Anisotropic Plasmonic Metasurfaces with Linear Polarization-Dependent Focusings

As a burgeoning approach to modulate electromagnetic waves, metasurfaces fascinate many researchers. However, it is a persistent problem to realize independent wavefront tailoring in different polarization states. In this work, anisotropic plasmonic metasurfaces are presented with linear polarization-dependent focusings. The designed plasmonic meta-atoms consist of cross-shaped gold, silica spacer, and gold substrate. Phase modulation in different polarization channels is independently achieved by adjusting the dimensions of cross-shaped gold in x- and y-directions. Three metasurfaces are presented to verify linear polarization-dependent focusings at 200 THz. First, a focusing metasurface is designed with focal lengths of 5.2 & mu;m under x-polarized incidence and 6.5 & mu;m under y-polarized incidence. Second, by applying convolution operation, the second metasurface exhibits different focusings with different deflection angles at opposite directions under orthogonally polarized incidences. Finally, a multi-focal metasurface is demonstrated, which switches between dual- and quad-focal points depending on polarization state. The work may provide a novel platform for near-infrared integrated photonics.