Enhanced measurement of smooth surface using the Spin Hall Effect of Light ellipsometry with near Brewster’s angle incidence

Advances in optical fabrication have now achieved angstrom-level control of thin film thickness and surface quality, creating demand for a measurement method that can achieve a comparable scale. This work proposes Spin Hall Effect of Light (SHEL) ellipsometry, a non-contact optical measurement technique for characterization of interfacial axial properties, such as film thickness and surface roughness at the nanometer scale. The method exploits spin-dependent transverse beam shifts of linearly polarized light amplified by weak measurement. Operation near the Brewster angle enables enhanced sensitivity, accessible by tuning the post-selection angle of weak measurement. Experiments confirmed the enhanced detection capability at near Brewster incidence, with quantitative validation through pseudo-refractive index retrieval. Furthermore, extension of the measurement mode to one-dimensional and two-dimensional scanning demonstrates spatial mapping capabilities. These results demonstrate SHEL Ellipsometry as a promising non-contact technique for surface characterization, particularly well-suited for optically smooth samples. • Novel ellipsometry based on the Spin Hall Effect of Light. • Near-Brewster operation enabled by post-selection angle tuning. • Non-contact technique for optically smooth surface characterization. • Scalable from single-point to 2D spatial surface mapping.