Electron Beam Third Harmonic Amplification Generates High-Power Tunable Terahertz Radiation

A novel approach to extract and amplify the third harmonic of electron beam to generate high-power terahertz radiation is presented. Three planar grating structures operating in the backwave region are used for the extraction and amplification of the electron beam from the fundamental modulation, the fundamental amplification, and the third harmonic. This results in an amplified output of the fundamental wave and a high power output of the fundamental triplet frequency. The planar grating structure is easier to machine and assemble than conventional harmonic amplifiers and increases the flow rate of the electron beam. Calculations show that with an input signal of 119.5–120.6 GHz at 80 mW and a 35-A/cm2 electron beam in adjustment from 27.5 to 29.3 keV, the structure has an output signal of hundreds of milliwatts in the range of 358.5–361.8 GHz, with a power output of 583.2 mW at the central frequency point of 360 GHz. The harmonic signal is output while a watt-level fundamental signal can be output.