Design of a diode oscillator with a fieldemission cathode placed in a photonic crystal (PC) resonator is described. Results of numerical calculation of basic electrodynamic parameters of the PC resonator are presented. The 3D electrodynamic simulation by using the modern software package HFSS shows that varying the design of the energy output allows control of the loaded Qfactor in a wide range. Selection of the optimal value of the loaded Qfactor provides rather high output power and efficiency for reasonable values of the fieldemission cathode current density.
