Pixel-scale NIR-VIS Spectral Routers Based on 2D Mie-type Metagratings

TL;DR

This paper introduces a pixel-scale spectral router using 2D Mie-type metagratings that efficiently separates NIR and VIS light, enhancing signal quality for imaging devices without complex reconstruction.

Contribution

The work demonstrates a scalable, high-efficiency spectral routing device based on 2D Mie scattering metagratings, suitable for mass production and capable of broadband NIR-VIS separation.

Findings

Achieves 42% and 30% signal enhancement for NIR and VIS bands.

Exhibits polarization insensitivity and incident angle tolerance.

Enables simultaneous NIR-VIS imaging without complex algorithms.

Abstract

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.