Anisotropic Meta-Mirror for Achromatic Electromagnetic Polarization Manipulation

Polarization states are of particular importance for the manipulation of electromagnetic waves. Here, we proposed the design and experimental demonstration of anisotropic meta-mirror for achromatic polarization tuning. It is demonstrated that linear polarized wave can be achromatically transformed to its cross-polarization state or to arbitrary circular polarization after its reflection from the mirror. Microwave experiments verified that the fraction bandwidth for 90 transformation efficiency can be larger than 3:1. Furthermore, by utilizing photoinduced carrier generation in silicon, a broadband tunable circular polarizer is demonstrated in the terahertz regime.