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.
© 2005 Optical Society of America
(030.1640) Coherence and statistical optics : Coherence
(140.4780) Lasers and laser optics : Optical resonators
(260.2110) Physical optics : Electromagnetic optics
(260.5430) Physical optics : Polarization
Toni Saastamoinen, Jari Turunen, Jani Tervo, Tero Setälä, and Ari T. Friberg, "Electromagnetic coherence theory of laser resonator modes," J. Opt. Soc. Am. A 22, 103-108 (2005)