Simple technique for determining substrate indices of isotropic materials by a multisheet Brewster angle measurement

When an H-polarized light is incident upon a substrate at the Brewster angle, the reflected light becomes zero. Stacking many identical substrates together forms a multisheet structure. The valley of this reflected intensity pattern centered at the Brewster angle becomes narrower owing to the overlap of these similar reflections from many parallel interfaces of air and substrates. Therefore measuring the Brewster angle of this multisheet structure leads to an accurate determination of the substrate index, which is up to the third decimal place (0.00075).