Multiple-Scattering of Millimeter Waves in Random Dielectrics*

We investigate millimeter wave localization in random binary-layered dielectrics composed of sub-wavelength scatterers. We measure the broad-band phase-dependent reflection and transmission response of the system. The random dielectrics exhibit band gaps and transmission resonances, the hallmark of localization. The band gaps correspond to forbidden mode propagation; the resonances to effective cavities in the system. These cavities are associated with enhanced attenuation and slow light which we observe in both experiment and theory. These effects are a result of weak multiple-scattering by the layer boundaries due to the disorder in the dielectric stack.