LAUSR

In this letter, the studies of the vertical split-ring resonator (VSRR) at its second resonant mode are carried out for the first time. The VSRR can be regarded as an electric resonator at such resonant mode, which is proven by its resonant current distribution. Then, a new type of rejection plasmonic filter is constructed by adding the VSRR on the planar spoof surface plasmon polariton (SPP) waveguide using double-side corrugated metallic strips. The second resonance of the VSRR is excited by the $z$ -component of the electric field of the spoof SPP mode, near which the SPP propagation is prevented. Utilizing this principle, a plasmonic filter with broadband rejection is designed and fabricated. The measurement result is presented to confirm the highly efficient filtering performance of the proposed filter, which makes it possible to be applied in the advanced integrated plasmonic devices and circuits at microwave and terahertz frequencies.