We have performed measurements of the scattering mean free path $\left({\ell }_s\right)$ in photonic crystals with different and controlled amounts of disorder. In the most perfect crystals, 1 order of magnitude chromatic variation in ${\ell }_s$ for just 3% shift around the band gap (27 nm in wavelength) is obtained. It is argued that the ${\ell }_s$ dispersion is governed by both the total density of states and the group index in the incident direction, with this last quantity being responsible for the large dispersion of ${\ell }_s$.

• Received 9 June 2009

DOI:https://doi.org/10.1103/PhysRevB.79.241109