Degree of Paraxiality of a Partially Coherent Field

We extend the concept of the degree of paraxiality, introduced recently for monochromatic fields, to the domain of stochastic fields. As an example we analytically evaluate the degree of paraxiality for a broad class of model stochastic fields, the Gaussian Schell-model fields, without and with truncation and twist phase. The dependence of the degree of paraxiality on the size and the state of coherence of the source as well as on the truncation parameter and the magnitude of twist phase is analyzed by a number of numerical examples