Strong narrowband chiral absorption in anisotropic metasurface induced by high-k dielectrics

Chiral absorption is the phenomenon of different absorption for different circularly polarized light, and it has important significance in chiral optical modulation and related fields. In this work, we investigate the strong narrowband chiral absorption of an anisotropic α -MoO 3 metasurface induced by a high-dielectric constant medium. The results show that when an incident medium with a high dielectric constant ( k =5.5) is introduced, a pronounced absorption peak appears at 11.47µm, with a maximum circular dichroism (CD) value reaching 0.948. In contrast, when the dielectric constant is low ( k =1), the CD response is significantly suppressed. The underlying physical mechanism can be attributed to the enhanced evanescent field induced by the attenuated total reflection effect at the α -MoO 3 /high-k dielectric interface. It is found that the incident angle, azimuth angle, filling factor, and α -MoO 3 strip thickness all have significant modulation effects on the CD response. Specifically, a pronounced high-CD region appears when the incident angle exceeds 25 ∘ , and the CD reaches its maximum at an azimuth angle of ψ =40 ∘ . In addition, increasing the filling factor leads to a redshift of the CD peak and enhanced polarization selectivity, while varying the α -MoO 3 strip thickness redistributes the absorption difference and the high-CD spectral region. We believe that this study not only clarifies the physical mechanism of high-k-induced resonance enhancement in anisotropic metasurfaces but also provides valuable insights for the design of chiral metasurfaces and polarization-selective photonic devices.