Random Silicon Micromirrors for Enhanced Emission Rate and Spin Readout Contrast of NV Centers

ABSTRACT

The nitrogen‐vacancy (NV) center in diamond exhibits spin‐dependent optical response at room temperature, making it a driving force in quantum computing, memory, and sensing. In practice, shot‐noise magnetic sensitivity is often constrained by very low collection efficiency, dephasing, and spin contrast, which calls for broadband emission enhancement. Here, we present broadband engineering of the NV center emission using a random array of silicon (Si) micromirrors, acting as nanocavities. We observe broadband emission enhancements, increased spin‐readout contrast, and reduced linewidth, thereby enhancing magnetic sensitivity for an NV‐based quantum sensor. The experimental and simulation results demonstrate broadband Purcell enhancement, resulting in a two‐fold reduction in the emission lifetime. We even observe a stronger lifetime reduction, exceeding four‐fold, accompanied by an intensity enhancement of more than ten‐fold. An improved signal‐to‐noise ratio in the spin readout contrast is observed with an eight‐fold improvement in magnetic sensitivity for NV centers coupled to Si micromirrors. The results confirm that random Si micromirrors demonstrate a practical, fabrication‐tolerant route to achieve broadband emission enhancement and more sensitive quantum sensors.