  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 visible (VIS) light and near-infrared
(NIR) photons as well. The existing solutions mostly explore complex photonic
nanostructures, which are often too complicated for production. In this work,
we demonstrate a pixel-scale spectral router utilizing two-dimensional (2D)
Si3N4 Mie scattering metagratings 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, our router can gain
about 42% and 30% signal enhancement for NIR and VIS band, respectively. We
show 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 multipolar
scattering of our Mie-type metagratings provides the necessary degrees of
freedom to spatially optimize the routing functions for broadband photons.
