Photon Localization in Time and Space

Abstract

Wave propagation in strongly scattering random media has been a subject of continuing interest to physicists for decades. Anderson’s predictions⁽¹⁾ that electron wave function behavior in the presence of strong disorder can lead to particle localization have led to a variety of experiments and theories aimed at elucidating coherent effects in disordered systems. Although many phenomena (coherent backscattering, mobility edge, universal conductance fluctuations) have been at least qualitatively understood by examining electronic transport,⁽²⁾ detailed comparisons with theory are still lacking partly because theories have not treated the strong effects of electron-electron and electron-phonon interactions.⁽³) Indeed the nature of the transition from extended to localized electronic states in three dimensions still involves some open questions. Even if the transition is continuous, the value of the critical exponent remains very much in dispute. In principle, photons offer many advantages for improved quantitative study of localization phenomena: First, their self-interaction is quite negligible; second, their energies (hv) and momenta (hk) can be easily measured, controlled and varied; third, detailed studies of subtle wave interference phenomena over several decades in intensity are easy; fourth, the relevant spatial scale on which randomness is important (∼λ) is subject to control and characterization.