Ultraspectral Imaging Based on Metasurfaces with Freeform Shaped Meta‐Atoms

Abstract Metasurfaces have an exceptional capacity to manipulate the phase, amplitude, polarization, or spectrum of light. However, unit cells, or meta‐atoms, of metasurfaces are conventionally designed using regular shapes, limiting performance improvement. The utilization of metasurfaces with freeform shaped meta‐atoms for on‐chip ultraspectral imaging is proposed, where the freeform shaped patterns are generated with controllable feature sizes and boundary curvatures for feasible fabrication. These patterns broaden design diversity and enrich metasurface‐unit spectral response with complicated Bloch modes, thus improving spectral imaging performance with enhanced spectrum recovery precision for broadband spectra and smaller center‐wavelength deviation for narrowband spectra. A snapshot on‐chip ultraspectral imaging, with 356 × 436 spectral pixels is experimentally demonstrated. Spectral resolution is state‐of‐the‐art, at 0.5 nm, and mean fidelity of spectral reconstruction for a standard color board reaches 98.78%. These results support future applications in the field of precise intelligent perception. Moreover, the generating method for freeform shaped patterns also benefits for the forward and inverse designs for high‐performance metasurfaces.