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.

65,536-ary orbital angular momentum-shift keying free-space optical communication based on few-shot learning.

In an orbital angular momentum-shift keying free-space optical (OAM-SK FSO) communication system, precisely recognizing OAM superposed modes at the receiver site is crucial to improve the communication capacity. While deep learning (DL) provides an effective method for OAM demodulation, with the increase of OAM modes, the dimension explosion of OAM superstates results in unacceptable costs on training the DL model. Here, we demonstrate a few-shot-learning-based demodulator to achieve a 65,536-ary OAM-SK FSO communication system.