Nonseparable surface-relief gratings that generate large arbitrary intensity beam arrays

摘要

Abstract: Custom designed surface-relief gratings are used to generate two-dimensional, uniform intensity beam arrays in several current digital free-space photonic system demonstrators. Although the design process for creating these gratings depends intrinsically on the size of the beam array; the optimization algorithm and the available computational resources ultimately determine the greatest complexity grating that is easily obtained. A new design algorithm is presented that has proven its ability to quickly design large beam array generators (128 $MUL 128 and larger solutions) composed of either uniform intensity or arbitrary intensity beams. The algorithm produces two-dimensional non-separable binary phase or multiphase level solutions that yield a higher diffraction efficiency than separable dimension designs. Although the algorithm must optimize up to the order of 10$+6$/ parameters that determine the intensities of from 16 to 32 K beam intensities, a personal computer will generate solutions in a matter of a few minutes to a few hours. We evaluate the algorithm performance for a number of designs and demonstrate several patterns that have been fabricated onto fused silica substrates via microlithography and reactive ion etching. !8