High-Performance Plasmonic Sensor with Photonic Spin Hall Effect for NaCl Detection: Role of an Active Voltage Biasing of Graphene Monolayer in Near Infrared
摘要
In this work, a transverse spin-dependent shift of the horizontal photonic spin Hall effect at fixed wavelength (850 nm, 800 nm, 750 nm and 700 nm) is numerically demonstrated for NaCl detection. A five-layer (BK7 prism, silver, gold, graphene, and NaCl solution) plasmonic spin Hall effect refractive index sensor is proposed with the consideration of chemical potential, and applied electrical voltage variations. Analysis is started with the effect of induced voltage (1–3 V) on the chemical potential of graphene which in turn considerably responsible for the variation in the performance parameters. Initially for each value of induced voltage and for a given gold layer thickness of 3 nm, the silver layer thickness is optimized with a step of 0.01 nm for minimum reflectance in simulations. Considering increase in the concentration of the NaCl solution from 0 to 60 g/L (refractive index dependent) at fixed wavelength (850 nm, 800 nm, 750 nm, 700 nm) with applied potential (2.25 V, 2.75 V, 2 V, 3.023477 V) and corresponding chemical potential (1.201022 V, 1.224885 eV, 0.955974 eV, 1.063291 eV) of graphene, calculated values of refractive index resolution and limit of detection are (1.42 × 10–13 RIU, 4.73 × 10–12 RIU, 5.45 × 10–12 RIU, 4.64 × 10–13 RIU) and (0.000796 μg/L, 0.0219 μg/L, 0.0272 μg/L, 0.0027 μg/L), respectively. The obtained values of performance parameters (resolution and limit of detection) are better than for the case when the spin Hall effect is not applied (1.96 × 10–6 RIU, 0.0110 g/L; 1.89 × 10–6 RIU, 0.0088 g/L; 1.83 × 10–6 RIU, 0.0092 g/L; 1.76 × 10–6 RIU, 0.0101 g/L). Our values of refractive index resolution and limit of detection are better than recently published values (6.55 × 10–4 RIU and 0.217 g/L).