MIM waveguide structure consisting of a semicircular resonant cavity coupled with a key-shaped resonant cavity.

Abstract

We describe the optical transmission properties of a surface plasmon polariton waveguide structure consisting of a metal-insulator-metal (MIM) waveguide and a semicircular resonant cavity coupled with a key-shaped resonant cavity. Finite element algorithm simulated the optical response of a MIM waveguide structure. The influence of coupling length, geometrical size, and asymmetry of the key-shaped cavity and the radius of the semicircular resonant cavity on the Fano resonance line was investigated. Results demonstrate that variation of the key-shaped cavity asymmetry leads to the appearance of dual Fano resonances. When materials with different refractive index fill in the key-shaped cavity, the MIM waveguide structure achieves a sensitivity of 1261.67 nm/RIU. This performance allows the waveguide to be used for nanoscale biosensor applications such as measuring glucose concentrations. We simulated various spiked glucose concentrations by calculating the frequency shift as the second Fano resonance line moves towards longer wavelength. Glucose concentrations were calculated from variations of the Fano resonant wavelength. The waveguide structure proposed in this paper shows impressive practical prospects for many applications in the chemical sensing and biomedical fields.