Recent Progress on Plasmonic and Dielectric Chiral Metasurfaces: Fundamentals, Design Strategies, and Implementation

Over the years, researchers have been exploring ways to artificially design chiral structures and materials, namely metamaterials and metasurfaces. They exhibit unique optical properties that can be used for various applications. However, metasurfaces comprise symmetry-breaking structures that provide a more convenient solution for planar chiral optics regardless of whether they are plasmonic or dielectric. In general, plasmonic chiral metasurfaces are more suitable for applications requiring a high confinement level and substantial optical near-field enhancement. In contrast, dielectric chiral metasurfaces are ideal for wide operating wavelength ranges and low losses. This review summarizes the recent progress on plasmonic and dielectric chiral metasurfaces. It includes the fundamental concepts, design strategies, and their implementation for applications in holographic displays, imaging and sensing, and detection. Moreover, an overview of chiral metasurfaces to generate the nonlinear effects, hosting bound states in the continuum, and the significant role of machine-learning-based design approaches are also discussed. Finally, some future developments are highlighted where chiral metasurfaces are expected to play a vital role.