We experimentally investigate the temporal development of photorefractive solitons in strontium-barium niobate waveguides at visible and infrared wavelengths. The development times in the infrared are shown to be comparable with those in the visible. The results are compared with predictions of a previously published model.

We have obtained photovoltaic lenses and dark spatial solitons in planar optical waveguides in lithium niobate doped with iron and copper. For TE modes of lower indices the photovoltaic nonlinearity only partly decreased the width of a dark notch within the outcoupled image of the recording light beam. The corresponding time to reach a steady state of this light-induced change ranged from about 0.1 to 30 s depending on the waveguide sample. For higher modes we observed a full compensation of the divergence of the dark notch on a time scale of some minutes. In some cases this was followed by an extinction of the dark solitons because the light was over-defocused in the highest modes.

We have obtained stationary bright spatial solitons in a planar photorefractive strontium barium niobate waveguide for visible light ranging from 514.5 to 780 nm. Even for larger wavelengths (lambda=1047 nm) strong self-focusing of the beam was observed; however, input power had to be some orders of magnitude higher than for visible light for self-focusing to occur. Furthermore, we found transient self-trapping of red light (lambda=632.8 nm) that corresponds to the formation of bright quasi-steady-state solitons.

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