Enhanced retroreflectance effects in the reflection of light from randomly rough surfaces

A review is made of theoretical and experimental work on retroreflection enhancements in the diffuse component of light elastically reflected from randomly rough surfaces. These effects are seen as a narrow peak in the angular distribution of the intensity of diffusely reflected light which is centered about the direction for reflected light motion antiparallel to the original incident beam. This peak is observed in the scattering of light from many different types of rough surfaces and has been studied in fields as diverse as solid state physics, astronomy, geophysics, meterology and radar. Work covering all of these fields will be presented in this review. eflection enhancements arise both from shadow casting properties of surface irregularities and from the phase coherence of retroreflected light. These mechanisms can act to create retroreflection enhancements from rough surfaces of dielectric and/or metallic compositions and of surface disorders characterizable on length scales which are large, comparable to or small compared to the wavelength of the scattered light. ic discussions will be presented of three types of enhanced retroreflectance: (1) A treatment of the optical glory and Heiligenschein phenomena which are concerned with the meterological and geophysical study of light reflected from clouds and terraine will be given. (2) The theory of the opposition effect, encountered in astronomy as an enhanced retroreflection in the light scattered from atmosphereless planets and space debris, will be used to provide a theoretical basis to understand shadowing effects. (3) A recently discovered phenomenon of enhanced retroreflection from weakly rough metallic mirrors, associated with the Anderson localization of surface waves, is also presented. This last phenomenon and its relationship to the study of the Anderson localization of surface waves will be emphasized throughout our discussions. r enhancement effects in the scattering of acoustic waves from rough surfaces and a brief outline of some recent work on optical backscattering enhancements due to the Anderson localization of bulk polariton modes, is also presented.