Incoherent transmissivity and reflectivity of an absorbing-plane plate or layer with linear variations in thickness.

The normal-incidence transmissivity and reflectivities (front and back) for the incoherent case are calculated for an absorbing-plane sample with linear variation of the thickness. Closed-form expressions for the direct determination of the energy (intensity) coefficients of a free-standing sample and of a film on a transparent substrate are given. The results are illustrated with the simulated infrared spectra of semiconductor InSb films of different thicknesses.