Theoretical And Experimental Study On Smith-Purcell And Surface Plasmon Excitons In Metal Micro-nano Structures

In recent years,with the rapid development of science and technology,people expect a higher quality terahertz radiation source.The main subjects that study the utilization of terahertz radiation sources are thermal radiation,electronics and photonics.However,the radiation source obtained simply by photonics or electronics cannot achieve a good combination of high frequency and high power.Therefore,scientists have creatively proposed the combination of photonics and electronics.In this way,the terahertz radiation source is well balanced in frequency and power.The subject studied in this thesis is based on this purpose.First,we analyze the situation of electron beams passing through a semi-infinite metal structure in parallel from three aspects: theoretical analysis,MATLAB numerical calculation,and CST simulation.The analysis results show that when the electron beam sweeps through the semi-infinite gold structure in parallel,a surface plasmon is generated on the surface of the gold structure,and the frequency of the surface plasmon changes with the metal material and the energy of the electron beam.As the thickness of the semi-infinite metal structure gradually thins to close to the metal film,surface plasmons appear symmetrical and asymmetrical modes on the upper and lower surfaces of the metal film,and the surface plasmon frequency of the two modes is affected by the film the effect of thickness.Subsequently,this paper studies the case where the electron beam passes through the pure metal grating and the gold grating in parallel.The study found that the electron beam parallel sweeping through the pure grating structure produces Smith-Purcell radiation and surface waves.The frequency of Smith-Purcell radiation increases with the increase of the energy of the electron beam and increases with the decrease of the period.The frequency of surface waves is always lower than the frequency of Smith-Purcell radiation.When the electron beam sweeps through the gold grating structure in parallel,the surface plasmon,Smith-Purcell radiation and surface wave are simultaneously excited.By adjusting the period of the metal grating and the energy of the electron beam,the frequency of the surface plasmon can fall within the frequency range of Smith-Purcell radiation.At this time,the surface plasmon radiation is decoupled by the grating to achieve enhanced Smith-Purcell the effect of radiation.Since the frequency of surface waves is always less than the frequency of Smith-Purcell radiation,surface waves cannot enhance Smith-Purcell radiation.In order to make the experiment get better results,this paper simulates the structure of pure metal substrate plus gold block excited by electron beam.Through research,it was found that in this structure,due to the discontinuity of the metal structure,the localized surface plasmon was generated by the electron beam excitation,and the enhancement effect of the plasmon was greatly enhanced.The use of this structure helps the experiment get more significant effect.Finally,a metal grating with a suitable structure is designed to verify the theoretical research results.In the experiment,a scanning electron microscope was used to obtain a high-energy electron beam with good bunching,and the designed optical path system was used to maximize the signal generated by the spectrometer.When the electron beam is excited vertically or parallel across the gold grating structure,surface plasmon radiation and surface-plasmon-enhanced Smith-Purcell radiation is observed,and the frequency of this radiation is basically consistent with the theoretical calculation value.