High-quality factor Quasi-BIC mode via selective symmetry-breaking approach in a terahertz metasurface

• Published in: New journal of physics Vol. 26; no. 6; pp. 63024 - 63035
• Main Authors: Kumar Bhowmik, Bhairov, Rohith, K M, John, Samuel, Prabhu, Shriganesh, Kumar, Gagan
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 01.06.2024
• Subjects: Broken symmetry; Fano resoance, BIC; metasurface; Perturbation; Q factors; Symmetry; terahertz; Unit cell
• ISSN: 1367-2630; 1367-2630
• DOI: 10.1088/1367-2630/ad570e

Abstract This study numerically and experimentally presents a novel approach to excite bound state in the continuum (BIC) mode with a high Q-factor in the THz meta-molecule (composition of meta-atoms) system, leveraging a unique method of selective symmetry breaking in a ring-shaped metamolecule system. Unlike conventional strategies that uniformly disrupt the symmetry across all resonators to excite a quasi-BIC mode, this innovative technique targets only half of the unit cell for symmetry perturbation. This selective symmetry breaking minimizes radiative losses and enhances the Q-factor of the quasi-bound states in continuum (quasi-BIC) modes. The selective symmetry breaking is achieved in a ring-shaped metamolecule system by simple radial perturbation. The results depict a notable improvement in the Q-factor, achieving values as high as 107 in simulation, a significant enhancement compared to the uniformly symmetry-breaking approach, which exhibits Q-factors around 25.80. The experimental transmission spectrum and the near-field scanning images firmly validate the existence of the high Q BIC mode under this strategic symmetry-breaking approach. This work may open new avenues for developing advanced THz devices with promising applications in sensing, filtering, and non-linearity in the THz domain.