Chiral-effect-based metasurfaces provide a new solution for the design of circular polarized light (CPL) detectors due to their high design flexibility and compact structure. However, the design of polarization-sensitive chiral metasurfaces still faces challenges in high bandwidth, high circular dichroism (C_D), and high extinction ratios. To further enhance the extinction ratio performance of infrared circular polarization detectors and achieve higher C_D and extinction ratios over a wide bandwidth, we propose a silicon-based two-dimensional chiral metasurface for circular polarization detection, thereby promoting the practical application of circular polarization detection.

We design and propose a high-performance, broadband all-dielectric two-dimensional chiral metasurface for circular polarization detection, thus achieving high bandwidth, high C_D, and high transmittance. Firstly, a chiral meta-atom with a high degree of freedom is introduced, composed of a lateral rectangle and two pairs of center-symmetric trapezoids, one large and one small (trapezoid ① and trapezoid ②). Subsequently, based on the finite-difference time-domain method, an optimization objective function targeting high C_D is established. Meanwhile, a chaotic particle swarm optimization algorithm is employed to conduct a global search in high-dimensional space, ultimately leading to a high-performance chiral metasurface for circular polarization detection.

The designed infrared broadband chiral metasurface enables efficient transmission of left-handed circularly polarized (LCP) incident light, achieving maximum transmittance of 95%. After passing through the chiral metasurface, the polarization state of LCP light is converted to right-handed circularly polarized (RCP) light, with extinction effects on RCP incident light shown (Figs. 2 and 3). When LCP light is incident, the device demonstrates high transmittance characteristics due to strong coupling effects and localized field enhancement between the LCP light and the metasurface structure, whereas it exhibits high reflectance characteristics under RCP incidence (Fig. 4). By adjusting the geometric parameters of the device, both the operating bandwidth and C_D can be tuned (Fig. 5). Given the current levels of micro-nano fabrication technology, we further analyze the influence of the sharp tip structure of the meta-atom on the device’s C_D. The results indicate that rounding the tip reduces the extinction ratio at 1.65 μm, with minimal influence on the device’s C_D within the operating bandwidth, thus demonstrating sound manufacturability (Fig. 6).

We design a silicon-based all-dielectric chiral metasurface for circular polarization detection, thereby achieving extinction ratio performance superior to that of other reported two-dimensional chiral metasurface devices for circular polarization detection. Additionally, it can function as a half-wave plate for LCP light while blocking the transmission of RCP light within the continuous wavelength range of 1416?1742 nm. The maximum circular dichroism reaches 0.94, the maximum extinction ratio (E_R) is 42 dB, and the transmittance is 95%, with excellent polarization characteristics shown at 1.65 μm. The designed all-dielectric two-dimensional chiral metasurface possesses features such as high bandwidth, high transmittance, high C_D, and easy manufacturing. It can be fabricated by adopting semiconductor manufacturing techniques compatible with standard CMOS technology, thereby presenting significant application potential in near-infrared polarization detection and on-chip polarization imaging systems.