Diamond bullseye antennas for enhanced quantum collection efficiency*

Color centers in wide bandgap materials such as diamond and silicon carbide are excellent candidates for quantum technologies due to their spin initialization, manipulation, and readout. Unfortunately, the host materials for these applications present high intrinsic optical indexes, limiting photon collection due to total internal reflection. In this work, we demonstrate improved collection efficiencies from these color centers with the use of photonic structures, paving the way for efficient communication and sensing protocols. Specifically, we show the fabrication of bullseye antenna resonators etched into thin diamond membranes improve signal collection via Purcell enhancement while simultaneously realizing higher collection efficiency into low NA objectives. The radius and pitch of these structures are numerically optimized to be in resonance with the emission wavelengths of the integrated color centers e.g., nitrogen, silicon, and germanium-vacancy centers. We also experimentally demonstrate that the resonances can be realized across a broad range of wavelengths in the visible and near-infrared. Fabrication of these photonic cavities is shown to be tailorable, enabling flexibility and ease of integration with the chosen emitters.