Rabi oscillations of azimuthons in weakly nonlinear waveguides

Rabi oscillation, an interband oscillation, describes periodic motion between two states that belong to different energy levels, in the presence of an oscillatory driving field. In photonics, Rabi oscillations can be mimicked by applying a weak longitudinal periodic modulation to the refractive index. However, the Rabi oscillations of nonlinear states have yet to be introduced. We report the Rabi oscillations of azimuthons - spatially modulated vortex solitons - in weakly nonlinear waveguides with different symmetries. The period of the Rabi oscillations can be determined by applying the coupled mode theory, which largely depends on the modulation strength. Whether the Rabi oscillations between two states can be obtained or not is determined by the spatial symmetry of the azimuthons and the modulating potential. Our results not only deepen the understanding of the Rabi oscillation phenomena, but also provide a new avenue in the study of pattern formation and spatial field manipulation in nonlinear optical systems.