Enabling strain tuning for cavity-coupled silicon vacancy centers in diamond

The silicon vacancy center (SiV^-) in diamond has emerged as a platform for quantum repeaters due to its bright emission, stability in nanostructures, as well as the long coherence times of its spin state. In particular, it has been integrated into wavelength-scale photonic cavities for realizing high cooperativity (C > 100) spin-photon interfaces as well as electromechanically actuated waveguides for overcoming the inhomogeneous distribution of SiV^- centers via strain tuning. Unfortunately, it is difficult to utilize strain tuning in previously demonstrated hole-based diamond nanocavities, due to the poor overlap between the applicable strain profile and the optical mode maxima where SiVs are located. Here we demonstrate a fishbone-like cavity structure that addresses this problem, enabling a color center platform with complete tuning over the inhomogeneous distribution as well as efficient photon extraction. These cavity designs are fabricated in diamond using a quasi-isotropic etching technique. The reflection spectrum of these optical cavities is characterized and an optical quality factor of 7.6 x 10³ is observed, corresponding to a spin-photon interface with estimated achievable cooperativity of 20.