Relativistic sub-THz surface-wave oscillators with transverse Gaussian-like radiation output

Surface-wave oscillators driven by intense relativistic sheet electron beams can produce sub-terahertz waves at sub-gigawatt level of output power; however, evanescent nature of the operating wave hampers further radiation transmission and application. For these devices, we propose a method of efficient conversion of the surface operating wave into the output Gaussian-like wavebeam radiated in transverse direction with respect to the grating by applying an additional corrugation with a period twice larger than the main period. The analysis based both on the quasi-optical model and on the PIC simulations shows feasibility of 150-GHz surface-wave oscillator with 35 % efficiency and 100 MW output power. The transverse energy extraction significantly reduces the Ohmic losses down to 10% of the radiated power, which is essential for sub-THz range.