Researchers from China and USA have developed a new type of holograms: “metaholograms”, capable of projecting multiple high-fidelity images free of crosstalk. This result paves the way for next-generation techno­logies including virtual/augmented reality (AR/VR) displays, information storage, and image encryption. Meta­holograms offer several advantages over traditional holograms, including broader operational bandwidth, higher imaging resolution, wider viewing angle, and more compact size. However, a major challenge for metaholograms has been their limited information capacity that only allows to project a few independent images. Existing methods typically can provide a small number of display channels and often suffer from inter-channel crosstalk during image projections.

To overcome this limitation, the new research introduces an innovative approach based on the k-space trans­lation design strategy, enabling multiple target images to seamlessly switch between “displayed” and “hidden” states. The proposed meta­hologram, developed at Huazhong University of Science and Technology, Wuhan, employs the geometric phase encoding method and consists of millions of subwave­length-scale poly-silicon nanopillars, each measuring approxi­mately 100 nanometers, all identical in size but with spatially varying rotation angles.

The device further incorporates a planar glass waveguide to convey incident light and leverages properties such as polarization and angle to switch the projection of up to six unique high-fidelity images without crosstalk. Addi­tionally, the researchers have created a two-channel full-color metahologram and even an eighteen-channel metahologram using a combination of different multi­plexing techniques.

This innovation has the potential to significantly improve AR/VR displays by enabling the projection of more complex and realistic scenes. It also holds promise for applications in image encryption, where the information is encoded into multiple holographic channels for enhanced security. The research is a significant step forward in developing high-performance meta­holograms with a vastly increased information capacity. This study paves the way for exciting new possibilities in various fields, from advanced displays to information encryption and information storage. (Source: LPC-CAS)

Reference: Z. Liu et al.: Broadband spin and angle co-multiplexed waveguide-based metasurface for six-channel crosstalk-free holographic projection, eLight 4, 7 (2024); DOI: 10.1186/s43593-024-00063-9

Link: Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan, China