Research On Graphene-based Photonic Devices

Graphene nanophotonics has attracted considerable interest due to its unique optical properties and many related applications, ranging from graphene-based optical modulation, transformation optics, field-effect transistors to numerous other devices. Apart from being the thinnest material, graphene is attractive for its physical flexibility, high electron mobility and the possibility of controlling its carrier concentration via external gate voltages or chemical doping. In this thesis, we demonstrate our research on graphene based photonic device foucused on three aspects, including broadband THz absorber, circular polarization beam splitter and enhanced magneto-optical Kerr effect.First, we introduce a broadband THz absorber with an array of graphene-dielectric multilayered frustum pyramids on a metal sheet. The multilayered graphene-dielectric structure can be considered an effectively homogeneous metamaterial with a hyperbolic dispersion and anisotropic permittivity. Surface plasmonic waves are excited on graphene layers and the incident waves of different frequencies are absorbed at different levels of the stacked pyramid, due to the squeezing effect of the slow waves at the tapered waveguide. An absorption dip is observed and explained physically, and finally removed by adding a rectangular portion to the pyramid unit cell. High absorption with an extremely broad bandwidth is achieved.Second, we suggest a graphene/dielectric-stacked structure, which has both the properties of an epsilon-near-zero material and the high Hall conductivity of graphene. The proposed sub-wavelength structure demonstrates efficient manipulation of circular polarization properties of light. In a quite broad frequency range and at a large oblique incidence angle, the present magnetically active structure is transparent for one circularly polarized wave, and opaque for another. Such an effect can be further tuned by changing the magnitude of the applied magnetic field and chemical potential of graphene.Third, we demonstrate that giant angle rotation in graphene in the terahertz range can be realized and further increased by introduction of surface plasmon and constructive Fabry-Perot interference with the supporting substrate. The maximum Kerr rotation angle is up to 15 degrees in a single layer of graphene ribbons at 6 THz for applied magnetic field 4 T. Such a magnification in magneto-optical Kerr effect can be realized in a fairly large incident angle.At the end of this thesis, we summarize all the content and also give the perspective of the research on graphene based photonic device.