Controllable refractive index sensing and multi-functional detecting based on the spin Hall effect of light

In this work, based on the spin Hall effect of light (SHEL), by considering the surface plasmon resonance (SPR) effect, a multi-functional detecting and controllable refractive index (RI) sensing structure containing sodium is theoretically established. The results reveal that the sodium layer has great influence on transverse shift (TS) of SHEL, while the polymethyl methacrylate (PMMA) layer has a large impact on the resonance angle. In the symmetrical distribution of TS, sodium has obvious advantages over gold and silver in the TS and sensitivity. The quantitative relationship between the TS and the RI of the sensing medium is established. Fermi energy, thicknesses of PMMA and sodium can be adjusted to measure the RI of three different orders. Remarkably, the sensitivity can be controlled by changing the thickness of sodium. The structure can also be used to measure the resonance angle and Fermi energy. Therefore, besides the advantages of sodium, this work realizes controllable sensing of RI and the functions of resonance angle and Fermi energy detecting. These studies may open avenues for the application of optical RI sensors and the precision measurement of other physical quantities.