Spectroscopic ellipsometry of anisotropic materials: Application to the optical constants of HgI2

A variable angle-of-incidence spectroscopic fixed-polarizer, rotating-polar izer, fixed-analyzer ellipsometer (PRPSE) across a spectral range from 300 to 800 nm is used to determine the optical properties of anisotropic uniaxi al tetragonal red mercuric iodide (HgI2). For the first time, to our knowle dge, the bulk crystal HgI2 surface measured by ellipsometry was not subject ed to potassium iodide cutting or etching. Measurements were made at an air -HgI2 interface with the optic axis parallel to the sample surface. To dete rmine the optical constants, we varied both the angle of incidence and the azimuth of the optic axis with the plane of incidence. The detailed formula s needed for reliable procedures for analyzing the data are presented. The ordinary and extraordinary complex indices of refraction, (n(o)-ik(o)) and (n(e)-ik(e)), respectively, are determined. Good agreement between PRPSE an d the prism technique for the refractive index is observed. The surface agi ng effects of the ellipsometric parameters of HgI2, during 30 h of exposure to air, were detected by PRPSE. (C) 1999 Optical Society of America OCIS c odes: 120.2130, 240.4350, 240.6490, 260.1180.