Design and Simulation of a D-Shaped Plasmonic Biosensor Utilizing Dual-Core Photonic Crystal Fiber

A surface plasmon resonance (SPR)-based photonic crystal fiber (PCF) for the detection of various analytes through surface plasmon has been proposed in this study. In this biosensor, the main workmanship of the structure is based on the coupling between the fundamental mode of the photonic crystal fiber and the plasmonic mode, which creates the resonance wavelength at different refractive index (RI) of the analyte. In this design, the plasmonic material silver (Ag) is deposited between the PCF and the analyte to detect the RI changes of the analyte, and considering that silver oxidizes quickly, a thin layer of titanium dioxide (TiO₂) is placed between the silver and the PCF; this solves the problem and strengthens the adhesion of silver on the fiber. For the optimal and suitable analysis of the performance of the proposed biosensor, the thickness of the structure layers, the lattice constant, and the diameter of the air holes of the structure have been analyzed. In this proposed biosensor, the maximum wavelength sensitivity is 10,000 nm/RIU, and the amplitude sensitivity is 250 RIU⁻¹, and this structure has provided a maximum resolution of 2 × 10⁻⁵ RIU in the RI of an analyte, which ranges from 1.32 to 1.37. According to these results, the proposed biosensor emerges as an exemplary candidate for applications in medical and chemical assays, as well as various assessments reliant on the RI of different analytes.