Study On Transmission Characteristics Of Surface Plasmon Polaritons In Several Graphene-based Waveguide Structure

Due to the special dispersion relation, surface plasmon polaritons(SPPs) are able to guide light in subwavelength by breaking the diffraction limit. As a novel two-dimensional material, graphene suggests excellent electronic and optical properties because of its unique band structure. It can support the propagation of SPPs as well, thus has attracted many attentions in recent years. Graphene surface plasmon polaritons(GSPPs) have high carrier mobility, strong confinement, low loss and highly tunable characteristics, thus has achievable and potential applications in optical information transmission, photodetectors, surface plasmon waveguides, nano-lasers, metamaterials and other fields. In this paper, the basic principles and characteristics of GSPPs are discussed. Based on theoretical analysis, several waveguide devices based on GSPPs are proposed and simulated by finite element method(FEM).Firstly, the transmittance spectra of the asymmetric double graphene ring and waveguide coupling structure are studied, and the generation of plasmon induced transparency is found. By changing the chemical potential of the graphene resonant ring, the transmission spectrum can be dynamically controlled. Furthermore, a three graphene ring and waveguide coupling structure is designed, and its transmission spectrum shows a clear plasmon induced transparency enhancement effect. At the same time, the modulation of the transmission spectrum can be realized by changing the resonant ring radius and the coupling distance between resonant rings. The results of the correlation analysis are of great significance to design a dynamically adjustable plasma-induced transparent device.The working principle and transmission spectrum of the graphene-based Fabry-Perot spectrometer are analyzed, and it's of great advantages with applications in photodetectors at mid-infrared region. The transmission characteristics of the graphene-based silicon grating structure are also discussed. The stop-band modulation can be achieved by altering the applied voltage and structure parameters.In addition, a three-dimensional graphene-based multi-cavity coupling system is designed. The transmission characteristics of the one-cavity coupling system are analyzed. When the wavelength of incident light satisfies the resonance equation,an obvious resonant effect can be generated, and thus transmission dips can be observed in the transmission spectrum. The increase of the number of the cavities gives rise to the number of the transmission dips. Meanwhile, the interaction between two adjacent dips can induce a transmission peak. It can be seen that the number of transmission peaks is always one less than the number of cavities. Based on this, the three-cavity coupling system is studied. The transmission peak can be actively modulated by changing the chemical potential of graphene and the coupling distance.