Inelastic scattering puts in question recent claims of Anderson localization of light

In a recent Letter in Nature Photonics, Sperling et al.1 reported the observation of Anderson localization of light in three dimensions. In contrast to previous studies, the authors designed their experiment to be insensitive to absorption. To this end, they measured the time-dependent broadening of a high-intensity, short laser pulse transmitted through a highly scattering medium made from compressed TiO2 powder. In analogy with the case of disordered optical fibres2, localized light is expected to be laterally confined to roughly the localization length ξ. Using an ultrafast imaging system, Sperling et al. experimentally observed the saturation of the time-dependent transverse width of the total transmitted light intensity, and from this, they derived the claim for the first unequivocal observation of the three-dimensional localization of light.