Ultrahigh Q-Guided Resonance Sensor Empowered by Near Merging Bound States in the Continuum

Bound states in the continuum (BICs) have attracted a lot of interest in the field of nanophotonics, and provide an important physical mechanism to realize high quality (Q) factor resonance. However, in practice, manufacturing error will greatly affect the Q factor. In this paper, we propose an asymmetric metasurface supporting near merging BIC under normal incidence. Such near merging BIC can achieve a higher Q factor (>10(7)) than common structures (Q similar to 10(5)) with the same degree of asymmetry in the structure. Moreover, the near merging BICs also show higher surface sensitivity than other resonant modes. Our work provides a promising approach for the realization of a high-performance biosensing platform.