Design, Microfabrication, and Characterization of a Subterahertz-Band High-Order Overmoded Double-Staggered Grating Waveguide for Multiple-Sheet Electron Beam Devices

At present, there is a great interest in increasing the power level of terahertz (THz) radiation sources. Aimed to improve the output power of sheet electron-beam devices, a sub-THz-band rectangular metal column-loaded double-staggered grating waveguide (RMC-DSGW) is proposed in this article, which is suitable for the interaction between the high-order overmoded wave and multiple-sheet electron beams. The RMC is used to suppress adjacent competing modes. To verify the idea, a sub-THz-band TM
₂₁
-like mode RMC-DSGW joined with two identical rectangular TE
₁₀
-TE
₂₀
mode converters was designed and manufactured by using nanocomputer numerical control milling. A reflection coefficient lower than ~ -12.6 dB and a transmission coefficient higher than ~ -8.9 dB were measured in the frequency range of 231.3-271.4 GHz. Beam-wave interaction simulations with the ohmic losses being taken into account for an RMC-DSGW-based dual-sheet beam traveling wave tube (TWT) predicted an output power of >332 W and a gain of >30.2 dB over a 3-dB bandwidth of 50 GHz (230-280 GHz). Its output power was approximately twice that of the conventional fundamental mode sheet beam TWT. It proves that the combination of the RMC-DSGW and multiple-sheet electron beams is an effective approach to improve the output power of sheet electron beam devices.