reported designs in diamond. At the same time, the cavity volumes are still relatively small, at less than two cubic wavelengths. The range of parameters, cavity length and the index changes that enables an ultrahigh-Q is quite broad improving prospects for defect-tolerant quantum architectures.