Comparison of different simulation methods for multi plane, computer generated holograms

Computer generated holograms (CGH) are used to transform an incoming light distribution into a desired output. Recently multi plane CGHs became of interest since they allow the combination of some well known design methods for thin CGHs with unique properties of thick holograms. Iterative methods like the iterative Fourier transform algorithm (IFTA) require an operator that transforms a required optical function into an actual physical structure (e.g. a height structure). Commonly the thin element approximation (TEA) is used for this purpose. Together with the angular spectrum of plane waves (APSW) it has also been successfully used in the case of multi plane CGHs. Of course, due to the approximations inherent in TEA, it can only be applied above a certain feature size. In this contribution we want to give a first comparison of the TEA & ASPW approach with simulation results from the Fourier modal method (FMM) for the example of one dimensional, pattern generating, multi plane CGH.