A rigorous diffraction theory for the optical properties of black chrome

Abstract

Quantitative three-dimensional studies of morphology together with analysis of validity of quasistatic effective medium theories show the need for a diffraction treatment of the optical properties of solar selective black chrome. The spectral absorptance A(λ) is calculated for a doubly periodic modulation of chrome overcoated with Cr₂O₃ or a cermet of Cr₂O₃ and Cr metal. Various profiles, depths and coating thicknesses are used. Diffraction caused by the surface morphology explains the major features of A(λ) for black chrome. Internal structure is of secondary importance.