Tunable Fano resonance in plasmonic MDM waveguide with a square type split-ring resonator

Plasmonic metal-dielectric-metal (MDM) type waveguide structures with a split ring resonator (SRR) or a complementary split-ring resonator (CSRR) are proposed. The waveguides can support Fano type transmission. It is observed that the asymmetric non-integer modes in addition to the symmetric integer modes can be excited in the SRR structure. Simulation results indicate that the transmission spectra can be efficiently tuned by changing the position of the split as well as other parameters. However, for the symmetrical CSRR structure, the non-integer modes can not be excited. The transmission properties of the proposed structure are numerically studied by the finite element method (FEM). The proposed structures have potential application in the area of the plasmonic filter, the refractive index nanosensor, the integrated slow-light devices, and so on.