High-NA Polarization-Independent Isotropic Spatial Differential Metasurface

Metasurface-based optical computing has been a topic of interest for many researchers, aimed at implementing high-speed and efficient image processing in small equipment. However, the existing designs cannot work well in the aspects of spatial resolution, polarization and azimuth angle simultaneously. Here, we present a 2D differential metasurface with a honeycomb photonic structure as the basic unit, which not only satisfies isotropy and polarization independence, but also has a NA as high as 0.44. Through numerical verification, the proposed metasurface can produce the result of second-order differential operation of Gaussian functions in 1D space, and can be used to implement edge detection of objects in an image as well. Our results provide new opportunities for optical analog computing and computer vision applications.