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Employing a medium-dependent quantum optics formalism and a Green function solution of Maxwell's equations, we study the enhanced spontaneous emission factors (Purcell factors) and Lamb shifts from a quantum dot or atom near the surface of a slow-light metamaterial waveguide. Purcell factors of approximately 250 and 100 are found at optical frequencies for p−polarized and s−polarized dipoles respectively placed 28 nm (0.02 λ0) above the slab surface, including a realistic metamaterial loss factor of γ/2π = 2 THz. For smaller loss values, we demonstrate that the slowlight regime of odd metamaterial waveguide propagation modes can be observed and related to distinct resonances in the Purcell factors. Correspondingly, we predict unusually large and rich Lamb shifts of approximately −1 GHz to −6 GHz for a dipole moment of 50 Debye. We also make a direct calculation of the far field emission spectrum which contains direct measurable access to these enhanced Purcell factors and Lamb shifts.

Light transmission measurements and frequency-delay reflectometry maps for GaAs photonic crystal membranes are presented and analyzed, showing 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 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.