Theoretical foundations for the evanescent mode oscillator (EMO) as a high-efficiency source of millimeter-wave and terahertz radiations

Evanescent mode oscillators (EMO) are investigated as high-efficiency sources of millimeter-waves and low-frequency parts of terahertz radiation. EMO can be considered a high-efficiency version of the extended interaction oscillator (EIO) using the evanescent resonance mode (ERM) of a slow-wave structure. It has been shown quantitatively that the efficiency of the EMO is superior to that of the conventional EIO having the same periodic unit cell. The condition to have an evanescent resonant mode in a chain is derived in this article. EMO threshold excitation condition is expressed in terms of the beam and RF mode parameters. A Typical EMO is systematically modeled, and its performance is checked with a particle-in-cell simulation software package. The excitation of the ERM modes is illustrated, with the results being close to the prediction of the non-linear model used in the paper.