Generation of partially coherent fields with twist

It is shown, theoretically and experimentally that any astigmatic beam with M 2 >1, coherent or partially coherent, can be transformed by a first order system into a beam with second intensity moments of circular symmetry and twist. Experiments were performed with coherent Gauss- Hermite beams of high order and partially coherent diode arrays. Furthermore it is demonstrated that the bema parameter product is not constant in ideal ABCD-system.