Effects of Source Correlations on the Spectrum of Radiated Fields.

摘要

It has long been assumed that the normalized spectrum of a radiated field remains invariant on propagation. Recent developments in coherence theory have demonstrated that, in general, the normalized spectrum of a radiated field changes on propagation depending on the state of coherence and the original spectrum of the source. This thesis examined the effect of the spatial correlations of the source fluctuations on the radiated fields. In investigating the radiation efficiency of three-dimensional, partially coherent, primary sources a method was developed for finding the correlation function that maximizes the radiation efficiency and the total power emitted by such sources. The case of quasi-homogeneous sources shows that the optimal degree of spatial coherence is sinkr'/kr' where r' is the offset and k is the wave number. The significance of this result is discussed in connection with blackbody radiation. In considering the effects of the source correlation on the spectrum of the radiation a simple physical configuration of two small sources demonstrated that one can choose correlation functions that give rise to line narrowing, line broadening, line shifting and line splitting. Similar results are also obtained when the full electromagnetic nature of the sources is taken into account. This fact is illustrated by considering radiation from two partially correlated linear dipoles.