Strong Coupling Between Planar SIW Cavity and Complementary Spoof LSP Particle at Microwave Frequencies

ABSTRACT Strong coupling is a distinct light–matter interaction regime, which can bring about intriguing physical phenomena and enable novel device functionalities. Here, we propose a planar guided‐wave pathway to realize strong cavity‐plasmon coupling at microwave (MW) frequencies, comprising a substrate integrated waveguide (SIW) resonator as the cavity and a complementary spoof localized surface plasmonic (LSP) particle as the artificial plasmon. The artificial plasmon modes are inherently excited by the resonant field of the SIW cavity, without the need for any special materials or additional external control conditions. More importantly, both the cavity and artificial plasmon modes can be independently tuned via their geometric parameters, thereby allowing the frequencies for strong coupling to be freely designed. As a proof of concept, we experimentally demonstrate that the proposed strong coupling system can be flexibly applied in the design of passband filter, even below the cutoff frequency of SIW cavity. The proposed guided‐wave strong coupling configuration has the advantages of planar integration, simple construction, and flexible design, opening a new path for the development of next‐generation microwave devices.