Abstract

Recent developments in coherence theory have shown that the spectrum of the field produced by a partially coherent source depends not only on the source spectrum but also on the spatial correlations of the source fluctuations.¹ In particular, it has been found that some correlations may give rise to frequency shifts of spectral lines.² Questions have been raised concerning energy conservation in such situations. In this paper we first discuss energy conservation laws pertaining to fields generated by sources of any state of coherence, and we use these fields to demonstrate that conservation laws are not violated when source correlations produce spectral changes in the emitted radiation. We also show that spectral shifts may be generated by isotropic sources, without violating energy conservation.

© 1990 Optical Society of America