  We prove Anderson localization in a disordered photonic crystal waveguide by
measuring the ensemble-averaged localization length which is controlled by the
dispersion of the photonic crystal waveguide. In such structures, the
localization length shows a 10-fold variation between the fast- and the
slow-light regime and, in the latter case, it becomes shorter than the sample
length thus giving rise to strongly confined modes. The dispersive behavior of
the localization length demonstrates the close relation between Anderson
localization and the photon density of states in disordered photonic crystals,
which opens a promising route to controlling and exploiting Anderson
localization for efficient light confinement.
