  We report on a direct experimental observation of dynamic localization (DL)
of light in sinusoidally-curved Lithium-Niobate waveguide arrays which provides
the optical analog of DL for electrons in periodic potentials subjected to ac
electric fields as originally proposed by Dunlap and Kenkre [D.H. Dunlap and
V.M. Kenkre, Phys. Rev. B 34, 3625 (1986)]. The theoretical condition for DL in
a sinusoidal field is experimentally demonstrated.
