Incidence angle-dependent broadband chiral metamaterial for near-infrared light absorption

The ability to spin-selectively absorb circularly polarized light plays a critical role in various photonic devices. Here we propose and investigate a broadband chiral metamaterial composed of asymmetric split-ring resonators, showing a wide spin-selective absorption band from 950 to 1200 nm with pronounced circular dichroism up to 20°. We demonstrate that the broadband absorption spectra originate from induced dual chiral resonance modes. Meanwhile, the two different resonances can be adjusted independently, suggesting great flexibility of the designed chiral absorption band for different purposes. Also, the chiral-selective absorption performance is highly dependent on the oblique incident angle due to the extrinsic chirality. The chiral resonance modes can be either enhanced or destroyed under oblique incidence. Such angle-dependent broadband chiral metamaterials may find potential applications for spin-orbit communications, chiral detection, polarimetric imaging, and biosensors.