BREWSTER ANGLES IN REFLECTION BY UNIAXIAL CRYSTALS

Reflection by anisotropic media is characterized by the four reflection amplitudes r(pp), r(ss), r(ps), and r(sp). We show that r(pp) can be zero at angles theta(pp) the anisotropic Brewster angles, and that a quantity related to theta(pp) satisfies a quartic equation. When the refractive index of the medium of incidence lies between the ordinary and the extraordinary indices of the crystal, it is possible for r(ss) to be zero at an angle theta(ss), and there exist four equivalent orientations of the crystal optic axis for which r(pp), r(ss), and either r(ps) or r(sp) are simultaneously zero, at angle of incidence equal to arctan (n(o)/n1).