Abstract

An explicit expression is derived for the cross- spectral density function of the field generated by homogeneous, isotropic, primary steady-state sources of a wide class. It is found that, in general, the degree of spectral coherence of the field is sinc-correlated, regardless of the nature of the source correlation. The only exceptions are fields generated by sources whose cross-spectral density at frequency ω does not contain spatial-frequency components of periods 2πc/ω (c = speed of light in vacuo). These exceptional cases are shown to be associated with nonradiating, stochastic source distributions. It is found that the field produced by such a source may be correlated over appreciably larger source regions.

© 1986 Optical Society of America