Recent Advances in Ultrathin Chiral Metasurfaces by Twisted Stacking

• Published in: Advanced materials (Weinheim) Vol. 35; no. 3; pp. e2206141 - n/a
• Main Authors: Han, Zexiang, Wang, Fei, Sun, Juehan, Wang, Xiaoli, Tang, Zhiyong
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 01.01.2023
• Subjects: Chirality; chiroptics; Dichroism; Interlayers; metadevices; Metamaterials; Metasurfaces; Nanomaterials; Nanostructure; Polarization; Stacking; Thickness; Thin films; twisted bilayers; polarization; chiroptics; twisted bilayers; metadevices; thin films
• ISSN: 0935-9648; 1521-4095; 1521-4095
• DOI: 10.1002/adma.202206141

Artificial chiral nanostructures have been subjected to extensive research for their unique chiroptical activities. Planarized chiral films of ultrathin thicknesses are in particular demand for easy on‐chip integration and improved energy efficiency as polarization‐sensitive metadevices. Recently, controlled twisted stacking of two or more layers of nanomaterials, such as 2D van der Waals materials, ultrathin films, or traditional metasurfaces, at an angle has emerged as a general strategy to introduce optical chirality into achiral solid‐state systems. This method endows new degrees of freedom, e.g., the interlayer twist angle, to flexibly engineer and tune the chiroptical responses without having to change the material or the design, thus greatly facilitating the development of multifunctional metamaterials. In this review, recent exciting progress in planar chiral metasurfaces are summarized and discussed from the viewpoints of building blocks, fabrication methods, as well as circular dichroism and modulation thereof in twisted stacked nanostructures. The review further highlights the ever‐growing portfolio of applications of these chiral metasurfaces, including polarization conversion, information encryption, chiral sensing, and as an engineering platform for hybrid metadevices. Finally, forward‐looking prospects are provided. Simple twisted stacking of two layers of nanomaterials can produce ultrathin planarized nanostructures with optical chirality. This review thoroughly examines the recent progress in ultrathin chiroptical metasurfaces prepared through chiral stacking, discussing the monolayer materials, fabrication strategies, and the induced circular dichroism. A special focus is placed on the flexible tunability of the chiroptical responses and relevant optical applications.