Resonant tunneling of surface plasmon polariton in the plasmonic nano-cavity.

We investigate the reflection and transmission characteristics of the low-dielectric constant cut off barrier in the metal-insulator-metal (MIM) waveguide and propose a novel plasmonic nano-cavity made of two cut off barriers and the waveguide between them. It is shown that the anti-symmetric mode in the MIM waveguide with the core of the low dielectric constant below the specific value cannot be supported and this region can be regarded as a cut off barrier with high stability. The phase shift due to the reflection at the finite-length cut off barrier is calculated and the design scheme of the cavity length for the resonant tunneling is presented. The transmission spectra through the proposed nano-cavity are also discussed.