Realization of tunable dual-type quasi-bound states in the continuum based on a Dirac semimetal metasurface

Abstract

In this study, two types of tunable quasi-bound states in the continuum (BIC) based on Dirac semimetal metamaterial (DSM) in the terahertz (THz) band are proposed in the same metasurface. The symmetry-protected BICs are achieved by altering the structural symmetry. The accidental BICs are realized by adjusting the structural parameters, and the quality factor (Q factor) of the corresponding quasi-BICs can be as high as 175. To better understand the excitation mechanism of the quasi-BIC, we investigated the magnetic field distribution and current distribution of the BIC and quasi-BIC, respectively. The results showed that the accidental BIC and the symmetry-protected BIC have a common resonance mode, and the two LC resonance modes are coupled with each other, which causes a strong resonance. The dynamic modulation of the transmission amplitude is achieved by changing the Fermi energy of the DSM at a nearly constant resonant frequency, and the difference in amplitude modulation is about 46%. Based on the idea of amplitude modulation, the design of the Dirac semimetal film (DSF) metasurface array for stereoscopic graphic display is realized.