Twisting of three-dimensional Hermite—Gaussian beams

The mode converter first applied by Tamm and Weiss and generalized by Allen and co-workers can be used to transform any general astigmatic beam into a stigmatic beam with twist. For the special case of three dimensional Hermite—Gaussian beams the transformed beams are twisted Hermite—Gaussian beams with complex arguments. Only if a set of conditions is fulfilled are the transformed beams Laguerre—Gaussian beams. The influence of the input beam parameters on the output beam is discussed.