Application examples of chemical solution detection and biosensing using photonic SHE. (a) Schematic and the experimental results of detecting the ion concentration in solution with weak measurements. Left: the experimental setup for ion concentration detection. HWP, 1/2 wave plate; GLP1 and GLP2, the Glan laser polarizers to obtain the pre- and post-selected states (represented on a Poincaré sphere in the inset). An external magnetic field is applied in such a weak measurement system, and the polarization plane will rotate (Faraday rotation) with a small angle Δ after the beam crossing the magneto-optical media, as shown in the top middle. Bottom middle: the dependence of amplified spin Hall shifts on Δ without the external magnetic field, where the insets show the corresponding intensity distributions. Right: the experimental detection result of ion concentration of three samples NaCl, MgCl2 and CaCl2 based on the amplified spin-Hall shifts. (b) Schematic and the experimental results of monitoring sucrose hydrolysis rates with weak measurements. Top left: schematic to illustrate the process of sucrose hydrolysis. Bottom left: the optical activity of chiral molecules. The polarization plane of a linearly polarized beam will rotate at an angle α1(α2) after passing through glucose and fructose. Middle: experimental system of weak measurements similar to that in (a) by replacing the sample and external magnetic field with CS (sucrose). The insets illustrate the variation of polarization states in weak measurements. Right: the amplified pointer shifts as functions of time (sucrose hydrolysis rates) for different concentrations of acid. Figure reproduced with permission from: (a) ref.160, AIP Publishing; (b) ref.161, under a Creative Commons Attribution (CC BY) license.