Depolarization and retardation of a birefringent slab

Mueller matrices for normal transmission of light through a birefringent slab are formulated to analyze retardation and depolarization. A finite wave band, wedge slab, and microroughness may cause a spread in retardance, which in turn produces depolarization. The spectra of depolarization, cross-polarized transmittance, and retardance by rotating-analyzer ellipsometry are simulated for the quasi-monochromatic effect with a finite bandwidth. These spectra agree excellently with the measured spectra for a sapphire slab. The depolarization spectrum simulated for the wedge effect fits the measured spectrum in the long-wave region but is too small in the short-wave region. The depolarization simulated for incoherent multiple reflections demonstrates the oscillating structure, which is small compared with the measured depolarization. The finite bandwidth effect contributes more than the other effects to the measured depolarization of a sapphire slab.