Spin hall effect of light ellipsometry for nanoscale areal surface measurement

This paper presents a novel method for the measurement of nanometer-scale surfaces. The proposed technique takes advantage of the spin hall effect of light (SHEL), which occurs as a sub-wavelength beam shift due to the spin-orbit interaction of light when it interacts with non-homogeneous optical media. Governed by the conservation of total angular momentum, the SHEL offers a sensitive approach to detecting the variations of optical properties at an interface. "SHEL Ellipsometry" applies weak measurement principles to observe beam shifts, analogous to traditional ellipsometry, which analyzes the polarization states of incident and reflected light. In ellipsometry, a homogeneous sample with surface roughness less than a tenth of the wavelength can be modeled as a thin film characterized by an equivalent thickness and refractive index. By measuring the transverse shifts of the reflected beam and using raster scanning, SHEL Ellipsometry can map the two-dimensional surface roughness distribution, showing significant potential for nanometer-scale surface measurement.