Dual Bound-States in the Continuum Enabled by Guided-Mode Resonance in Metallic Metasurface

Electromagnetic metasurfaces exhibit remarkable scattering effects that enable precise modulation of electromagnetic waves. Bound-states in the continuums (BICs) are able to confine the electromagnetic energy to a localized region without high radiative losses and therefore exhibit ultra-high quality (Q) factor resonances. This study presents a novel approach to achieving dual BICs within metallic metasurfaces, enabling the confinement of electromagnetic energy with minimal radiative losses and ultra-high factor resonances. We demonstrate that dual quasi-BIC (QBIC) with stable resonance frequencies can be realized by breaking translational symmetry while preserving C<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> symmetry. Importantly, BICs derived from both Fano resonance and electromagnetically induced transparency (EIT) can coexist at distinct frequencies. The design features a dimer structure in the metal metasurface, where the resonance point shows minimal dependence on the shape of the metal sheet. The resonance frequency of the QBIC can be effectively tuned by adjusting the periodicity, while the Q factor is modifiable through changes in the relative positioning of the metal sheets. Our findings indicate significant potential for high-Q factors and exceptional slow-light effects, paving the way for the development of high-performance filters, sensors, and modulators in terahertz applications.