Exploring Graphene Plasmonic Structures For Novel Applications

As a new type of plasmonic material,graphene shows great application potentials in the mid-and far-infrared as well as terahertz ranges.Compared to noble metals,graphene plasmons exhibit stronger spatial confinements of local fields,significantly less loss and tunability by changing the Fermi energy,thus,providing a powerful platform for controlling light–matter interactions.This thesis investigates tunable absorption enhancement based on graphene plasmons and near-field optical forces in graphene plasmonic structures.The main contents are summarized as follows:1.Graphene plasmonic light trapping and absorption enhancement is investigated.By excitating plasmonic resonances of graphene nanostructures,the optical energy of incident light can be confined in the surrounding subwavelength areas.This can significantly enhance the light-matter interactions which can be explored to enhance and control the absorption.With anisotropic structures such as graphene nanoribbons and graphene crosses,not only absorption enhancement up to tens of times but also polarization manipulation and selection can be realized.These results show significant importance for the development of new types of highly efficient mid-and far-infrared photodetectors with tunable spectral and polarization selectivity.2.With the excitation of graphene plasmons,optical forces exerted on nanoparticles near the graphene is investigated.The dependence of near-field forces on the Fermi energy of graphene,the refractive index,size and localization of the nanparticle are analyzed.This work will not only enhance our understanding of lightmatter interactions in the nanoscale but also show great significance for the development of new plasmonic nano-tweezers working with mid-infrared light.