Pixelated NIR-VIS Spectral Routers Based on 2D Mie-Type Metagratings

The out-of-band energy loss caused by in-built color filters significantly degrades the signal-to-noise ratio and the dynamic range of conventional image sensors, which has restricted the attempt to develop ultrahigh-density imaging devices by merely shrinking the pixel size. This issue will be more serious for security cameras, which need to collect both visible (VIS) and near-infrared (NIR) light. The existing solutions mostly explore complex photonic nanostructures, which are often too complicated for production. In this work, a pixelated spectral router is demonstrated utilizing a 2D Si3N4 Mie-type metagrating that can spatially divide NIR (850 nm) and VIS (400-700 nm) light to different pixels at high efficiencies. It has a minimum feature size larger than 360 nm, highly promising for massive production. Compared with the traditional filter design, this router can gain approximate to 42% and approximate to 30% signal enhancement for NIR and VIS bands, respectively. It is shown that it also has good polarization insensitivity and incident angle tolerance. The NIR-VIS simultaneous imaging is inspected without any complex reconstruction algorithm. Mode analysis indicates that the periodic interference of multipolar scattered fields caused by this metagrating provides the necessary degrees of freedom to spatially optimize the routing functions for broadband photons.