THz Cherenkov Oscillator Efficiency Increase by Use of Long Structures

Peculiarities of self-fields excited on a slow wave circuit when electron beam is moving along either uniform grating (Smith-Purcell radiation) or bi-periodic/nonuniform grating (leaky radiation of spoof surface plasmon polariton) have been considered. It is shown that deceleration of electrons (energy transfer from electrons to EM wave) may occur for relatively long distances (grating lengths) without overbunching that may result in both low starting current and relatively high efficiency in the THz devices based on the SPR (orotron/DRO) and based on the hybrid bulk-surface modes.