Star-shaped nanostructure-based multifunctional chiral metasurface for near-infrared wavelengths

Abstract: Here, we reported, for the first time, a chiral metasurface with multifunctional capabilities tailored for the near-infrared (NIR) wavelength range, garnering tremendous interest in applications such as optical communication and chiral sensing. The structure comprised star and bar-shaped silver antennas immersed in SiO2. In computational simulations based on the finite-difference time-domain method, the proposed architecture yielded a maximum circular dichroism of 0.7 at 971.5 nm wavelength and a maximum asymmetric transmission under linearly polarized excitation of 0.92 at 1020 nm wavelength. Moreover, this multifunctional structure manifested near-perfect cross-polarization conversions for both linear and circular polarizations, as well as linear to circular and elliptical polarization conversion effects at different bands within the NIR spectral region. The enhanced light-matter interaction of the proposed structure was utilized to detect and differentiate two enantiomers of 1,2-propanediol, yielding excellent chirality sensing capability. As a multifunctional compact chiral platform, the proposed structure is expected to find direct applications in integrated and miniaturized multi-channel optical communication platforms, materials and biomolecules sensing in attomolar concentrations, and the pharmaceutical industry.