Abstract
A class of partially coherent spherical sources is introduced whose
cross-spectral density across the surface has a modal expansion made
up of spherical harmonics. For such sources, the solution of the
propagation problem in all the outer spaces can be written through a
series of the propagated modes, which maintains the spherical harmonic
structure. The main features of this class of cross-spectral densities
are derived illustrating their coherence properties with examples.
Attention is paid to the properties of radial coherence. In
particular, it is clearly shown that sources with perfect radial
coherence exist with angular coherence that is only partial.
