Illusion Optics via Phase-Gradient Metasurfaces

Abstract Optical phase-gradient metasurfaces have garnered significant attention for enabling flexible light manipulation, with applications across diverse domains. In this work, we will demonstrate that the metasurfaces with phase gradient modulation can be used to achieve illusion optics, featuring the advantages of simple geometric structure and feasible implementation compared with the well-known transformation optics method. The underlying mechanism is the anomalous diffraction law caused by the phase gradient, which provides a theoretical basis for freely manipulating the propagation path of light. By considering a specific example, we will demonstrate that the phase gradient can transform spatial coordinates in real space into illusion space, thereby converting a plane in real space into a curved surface structure in illusion space to achieve the illusion effect. This approach provides a viable alternative to transformation optics for designing illusion devices.