A diamond-like carbon (DLC) film having refractive indices distributed in a pattern oriented within the plane of the film or on a bias with respect to the thickness of the film. Such films may be useful in low-cast Faraday rotators, in polarizers (analyzers), and in magnetic substances, and in Faraday rotators and optical isolators that can handle a plurality of wavelengths. The refractive index structure may be imparted to the DLC film, for example, by irradiating at least one region of the film with either a particle or energy beam.