Terahertz Planar Amplifier With Spoof Surface Plasmon Polariton Modes Based on Meta-Composite Slot Slow Wave Structures

To reduce the manufacturing difficulty of the slow wave structure (SWS) and enhance integration with passive devices for realizing terahertz (THz) integrated circuits (ICs), a spoof surface plasmon polariton (SSPP) mode planar SWS based on a meta-composite slot (MCS) SWS is proposed. The SSPP mode is employed in the MCS-SWS, which enables the enhancement of longitudinal field in the beam-wave interaction region, thus achieving an average interaction impedance of the first-order spatial harmonics over $4.7~\Omega $ at 340 GHz. Furthermore, the physical mechanism of field enhancement generated by the MCS-SWS is elucidated using the double electric dipole model. In addition, an effective strategy to suppress the backward wave oscillations is presented using a field analysis. Furthermore, the particle-in-cell (PIC) results indicate that under the conditions of a dual sheet electron beam (SEB) with a voltage of 10.6 kV and a current of 50 mA, the maximum saturated output power can reach 26.7 W at 341 GHz. The corresponding gain per unit length is 1.93 dB/mm, and the electron efficiency is 2.52%. The total SWS length, benefiting from such a high gain per length, is only 10.8 mm, which is much shorter than that of a conventional traveling-wave tube (TWT) in the same frequency band. These indicators suggest that MCS-SWS has great potential to be used as the core of THz amplifiers for THz ICs.