Transparent bilayer coatings that produce total refraction (TR) of obliquely incident monochromatic light into an underlying substrate are considered. When the substrate is transparent, it is shown that TR takes place without any accompanying change of polarization. Totally refracting bilayers are realizable in the IR where high-refractive-index substrates are available. This is illustrated by a BaF2–ZnSe bilayer on a Ge substrate at a 10.6-μm (CO2-laser) wavelength and 45° angle of incidence. Limited changes of the angle of incidence, wavelength, and refractive indices and thicknesses of the two films of the bilayer are introduced, and their effects on the condition of TR are determined. TR (hence absorption) is also possible for absorbing (semiconductor or metallic) substrates using transparent bilayers of films of nonquarter-wave optical thickness, as is further demonstrated in this paper.
R. M. A. Azzam and Karim Javily, "Total refraction at oblique incidence by a transparent bilayer coating on a high-index transparent or absorbing substrate," Appl. Opt. 24, 4454-4459 (1985)