Light Scattering and Non-Gaussian Fields

Abstract

Non-Gaussian fluctuations in scattered waves are a subject of longstanding interest. Almost all naturally occurring scattering phenomena visible to the naked eye, ranging from the glittering of random crystallites such as frost to the twinkling of starlight are non-Gaussian in character. Moreover, many important fading phenomena at other frequencies of the electromagnetic spectrum and also those resulting from acoustic wave scattering are non-Gaussian. Thus it is not surprising that many theoretical investigations of this kind of scattering have been pursued over the years. The acquisition of consistent statistical data on natural phenomena is a notoriously difficult task, however, because of the large number of uncontrolled variables both known and unknown which affect the measurements. This is particularly true of large-scale Geophysical phenomena such as ionospheric or interplanetary scintillation of radio waves, but also limits the reproducibility of optical data on long path laser propagation for example. Controlled laboratory experiments clearly provide the best means for testing non-Gaussian scattering theories and this limits such work to the shorter electromagnetic wavelengths. On the other hand coherent radiation is not essential for the investigation of non-Gaussian scattering — indeed the use of coherent waves introduces the extra complication of interference effects — so one is led to ask why quantitative laboratory experiments were not carried out until relatively recently?