The preparation of layered structures of polymers by coextrusion is well known. It is possible to fabricate a material containing many thousands of alternating layers of polymers with a layer thickness ranging from many microns to 10 nm . When different polymers are used for the alternating layers, the new materials possess a modulation in the refractive index, n, across the polymer film. When the modulation period is λ/4n, the materials show a high reflectivity at the wavelength, λ. They are effective 1D photonic crystal materials. When the layer thickness is substantially less than λ/4n, the optical properties are that of an effective medium composite. The refractive index and transmission are then an average of those of the component materials.
© 2003 Optical Society of AmericaPDF Article