Metallic and All‐Dielectric Metasurfaces Sustaining Displacement‐Mediated Bound States in the Continuum

Abstract

AbstractBound states in the continuum (BICs) are localized electromagnetic modes within the continuous spectrum of radiating waves. Due to their infinite lifetimes without radiation losses, BICs are driving research directions in lasing, non‐linear optical processes, and sensing. However, conventional methods for converting BICs into leaky resonances, or quasi‐BICs, with high‐quality factors typically rely on breaking the in‐plane inversion symmetry of the metasurface and often result in resonances that are strongly dependent on the angle of the incident light, making them unsuitable for many practical applications. Here, an emerging class of BIC‐driven metasurfaces is numerically analyzed and experimentally demonstrated, where the coupling to the far field is controlled by the displacement of individual resonators. In particular, both all‐dielectric and metallic as well as positive and inverse displacement‐mediated metasurfaces sustaining angular‐robust quasi‐BICs are investigated in the mid‐infrared spectral region. Their optical behavior with regard to changes in the angle of incidence is investigated and experimentally shows their superior performance compared to two conventional alternatives: silicon‐based tilted ellipses and cylindrical nanoholes in gold. These findings are anticipated to open exciting perspectives for bio‐sensing, conformal optical devices, and photonic devices using focused light.