Radiative properties of silicon-based thin films for partially coherent radiation

Radiative properties of thin films are derived based on the concept of optical coherence theory. Instead of the previous approach of deriving the property formulae based on the degree of coherence, a direct integration to obtain the averaged properties over a finite spectral resolution is developed. The resulting analytical formulae are in excellent agreement with the prior work. The formulae are compact in form and much easier to use to invert optical properties with measured reflectance or transmittance as compared with the prior work. The incoherent and coherent limits can be easily reduced from the general formulae and the resulting equations corresponding to those of geometric and wave optics, respectively. Rigorous criteria of incoherent and coherent regimes are developed. These criteria are very useful in determining under what situations that simpler wave optics and geometric optics formulae can apply.