Bahrdt, J.; Flechsig, U.; Gerhardt, S.; Schneider, I.: PHASE, a Universal Software Package for the Propagation of Time- Dependent Coherent Light Pulses along Grazing Incidence Optics. In: Sanchez del Rio, M. [u.a.] [Eds.] : Advances in computational methods for X-ray optics II : 21 - 24 August 2011, San Diego, California, United States. Bellingham, Wash.: SPIE, 2011 (Proceedings of SPIE ; 8141). - ISBN 978-0-8194-8751-3, p. 81410E

The software package PHASE includes routines for the propagation of coherent light within the stationary phase approximation (SPA). The code is based on a nonlinear analytic transformation of electric field arrays across longitudinally extended optical elements in normal and grazing-incidence geometries. Recently, the representation of the optical elements (OEs) has been extended to 8th-order polynomials in the OE-coordinates. Strongly curved mirror surfaces can be treated and systematic fabrication errors can be modeled up to 8th order. Each element is represented by an individual matrix and the combination of several elements is accomplished by simple matrix multiplications. The SPA-method can be interpreted as a thick lens approximation, whereas the Fourier Optics algorithm deals with thin lenses. Both methods have advantages and disadvantages. Recently, the PHASE package has been extended to Fourier Optics methods. The appropriate propagator or even a combination of different propagators can be selected from the same interface, which is running under IDL. This permits a one-by-one comparison of both methods via the same interface, which helps to evaluate the advantages and limitations of both methods.