Photoelectric Properties Of Phosphorene Plasmonic Microstructures

Surface plasmons have attracted extensive attention due to their subwavelength field constraints and field enhancement effects.With the progress of "top to down" and “down to top”micro-nano processing technology,plasmonic microstructures with various functions have been successfully prepared,which have important potential applications in many fields such as photoelectric detection,biosensing and optical imaging.At present,most plasmon microstructures are made of precious metals.Although the loss and process complexity of microstructures are reduced compared with three-dimensional structures,their tuning difficulty and long-wavelength weak field binding still limit further development.Therefore,at this stage,new materials are urgently needed to make up for the defects of metals.With the discovery of graphene,the field of two-dimensional materials has been developing at a rapid rate,and new content has been injected into related disciplines.Among them,phosphorene,as a new two-dimensional material,has excellent properties such as tunable band gap,in-plane anisotropy,and high mobility,which has attracted widespread attention.Using its longer carrier relaxation time,higher field confinement capability,and flexibly adjustable optoelectronic properties,it can change the traditional artificial microstructures with metal as the main material,increase the degree of freedom of control and reduce loss,which more high-performance and larger integration scale optoelectronic devices based on microstructures will be realized.This thesis is based on the classic Drude model to model the material,and uses the finite difference time domain method to perform performance simulation,aiming at the excitation of phosphorene surface plasmons,the coupling between different plasmon modes,and the anisotropic surface plasmon induced transparency has been studied,and the results obtained are as follows:1.The anisotropic localized surface plasmon resonances in the mid-infrared band of phosphorene nanoribbon array have been studied.By changing the array period,nanoribbon width and Fermi level of phosphorene,the resonance peak can be adjusted over a wide range.Secondly,the strong coupling between the localized surface plasmon and the propagating surface plasmon mode in the phosphorene nanoribbon-layer system has been investigated.The Rabi splitting energy exhibited on the spectrum can be as high as 17.3 me V.Finally,the dielectric grating is used to realize the excitation of anisotropic surface plasmons on the continuous phosphorene layer,which is adjusted by the grating period,grating width,grating height and Fermi level of phosphorene.2.Based on the anisotropic plasmons in phosphorene,the plasmon-induced transparency phenomenon in a π-type metastructure composed of three nano-strips was simulated.The near-field distribution is monitored and analyzed to find that the reason for the transparency phenomenon is due to the destructive interference between the dipoles in the lateral nanoribbons and the quadrupoles induced in the two vertical bands.By changing the Fermi level of phosphorene,flexible adjustment of the transparent window in the mid-infrared band is realized,and the quality factor of the transmission valley becomes higher as the Fermi level increases.By changing the Fermi energy level of a single nanoribbon in the dark state unit,the spatial symmetry of the structure is broken,thereby realizing a double transparent window.In addition,phosphene-based cascades π type and S-like microstructures have been constructed to achieve an increase in the number of transparent windows and a reduction in mode volume.3.The plasmon-induced transparency phenomenon caused by the coupling between the dipole mode（bright state unit）and the higher-order mode（dark state unit）in phosphorene and graphene nanoribbons was studied.The simulated transmission spectrum shows that there are multiple transparent windows in the mid-infrared band.Since the Q value of the high-order mode is only affected by its own ohmic loss,a transmission valley with a higher Q value is realized.By changing the carrier concentration of phosphorene and graphene,the transparent window can be flexibly tuned.In addition,the mobility of graphene and the refractive index of the substrate are also key factors affecting the coupling phenomenon.Strong dispersion changes near the transparent window will cause slow light,and the calculated maximum group delay can reach 0.09 ps.Finally,the plasmon-induced transparency in the vertically placed phosphorene-graphene nanoribbon system was calculated,which is also affected by the carrier concentration of materials,mobility,as well as refractive index of the substrate,and the group delay at the transparent window can be up to 0.14 ps.