The present invention provides polarizing devices and illumination devices that include the polarizing devices. The polarizing devices and illumination devices can be advantageously used in a wide variety of applications, such as in liquid crystal displays. Polarizing devices provided by the present invention include those having an isotropic waveguiding layer with a refractive index ni and an anisotropic separating layer having an anisotropic region with principal refractive indices nx and ny, wherein nx>ny and wherein ni is substantially smaller than nx and substantially larger than ny. An example of a further polarizing device provided by the present invention is one having a waveguiding layer and a separating layer, wherein the separating layer includes a form birefringent region.