Quasi-BICs Enabled Proximity Sensing Based on Metal Complementary H-Shaped Arrays at Terahertz Frequencies

All metal sensing based on complementary H-shaped arrays (HSAs) is numerically and experimentally investigated at terahertz frequencies. The symmetry-protected bound states in the continuum (BICs) are activated by adjusting one arm's length of the H-shaped, enabling high- Q quasi-BICs. The Q -factor of quasi-BICs is modulated in terms of structural parameters and metal conductivity. With optimal structural parameters of copper HSAs, the proximity sensing performances are studied as a function of the film thickness and the refractive index. High sensitivity of 151 GHz/RIU and FOM of 18.7 are obtained, respectively, which are high compared with the previous metamaterials with planar substrates. In addition, the HSAs are even sensitive to the ultrathin graphene film. These findings indicate that such HSAs-based sensor has great potential for practical applications in chemical and biomolecular fields.