Surface Plasmon Resonance Sensor Based on Modified <inline-formula> <tex-math notation="LaTeX">$D$ </tex-math> </inline-formula>-Shaped Photonic Crystal Fiber for Wider Range of Refractive Index Detection

A wider range of refractive index (RI) detecting $D$ -shaped photonic crystal fiber (PCF)-based surface plasmon resonance (SPR) sensor is proposed in this paper for the RI detection of analyte ranging from 1.18 to 1.36. To make the proposed sensor practically implementable, analyte sensing layer and chemically stable gold (Au) as a plasmonic material layer for SPR are placed outside the $D$ -shaped PCF structure as a part of simple detection technique. Using the finite-element method with a circular perfectly matched boundary layer, it is shown through simulations that the proposed $D$ -shaped PCF-based SPR sensor offers maximum wavelength interrogation sensitivity of 20 000 nm/RIU (refractive index unit) and maximum amplitude interrogation sensitivity of 1054 RIU ⁻¹ . In addition, the proposed sensor shows maximum wavelength interrogation resolutions of $5\times 10^{-6}$ RIU and amplitude interrogation resolutions of $16.7\times 10^{-6}$ RIU. Due to high wavelength and amplitude sensitivity over wider range of analyte RI and improved sensing resolutions, this proposed sensor can be implemented for the detection of biological analytes, organic chemicals, bio-molecules, and other analytes.