  We report the realization of a Pancharatnam-Berry phase optical element [Z.
Bomzon, G. Biener, V. Kleiner, and E. Hasman, Opt. Lett. \textbf{27}, 1141
(2002)] for wavefront shaping working in the visible spectral domain, based on
patterned liquid crystal technology. This device generates helical modes of
visible light with the possibility of electro-optically switching between
opposite helicities by controlling the handedness of the input circular
polarization. By cascading this approach, fast switching among multiple
wavefront helicities can be achieved, with potential applications to
multi-state optical information encoding. The approach demonstrated here can be
generalized to other polarization-controlled devices for wavefront shaping,
such as switchable lenses, beam-splitters, and holographic elements.
