Localized spin-selective interference assisted broadband tunable chirality with diatomic all-dielectric metasurfaces

Chiral metasurfaces with spin-selective properties have shown an unprecedented ability to modulate optical properties on the subwavelength scale. Alternatively, the simultaneous implementation of broadband tunable chiral response and wavefront manipulation on minimalistically constructed monolayer metasurfaces can lead to a plethora of applications such as optical converter diodes, chiral imaging, and sensing. Benefiting from a localized interference between two pairs of achiral meta-atoms whose optical behavior is similar to that of a halfwave plate (HWP), we theoretically provide a design strategy for constructing meta-molecules for asymmetric transmission (AT) parameters using interference mechanisms, each of which achieves a specific modulation function in the terahertz (THz) band. Localized interference effects with polarization-selective properties permit the incident circular polarization to be transformed into its orthogonal polarization mode. Benefiting from spinselective transmission, the proposed metasurface simultaneously implements polarization filtering and wavefront manipulation with the assistance of a geometric phase mechanism. Not only that, chiral imaging schemes are also evaluated under such a design mechanism. As a result, this generalized assembly scheme can not only be extended to arbitrary working bands, but also find a variety of applications in photodetectors.