Optical optimization of binary phase fan-out elements

Binary phase fan-out elements, often referred to as Dammann gratings, produce a two-dimensional array of beams. In some cases the multiple beams have to be uniform in intensity, while in others a varied distribution of intensities is desired. In all cases, these elements need to be efficient, so to avoid losses. The authors apply an optical parallel processor to perform the simulated annealing stage of the optimization procedure. A liquid crystal television is used to actively modulate the phase of individual points within the base unit cell of the diffractive element. Once the element has been optimized by the optical processor for high efficiency, a downhill algorithm on the mainframe computer is employed to improve uniformity. This last stage also serves to remove any noise effects introduced during the optical optimization