We demonstrate the first fully controlled generation of immobile and slow
spatial gap solitons in nonlinear periodic systems with band-gap spectra, and
reveal the key features of gap solitons which distinguish them from
conventional counterparts, including a dynamical transformation of gap solitons
due to nonlinear inter-band coupling. We also predict theoretically and confirm
experimentally the effect of anomalous steering of gap solitons in
optically-induced photonic lattices.Comment: 4 pages, 5 figure