Abstract
We consider cross-spectral purity in random nonstationary
electromagnetic beams in terms of the Stokes parameters representing
the spectral density and the spectral polarization state. We show that
a Stokes parameter being cross-spectrally pure is consistent with the
property that the corresponding normalized time-integrated coherence
(two-point) Stokes parameter satisfies a certain reduction formula.
The current analysis differs from the previous works on cross-spectral
purity of nonstationary light beams such that the purity condition is
in line with Mandel’s original definition. In addition, in
contrast to earlier works concerning the cross-spectral purity of the
polarization-state Stokes parameters, intensity-normalized coherence
Stokes parameters are applied. It is consequently found that in
addition to separate spatial and temporal coherence factors the
reduction formula contains a third factor that depends exclusively on
polarization properties. We further show that cross-spectral purity
implies a specific structure for electromagnetic spectral spatial
correlations. The results of this work constitute foundational
advances in the interference of random nonstationary vectorial
light.
Subject
Atomic and Molecular Physics, and Optics