All-optical controlled-NOT logic gate achieving directional asymmetric transmission based on metasurface doublet

Optical logic gates play important roles in all-optical logic circuits, which lie at the heart of the next-generation optical computing technology. However, the intrinsic contradiction between compactness and robustness hinders the develop-ment in this field. Here, we propose a simple design principle that can possess multiple-input-output states according to the incident circular polarization and direction based on the metasurface doublet, which enables controlled-NOT logic gates in infrared region. Therefore, the directional asymmetric electromagnetic transmission can be achieved. As a proof of concept, a spin-dependent Janus metasurface is designed and experimentally verified that four distinct images corres-ponding to four input states can be captured in the far-field. In addition, since the design method is derived from geomet-ric optics, it can be easily applied to other spectra. We believe that the proposed metasurface doublet may empower many potential applications in chiral imaging, chiroptical spectroscopy and optical computing.