Higher-order Poincaré spheres and spatiospectral Poincaré beams

Light with a complex structure has become a powerful tool in many studies in classical and quantum optics. Here, we introduce a visual representation of light that is structured simultaneously in space, frequency, and polarization in the form of a higher-order Poincaré sphere and describe interesting links to its fundamental counterpart. We leverage the description to show and experimentally generate light possessing all possible polarization states across its spatiospectral shape, which we term spatiospectral Poincaré beams. By extending the powerful description of higher-order Poincaré spheres to the spatiospectral domain, our work will help to gain a deeper understanding and to develop beneficial applications of structured light.