Experimental investigation on generalized Brewster effect for s-polarized terahertz waves at planar Si-air interfaces...

The disappearance of reflection at dielectric interfaces, called the Brewster effect (BE), is one of the fundamentals of optics. Although it occurs, in the original concept, only for p-polarized waves incident at a specific angle, called the Brewster angle (BA), which is determined solely by the permittivity of the two media, the BA for p-polarization is altered, and a similar zero-reflection can also occur for s-polarization in the cases involving magnetic material, anisotropic material, two-dimensional (2D) conducting material such as graphene, and artificial structures such as metamaterial and metasurface. They are called generalized Brewster effect (GBE) and are expected to be a noble tool for various wave control including efficient absorption. In addition, we have recently found that the GBE for the s-polarization at a flat interface sandwiching a conducting layer, similar to the 2D material case, is a key for improving the sensitivity of terahertz spectroscopy to the carrier transport at semiconductor surfaces. However, so far, there has been no report of an experiment on the GBE for s-polarization at such a flat dielectric interface. In this work, we present an experiment that clearly demonstrates the GBE of this type using a thin doped layer on the surface of a Si substrate.