title: Electromagnetic coherence theory of laser resonator modes.
abstract: A theory of open laser resonators is formulated within the framework of the electromagnetic coherence theory. It is shown that if only one Fox-Li mode contributes to the field at a given frequency, then the field at that frequency is necessarily completely coherent in view of the space-frequency counterpart of the recently introduced degree of coherence of electromagnetic fields [Opt. Express 11, 1137 (2003)]. It is also shown that the relation between the number of Fox-Li modes and the new degree of coherence is analogous to the relation established in the scalar theory of laser resonator modes. Difficulties that arise with the formerly introduced visibility-based definition of the electromagnetic degree of coherence are briefly discussed.
authors.affiliation: University of Joensuu, Department of Physics, FI-80101 Joensuu, Finland. toni.saastamoinen@joensuu.fi
authors.forename: Toni
authors.initials: T
authors.lastname: Saastamoinen
authors.forename: Jari
authors.initials: J
authors.lastname: Turunen
authors.forename: Jani
authors.initials: J
authors.lastname: Tervo
authors.forename: Tero
authors.initials: T
authors.lastname: Setälä
authors.forename: Ari T
authors.initials: AT
authors.lastname: Friberg