Design and analysis of birefringent SPR based PCF biosensor with ultra-high sensitivity and low loss

A novel, perfectly hexagonal lattice photonic crystal fiber (PCF) biosensor based on surface plasmon resonance (SPR) is proposed in this research. To design and investigate the influence of several initial geometric parameters on the sensing properties of the sensor, finite element method (FEM) based commercially available COMSOL Multiphysics version 5.3a is used. A 20 nm layer of chemically stable plasmonic material gold (Au) is used to make the excitation possible between the core and plasmonic modes. A thin film of TiO2 is placed on the glass surface, which allures the field from the core guided mode and also assists in the adhesion of gold (Au) on the fiber. By exploiting the geometric parameters, simulation results show a maximum wavelength sensitivity of 16,000 nm/RIU (Refractive Index Unit) and 17,000 nm/RIU for x-polarization and y-polarization respectively due to the dielectric refractive index (RI) variation from 1.33 to 1.41. It is shown that the highest obtained amplitude sensitivity of the proposed sensor reaches 4596 RIU-1 and 4557 RIU-1, respectively, for x-polarization and y-polarization with the maximum loss of 3.73 dB/cm and 4.48 dB/cm. Additionally, the maximum sensor resolution (amplitude) of 2.18 x 10(-6) and 2.19 x 10(-6), the maximum sensor resolution (wavelength) of 6.25 x 10(-6) and 5.88 x 10(-6) for x- and y-polarization modes respectively and maximum birefringence of 8.8984 x 16(4) is attained. Due to its high sensing characteristics, the mentioned sensor is expected to contribute to the accurate detection of biological and organic chemical analytes.