Generation of light with orbital angular momentum in optical fiber via acousto-optic interaction

We examine acousto-optic interaction in optical Fiber from the perspective of co-propagating optical and acoustic vortex modes. Calculation of the coupling coefficient between different optical modes shows independent conservation of spin and orbital angular momentum of the interacting photons and phonons. We show that orbital angular momentum of the acoustic vortex can be transferred to a circularly polarized fundamental optical mode to form a stable optical vortex in the fiber carrying orbital angular momentum, thus providing a useful way of generating stable optical vortices in the fiber medium.