Efficient Amplification of Large‐Signal Spoof Surface Plasmon Polaritons in a Subwavelength Size

Abstract The advancement of communication systems demands ever‐smaller sizes, leading to the integration of more circuits in compact forms. A promising solution lies in Spoof Surface Plasmon Polaritons (SSPPs), which enable strong confinement, low interference, and a significant wave vector, thereby facilitating smaller sizes. However, the amplification of large plasmonic signals in a compact size remains a daunting scientific challenge for the further development of SSPPs communication systems. In this study, this challenge is tackled by selecting GaN High Electron Mobility Transistors (HEMTs) and load/source‐pull technologies. To ensure efficient operation, impedance‐matching networks are designed, resulting in a remarkably small amplifier structure. The approach involves utilizing the Bayesian optimization (BO) algorithm to fine‐tune the matching network, leading to exceptional amplification performance. The results obtained in the frequency range of 1–3 GHz are highly promising, with both simulated and measured results demonstrating an impressive output power exceeding 40 dBm, a power added efficiency (PAE) surpassing 60%, and a gain exceeding 10 dB. These remarkable achievements underscore the viability of amplifying large‐signal SSPPs and outputting high‐power SSPPs waves within a subwavelength size, opening exciting possibilities for SSPPs communication, sensing, and imaging systems.