Giant circular dichroism and ultra-high Q-factor resonance induced by qBIC excitation in oblique lattice metasurfaces

Chiral metasurfaces exhibiting narrow-band circular dichroism play a crucial role in chiral optics. Enhancing the quality factors ( Q -factors) of their chiral response and achieving dynamic tuning of circular dichroism (CD) have emerged as research hotspots in this field. This study proposes a novel metasurface structure based on a slanted lattice, which can simultaneously achieve high Q -factors and strong CD under the drive of qBIC. Numerical calculations indicate that under vertical incidence conditions, the CD of this metasurface can reach −0.82, with Q -factors exceeding 10 4 . Further research reveals that dynamic tuning of CD can be achieved by regulating the external electric field. In addition, based on this chiral structure, a high-sensitivity refractive index sensor was designed. Simulation results show that the sensor exhibits excellent environmental sensing performance, with sensitivities ( S ) of 125 nm/RIU and 215 nm/RIU in typical gas and liquid environments, and corresponding figures of merit (FOM) of 2221 RIU −1 and 3988 RIU −1 , respectively. Our research provides new insights for the design of chiral nanodevices, with promising applications in optical communication, chiral sensing, and optical switching.