Simulation of Smith purcell radiation at THz frequency

Summary form only given. In this paper, Particle-In-Cell (PIC) simulation has been used to simulate the coherent Smith-Purcell (SP) radiation source at about 1 THz frequency. We have studied three different kinds of methods in order to decrease the required threshold to gene rate coherent THz radiation. The first method is to optimize the geometrical size of the grating with a CW electron beam. For a given grove height (or width), there is an optimal value of grove width (or height) where the threshold current is minimum. The second method is to use a pre-bunched electron beam to study the superradiant radiation with zero threshold current. The third method is to add a perfect conductor directly above the grating with appropriate distance, which will enhance radiation significantly at the same injected current.