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Gain‐Associated Nonlinear Phenomenon in Single‐Conductor Odd‐Mode Plasmonic Metamaterials

Nonlinear phenomena such as second‐harmonic generation (SHG) play an important role in both optical and microwave technologies. To achieve high second‐harmonic (SH) conversion efficiency and single‐conductor system adaptability simultaneously, a gain‐associated SHG method based on odd‐mode spoof surface plasmon polaritons (SSPPs) is proposed. Field analysis indicates that the odd‐mode SSPPs can support internal electric potential difference on the cross sections of single‐conductor transmission structures to feed active semiconductor chips, which is hardly achieved by the even modes of single‐conductor structures. Measured results demonstrate the realization of SHG with a gain of 4.93 dB at 9 GHz based on the odd‐mode SSPPs, accompanied by the third‐harmonic suppression and backward SH isolation as a result of the customized passband of odd‐mode SSPPs. The ingenious detachable chip carrier can easily be disassembled, replaced and repaired, bringing big convenience and adaptability to practical applications. Moreover, the proposed single‐conductor active integration method can be extended to other single‐conductor devices, which has great potentials in the flexible systems and wearable devices.