Spatiotemporal toroidal light beams with arbitrary polarization and orientation through a multimode fiber

Abstract: Optical toroidal beams, with donut-shaped intensity profiles and orbital angular momentum (OAM), are promising for applications such as optical manipulation, metrology, and advanced light-matter interactions. However, practical implementations are limited by challenges in controlling their full 3D geometry and the orientation of their OAM. In this paper, we experimentally demonstrate high-dimensional, polarization-resolved, programmable 3D spatiotemporal toroidal beams with arbitrary 3D geometry. The beams are delivered after propagation through an optical multimode fiber (MMF) that supports 90 spatial/polarization modes. However, if desired, this system can also deliver these beams directly into free space as well. Our approach leverages 25,000 programmable spatiotemporal and polarization degrees of freedom to achieve precise manipulation of the amplitude, phase, polarization and temporal properties of toroidal beams. These beams feature highly customizable 3D geometries, allowing independent control of their aspect ratio and orientation. We further demonstrate the generation of beams with arbitrary OAM orientation, with beam rotations about any 3D spatiotemporal axis. These beams are delivered through an MMF which enables their transport deep into scattering materials and into otherwise hard-to-access regions which could include biological tissues. Hence, this device could enable the application of completely customizable optical manipulations, including rotations, deep within these materials.