FOCUSING OF TWISTED GAUSSIAN SCHELL-MODEL BEAMS

Introduction of a twist phase into the cross-spectral density function of a gaussian Schell-model (GSM) field is known to increase the beam divergence and to rotate the beam upon propagation. The focusing of these partially coherent, twisted wave fields is investigated by deriving explicit expressions for the beam propagation parameters in the image space of an arbitrary rotationally symmetric paraxial optical system. The presence of the twist phase is shown to increase the size of the best focus, and to move it towards the image of a completely incoherent source. The results are verified experimentally using an acousto-optically coherence-controlled twisted GSM beam.