Harnessing Evanescent Waves by Bianisotropic Metasurfaces

The exponentially decaying nature of evanescent waves renders it difficult to capture, extract and engineer the wealth of energy and information that they can carry. Utilizing the out-of-plane electric dipoles and in-plane magnetic diploes produced by a bianisotropic C-aperture metasurface, in this work, it is shown that evanescent waves can be effectively molded. More specifically, it is demonstrated that the phase, polarization state or beam profile of the emission from evanescent waves can be controlled via the orientation of C-aperture nanostructures. The work opens a new avenue for metasurfaces to work in the critical near-field region to efficiently harness evanescent waves, and promises many potential applications, including on-chip free-electron light sources, tabletop particle detectors and near-field energy harvesting.