Symmetrization of astigmatic high power diode laser stacks

The astigmatic high power diode laser beam emitted from a two-dimensional s tacked array is transformed into a beam with rotational symmetry. The symme trization optic is a first order optical system consisting of a bifocal tel escope and three rotated cylindrical lenses. The symmetrized beam has equal beam radii, far field divergence, and waist positions in x, y directions. Additionally a twist appears. The beam parameter product of the symmetrized beam is the average of the beam parameter products of the input astigmatic beam along x-, y-axes. The twist arises from the astigmatism of the origin al beam. The theoretical calculations are confirmed by the experiments.