LOCALIZATION OF LIGHT IN A DISORDERED MEDIUM

Among the unusual transport properties predicted for disordered materi als is the Anderson localization(1) phenomenon, This is a disorder-ind uced phase transition in the electron-transport behaviour from the cla ssical diffusion regime, in which the well-known Ohm's law holds, to a localized state in which the material behaves as an insulator, The ef fect finds its origin in the interference of electrons that have under gone multiple scattering by defects in the solid(2-10), A similar phen omenon is anticipated for multiple scattering of electromagnetic waves , but with one important simplification: unlike electrons, photons do not interact with one another. This makes transport of photons in diso rdered materials an ideal model system in which to study Anderson loca lization(10-17). Here we report direct experimental evidence for Ander son localization of light In optical experiments performed on very str ongly scattering semiconductor powders.