A Scalable Method for Cavity‐Enhanced Solid‐State Quantum Sensors

Abstract Photoluminescent color centers in diamond and hexagonal boron nitride (hBN) are powerful nanoscale solid‐state quantum sensors that are explored in a plethora of quantum technologies. Methods for integrating them into macroscopic structures that improve their sensitivity and enable their large‐scale deployment are highly sought after. Here, cavity‐enhanced photoluminescence (PL) of fluorescent nanodiamonds (FNDs) and hBN nanoparticles (NPs) embedded in polymer‐based thin‐film optical cavities on the centimeter scale is demonstrated. The cavity resonances efficiently modulate the spectral PL peak position of nitrogen‐vacancy (NV) centers in FNDs across the NV PL spectrum and lead to an up to 2.9‐fold Purcell‐enhancement of the NV PL decay rate. The brightness of hBN NPs increases by up to a factor of three and the PL decay rate is enhanced by up to 13‐fold inside the cavities. Finally, a 4.8 times improved magnetic field sensitivity of 20 nm FNDs is found in thin‐film cavities due to cavity‐enhanced optically detected magnetic resonance contrast and PL brightness. This study demonstrates a low‐cost and scalable method for the fabrication of quantum sensor‐doped thin‐film cavities, which is an important step toward the development of advanced quantum sensing technologies.