Encoding Higher-Order Polarization States into Robust Partially Coherent Optical Beams

Optical vector beams with a higher-order polarization state, represented by a point on a higher-order Poincar\'e sphere, have recently found advantages in various applications. However, the considered beams are usually spatially fully coherent (monochromatic), which makes them susceptible to complex environments. In this work, we introduce a coherence-engineering protocol to generate partially coherent vectorial secondary light sources in which a higher-order polarization state is encoded into the structure of electromagnetic spatial coherence. The encoded complex polarization state is well reconstructed in the far field whose global degree of polarization can be controlled with the transverse coherence length of the source. In particular, the produced partially coherent beams are highly robust against obstructions, which is demonstrated theoretically and experimentally by inserting a static obstacle against the source or introducing strong atmospheric turbulence into the transmission link. The results of this work can find useful applications in the transfer of complicated polarization-encoded information in harsh environments.