Spin–orbit interaction-mediated measurement of surface chirality

The spin-orbit (<i>σ</i> - <i>l</i>) interaction in a focused-reflected beam of light results in spatially nonuniform polarization in the beam cross section due to the superposition of orthogonal field components and polarization-dependent interface reflection coefficients. Polarization filtering the output beam leads to an interchangeable transformation of <i>l</i>=∓2 charge vortex into two (∓) unit charge vortices, for <i>σ</i> = ±1 circular polarization of the input Gaussian beam. This transformation follows a trajectory, named optical vortex trajectory, that depends on the input beam's <i>σ</i> and hence the <i>l</i> and reflecting surface characteristics. The vortex trajectory is used here to quantify both the sign and the magnitude of the chiral parameter of a quartz crystal. The Jones matrix-based simulation anticipates the chirality-dependent vortex trajectory that matches with experimental measurements.