High Q-factor chiroptical response based on unidirectional guided resonances

The maximal chiroptical response with a high Q-factor is demonstrated based on the unidirectional guided resonance state by a one-dimensional metasurface composed of periodical tilted silicon nano-pillars. The structural chirality leads to differences in the far-field polarization and radiation Q-factor between the upward and downward radiation channels. By numerical calculation, it can be found that the maximal chiroptical response with the circular dichroism of ±0.99 and Q-factor of 537.99 is realized at ϕ=87∘ and ϕ=273∘ under conditions of θ=4.5∘ and λ=1449.5 nm. In addition, the metasurface can also maintain the polarization state of incident light with a high efficiency of 0.88. It is believed that our scheme is meaningful in the emission and modulation of monochromatic light.