Correlating Space, Wavelength, and Polarization of Light: Spatiospectral Vector Beams

Increasing the complexity of a light field through the advanced manipulation of its degrees of freedom (DoFs) provides new opportunities for fundamental studies and technologies. Correlating polarization with the light’s spatial or spectral shape results in so-called spatial or spectral vector beams that are fully polarized and have a spatially or spectrally varying polarization structure. Here, we extend the general idea of vector beams by combining both approaches and structuring a novel state of light in three nonseparable DoFs, i.e., space, wavelength, and polarization. We study in detail their complex polarization structure, show that the degree of polarization of the field is only unveiled when the field is narrowly defined in space and wavelength, and demonstrate the analogy to the loss of coherence in nonseparable quantum systems. Our work extends the toolbox of structured light and might inspire new applications benefiting from the quantum-like features of nonseparable light fields.