Waveguide-Based Four-Channel Crosstalk-Free Metahologram Multiplexed by Diffraction Orders.

Metaholograms have attracted significant attention for their ability to project high-quality images within a compact form factor. Although various multiplexing strategies have been explored for multi-channel metaholograms, current approaches still face limitations in display channel extension and inter-channel crosstalk elimination. Here, we introduce a waveguide-based metahologram that enables four independent, crosstalk-free display channels via diffraction-order multiplexing. The metaholograms are integrated onto the top surface of a flat glass waveguide and modulate guided light through detour phase. With carefully designed device parameters, light diffracted into four distinct orders is selectively out-coupled to form crosstalk-free holographic images. To decouple the detour phase modulations between different orders, we develop an adaptive-weight phase-retrieval algorithm that simultaneously optimizes phase profiles across multiple diffraction orders to realize independent image encoding. Extending this strategy, we also demonstrate a six-channel metahologram for two full-color image projection, highlighting the versatility and scalability of the design. This work offers a new pathway toward compact, high-capacity holographic devices, with promising applications in AR/VR displays, information storage, and image encryption.