Spin-selective chiral mirror driven by guided-mode resonance

Abstract

Manipulating the polarization of light is of great importance for remote sensing, microscopy, data storage, and quantum cryptography. Metasurfaces, comprising deliberately designed subwavelength units in a two-dimensional plane, present a new approach for creating multi-functional and ultracompact optical elements. The polarization manipulation in metasurfaces has been actively explored thanks to the birefringence of the subwavelength anisotropic meta-atoms. This thesis reports the realization and verification of compact all-dielectric chiral mirror in the visible. Notably, the chiral mirrors have been mainly presented as plasmonic devices, making our structure, to the best of our knowledge, the first dielectric counterpart operating in the visible spectra. Our approach utilizes high refractive index and low-loss nanostructures to induce the near-unity circular dichroism (CD) when two orthogonal circularly polarized light (CPL) beams are incident. In this scheme, the chiro-optical response is induced by the periodicity and the geometry of our chiral metasurfaces, which lacks mirror symmetry. Our chiral metasurfaces provides robust, high-efficiency, near-unity CD, and polarization-conserved CPL reflection. Moreover, by harnessing guided-mode resonance (GMR), our structure has high quality factor, making it suitable for various applications such as color filter, display, and enantioselective molecular biosensing. As a demonstration of our approach, we explore our chiral mirror through some numerical simulations. In addition, we illustrate methods for measurement to characterize experimentally. Our chiral mirror has the potential to unlock new opportunities for various applications such as polarized light sources, sensors, encryption, and biomedical optics.