Au-TiO2-Graphene Grated Highly Sensitive D-Shaped SPR Refractive Index Sensor

Surface plasmon resonance (SPR) integrated with fiber optic technology offers a new perspective to sensing applications in the fields of physics, chemistry, and biology. A numerical simulation of a highly sensitive D-shaped optical fiber SPR refractive index (RI) sensor based on Au-TiO2-graphene grating structures is presented in this paper, for the first time. Simulation studies were carried out in a FEM-based software program. Coatings of titanium dioxide (TiO2) and graphene are applied on top of the gold (Au) layer to improve the sensor performance. The effect of material thickness and other parameters including gap size between gratings, residual cladding thickness, gratings numbers, and thickness of coating layers is investigated, and optimum values are found to achieve the highest sensitivity. In this study, the maximum sensitivity of 12,415 nm/RIU in the range of 1.33 to 1.4 RI is reached, for a single-mode fiber expressing a major advancement in the sensing ability. These results show improved responses in comparison with other reported D-shaped fiber optic SPR sensors. Therefore, the proposed SPR sensor structure will have the great sensing potential for applications such as chemical and biochemical.