Optically induced refractive index patterns, which can be used for waveguides, were formed inSrxBa1−xNb2O6crystals using an erasable fixing mechanism, based on domains formation by the screening effect. The sign and strength of the refractive index change of the fixed waveguides was controllable by an applied electric field. Fixed patterns are shown to allow the storage of many spatially multiplexed holograms. ©1998 American Institute of Physics.