Nanophotonic manipulation of optical angular momentum for high-dimensional information optics

Light has played a crucial role in the age of information technology and has facilitated the soaring development of information optics. The ever-increasing demand for highcapacity optical devices has prompted the use of physically orthogonal dimensions of light for optical multiplexing. Recent advances in nanotechnology, mainly stemming from functionalized nanomaterials and powerful nanofabrication tools, have propelled the fusion of optical multiplexing and nanophotonics (the study of light at nanoscale and of its interactions with nanostructures) by enabling ultrahigh-capacity information technology. This review aims to introduce the emerging concept of angular momentum (AM)-involved information optics and its implementation in nanophotonic devices. First, previous researches on the manipulation of spin angular momentum (SAM) and orbital angular momentum (OAM) by nanostructures will be reviewed. We then summarize the SAM multiplexing technology on the platform of metasurfaces. Particularly, we elaborately summarize our recent progress in the area of information optics, including OAM holography and on-chip AM multiplexing technology. Finally, a perspective in the combination of this emerging field with optical artificial intelligence (AI) will be given.