Plasmonic moiré metamaterials and metasurfaces : tunable optical properties and nanophotonic applications

Optical metamaterials and metasurfaces, which are properly designed assembly of man-made building blocks with strong interactions with electromagnetic waves, have emerged as promising candidates to replace natural materials due to extraordinary capabilities in light manipulation. In particular, plasmonic metamaterials and metasurfaces have shown their potentials in surpassing diffraction limit, manipulating light beams, and enhancing energy conversion by substantially enhancing light-matter interactions through effects of surface plasmon polaritons (SPPs) or localized surface plasmons (LSPs). Although enormous breakthroughs in plasmonic metamaterials and metasurfaces have been made in the recent decades, the further development of this field towards practical applications has been limited by the lack of high throughput fabrication and the poor tunability in conventional designs. This dissertation presents the cost-effective nanofabrication, rationale design, numerical modelling, experimental demonstration, and application prototyping of new classes of plasmonic metamaterials and metasurfaces featured by moiré patterns. Firstly, we developed novel techniques based on conventional nanosphere lithography to achieve high-throughput nanofabrication of metamaterials and metasurfaces with three-dimensional (3D) and two-dimensional (2D) moiré configurations. Secondly, we demonstrated multiband moiré metasurfaces with flexible tunability based on plasmonic materials including Au and graphene, which have shown potentials as multifunctional biomedical platforms. Thirdly, we developed moiré chiral metamaterials with ultrathin thickness and precisely tunable chiroptical responses, which have been applied as ultrasensitive sensors to achieve label-free enantiodiscrimination of chiral molecules. Finally, we introduced dynamic tunability in moiré chiral metamaterials through stimuli-responsive manipulation of optical coupling in the metamaterials. The results presented in this dissertation could provide guidance to the development of tunable moiré metamaterials and metasurfaces from design and fabrication to characterization and device implementation, benefiting a range of applications from light manipulation to molecular sensing