Algorithm for Fourier propagation through the near-focal region.

A standard technique for beam propagation modeling of large and complex optical systems, such as the National Ignition Facility, is the Talanov approach. We describe a modification to the Talanov algorithm that avoids its inherent inability to treat interactions in the Rayleigh region. The algorithm has been validated with analytic and numerical calculations and is demonstrated to function as expected in the case of a NIF spatial filter.