Perturbation theory as a unified approach to describe diffractive optical elements

First-order perturbation theory is used to describe diffractive optical elements. This method provides an extension of Kirchhoffs thin element approximation. In particular, the perturbation approximation considers propagation effects due to a finite depth of diffractive structures. The perturbation method is explicitly applied to various problems in diffractive optics, mostly related to the analysis of surface-relief structures. As part of this investigation this approach is compared with alternative extensions of the thin dement model. This comparison illustrates that perturbation theory allows a consistent unified treatment of many diffraction phenomena, preserving the simplicity of Fourier optics. (C) 1999 Optical Society of America [S0740-3232(99)00905-9].