Far-Field Subwavelength Imaging Using Phase Gradient Metasurfaces

Imaging subwavelength features of an object is in close relationship with extracting information included in evanescent waves scattered from the object. These evanescent waves decay exponentially with distance; therefore, they cannot be captured at far field, resulting in a resolution limited image of the object. Here, we propose a far-field imaging technique based on gradiant metasurfaces, with the ability to provide an image of subwavelength features. In this technique, gradient metasurfaces are used to convert evanescent waves scattered by subwavelength features into propagating waves resulting in a resolution beyond the diffraction limit. The performance of the proposed imaging technique is evaluated using full-wave numerical analysis, and the results validate its capability for imaging beyond the diffraction limit.