High-performance sensor based on bound states in the continuum

The bound states in the continuum (BIC) were first discovered by von Neumann and Wigner in quantum mechanics. It was subsequently identified in photonics. BIC represents an embedded eigenmode that can perfectly confine light. The optical resonators that support this mode can have very large field enhancements and infinite Q factor in theory. Considering these advantages as well as the negligible heat generation, the dielectric metasurface using BIC mode is a more promising platform for sensor applications. Nevertheless, their performance is quite constrained by factors such as inevitable fabrication imperfections, the array size of chips, and up-down symmetry breaking. To mitigate these challenges, we construct merging BICs with the accessible electric field distribution in a Lieb lattice. Meanwhile, we integrated this system with a lateral photonic crystal mirror to enhance its performance in compact conditions. The design we propose remains robust, sustaining a very high Q factor (up to 105) even when the up-down symmetry is broken, which provides a potential platform for optical trapping and biomedical sensing applications.