This book describes the propagation of light in biaxial media, the properties of biaxial thin films, and applications such as birefringent filters for tuning the wavelength of dye lasers. A novel feature of the first part is the parallel treatment of Stokes, Jones, and Berreman matrix formalisms in a chapter-by-chapter development of wave equations, basis vectors, transfer matrices, reflection and transmission equations, and guided waves. Computational tools for MATLAB are included. The second part focuses on an emerging planar technology in which anisotropic microstructures are formed by oblique deposition in vacuum. Methods for characterizing dielectric and metal films are discussed. Topics such as form birefringence, effective medium theory, anisotropic scatter and anisotropic fluid transport are discussed in detail. Practical applications of bulk and layered birefringent media are considered in the final part. Separate chapters are devoted to linear polarizers, phase retarders, and birefringent filters. Traditional bulk-media polarizing elements are included and compared with thin film designs.