Equations are presented for determining the optical properties of an absorbing uniaxial crystal by measuring the reflectance from a basal plane as a function of the angle of incidence and the angle of polarization. The technique is applied to a pyrolytic graphite crystal to determine the optical properties at 632.8 nm. The results are calculated numerically by use of a combination of the Taylor-series and gradient methods. The best-fit values found for the optical constants of pyrolytic graphite at 632.8 nm are n0=2.55, ne=1.78, k0=0.66, and ke=0.00.
M. BERMAN, H. R. KERCHNER, and S. ERGUN, "Determination of the Optical Properties of Absorbing Uniaxial Crystals from Reflectance at Oblique Incidence," J. Opt. Soc. Am. 60, 646-648 (1970)