Correlation-induced spectral changes

Abstract

This paper presents a review of research, both theoretical and experimental, concerning the influence of coherence properties of fluctuating light sources and of correlation properties of scattering media on the spectra of radiated and scattered fields. Much of this research followed a discovery made in 1986, that the spectrum of light may change on propagation, even in free space. More than 100 papers on this topic have been published to date and many of them are reviewed, or at least mentioned, in this article.After an introduction and a summary of some of the main mathematical results relating to second-order coherence theory of statistically stationary optical fields, spectral changes that may take place on superposing fields produced by two partially correlated sources are discussed. Spectral effects in fields produced by two-dimensional secondary sources and by three-dimensional primary sources are then considered.The section which follows describes spectral changes that may arise when polychromatic light is scattered on media whose physical properties vary randomly either in space and/or in time. A review is also presented of recent research, which has revealed that under certain circumstances the changes in the spectrum of light scattered on random media may imitate the Doppler effect, even though the source, the medium and the observer are all at rest with respect to one another.In the final section a brief review is given of a new emerging technique sometimes called spatial-coherence spectroscopy. It is based on the discovery that it is possible, under certain circumstances, to determine field correlations from spectral measurements.

Near-Field Spectral Effects due to Electromagnetic Surface Excitations

“…In the 1980's, Wolf [3] predicted that the spectrum of light can be changed on propagation from the source to the observer, even through empty space. This effect, whose origin lies in the fluctuating nature of the source, has been intensively studied in a variety of systems [4,5]. Typically, the Wolf effect is manifested in small spectral shifts and can be viewed as a redistribution of the weights of different spectral components.…”

Grazing angle enhanced backscattering from a dielectric film on a reflecting metal substrate

“…59 Because of the close analogy that exists between the processes of radiation and scattering, a similar effect is expected to occur when radiation is scattered by a static medium or rough target. This phenomenon also has a significant relationship to enhanced backscattering, which is one of the most interesting phenomena associated with the scattering of light from a randomly rough surface.…”

Spectral Shift Amplification and Polarization-Controlled Spectral Shift with Silver Metal

“…Some interesting phenomena have been found, such as phase singularities [6], spectral switches [7], Talbot spectra [8]. Some applications have been suggested, such as lattice spectroscopy [9] and spatial-coherence spectroscopy [10]. Another new effect called the spectral shift amplification with water has been proposed by the author [11].…”