Multiple Independently Controllable Fano Resonances Based on the MIM Waveguide and Their Application in Sensing

A multi-purpose waveguide structure utilizing surface plasma polariton (SPPs) has been developed. This structure consists of a metal–insulator-metal (MIM) straight waveguide with a silver baffle, an analogous M-shaped cavity, and a semi-ellipse cavity. Utilizing the finite element method, the structure’s optical transmission properties and magnetic field distributions are examined. The results show that Fano peaks maybe originate from different resonance cavities. Fano resonances can be adjusted individually by modifying the geometrical properties of the corresponding cavity. The refractive index sensing technique is investigated, and it is discovered that the refractive index sensitivity may reach up to 1980 nm/RIU. This proposed structure can detect cholesterol and ethylene glycol concentrations simultaneously by separating the analogous M-shaped cavity and the semi-ellipse cavity, with sensitivities reaching 30.2 nm mL/mg and 137.5 nm/%, respectively. Thus, it has the potential to be employed as a multifunctional nanoscale sensor.