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

Abstract

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.

Polarization-insensitive quasi-bound states in the continuum supported by terahertz all-metallic complementary periodic cross-shaped resonators

“…Incident waves with polarization that parallel to the metal grating are reflected, while the perpendicular polarization is transmitted. One of the biggest drivers for the research polarization control is the application of THz sensors [19][20][21][22][23][24]. For high-sensitivity sensing, the quality (Q) factor is crucial for metasurfaces-based sensors.…”

“…Such quasi-BICs possessing polarization-insensitive properties originate from guided mode resonances in metasurfaces via symmetry-breaking. Meal-dielectric or all-metal metasurfaces are also proposed for BICs manipulations although the Ohmic loss is not negligible [22,32,[42][43][44][45][46][47][48][49][50][51]. Kyaw et al reported an asymmetric split-ring resonator-based metasurfaces, realizing polarization-dependence of accidental BICs [32].…”

“…The accidental BIC originates from the coupling between plasmonic dipole and higher-order quadrupole modes, which is not obviously affected by the polarization angles. All-metal metasurfaces have stable optical performance after sensing various molecules [22,[46][47][48]52]. Wang et al proposed an H-shaped based all-metal metasurface, whose induced quasi-BICs are sensitive to the ultrathin graphene film [22].…”

“…All-metal metasurfaces have stable optical performance after sensing various molecules [22,[46][47][48]52]. Wang et al proposed an H-shaped based all-metal metasurface, whose induced quasi-BICs are sensitive to the ultrathin graphene film [22]. The H-shaped structure selects the polarization waves in which only TE waves are able to excite quasi-BICs.…”

Double-Strip Array-Based Metasurfaces with BICs for Terahertz Thin Membrane Detection

“…By tuning the structural parameter, a maximum Q-factor of 102 of quasi-BICs can be measured. Subsequently, Wang et al used such kinds of BICs metasurfaces for polymer membrane sensing [ 24 ]. A sensitivity of 151 GHz/RIU for 50-μm polymer was obtained, higher than bulky dielectric substrate metamaterials.…”