MIM waveguide structure consisting of two triangle stubs, side-coupled with an eight-like resonant cavity

Abstract Herein, a Fano resonance based optical sensor with high sensitivity is proposed. The sensor comprises a metal–insulator–metal (MIM) waveguide with two symmetric triangle stubs, side-coupled with a square ring resonator with a stub (SRS). Utilizing the 2D finite element algorithm, the transmission characteristics of the MIM waveguide structure are systematically explored. This analysis reveals that the coupling effect between the MIM waveguide and the SRS leads to the appearance of Fano resonance. After using a polydimethylsiloxane (PDMS)-sealed resonator, an outstanding temperature sensitivity of −20.3 nm/ ∘ C is obtained. In addition, the influence of the width of the MIM waveguide, the coupling distance, the distance between two symmetric triangle stubs and the geometric parameters of the resonator on the Fano resonance line is also studied in detail. Optimizing these structural parameters results in a peak refractive index (RI) sensitivity of 6000 nm/RIU, and the figure of merit (FOM) is 17RIU−1. These results not only help to narrow the gap with the optical fiber sensor, but also pave the way for the design and application of ultra-high sensitive RI sensor and temperature sensor.