Optical Coupling Characteristics Based On Two-Dimensional Graphene/Dlack Phosphor Grating-film Composite Structure

Surface plasmon is the surface electromagnetic mode due to resonant oscillation of free electrons at the interface between metal and dielectric stimulated by the incident light.It is characteristic of large local field enhancement beyond the diffraction limit,great sensitivity to the environmental medium.However,it also has the high Ohmic loss due to absorption of metal.Recently,surface plasmon resonance based on the new emerging two-dimensional materials such as graphene and black phosphorus have aroused the increased interest worldwide.The surface plasmon coupling in these structures can produce many interesting phenomena,such as electromagnetically induced transparency(EIT),Fano resonance,Rabi splitting,which hold the potential in area of photodetection,sensing,filtering and nano nonlinear optics.In this dissertation,by using the finite difference time domain method and the finite element method,the characteristics of surface plasmon coupling in periodic ribbons/sheet coupled structure of two-dimensional graphene and black phosphorus has been investigated numerically and theoretically.The main contents of this work are listed as follows:(1)The optical properties of graphene materials and black phosphorus materials were summarized.The dependence of the conductivity and dielectric constant of graphene and black phosphorus on the frequency of electromagnetic waves were investigated in detail.(2)The longitudinal plasmonic coupling between the localized and the delocalized surface plasmon polaritons in a graphene nanoribbon arrays and monolayer structure has been theoretically investigated at mid-infrared region.It has been demonstrated that vertical plasmonic coupling can be actively controlled by either the geometric parameters or the Fermi energy in graphene,allowing for the strong light-matter interaction.Thanks to the strong plasmon coupling,a dual-band perfect absorption with A ? 100% and a large Rabi splitting exceeding 17.2 meV have been obtained in absorption spectra of this hybrid system.More intriguingly,we found,by varying the distance between graphene sheet and metallic substrate,periodic spectral nodes can emerge in absorption response of the hybrid mode,which was explained by mechanism of longitudinal microcavity resonance in this coupled system.The controllable plasmonic coupling and ultrahigh dual-band absorption capability offered by this coupled structure opens new avenues for designing the tunable multi-channel graphene optoelectronic devices with high performance.(3)A composite structure composed of black phosphorus nanoribbon array/monolayer was designed.The strong coupling and absorption response of black phosphorus ribbons surface plasmons and black phosphorus monolayer surface plasmons were systematically investigated.It was also found that the mode coupling and absorption response of the composite structure were both closely related to its geometric parameters and the electron density and anisotropy of black phosphorus.By changing the distance between the black phosphorus ribbons and black phosphorus monolayer,the coupling between two surface plasmon modes could be modulated.Furthermore,the distance between the black phosphorus nanoribbons and black phosphorus monolayer could be varied to tune the dual band absorption of the system.The mechanism of surface plasmon coupling in this proposed structure will be helpful in designing many black phosphorus-based optoelectronic devices.By investigating the coupling and absorption characteristics of the localized surface plasmon and delocalized surface plasmon modes of two-dimensional materials,the work in this dissertation can provides useful guidance for designing optoelectronic devices such as tunable photodetector,modulator and multi-channel absorbers.