Locking Orbital Angular Momentum with Linear Momentum of Light.

Correlation between the propagation direction of light and spin can be induced via the spin-orbit interaction and has been proven to be the workhorse in the emerging field of chiral quantum optics and in the spin-related Hall effects of light. Photonic orbital angular momentum (OAM) provides a high-dimensional degree of freedom in classical and quantum information processing. However, integrated OAM-based information technology is an open challenge, because OAM modes are always generated in pairs with opposite topological charges due to their degeneracy. Here, we observe locking of the OAM and linear momentum of light by using a chiral optical waveguide with an Archimedean cross section to induce the orbit-orbit interaction. This OAM-momentum locking enables the deterministic and robust generation of on-demand OAM vortex light beam in a photonic chip. This new correlation paves the way toward exotic high-dimensional chiral physical effects and also provides the capability of on-chip manipulation of light in high-dimensional space.