Polarized topological invariance frequency conversion on high-fidelity information transfer

A cross-band information converter, which links communication and storage modules operating at different wavelengths, is crucial for the development of optical vortex-based information networks. However, due to nonlinear efficiency dependence on orbital angular momentum (OAM), the traditional intensity or polarization distribution-based recognition distortion emerges. Here, by employing the optical vector vortex with a tailored polarization mode as the information carrier of communication network, and the polarization topology one-to-one mapping as the mode identification method, we demonstrate a simple yet flexible frequency converter based on sum-frequency generation (SFG) that preserves the topological invariance of polarization, enabling high-fidelity information transmission. In a proof-of-concept experiment, vector vortex-encoded image information is successfully transferred from a 1064 nm band to 630.9 nm without any quality degradation. This approach has the potential to enable cross-platform information transmission in optical networks, paving the way for broader applications.