Azimuth‐Resolved On‐Chip Meta‐Hologram

Abstract The invention of chip‐integrated metasurface onto waveguide has exhibited unprecedented capabilities for high‐performance miniature on‐chip optical devices. Various controllable optical parameters have been explored to serve as independent degrees of freedom (DoF) in guided wave manipulation and optical‐field multiplexing, including wavelength, polarization, propagation path, etc. However, one critical parameter for on‐chip scheme, the DoF for incident azimuthal angle has not been fully exploited and remains challenging because imparting meaningful phase encoding to arbitrary angular directions is limited by no effective phase encoding mechanism. Here, the DoF in illumination azimuths is originally proposed to realize an azimuth‐resolved holographic display beyond conventional orthogonal propagations. Specifically, through correlating meta‐atom displacements to oblique azimuths and optimizing the azimuth‐resolved detour phases, up to six‐channel meta‐holograms with independent encoding freedom are successfully observed by switching the illumination azimuths gradually from 0° to 150° by an interval of 30°. Moreover, thanks to the on‐chip scheme, the extracted holograms fully eliminate any zero‐order diffraction and deliver remarkable visualizations. The proposed DoF of on‐chip azimuth‐multiplexing finds a new pathway for enhancing the optical capacity with azimuth‐resolved multiplexing, and potential applications in optical encryption/storage and multifunctional photonics integrated circuits are envisaged.