A highly sensitive quadruple D-shaped open channel photonic crystal fiber plasmonic sensor: A comparative study on materials effect

A highly sensitive dual-polarized 'X' oriented quadruple D-shaped open channel photonic crystal fiber (PCF) based surface plasmon resonance (SPR) sensor for various analyte detection is proposed in this paper. Gold is taken as a plasmonic material for its stability and compatibility. Silicon nitride (Si₃N₄) and titanium oxide (TiO₂) has been used separately as an adhesive layer of gold to elevate the sustainability of the evanescent field. This paper shows a comparative study and inspects the effect of sensing performance between Si₃N₄ and TiO₂ as an adhesive layer of gold. Numerical investigations have been followed up using the finite element method (FEM). For practical feasibility, analyte and plasmonic materials have been placed at the outer surface of the sensor. After watchful investigation, the maximum wavelength sensitivities of 21,000 nm/RIU (Refractive Index Unit) and 18,000 nm/RIU have been found for the y-polarization when using TiO₂ and Si₃N_4, respectively. The highest amplitude sensitivities are of 914RIU⁻¹ and 625RIU⁻¹ for TiO₂ and Si₃N_4, respectively. Furthermore, minimum wavelength resolutions of 4.76 × 10⁻⁶ RIU and 5.55 × 10⁻⁶ RIU have been observed in y-polarization for TiO₂ and Si₃N_4, respectively. The sensor evinces a maximum figure of merit (FOM) of 236RIU⁻¹ for TiO_2. This sensor has the analyte sensing range of 1.31–1.38RI (Refractive Index) for TiO₂ and 1.32–1.39RI for Si₃N₄. The sensor also delivers low confinement loss for Si₃N₄ and TiO_2, which certifies viability in fabricating the design. Recognizing this sensor's wavelength sensitivity, amplitude sensitivity, and sensing RI range, it could be a promising candidate for detecting different liquid analytes with excellent accuracy.