Hybrid Bound States in Continuum for Enhanced Sensing and Light Manipulation

Abstract: Light can be influenced by permittivity changes in optical resonators, enabling optical sensors, modulators and optical switches. It is straightforward that a high relative change of intensity per change of permittivity, labelled as figure of merit FOM*, is sought. This FOM* is proportional to the product of quality factor Q and sensitivity S of the resonator. In known resonators, an increase of Q is always accompanied by a decrease of S leaving FOM* constant. Hybridization of resonators has always been reported to lead to an averaging of their performance, only. Here, we theoretically show that light diffracted by bound states in continuum (BICs) breaks that rule. Its FOM* is strongly increased by hybridization, thus outperforming both purely dielectric or plasmonic BICs. We suggest a symmetric waveguide geometry for realising topologically protected hybrid BICs, develop a polymer based fabrication technology and show first experimental evidence of hybrid BICs.