Metasurfaces enabled dual-wavelength decoupling of near-field and far-field encoding

The metasurface is a platform with small footprint and abundant functionalities. With propagation phase geometric phase, polarization multiplexing possible. However, different response behaviors of to wavelength have not been fully employed widen the capabilities metasurfaces. Here, we theoretically demonstrate that metasurfaces can achieve near-field far-field decoupling same at two wavelengths. First, found set pillars whose difference between wavelengths covers full range 2π. Then, by rotating control both cover Finally, means interference principle, arbitrary independent coding for near field far dual realized. In addition, when function focusing, focused spot close diffraction limit, and, NA lens very small, final output focal length four times initial input length. This work circumvents strong wavelength-dependent limitation planar devices paves way toward designing multi-wavelength multi-functional metadevices scenarios such as AR applications, fluorescence microscopy, stimulated emission depletion microscopy.