1.2THz backward wave radiation generated by double bunched sheet beams

Coherent terahertz radiation obtained from double bunched sheet electron beams over a surface evanescent wave provides an effective method to extend the operating frequency and power capacity. An overmoded ridge-loaded grating waveguide was introduced in our double sheet beam backward wave oscillator (BWO) design. The fundamental mode TM11 was updated to the TM₂₁⁺⁺ mode, which is compact to integrate with the multi-beam concept. Pierce small signal theory (PSST) was used to predict the growth rate and start current. Particle-in-cell (PIC) analysis showed the BWO can radiate 21.1dBm (150mW) pulse output power at 1.209THz with the beam parameters of 20kV and total current 5mA.