A metasurface color router facilitating RGB-NIR sensing for an image sensor application

Abstract

CMOS image sensor (CIS) plays a crucial role in diverse optical applications by facilitating the capture of images in the visible and near-infrared spectra. The enhancement of image resolution in CIS by an increase in pixel density is becoming more significant and realizable with the recent progress of nanofabrication. However, as pixel size decreases towards the diffraction limit, there is an inevitable trade-off between the scale-down of pixel size and the enhancement of optical sensitivity. Recently, to overcome this, an entirely new concept of spectral sensing using a nanophotonic-based color router has been proposed. In this work, we present a metasurface-based spectral router to effectively split the spectrum from visible to near-infrared and redirect through the four optical channels to the targeted pixel surfaces. We optimize the metasurface that simultaneously controls the phases of the transmitted light of targeted spectra, i.e. red (R), green (G), blue (B), and near-infrared (NIR), which is the largest number of channels reported based on a single layered metasurface and has an optical efficiency that surpasses the efficiency of conventional color filter systems.

Towards subwavelength pixels: nanophotonic color routers for ultra-compact high-efficiency CMOS image sensors

“…However, simple cuboid structures adopted in most of the early works often fail to provide sufficient phasedispersion coverage to ensure color router operation. To overcome this issue, one can increase the structural complexity of a unit cell to secure enough degrees of freedom to cover a larger portion of the phase-dispersion space, either by diversifying the shape of the nanoposts [36,[85][86][87] or by stacking multiple layers vertically [88,89] to increase the structural complexity of a unit cell.…”

“…The measured average sorting efficiency and acceptance angle were 51% and 16.5 • , respectively. Several other studies have used similar principles to design NIR-visible color routers [86,87].…”