Coherent Backscattering and Anderson Localization of Light

Abstract

The propagation of classical waves such as light in strongly multiple scattering media has been the subject of renewed interest. One motivation for this interest has been the suggestion that Anderson localization might be observed in such systems [1,2]. Coherent backscattering of waves in a random medium is the precursor to Anderson localization. The enhanced backward scattering in highly disordered materials is responsible for the renormalization of the energy diffusion coefficient as described by the scaling theory of localization [3]. In moderately disordered materials, in which localization is not evident, coherent backscattering has nevertheless been observed. This phenomenon of weak localization has been discussed in the context of electrons in metals by KHMEL’NITSKII [4] and BERGMANN [5]. A number of experiments beginning in 1984 with KUGA and ISHIMARU [6] have demonstrated the coherent backscattering of light [7–10]. The coherent backscattering enhancement was discussed as early as 1969 for scattered radar waves [11]. GOLUBENTSEV [12] calculated the enhancement of the albedo for retroreflectance of scalar waves from a random collection of point-like scattering centers. AKKERMANS, WOLF and MAYNARD [13] obtained a calculated line shape of the backscattered intensity for scalar waves as a function of scattering angle which agreed qualitatively with the experimental data. Although the vector nature of the electromagnetic field does not alter the localization critical point, polarization effects are apparent in angle resolved studies of the backscattered intensity [6–8]. STEPHEN and CWILICH [14] have demonstrated theoretically that for linearly polarized light incident on a scattering medium, the backscattering peak consists of a sharp narrow peak polarized parallel to the incident light as well as a broader depolarized peak.