Changes in the Spectrum of a Partially Coherent Light Beam Propagating in Free Space

摘要

The effect of spatial coherence of a source on the spectrum of the emitted light is studied for a class of beam-like fields. The source is assumed to be planar, secondary, and quasi-homogeneous. Consider in detail the situation in which the source spectrum is a line with a Gaussian profile and the degree of spectral coherence is characterized by a Gaussian distribution. The changes that the spectrum undergoes as the emitted light propagates from the source plane to the far zone are illustrated by computed curves. Two factors are shown to contribute to changes in the spectrum: effects due to the finite size of the source, which tend to shift the emitted spectral light toward the shorter wavelengths (a blue shift), and effects due to source correlations, which tend to shift in the far zone depends on the direction of observation. These results are in qualitative agreement with the recent experimental observations. Keywords: Spectra; Light beams; Partially coherent light; Reprints. (jhd)