Diamond-Spin Resonant Metasurfaces for Magnetic Field Imaging

Atom-sized quantum sensors constructed from a spin-based qubit system can provide unparalleled sensitivity along with atomic resolution. Among solid-state quantum systems, nitrogen vacancy (NV) centers in diamond stand out with coherence times exceeding one second even at room temperature. These color centers are capable of optically measuring magnetic field, temperature, and electric field, making them a versatile platform for sensing and imaging applications. However, the central challenge lies in suboptimal optical readout restricted by an inefficient spin-photon interface. In this presentation, I will explore resonant nanophotonic strategies that can achieve near-unity optical spin readout fidelity for absorption-based readout. I will discuss various sensing modalities achieved with resonant photonic structures, tailored to applications that require distinct resolvable lateral dimensions and volume-normalized sensitivity. Our research demonstrates that diamond metasurfaces hosing NV ensembles serve as an effective imaging surface for mapping local magnetic field, electric field, and temperature via free-space illumination. They coherently encode information about the local magnetic field (and also other quantities like electric field and temperature) on spin-dependent phase and amplitude changes of near-telecom light, that is suitable for advanced signal processing and computational imaging techniques that rely on phase information. I will first introduce a plasmonic metasurface supporting the Rayleigh-Wood anomaly mode. Subsequently, I will discuss an all-dielectric dual-resonance metasurface. The studied metasurface consists of dimer clusters arranged in a 2D array, coupling with both visible and IR optically active transitions of NV centers – the triplet and singlet state transitions, respectively. We introduce sharp Fano resonances through symmetry breaking, making the mode accessible with free space illumination while maintaining a quality factor exceeding 10⁴. I will explore the effects of resonantly enhanced spin-photon interactions on the steady-state NV dynamics for both IR emission and absorption readout schemes. Furthermore, I will discuss design criteria to consider at different operating temperatures, addressing the challenges of operating in bad-emitter versus bad-cavity regimes. I will also show that we can improve spatial imaging resolution by maximizing the lateral localization of the mode with a slow-light effect. Spin-coupled resonant nanophotonic devices are projected to particularly benefit applications that require high readout fidelities from spins in a confined volume. The projected performance makes the studied quantum imaging metasurface appealing for the most demanding applications such as imaging through scattering tissues and spatially resolved chemical NMR detection.