Dual-polarized transmissive metasurfaces for near-unitary-NA analog spatial computing empowered by impedance matching and mismatching

In recent years, due to the increasing requirement for real-time and massive data processing, optical analog computation has arisen as a promising alternative to digital computation. Optical spatial differentiation plays a fundamentally important role in various emerging technologies, including augmented reality, autonomous driving, and object recognition. However, previous demonstrations encountered several limitations, such as the dependence on polarization states and a typically limited numerical aperture (NA) of about 0.5, especially in the transmission mode. Here, a new, to our knowledge, design strategy based on the evolution between impedance matching and mismatching in a metasurface is proposed to fill this gap, which can perform dual-polarized second-order derivative for image processing. Our scheme enables high transmission under dual polarization over an 85° incident angle range (NA = 0.996), resulting in more than twofold spatial resolution. Our work paves the way for polarization-insensitive high-resolution signal and image processing in the terahertz region.