Efficiency enhancement in a Cherenkov laser loaded with a Kerr-like medium

Efficiency enhancement in energy conversion for a Cherenkov free elctron laser loaded with a Kerr-like medium is discussed with the aid of particle simulation. For the analysis of the problem, a two-dimensional model for the Cherenkov free electron laser is considered which is composed of a planar relativistic electron beam and a parallel plate waveguide one plate of which is loaded with a nonlinear dielectric sheet exhibiting a Kerr-like effect. To follow the growth of an electromagnetic wave and the decrease in the kinetic energy of the electron beam in the specified model of the Cherenkov free electron laser, a particular segment of the electron beam with the longitudinal length of one guide wavelength is picked out. In that segment, as it travels down the waveguide, the interaction between the electromagnetic wave and a group of electrons is analyzed with the use of the finite-difference time-domain (FDTD) method. The result of numerical simulation shows that the efficiency of energy transfer from the electron beam to the electromagnetic wave is greatly enhanced by the proper choice of the nonlinear parameter for a Kerr-like medium. The enhanced efficiency is due to the improved velocity matching between the electron beam and the electromagnetic wave, and to the self-focusing effect of a Kerr-like medium