Optimization of Volume Free-Electron Laser with Photonic Crystal Foil Grid Structure for Operation in Sub-Terahertz Range

In this work we present the results of numerical optimization of volume free-electron laser based on the interaction between electron beam and periodic structure of microwave photonic crystal. The optimization aims at advancement of such device to sub-terahertz frequency range. We show that reduction of characteristic geometric dimensions allows to increase the oscillation frequency of photonic crystal fundamental mode f(0) up to 12.5 GHz. Moreover, we observe the possibility to generate microwaves at higher harmonics of fundamental frequency, namely at f(5) = 5 x f(0) = 62.5 GHz, and obtain output power level of about 3.6 kW.