Recent progress in chiral absorptive metamaterials

Chiral metamaterial absorbers (CMMAs), a particular class of chiral metamaterials that refuse the transmission of incident radiation and exhibit different optical responses upon interactions with left and right circularly polarized (LCP, RCP) light, have gained research traction in recent years. CMMAs demonstrate numerous exotic and specialized applications owing to their achievable compatibility with various physical, chemical, and biomolecular systems. Aside from their well-evolved fabrication modalities for a broad range of frequencies, CMMAs exhibit strong chiroptical effects, making them central to various detection, imaging, and energy harvesting applications. Consequently, within the past decade, studies encompassing the design, optimization, and fabrication, as well as demonstrating the diverse applications of CMMAs have emerged. In this review, the theory, design, and fabrication of CMMAs are discussed, highlighting their top-down fabrication techniques as well as recent algorithmic and machine-learning (ML)-based approaches to their design and optimization. Some of their broad-spectrum applications are also discussed, spanning their roles in enantioselective photodetection, chiral imaging, generation of hot electrons, selective temperature sensing, and active chiral plasmonics.