NONLINEAR SATURATION AND EFFICIENCY ENHANCEMENT IN A CHERENKOV LASER USING A DIELECTRIC GRATING

With the aid of particle simulation, this paper discusses nonlinear sa turation and efficiency enhancement in a single-pass Cherenkov laser u sing a dielectric grating, taking into account the nonlinear propertie s of a relativistic electron beam, For the analysis of the problem, a two-dimensional model for the Cherenkov laser is considered which is c omposed of a planar relativistic electron beam and a parallel plate wa veguide, one plate of which is loaded with a dielectric grating, First , the nonlinear characteristics for the growth of the electromagnetic wave are considered for a dielectric grating with constant parameters, The variation of the groove depth or the slot width in a dielectric g rating is found to have the same effect on the growth characteristics as the variation of the permittivity of a dielectric sheet with consta nt thickness, Then, in order to enhance the efficiency in energy trans fer from the electron beam to the electromagnetic wave in the Cherenko v laser, one of the grating parameters or the groove depth is adiabati cally decreased in accordance with the decrease in the average velocit y of the electron beam, The result of numerical simulation shows that sufficient efficiency enhancement in energy transfer is achieved with the use of a dielectric grating with a variable parameter.