Metamaterials are artificial materials structured on the subwavelength scale. They are composed of resonant meta-atoms; by tailoring their geometry and material composition, the electromagnetic properties can be tuned at will allowing to access new regimes (e.g., negative index of refraction). The demand for miniaturization has recently driven research to two-dimensional metamaterial sheets, termed metasurfaces. Despite their ultrathin thickness, metasurfaces have shown great promise for enhancing light-matter interactions. The objective here is to study metasurfaces for applications in photonics and optoelectronics and to achieve control over practically all aspects of the electromagnetic wave: amplitude, phase & dispersion, polarization, wavefront, frequency content. Importantly, we are targeting tunable, reconfigurable, and multifunctional metasurfaces, that can enable multiple functionalities and dynamically switch between them. Our research activity in this area is recently focused on a novel class of metasurfaces supporting multiple resonances, which can push performance to the extreme offering broad aggregate operating bandwidths, large phase delays despite the subwavelength thickness, and tailored phase and amplitude dispersion in the reflection/transmission coefficients.
