Analytic design of a zoom XY-beam expander with freeform optical surfaces.

Many laser applications require specific irradiance distributions to ensure optimal performance. In addition, some applications can benefit from time-varying distributions. In this work, we present the analytic design of a zoom XY-beam expander based on movable freeform optics that allows to simultaneously vary the magnification in x- and y-direction, respectively. This concept is not new: the new is to design and optimally exploit freeform lenses to achieve such an optical functionality. In comparison with zoom beam expanders that use combinations of rotated cylindrical lenses, a freeform system can be more compact, yet achieving excellent overall optical performance throughout the full zoom range.