Multifunctional metaoptics based on bilayer metasurfaces

Abstract

Optical metasurfaces have become versatile platforms for manipulating the phase, amplitude, and polarization of light. A platform for achieving independent control over each of these properties, however, remains elusive due to the limited engineering space available when using a single-layer metasurface. For instance, multiwavelength metasurfaces suffer from performance limitations due to space filling constraints, while control over phase and amplitude can be achieved, but only for a single polarization. Here, we explore bilayer dielectric metasurfaces to expand the design space for metaoptics. The ability to independently control the geometry and function of each layer enables the development of multifunctional metaoptics in which two or more optical properties are independently designed. As a proof of concept, we demonstrate multiwavelength holograms, multiwavelength waveplates, and polarization-insensitive 3D holograms based on phase and amplitude masks. The proposed architecture opens a new avenue for designing complex flat optics with a wide variety of functionalities.Metasurfaces: Bilayers allow more complex control over lightThe ability to manipulate light using metasurfaces - surfaces patterned at scales shorter than the wavelengths of the interacting light – can be significantly enhanced using bilayer metasurfaces rather than single layers. Metasurfaces are one of the most active areas of current optical research. Exploring their potential, however, has been restricted by the limitations of single-surface materials. Researchers in the USA, led by Jason Valentine at Vanderbilt University in Tennessee, demonstrate the potential of silicon-based metasurface bilayers for independently controlling the phase, amplitude and polarization of light. Each layer is designed and engineered to manipulate transmitted light differently. This proof of concept work opens a new avenue for creating layered flat and thin materials with complex optical properties. Potential applications should include sophisticated holographic systems and improved methods for optical sensing and optical computing.