Microcavity Sensor Enhanced By Spontaneous Chiral Symmetry Breaking

An optical microcavity provides a prominent platform for single-nanoparticle detection with ultrahigh sensitivity. Recently, microcavity sensors working at the exceptional point have caught great attention due to their ability to enhance sensitivity, but suffer from simultaneously amplified noise. Here, we propose employing a nonlinear microcavity to enhance the sensitivity of single-nanoparticle detection based on spontaneous chiral symmetry breaking. It is found that sensors operating at the symmetry-breaking threshold experience a gigantic enhancement in sensitivity, which is caused by the square-root response to perturbation in a lossless microcavity. Through the analysis for a realistic microcavity, a 30-fold sensitivity enhancement is demonstrated by working at the threshold, and the enhancement is also confirmed by numerical simulation. Furthermore, the noise performance is analyzed to be superior in thermorefractive noise and quantum noise performance in comparison to a conventional microcavity-sensing scheme. Merging the spontaneous chiral symmetry-breaking effect with practical sensing applications, the results pave a universal way for high-performance microcavity sensing with enhanced sensitivity and reduced noise.