TiO2/gold-graphene hybrid solid core SPR based PCF RI sensor for sensitivity enhancement

We propose a D-shaped photonic crystal fiber (PCF) refractive index (RI) sensor based on surface plasmon resonance (SPR), capable to work in both visible and near-infrared (NIR) wavelength (410-1790 nm) region. Gold (Au) is deposited on the flat outer surface of the PCF to excite the plasmons. A thin titanium dioxide (TiO2) layer is sandwiched between fiber surface and gold layer so that the gold nanoparticles can strongly attach with the fiber surface. It also helps to shift the resonance wavelength of the proposed sensor to near IR region which is much advantageous for biosensing. A thin graphene layer is applied on Au to assist adsorption of ample biomolecules on its surface. It also prevents gold from oxidation. Simulation results show the theoretical maximum wavelength sensitivity of 48,900 nm/RIU and average sensitivity of 13112.5 nm/RIU in the RI rage of 1.32-1.40. Besides this, the proposed sensor shows the higher amplitude sensitivity of 738.74/RIU with high resolution and maximum figure of merit (FOM) of 7.604 x 10(-6)RIU and 611.25/RIU, respectively. These promising outcomes of the proposed sensor make itself to be a potential candidate for the various analyte (organic chemicals, biomolecules) detection. Moreover, the fabrication feasibility of our proposed D-shaped sensor becomes easier than the circular PCF sensors as it avoids the internal coating of the plasmonic metals.