Cross correlation of optical properties of thin films under thermal radiation

Optical property and temperature distributions of a multilayer thin- (∼1 μm) film structure exposed to thermal radiation (1 μm≤λ≤8 μm) are dependent on film thicknesses, geometry, and material properties. Film thickness variation, simulated numerically, resulted in local minima and maxima in reflectivity and temperature distribution of these structures. We attribute this to a cross correlation phenomenon that occurs when the optical thickness of any two films in the structure is equal over a broad radiation spectrum.