Soft-Matter-Based Hybrid and Active Metamaterials

Metamaterials are artificial electromagnetic media structured on the subwavelength scale for controlling the propagation of waves by means of transformation optics. The research activity is now focusing on attaining active metamaterial functionalities, including tunability, and the shaping and modulation of electromagnetic waves. Among all the different architectures, soft-matter-based active metamaterials, or hybrid composites, have gained special importance as they allow a variety of tuning strategies to be used, including those based on temperature, application of external electric or magnetic fields, and all-optical methods that benefit of the strongly nonlinear responses of materials. This review aims to summarize recent and ongoing progress on active metamaterials exploiting resonances in plasmonic and dielectric materials hybridized with soft-matter assemblies including liquid crystals, colloids, polymers, and granular matter. The theoretical background of these hybrid systems is outlined, experimental realizations are overviewed, and state-of-the-art applications in multifunctional platforms for light–matter interactions are presented. Finally, up to date challenges in the field that still remain open for further research are discussed.