Quasibound states in the continuum in terahertz free-standing metal complementary periodic cross-shaped resonators

TL;DR

This paper demonstrates the design, realization, and analysis of quasi-bound states in the continuum with high-Q factors in terahertz free-standing metal cross-shaped resonators, advancing terahertz wave manipulation technologies.

Contribution

It introduces a novel free-standing metal resonator design that achieves high-Q quasi-BICs through symmetry breaking, with experimental validation and potential applications in sensing.

Findings

Measured Q factor reaches 102, close to the simulated 166.

Quasi-BICs originate from mirror symmetry breaking in CPCRs.

Electric field distributions show out-phase electric dipole alignment.

Abstract

We numerically and experimentally achieve quasi-bound states in the continuums (BICs) with high-Q factors in the free-standing metal complementary periodic cross-shaped resonators (CPCRs) at terahertz (THz) frequencies. Such induced quasi-BICs arises from the breaking of the mirror symmetry of CPCRs. By properly tuning the asymmetric factor, the measured Q factor of quasi-BIC can reach 102, which is lower than the simulated Q factor of 166 due to the limited system resolutions. We also simulate the electric field magnitude and vector distributions at the quasi-BICs, where the out-phase alignment between the electric dipoles is found. The sharp quasi-BICs realized in this thin free-standing metal structure may immediately boost the performance of filters and sensors in terahertz wave manipulation or biomolecular sensing.