Measurement of surface chirality at near-normal incidence

The chirality of a medium is typically measured either by transmitting a beam of light through it or by single or multiple interface reflection at large and/or special angles of incidence. We propose and demonstrate here the experimental measurement of surface chirality of z-cut quartz crystal by reflecting a focused beam of light at a near-normal angle of incidence. A small difference in the reflection coefficients between orthogonal elliptically polarized incident beam of 10(-4) is measured in the dark-field region of the reflected light via the weak measurement method, taking advantage of the significant transverse spin-shift (TSS) that arises due to the interaction. The TSS behavior is simulated for different chiral parameters (+/-gamma) of the material. The experimental results match well with the theoretically simulated behavior to quantify gamma of quartz crystal used as an example interface. The significance of our method can be of interest for a wide variety of fundamental and applied investigations.