Enhancing the Sensitivity of Frequency and Energy Splitting Detection by Using Exceptional Points: Application to Microcavity Sensors for Single-Particle Detection

Several types of sensors used in physics are based on the detection of splittings of resonant frequencies or energy levels. We propose here to operate such sensors at so-called exceptional points, which are degeneracies in open wave and quantum systems where at least two resonant frequencies or energy levels and the corresponding eigenstates coalesce. We argue that this has great potential for enhanced sensitivity provided that one is able to measure both the frequency splitting as well as the linewidth splitting. We apply this concept to a microcavity sensor for single-particle detection. An analytical theory and numerical simulations prove a more than threefold enhanced sensitivity. We discuss the possibility to resolve individual linewidths using active optical microcavities.