Tunable plasmonic refractive index sensor based on enhanced photonic spin Hall effect

Abstract

The present work presents a novel approach to improve and tune the conventional spin-dependent shift (CSDS) by using the photonic spin Hall effect (PSHE). The phenomenon known as the PSHE arises from the separation of spin states with opposing orientations upon the interaction of light with linear polarization incident on the multilayer structure interface of exhibiting a refractive index gradient. The PSHE may be achieved by using a composite structure of silicon (Si), silver (Ag), and Graphene. In this context, as a plasmonic material, Ag is employed. Si is used to augment the evanescent field in proximity to the contact between the uppermost layer of Graphene and the surrounding air. further, for adjusting the CSDS, graphene is utilized as a polarizer. The highest CSDS of 1215 μm is achieved when the thickness of Si is optimized at 13 nm. This can be accomplished by adjusting the chemical potential (CP) to a value of 1.982 eV for left-hand horizontal polarization. Notably, this magnitude of CSDS is bigger than what has been previously reported studies on the PSHE. A spin-dependent sensitivity (Ssd) of 25158.28 μm/RIU is attained when the CP is about 1.984 eV for refractive index (RI) sensing with a change in RI (△n) of 5 × 10-3. Furthermore, the suggested sensor (namely, structure 3) achieves a more precise limit of detection, with a value of 3.974×10-8 degree.RIU/μm.