Ultra-Degree-of-Freedom Structured Light for Ultracapacity Information Carriers

Structured light recently highlighted the higher-dimensional control with many tailored degrees of freedom (DoFs) such as amplitude, wavelength, polarization, and orbital angular momentum (OAM), spurring the extension of fundamental science and advanced applications, especially as the novel information carrier to meet the requirement of everlastingly increasing communication bandwidth and security. In addition to the basic DoFs in light, there are also several complex DoFs hidden in spin–orbital coupled vector beams, ray-wave geometric modes, spatiotemporal vortex rings, etc., extending the structured light manipulation. In this Review, we summarize a systematic technical roadmap on how to extend multiple DoFs step-by-step beyond the conventional OAM beams, creating new forms of ultra-DoF structured light, and present a tutorial on how to exploit multiple DoFs of light as advanced information carriers, especially with the recent assistance of artificial intelligence or deep learning method, enhancing the capacity, security, and dimension for the next-generation information technologies.