Research On Near-field Imaging And Manipulation Of The Excitation Efficiency Of Ultrafast Propagating Surface Plasmon

Propagating Surface Plasmon(PSP)is the most notable characteristic of confining energy to the sub-wavelength scale,the propagation speed is close to the speed of light,and it has an unprecedented terahertz bandwidth.The characteristics of PSP make it hopeful to become a carrier of information transmission in the nano-circuit in the future.Among them,achieving efficient excitation of PSP is the key to designing PSP-based nanophotonic devices.Effective excitation of PSP in a small space is essential for the development of surface plasmon photonic circuits.Therefore,it is necessary to explore how to couple light to the coupling of PSP.It is more efficient and conducts research on the regulation of its excitation efficiency.The study of systematic imaging of PSP and the regulation of its excitation efficiency can promote the process of miniaturization and integration of plasmon components.Since the energy of PSP is constrained in the sub-wavelength scale,the use of near-field microscopy to perform imaging and characterization studies is a prerequisite for revealing its physical properties and optimizing its excitation efficiency.In this paper,PEEM technology is used to conduct systematic near-field imaging of the PSP excited at the groove coupling structure etched on the silver nano-film,and the dual-beam pump-probe experiment is used to study the regulation of PSP excitation efficiency.The specific research content and results are as follows:(1)Carry out research on near-field characterization of PSP.Use PEEM technology to perform near-field characterization of PSP,and obtain the PEEM near-field interference image of PSP.The system measured that when the wavelength of the incident laser is720-900 nm,the fringe period of the interference pattern between the PSP and the incident laser is 5.9?m-7.7?m,and the wavelength of the PSP is 700nm-879 nm.The experimental results are consistent with the theoretical simulation results.(2)Carry out research on the regulation of PSP excitation efficiency by a single beam.Use PEEM technology to control the excitation efficiency of PSP.The results show that the excitation efficiency of the PSP can be controlled by adjusting the polarization direction of the incident laser.It can be seen from the experimental results that when the incident laser polarization is close to 0°(P polarization),the excitation efficiency of PSP is the highest,and when the incident light polarization is close to 90°(S polarization),the excitation efficiency of PSP is the lowest.The simulation results of the single beam time finite time domain difference method(Finite Difference Time Domain,FDTD)are consistent with the experimental results.(3)Carry out research on the use of dual-beam pump-detection to control the excitation efficiency of PSP.Because of the interference of pump light in single-beam research,we use double-beam pump-probe experiments to eliminate the interference of pump light on the excitation efficiency of the PSP.It can be seen from the experimental results that when the incident laser polarization is close to 0°(P polarization),the excitation efficiency of PSP is the highest;when the incident light polarization is close to 90°(S polarization),the excitation efficiency of PSP is the lowest.The reason for the same result as the single-beam experiment is that the excitation efficiency of the PSP is dominated by the vertical component of the pump light.Compared with the finite time domain difference method(Finite Difference Time Domain,FDTD)simulation results,in the dual-beam pump-detection experiment,the curve of the normalized light emission electron yield with the polarization direction of the incident laser appears in the plateau area.This phenomenon is attributed to the background noise of the detection laser drowning the change in the excitation efficiency of the PSP.