title: Cross-spectral purity of electromagnetic fields.
abstract: We extend Mandel's scalar-wave concept of cross-spectral purity to electromagnetic fields. We show that in the electromagnetic case, assumptions similar to the scalar cross-spectral purity lead to a reduction formula, analogous with the one introduced by Mandel. We also derive a condition that shows that the absolute value of the normalized zeroth two-point Stokes parameter of two cross-spectrally pure electromagnetic fields is the same for every frequency component of the field. In analogy with the scalar theory we further introduce a measure of the cross-spectral purity of two electromagnetic fields, namely, the degree of electromagnetic cross-spectral purity.
authors.affiliation: Department of Physics and Mathematics, University of Joensuu, P.O. Box 111, FI-80101 Joensuu, Finland. timo.hassinen@uef.fi
authors.forename: Timo
authors.initials: T
authors.lastname: Hassinen
authors.forename: Jani
authors.initials: J
authors.lastname: Tervo
authors.forename: Ari T
authors.initials: AT
authors.lastname: Friberg