Ultrasensitive detection of ion concentration based on photonic spin Hall effect

Abstract

We propose a unique application of the photonic spin Hall effect for ultrasensitive detection of the ion concentration in solution. By incorporating the quantum weak measurement, the photonic spin-Hall shift acts as the measurement pointer and the optical rotation of solution in the magnetic field acts as the postselection state. The optical rotation is related to the Faraday effect, which is sensitive to the ion concentration of the solution. The high measurement resolution with 1.4×10−4 degree for the optical rotation angle is achieved, which outperforms the standard polarimeter. Furthermore, the high resolution with 2×10−5mol/ml for the ion concentration is obtained due to the weak-value amplification in the quantum weak measurement. In our scheme, the ion concentration is real-time detected by the amplified spin-Hall shift and thereby provides possible applications in biochemical sensing and water-quality monitoring.