Coupling of Spoof Surface Plasmon Polariton With Multiple-Order SmithPurcell Radiation in THz Cherenkov Oscillator

We propose a novel concept of a Cherenkov vacuum electron device (VED) based on the coupling of leaky-wave spoof surface plasmon polaritons (LW SSPPs) with multiple-order Smith-Purcell radiation (SPR) in a circuit with a biperiodic double grating (DG) for electromagnetic radiation generation in the THz range. We show that both effective feedback and a radiation output are realized when the order of SPR in a dielectric slab is used for a feedback loop while the order of SPR into a free space serves as a radiation output. The employed biperiodic DG provides a strong coupling of the SPR with the LW SSPP in a wide bandwidth as well as an enhanced beam-wave coupling impedance. The carried-out particle-in-cell simulations demonstrate significant increase of output efficiency of up to 3% as well as expansion of frequency tunning range up to 20% (0.53-0.64 THz).