Research On Surface Plasmon Polaritons By Free Electron Beam Excited Metal

Combining electronics with photonics to produce electromagnetic radiation is a new field of research that has aroused the interest of researchers.There is important value in researching the combination of electronics and photonics in-depth by free electrons and surface plasmon polaritons.In this paper,the study of surface plasmon in free electron excited metal is carried out.In this paper,we first analyze the surface plasmon polaritons excited by the electron beam passing through the surface of semi-infinite metal structure and metal film structure.For the semi-infinite metal structure,the frequency of surface plasmon polaritons is related to the properties of metal material and the energy of electron beam.For the metal film structure,surface plasmon polaritons have a symmetrical mode and an asymmetric mode,and its frequency is related to the properties of metal material,the thickness of metal film and the energy of electron beam.In order to research the radiation problem of surface plasmon polaritons,this paper studies the Smith-Purcell radiation and surface wave generated by the electron beam parallel passing through the perfect electrical conductor grating.Smith-Purcell radiation is related to the energy of electron beam and the period of grating,and its frequency increases corresponding to the increase in electron beam energy and the decrease in the period of grating.The frequency of surface wave is affected by the energy of electron beam and the structural parameters of grating(such as period,gap depth,duty cycle),and it is always smaller than the frequency of Smith-Purcell radiation.In the non-ideal metal grating,surface plasmon polaritons,Smith-Purcell radiation and surface wave can be excited by the electron beam at the same time.The physical process is analyzed in detail in this paper.Smith-Purcell radiation does not change despite the introduction of metal materials.Surface plasmon polaritons have two modes with different frequency.As the grating gap depth increases,the frequency difference between the two modes becomes larger.If the period of metal grating and the energy of electron beam are suitable,Smith-Purcell radiation is enhanced by surface plasmon polaritons.Finally,the suitable metal grating is designed according to the results of simulation analysis in this paper,and the experimental study was carried out by scanning electron microscopy and spectrometer.Scanning electron microscope provides a well-behaved electron beam.Spectrometer collects the signal stimulated in scanning electron microscope by fiber,and analyzes the composition of the signal to obtain its spectrum.The multiple spatial harmonics of Smith-Purcell radiation and the phenomenon of suspected surface plasmon polaritons is observed when electron beam parallel passes through gold and silver grating.Surface plasmon polaritons is observed when electron beam interacts with the gold grating at an angle.