Brillouin-enhanced four-wave mixing with optical chiral states

Abstract: Brillouin-enhanced four-wave mixing - also known as Brillouin dynamic gratings - is an important nonlinear effect in photonics that couples four light waves by travelling acoustic waves. The effect has received a lot of attention in the last few decades, especially for applications in fiber sensing, signal processing and optical delay lines. Here, we report Brillouin-enhanced four-wave mixing with optical chiral states (i.e. circular polarization and vortex states) in twisted photonic crystal fiber, by leveraging the topology-selective Brillouin effect. Phase-matching has the consequence that the travelling acoustic gratings created by circularly-polarized vortex pump and Stokes in the stimulated Brillouin scattering can be used to modulate a frequency-shifted probe, where the pump/Stokes and probe have different circular polarization or topological charges. We demonstrate cross-frequency selective information transfer and show that the information is transferred only when pump and probe have opposite circular polarization.