Stimulated Brillouin scattering (SBS) is a widely studied nonlinear optical effect where light waves interact with traveling acoustic waves. Many applications such as optical fiber sensing, microwave filters or signal manipulation can be realized based on SBS. So far, most research focuses on straight homogenous waveguides and optical fibers. In this work, we report on the experimental investigation of SBS in chiral photonic crystal fibers (PCFs), where the light travels following the helical channels along the waveguide axis. Chiral PCFs robustly maintain circular polarization states and orbital angular momentum (OAM) modes against external perturbations. This allows us to demonstrate the interaction of optical orbital angular momentum (OAM) modes with acoustic waves via SBS. We show pure amplification of circularly polarized light, the first optical vortex Brillouin fiber laser and nonreciprocal devices based on chiral SBS. The results can pave the way to a new generation of Brillouin applications such as in quantum manipulations, optical tweezers, gyroscopes and fiber sensing.
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