Flat Optics for Polarization Structure Engineering from 2D to 3D

Light beams with spatially variant polarization structures are playing a more vital role in optics due to their unique optical properties and additional degrees of freedom for encoding technologies. Traditional methods for generating and manipulating these structures are often limited by system complexity, large size, high cost, and restricted control. Optical metasurfaces have shown significant promise in polarization control. They have been successfully employed to generate and manipulate various 2D polarization structures, often incorporating engineered intensity and color information. More recently, they have also been utilized for the generation of 3D polarization structures, transforming the understanding of optical design and establishing a foundation for full 3D polarization manipulation. This review highlights the evolution of metasurface‐based devices for polarization control, tracing the transition from 2D to 3D. The unprecedented capabilities of metasurfaces in this area are poised to unlock a wide range of practical applications, including vector beam engineering, volumetric displays, virtual reality, and security technologies.