Giant enhancement of the Goos–Hanchen shift based on quasi-bound states in the continuum in terahertz band through silicon based metasurface

Abstract

By breaking the symmetry of the structure, we obtain bound states in the continuum (BIC) in terahertz (THz) using metasurfaces which were prepared with Si and/or Si-compatible materials. With the help of the quasi-BIC with an ultra-high Q factor, the enhanced Goos–Hanchen (GH) shift can reach 5812 times of wavelength. At the same time, the high reflectance is maintained, which makes up for the defect of low reflectance when the GH shift is enhanced by the Brewster angle effect and transmission-type resonances and is convenient for experimental measurement. In addition, the metasurface can be used as an environmental refractive index sensor, and its maximum sensitivity can reach 1.27 × 107mm/RIU, which promotes the development of THz high-resolution sensors. The results could boost the development of silicon-photonics to provide low-cost, highly efficient integrated devices benefited from the same fabrication process as that of large-scale integrated circuit production.