Graphene Surface Plasmon Applications in Designing Novel Nano-Heterostructure Arrays

Abstract

Graphene is the flat monolayer of carbon atoms constructing a two-dimensional honeycomb lattice with an exotic mechanic, electronic, magnetic, and optical properties. Interestingly, the graphene has been experimentally shown its unique properties in photonics, where the first commercial application of graphene has been realized. Graphene possesses intrinsic plasmons that are electronically tunable, adjustable, and have low dissipation. Recently, the combination of graphene with noble metals and semiconductors structures promises a variety of exciting applications for conventional plasmonics and photonics. In this thesis, we present how to efficiently design heterostructure by combining graphene plasmonic metasurface with noble metals and semiconductors. First, we propose and demonstrate electronically tunable resonant nearly perfect absorbers in graphene coupled to the metallic subwavelength structure. The absorption is enhanced by the noble metals plasmonic effect, which results in modulating reflecting light. The coupling efficiency of our proposed structure is increased to overcome the mismatch wavevector using surface gratings. In our proposed device, numerical simulation results show that even with low-quality graphene, the perfect absorber is achievable in the near-infrared spectrum. In the second device, we propose and demonstrate a tunable flat-top reflecting bandpass by combing graphene plasmonic metasurface with subwavelength noble metal nanosphere arrays. In this device, the broad range of tunability in the near-infrared is achieved. By implementing the suitable number of gold nanospheres in each unitcell, the high order flat-top bandpass filter in the near-infrared range is introduced. Besides, the graphene monolayer, coupled to the subwavelength metallic structure overcomes the low modulation depth in the conventional graphene plasmonic devices. Top-gated electrostatic gating, along with a rapid cooling method, is proposed to increase the carrier density for high Fermi levels dramatically. Finally, we devise a platform to demonstrate a low threshold graphene-based plasmonic ultraviolet nanolaser. In this device, we incorporated ZnO nanobars coupled to graphene SPs along with using ITO/a-Si as a back reflector to mitigate the ohmic loss (in the conventional metal-semiconductor lasing nanostructure), increase the exciton-plasmonenergy transfer and to miniaturize the nanolaser dimension.