Multiple band-rejection filters in dual-frequency bands based on spoof surface plasmon polaritons

Multiple band-rejection filters based on spoof surface plasmon polaritons (SPPs) are designed in dual frequency bands using interactions between spoof SPP waveguide and metamaterial particles. The multi-band rejections are achieved by etching π-type decorations on the spoof SPP waveguide. More importantly, the bandwidths, isolation and shifting of the rejection frequencies of filters can be controlled very efficiently by varying different geometrical parameters of the π-type decorations. Both numerical and experimental results are demonstrated to verify the large flexibility and excellent functionality of the multiple band-rejection filters in both lower and higher frequency bands. We are fully confident that the use of two frequency bands in realizing multiple band-rejections filtering by the proposed spoof SPP waveguide makes it unique in giving a boost to the development of plasmonic integrated circuits and systems.