Resonant Near-Field Effects in Photonic Glasses

A fundamental quantity in multiple scattering is the transport mean free path whose inverse describes the scattering strength of a sample. In this letter, we emphasize the importance of an appropriate description of the effective refractive index $n_{\mathrm{eff}}$ in multiple light scattering to accurately describe the light transport in dense photonic glasses. Using $n_{\mathrm{eff}}$ as calculated by the Energy Coherent Potential Approximation we are able to predict the transport mean free path of monodisperse photonic glass. This model without any fit parameter is in qualitative agreement with numerical simulations and in quantitative agreement with spectrally resolved coherent backscattering measurements on new specially synthesized polystyrene photonic glasses. These materials exhibit resonant light scattering perturbed by strong near field coupling, all captured within the model. Our model might be used to maximize the scattering strength of high index photonic glasses, which are a key in the search for Anderson Localization of light in 3D.