Abstract This study proposes a highly refractive index sensor based on Fano resonances in metal–insulator-metal waveguide with Nano-wall side-coupled to eye-like resonator with rectangular defect and two slots. The Fano resonance is originated from the coherent coupling and interference between the discrete and the continua state. It shows a different profile, which is typically asymmetric and sharp line, in comparison with the Lorentzian resonance profile. By using a numerical solution in the finite difference time-domain, the sensing properties of the proposed design are studied. The results of our study indicate that there exist five fano resonance peaks in the transmission spectrum, and they reveal a linear relationship between the material’s refractive index and the wavelength of resonances. With optimizing structure parameters, the calculated maximum refractive index is 3144 nm/RIU. The application of the structure for temperature sensing is discussed, and the sensitivity can reach up to 1.274 nm/°C respectively. The proposed structure with extremely high sensitivity and compactness can provide an excellent case for designing high-performance integrated plasmonic devices.
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