Absorption-Based Diamond Spin Microscopy on a Plasmonic Quantum Metasurface

Nitrogen vacancy (NV) centers in diamond have emerged as a leading quantum sensor platform, combining exceptional sensitivity with nanoscale spatial resolution by optically detected magnetic resonance (ODMR). Because fluorescence-based ODMR techniques are limited by low photon collection efficiency and modulation contrast, there has been growing interest in infrared (IR)-absorption-based readout of the NV singlet state transition. IR readout can improve contrast and collection efficiency, but it has thus far been limited to long-path length geometries in bulk samples due to the small absorption cross section of the NV singlet state. Here, we propose to amplify the IR absorption by introducing a resonant diamond metallodielectric metasurface that concentrates the optical field near the diamond surface. This "plasmonic quantum sensing metasurface"(PQSM) supports plasmonic surface lattice resonances and achieves desired balance between field localization and sensing volume to optimize spin readout sensitivity. From combined electromagnetic and rate-equation modeling, we estimate a near-spin-projection-noise-limited sensitivity below 1 nT Hz-1/2 per μm2 of sensing area using numbers for present-day NV diamond samples and fabrication techniques. The proposed PQSM enables a new form of microscopic ODMR sensing with infrared readout near the spin-projection-noise-limited sensitivity, making it appealing for the most demanding applications such as imaging through scattering tissues and spatially resolved chemical NMR detection.