Design of embedded square nanoholes Si₃N₄ metasurface sensor in the visible light spectrum

Abstract

The phenomenon of Bound States in the Continuum (BICs), recognized for its remarkable ability to suppress radiation loss and achieve ultra-high quality factors (Q-factors), has garnered significant attention in recent years, particularly in the study of metasurfaces. BICs enables resonant modes with exceptional Q-factor, presenting immense potential for applications in the design of optical devices. This study introduces an asymmetric metasurface designed to generate quasi-bound states in the continuum (Q-BICs) modes, highlighting the critical influence of structural geometry and intentional symmetry breaking in achieving Q-BICs and enhancing their Q-factors. By carefully tuning the structural parameters of metasurface units, BICs and Q-BICs modes demonstrate outstanding performance in fields such as optical sensing, nonlinear optics, and optical modulation. These modes can achieve Q-factors up to 9644 and sensitivity of 127 nm/RIU. Metasurfaces based on BICs offer innovative approaches for design of next-generation high-performance optical devices, with promising applications in biological sensing, optical filters, and energy-efficient optical communication systems.