Precise measurement of the optical characteristics of the subsurface layer of solids

A measurement method and a calculation algorithm based on the three-layer structure model have been proposed for the refractive index of optical materials. The method has been experimentally tested with refractive index standards. The uniqueness of the reconstruction of the refractive indices of the substrate and subsurface layer, as well as the thickness of the layer, from the measured reflection coefficient of probe radiation near the Brewster angle and the angle of normal incidence has been demonstrated numerically. The measurements of the refractive index of the subsurface layer with an absolute error of 10$^{-4}$ and the thickness of the subsurface layer with a confidence error of $1$ nm have been performed for the first time.