Terahertz optical modulator and highly sensitive terahertz sensor governed by bound states in the continuum in graphene-dielectric hybrid metamaterial

We propose a graphene-dielectric hybrid metamaterial (GDHM) that supports the quasi-bound state in the continuum (BIC). By rotating one of the LiTaO 3 bars, the quasi-BIC resonance with high quality (Q) factor can be excited. The analysis of multipole decomposition confirms that electric quadrupole dominates this resonance. Moreover, the Q factor of quasi-BIC significantly decreases as the chemical potential of graphene increases, and the tuning transmission is achieved by changing the chemical potential of graphene. A low-energy THz-wave modulator is designed based on this scheme, and the designed modulator shows 97% modulation depth with a chemical potential shift of only 16 meV. In addition, the sensing performance of GDHM is investigated, and it is found that the sensitivity can be controlled by chemical potential. The minimum value of the sensing sensitivity can reach up to 308.91 GHz/RIU, and the maximum figure of merit (FOM) is 257.43 RIU−1. When the losses of LiTaO 3 are considered. The modulation depth, sensitivity, and maximum FOM achieve 90%, 309.54 GHz/RIU, and 121.39 RIU−1, respectively. This work provides a valuable reference for designing dynamic optical modulators and sensors in the THz region.