Generation of optical vortices via induced by acousto-optic interaction helical fiber grating

摘要

We consider the light propagation in circular optical fibers with a higher-order flexural sound wave. The analytical expressions for fiber eigenstates and the corresponding propagation constant are obtained by applying the resonance perturbation theory to the wave equation and thoroughly analyzed. It is shown that the acosucto-optic interaction in the problem induces two travelling long-period helical fiber gratings characterized by a different order of rotational symmetry. In fact only one of them turns out to has a non-zero strength and gives rise to a resonance coupling of optical fiber modes with adjacent by 2 azimuthal numbers. A novel method of stable efficient wavelength tunable producing of optical vortices from a regular Gauss-like beam is demonstrated.