All-dielectric terahertz metasurface governed by bound states in the continuum with high-Q factor

The method of terahertz(THz) resonance with a high-quality(high-Q) factor offers a vital physical mechanism for metasurface sensors and other high-Q factor applications. However, it is challenging to excite the resonance with a high-Q factor in metasurfaces with proper sensitivity as well as figure of merit(FOM) values. Here, an all-dielectric metasurface composed of two asymmetrical rectangular blocks is suggested. Quartz and silicon are the materials applied for the substrate and cuboids respectively. The distinct resonance governed by bound states in the continuum(BIC) is excited by forming an asymmetric cluster by a novel hybrid method of cutting and moving the cuboids. The investigation focuses on analyzing the transmission spectra of the metasurface under different variations in structural parameters and the loss of silicon refractive index. When the proposed defective metasurface serves as a transmittance sensor, it shows a Q factor of 1.08×104and achieves an FOM up to 4.8×106, which is obtained under the asymmetric parameter equalling 1 μm. Simultaneously, the proposed defective metasurface is sensitive to small changes in refractive index. When the thickness of the analyte is 180 μm, the sensitivity reaches a maximum value of 578 GHz/RIU. Hence, the proposed defective metasurface exhibits an extensive number of possible applications in the filters, biomedical diagnosis, security screening, and so on.