High-Performance Plasmonic Sensor for Detection of Cortisol Biomarker in Near Infrared With Photonic Spin Hall Effect

In this work, a transverse spin-dependent shift of the horizontal photonic spin Hall effect (PSHE) at a fixed wavelength of 830 nm is simulated and demonstrated for cortisol detection. A five-layer (Ge20Ga5Sb10S65 chalcogenide or BK7 prism, silver, gold, graphene, and cortisol medium) plasmonic spin Hall effect sensor is proposed with the consideration of chemical potential and applied electrical voltage variations. The analysis is started with the effect of induced voltage (1–4 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 0.1 nm for minimum reflectance in simulations. Considering the increase in the refractive index (RI) of the cortisol solution from 1.3297 to 1.33 (concentration dependent) with a fixed chemical potential of graphene as 0.8967 eV, calculated values of limit-of-detection (LOD) and RI resolution are 0.0015 fg/mL and
$1.2516\times 10^{-12}$
RIU, respectively. The obtained values of performance parameters (LOD and resolution) are better than for the case when the spin Hall effect is not applied (0.002354 ng/mL and
$1.9619\times 10^{-6}$
RIU).