Stabilization of optical vortices in noninstantaneous self-focusing medium by small rotating intensity modulation

We observe the stabilization of a single-(double-) charge optical vortex propagating in a self-focusing medium. The optical vortex, which carries a phase singularity at its center, usually breaks up in a self-focusing medium due to the so-called azimuthal instability. However, by adding a small rotating azimuthally-periodic intensity modulation on the vortex light beam, which propagates in a noninstantaneous self-focusing medium, we successfully suppress the azimuthal instability. This observation is confirmed by both numerical simulation and perturbational analysis.