Intense wideband terahertz amplification using phase shifted periodic electron-plasmon coupling

We report efficient wideband amplification of terahertz frequency electromagnetic waves from sequential electron-plasmon coupling along a half-period staggered double grating structure. Numerical eigenmode calculations show that the fundamental plasmonic band has a strong symmetric TE-mode, with a significant longitudinal electric field component, that is confined to the electron beam channel. A particle-in-cell simulation analysis with a single frequency excitation, combined with a short pulse broad spectrum drive, confirms that this terahertz plasmonic circuit produces three or four orders of magnitude power amplification with up to 30% bandwidth and 3%–5.5% saturated energy conversion efficiency.