Highly Sensitive TiO2-Gold Coated Plasmonic Biosensor with Microchannel-Based D-shaped Photonic Crystal Fiber

Abstract

A microchannel-based D-shaped photonic crystal fiber (PCF) biosensor utilizing surface plasmon resonance (SPR) to measure the refractive index (RI) of an analyte in the near-infrared (IR) region is proposed in this paper. The sensor's design incorporates a hexagonal lattice with four rings of circular air holes, where the upper row of holes is etched to create a D-shaped plane and a microchannel is integrated. The external sensing mechanism allows plasmonic gold (Au) deposition on the interior surface, with a thin titanium dioxide (TiO₂) layer to improve adhesion. Numerical simulations utilizing the finite element method (FEM) with perfectly matched layer (PML) boundary conditions were employed to optimize the important parameters, executed through COMSOL Multiphysics. The simulation results indicate that the optimized sensor achieves a peak wavelength sensitivity of 23,500 nm/RIU, amplitude sensitivity of 489.3 RIU⁻¹, resolution of 4 × 10⁻⁶ RIU, and FOM of 412.28 within the refractive index (RI) range of 1.31 to 1.42. With its high sensitivity, wide detection range, and fabrication tolerance, the proposed sensor shows strong potential for biological and biochemical analyte detection.