A novel design of symmetrical grating built on D-shaped optical fiber sensor-based surface plasmon resonance

Surface Plasmon Resonance (SPR) is an electromagnetic phenomenon that occurs during the interaction between metals and dielectric materials. Fiber sensors show much attention in the last few decades because of their extremely sensitive performance. A novel design of a Dual symmetrical grating D-shaped fiber (Dual SGD-SF) based plasmonic sensor was theoretically studied. The effects of grating depth and gold and silver thickness were investigated. For the Dual SGD-SF sensor design at analyte RI = 1.5 and grating depth = 0.3 μm, the resonance wavelength at the maximum loss was 2.4 μm. The maximum wavelength sensitivity, resolution, and FOM for Dual SGD-SF were obtained at 2000 nm/RIU, 0.00005 RIU, and 22.22 RIU−1, respectively. This design was proposed for sensing very low concentrations of analyte and helps to discover the variations of refractive indices compared to high-purity liquids. To the best of our knowledge, using a symmetrical grating design as a refractive index sensor has not previously been reported.