Chirality and concentration detection of biomolecules based on spin Hall effect of light

Abstract

The chirality and concentration of biomolecules can be simultaneously determined by weak measurement techniques through spin Hall effect of light (SHEL)effect, which is theoretically and experimentally demonstrated in this paper. The theoretical model concerning the concentration of chiral biomolecules and SHEL has been revealed, taking tryptophan solution as an example, which shows great linearity and the sensitivity can reach to 13 um/mdeg which just use SiO2 as the reflective interface. Moreover, by inducing a film such as Ce1Y2Fe5O12(CeYIG) film with the optimized thickness, the sensitivity is increase to 23 um/mdeg for the refractive index gradient formed by the film enhances SHEL. In order to distinguish these isomers, these two isomers are called L-left-handed and D-right-handed, because the interaction between these chiral biomolecules and polarized light causes the plane of polarization to rotate in the opposite direction. In order to verify our theoretical results, we experimentally measured the SHEL of L- and D-tryptophan solutions with different concentrations. The results indicate that the sensitivity is 20.5 um/mdeg and 20.6 um/mdeg for L- and D-tryptophan solutions, respectively, and increased 1.75 times by introducing the CeYIG film, which is in good agreement with our theoretical results. At the same time, the theoretical model can obtain impurities content between optical isomers in mixed chiral solution. Our study shows great applying potential of weak measurement techniques in exactly and non-contact measurement for chirality and concentration of biomolecules.