Enhancement of coherent Smith-Purcell radiation at THz frequency

This paper explores several mechanisms to enhance the coherent Smith-Purcell radiation (SPR) at THz frequencies. A simple analytical dispersion relation is derived to predict the operating frequency for both open grating and Orotron-like devices. The analytical predictions are in excellent agreement with particle-in-cell simulations. It is found that the start current for a continuous electron beam to excite coherent SPR can be reduced by orders of magnitude, by merely varying the groove width and height of the grating, with grating period and beam energy being held constant. Other mechanisms, such as prebunched beams and open cavity configurations are also investigated for the enhancement of coherent SPR.