Observation of the enhancement of coherence by backscattering through turbulence

<title>Coherence enhancement of light after double passage through a turbulent medium</title>

“…This approach was taken for the first experimental observation of the phenomenon of coherence enhancement after double passage through turbulence [3]. In that particular case when, in the absence of random inhomogeneit.ies, the spatial distribution of the scattered wave intensity in the plane of the The scattered waves produced by each source POSSeS a non-zero degree of coherence not only at the exact.…”

“…The magnitude of this effect is most significant, when we consider the coherence properties of a backscattered wave which is produced by two mutually coherent points in the source plane. The particular coherence phenomenon which results from this geometry was termed the coherence enhancement effect [3] and has also been referred to as the long-distance correlation effect i1,24]. The physical nature of this phenomenon consists basically in the appearance of correlation in the hackscattered field in regions around the illumination sources.…”

Use of polarization in interferometry after double passage through turbulence

“…When the turbulence is switched off we observe an interference pattern (Fig. 2), the visibility of which is v Imax -'in (1) Imax + min The measured visibility was V = 0.91. This visibility is unaffected by the presence or absence of the quarter-wave plates.…”

Measurements of the four-point coherence function by the use of the coherence enhancement phenomenon

“…The phenomenon of coherence enhancement after double-passage propagation through turbulence has been experimentally observed for a basic system comprising a mirror target illuminated by two mutually coherent point sources. 1 The degree of coherence enhancement obtained was increased significantly in an experiment that manipulated the polarization states of the illumination and reflected light. 2 The physical nature of this phenomenon consists basically of the appearance of correlation in the backscattered field in regions surrounding the illumination sources and has been discussed in detail in previous publications.…”

“…2 The physical nature of this phenomenon consists basically of the appearance of correlation in the backscattered field in regions surrounding the illumination sources and has been discussed in detail in previous publications. [1][2][3] Essentially it is a result of reciprocity-any optical path through the turbulence that begins at one source and ends at the other has a corresponding partner that traverses the same path in the reverse direction. Experiments have demonstrated 4 the existence of a region where coherence enhancement after backscattering through turbulence from an optically rough object may be observed.…”