All-on-chip reconfigurable generation of scalar and vectorial orbital angular momentum beams

Structured light carrying angular momentum, such as spin angular momentum (SAM) and orbital angular momentum (OAM), has been at the core of new science and applications, driving the need for compact on-chip sources. While many static on-chip solutions have been demonstrated, as well as on-chip sources of free-space modes, no architecture that is fully reconfigurable in all angular momentum states and all on-chip has so far been possible. Here we report the first all-on-chip structured light generator for the creation of both scalar and vectorial angular momentum beams, facilitated through a silicon-on-insulator (SOI) chip with a silica mode multiplexer (silica chip). We selectively stimulate six linearly-polarized (LP) modes of the silica multimode bus waveguide, precisely controlling the modal powers and phases with the SOI chip. This allows us to tailor arbitrary superpositions of the mode set thus synthesizing common cylindrical vector vortex beams as well as OAM beams of controlled spin and topological charge. Our compact structured light generator exhibits high switching speed and operates across the telecom band, paving the way for applications such as optical communication and integrated quantum technologies.