Self-Trapping of an Optical Vortex by Use of the Bulk Photovoltaic Effect

We report the first observation of self-trapping of an optical vortex due to the bulk photovoltaic effect. A singly charged vortex nested on a broad cw laser beam is trapped in both transverse dimensions in a lithium niobate crystal. Although the optically induced photovoltaic current is inherently polar, the space charge field gives rise to two-dimensional self-defocusing effects. We observe both circular and elliptical self-trapped vortices, as well as beam deformation due to modulation instability.