# High-Extinction-Ratio Chiral Mid-Wave Infrared Photodetector Using Trapezoidal Si Pillars

## TL;DR

This paper introduces a new type of photodetector that can detect circularly polarized light with high accuracy using a chiral metasurface design.

## Contribution

The novelty lies in achieving a high extinction ratio of 31 dB through geometric and tilt angle manipulation in a miniature photodetector.

## Key findings

- The device achieves an extinction ratio of up to 31 dB for circular polarization detection.
- Symmetry-breaking effects create distinct spectral responses for left and right circularly polarized light.
- The design offers potential for on-chip polarization detection and quantum optics applications.

## Abstract

Although the polarization state, as a key physical dimension of light, plays an irreplaceable role in many frontier fields such as quantum communication and chiral sensing, traditional photodetectors are limited by the inherent optical isotropy of materials and thus are unable to directly distinguish circular polarization information. This paper numerically reports a miniature circular polarization photodetector based on chiral metasurfaces, which achieves an excellent extinction ratio of up to 31 dB through the collaborative regulation of geometric displacement manipulation and tilt angle operation. This device utilizes the symmetry-breaking effect to construct significantly different transmission spectral responses between left circularly polarized light (LCP) and right circularly polarized light (RCP). Our research not only provides a high-performance implementation solution for on-chip polarization detection but also opens up new paths for the future development of quantum optics, integrated sensing, and ultra-compact polarization optical systems.