Disorder-induced coherent scattering in slow-light photonic crystal waveguides

We present light transmission measurements and frequency-delay reflectometry maps for GaAs photonic crystal membranes, which show the transition from propagation with a well defined group velocity to a regime completely dominated by disorder-induced coherent scattering. Employing a self-consistent optical scattering theory, with only statistical functions to describe the structural disorder, we obtain an excellent agreement with the experiments using no fitting parameters. Our experiments and theory together provide clear physical insight into naturally occurring light localization and multiple coherent-scattering phenomena in slow-light waveguides.