Dual-core-enhanced surface plasmon resonance for sensing high refractive index liquid based on photonic crystal fiber

A dual-core photonic crystal fiber sensor based on surface plasmon resonance is theoretically proposed for the high-sensitive detection of high refractive index liquid analytes. Dual-core construction can effectively enhance the coupling effect between the fiber-core mode and the surface plasmon polariton modes, leading to sharp loss peaks at the resonance wavelengths. As the refractive index of the targeted analyte varies, the resonance condition will change as well and cause a certain shift of loss peak. Numeric results show that this dual-core fiber sensor exhibits an average linear sensitivity 9538 nm/RIU and a maximum sensitivity is 11400 nm/RIU with a resolution 8.77 × 10⁻⁶ RIU. The detected range is broad and covers the high refractive index range from 1.45 to 1.58 with an average figure of merit 284.5 RIU⁻¹. The dependence of structure parameters and the thickness of coated-metal thin-film on sensing performance is performed systemically and suggests different responses. The proposed sensor is highly promising in detecting high refractive index liquid analytes in the fields of biological detection, environmental monitoring and chemical analysis.