On-chip plasmonic nanosensor based on multiple Fano resonances in rectangular coupled systems

The transmission characteristics of coupled multi-resonators integrated in metal-insulator-metal (MIM) waveguide systems are studied and used to design refractive nanosensors. The symmetry of this nanostructure can be easily broken by changing the relative distance between the multi-resonators, and the transmission spectrum for the system will exhibit double sharp Fano profiles. Simulation results show that the Fano profiles can be used for high-sensitivity refractive sensing with a sensitivity reaching ∼800nm/RIU and figure of merit (FOM) of ∼1.845×104. Moreover, the structure can be easily extended by adding another slender rectangular resonator, and multiple Fano resonances will appear in the spectrum. The new formed nanostructure can achieve a higher sensor sensitivity about ∼875 nm/RIU, and the FOM is 1.861×104. The proposed nanostructures will have great application prospects in on-chip information processing, biosensors and analytical chemistry.