Harnessing Evanescent Waves by Metasurfaces: An All-Optical Analogue of On-Chip Control of Smith-Purcell Emission

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 C-aperture metasurface, in this work we show that we can mold evanescent waves on demand. Specifically, we demonstrate an all-optical analogue of manipulating Smith-Purcell emission, in which the evanescent waves are produced by attenuated total reflection rather than moving electrons, and subsequently tailored by the designer metasurfaces. The phase, beam profile and polarization state of the Smith-Purcell emission can be controlled via the orientation of C-aperture nanostructures. Our 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.