Fluoride Fiber Sensor With Huge Performance Enhancement via Optimum Radiative Damping at Ag–Al2O3–Graphene Heterojunction on Silicon

Surface plasmon resonance-based fiber optic sensor with multilayer heterojunction is simulated and analyzed. The constituent materials are ZBLAN fluoride core, NaF clad, amorphous Si layer, Ag layer, Al2O3interlayer, and graphene monolayer. The main idea behind the study is to optimize the radiative damping (i.e., optimum radiative damping, ORD) at the Ag-Al2O3- graphene heterojunction in order to enhance the sensor's figure of merit (FOM) as much as possible. The effect of graphene monolayer's presence on sensor's FOM is also examined. Multiple occurrences of ORD may be achieved by coordinated variation of Ag and Al2O3layer thicknesses along with light wavelength. Among the several prominent ORD conditions, the combination of 45.3-nm-thick Ag layer, 11-nm-thick Al2O3layer, and 938.7-nm wavelength leads to a massively large FOM of 31806.65 RIU-1. The above FOM of the FOSPR sensor is nearly six times that for the corresponding prism-based SPR sensor (i.e., 5500 RIU-1) reported earlier with Al2O3interlayer and MoS2monolayer at λ = 1200 nm. Further, the proposed sensor provides substantially greater FOM compared to existing prism-based and FOSPR sensors.