Broadband spin and angle co-multiplexed waveguide-based metasurface for six-channel crosstalk-free holographic projection

Metasurface-based holograms, or metaholograms, offer unique advantages including enhanced imaging quality, expanded field of view, compact system size, and broad operational bandwidth. Multi-channel metaholograms, capable of switching between multiple projected images based on the properties of illuminating light such as state of polarization and angle of incidence, have emerged as a promising solution for realizing switchable and dynamic holographic displays. Yet, existing designs typically grapple with challenges such as limited multiplexing channels and unwanted crosstalk, which severely constrain their practical use. Here, we present a new type of waveguide-based multi-channel metaholograms, which support six independent and fully crosstalk-free holographic display channels, simultaneously multiplexed by the spin and angle of guided incident light within the glass waveguide. We employ a k-space translation strategy that allows each of the six distinct target images to be selectively translated from evanescent-wave region to the center of propagation-wave region and projected into free space without crosstalk, when the metahologram is under illumination of a guided light with specific spin and azimuthal angle. In addition, by tailoring the encoded target images, we implement a three-channel polarization-independent metahologram and a two-channel full-color (RGB) metahologram. Moreover, the number of multiplexing channels can be further increased by expanding the k-space’s central-period region or combing the k-space translation strategy with other multiplexing techniques such as orbital angular momentum multiplexing. Our work provides a novel approach towards realization of high-performance and compact holographic optical elements with substantial information capacity, opening avenues for applications in AR/VR displays, image encryption, and information storage.