Impact of polydispersity on light propagation in colloidal photonic crystals

The influence of polydispersity, or variations in the size of particles, on the transmittance of slabs of colloidal photonic crystals is analyzed. A model based on simulated annealing simulates the assembly of particles with a given size distribution into a dense array. The model reveals the existence of a transition between ordered and random packing at a polydispersity between 3% and 4%; this transition is associated with large changes in optical properties, in the form of greatly increased scattering and reduced contrast associated with the transmittance in and out of the stop band. The predictions of the model correspond closely to experimental measurements. (C) 2004 American Institute of Physics.