Recent Progress in Active Optical Metasurfaces

Evolving from metamaterials, optical metasurfaces not only inherit their unprecedented flexibility in tailoring light–matter interaction but also the generally fixed response determined by the metaatoms' geometries—an undesirable property that hinders the development of practical metadevices. Consequently, novel optical metasurfaces that can be tuned in an active manner are intensively studied in recent years. Due to their optically thin structures, optical metasurfaces present unique characteristics in the realization of dynamic tuning. In this review, a detailed summary of the recent advances in active optical metasurfaces is provided including discussions reviewing a variety of active materials and approaches that enable faster, stronger, and more accurate tuning. Beyond facilitating practical metadevices, studies of active metasurfaces have, and will continue to deepen the understandings of the interaction between light and nanostructured photonic architectures and to promote the development of nanofabrication techniques involving high-complexity.