Polarization Structured Beams go the Extra Mile
Alison Yao, Christopher Travis and Gian-Luca Oppo
Light beams that can propagate without a significant change to their spatial profile are of interest for modern optical technologies and high-power laser systems. Self-trapped light filaments, or spatial solitons, are formed when the spreading due to linear diffraction is carefully balanced by a self-focusing (Kerr) nonlinearity that causes the beam to narrow. Because of their potential to carry an increased information content, there has been significant interest in the formation of spatial solitons carrying orbital angular momentum (OAM) for high-bandwidth communications protocols. However, even with saturable self-focusing media, it is known that optical beams with OAM will fragment into multiple solitons each possessing particle-like attributes.
In a recent Physical Review Letters (Phys. Rev. Lett. 117, 233903, 2016) Alison M. Yao, Christopher Travis and Gian-Luca Oppo of the CNQO group in the Department of Physics, in collaboration with Robert Boyd’s group at the University of Ottawa in Canada, demonstrated both numerically and experimentally that propagation of OAM-carrying beams is more stable if the polarization is spatially structured. By studying the nonlinear optical propagation of two different classes of fully-structured light beams - vector vortex beams and full Poincaré beams - in a rubidium vapour cell they observed that their propagation was not marked by beam breakup and still exhibited useful traits such as nonlinear confinement and self-focusing. Their work is the first to show that it is the polarization structure rather than the net OAM that is integral to the increase in stability and suggests that the effects of nonlinear propagation can be effectively controlled by tailoring the spatial structure of the polarization. These findings provide a novel approach to transport high-power light beams in nonlinear media with controllable distortions to their spatial structure and polarization properties.