Anisotropic metasurfaces for efficient polarization independent wavefront steering

Polarization-independent metasurfaces are highly required in many applications, however, their constitutional elements are usually restricted to isotropic meta-atoms with one geometric parameter. Here we propose a general scheme for designing polarization-independent metasurfaces that constructed of anisotropic meta-atoms. The anisotropic metasurfaces (with extra geometric parameters in design) can not only implement comparable functionalities with isotropic metasurfaces, but also provide additional wavefront controls that are not feasible for isotropic metasurfaces with single programmable parameter. As a proof of concept, we demonstrate a polarization-independent focusing vortex generator constructed of anisotropic meta-atoms, which shows well performance (with efficiency up to 62%). Moreover, for the anisotropic meta-atoms own two programmable parameters, complete and independent phase control at two wavelengths are achieved by using the wavelength multiplexed technology. Then, a polarization-independent metalens with achromatic focusing at wavelengths 0.85 µm and 1.55 µm is demonstrated. The wavelength multiplexed technology presented here is generalized and can be extended to multiple wavelengths. These results will open up new doors for designing multiple-wavelength, polarization-independent metasufaces-based devices. (paper)