  We report on the experimental observation of weak localization in an
optically induced disordered (2+1)-dimensional photonic structure. Our flexible
method of optical induction is applied with a nondiffracting random intensity
distribution. We focus on the analysis of a statistical output spectrum for
many probe events with variance of the incoming beam's transverse spatial
frequency. For particular spatial frequencies we find considerable signatures
of transverse coherent backscattering.
