Chiral flatband in refractive index modulated metasurfaces

-direction. Building on this framework, we employ a theoretical model based on refractive index modulation and partial etching, which lead to a metasurface with a pronounced flatband with chiroptical response. This metasurface holds significant potential for applications in chiral light source emission and detectors, chiral sensing, and enantioseparation, particularly at wide incidence angles.