  It has long been a challenging task to improve the light collection
efficiency of conventional image sensors built with color filters that
inevitably cause the energy loss of out-of-band photons. Although various
schemes have been proposed to address the issue, it is still very hard to make
a reasonable tradeoff between device performance and practicability. In this
work, we demonstrate a pixelated spectral router based on sparse meta-atom
array, which can efficiently separate the incident R (600-700 nm), G (500-600
nm), and B (400-500 nm) band light to the corresponding pixels of a Bayer image
sensor, providing over 56% signal enhancement above the traditional color
filter scheme. The CMOS-compatible spectral router has superior characteristics
of polarization insensitivity and high incident angle tolerance (over
30{\deg}), enabled by simple compound Si3N4 nanostructures which are very
suitable for massive production. Imaging experiments are conducted to verify
its potential for real applications. Our pixelated spectral router scheme is
also found to be robust and could be freely adapted to image sensors of various
pixel sizes, having great potential in building the new generation of
high-performance image sensing components.
