Coupling-assisted quasi-bound states in the continuum in heterogeneous metasurfaces

TL;DR

This paper introduces a universal coupled mode theory-based approach to realize bound states in the continuum (BIC) and quasi-BIC in heterogeneous metamaterials, demonstrated through simulations and experiments with CW and SRR structures.

Contribution

It extends BIC concepts to heterogeneous structures using a universal physical parameter framework, enabling new design possibilities.

Findings

BIC occurs when resonant frequencies and phases are equal in structures.

Slight variations in frequency and phase produce quasi-BIC states.

Experimental results confirm the theoretical predictions.

Abstract

In this paper, we present a Bound states in the continuum (BIC) metamaterial in heterogeneous structures based on the universal coupled mode theory. We find the more general physical parameters to represent BIC, which are the resonant frequencies and corresponding phases of metamaterial structures. Therefore, BIC metamaterial comes from the equal value of the resonant frequencies and phases of metamaterial structures which are not only for homogeneous structures. Meanwhile if slightly vary one of metamaterial structure's resonant frequency and phase by varying geometry, we can obtain the quasi-BIC instead of broken symmetry of homogeneous structures. In this paper, we provide the BIC and quasi-BIC with one example of two heterogeneous structures which are cut wire (CW) and Split-Ring Resonator (SRR), to widely extends the metamaterial BIC beyond common sense. Furthermore, we demonstrate the simulation results and experimental results to proof our idea.