On the spatial orientation of the transverse irradiance profile of partially coherent beams.

ABSTRACT

On the basis of the irradiance-moments formalism, four matrices are proposed whose elements, defined for any partially coherent field, are closely related with the second-order measurable parameters handled in the ISO standard 11146. These matrices are shown to exhibit a number of properties concerning the orientation of the transverse profile of a partially coherent beam. This behavior is described by the rotation of the principal axes of the field around its propagation axis. In addition, these matrices provide information about the spatial structure of the field (beam spread product and orbital part of the angular momentum). A new overall parameter is introduced in terms of the above matrices, which remains invariant under rotation of the Cartesian coordinate axes and upon propagation through rotationally-symmetric first-order optical systems.