Return-path Ellipsometry and a Novel Normal-incidence Null Ellipsometer (NINE)

The condition for light extinction after a round trip through an optical system is put in a convenient and general form. This provides the basis for a unified analysis of return-path null ellipsometers (RPNE) that operate at a fixed or variable angle of incidence, with isotropic or anisotropic surfaces. A novel normal-incidence null ellipsometer (NINE) is described which is suited for perpendicular-incidence ellipsometry (PIE) of anisotropic surfaces with diagonal reflection matrices.