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Li Zhongyang's research group has made a series of new progress in the realization of AR holographic display in metasurface optical chips

Author:Administrator Source:website Time:2022-07-14 09:41:02

        Recently, Prof. Li Zhongyang’s research group (Nanophotonics & Emerging Application Laboratory, NEAL) from School of Electronic Information has made a series of new progress in the realization of AR holographic display in metasurface optical chips. These research achievements were published in the optical authoritative journal Laser & Photonics Reviews, the authoritative materials journal Nano Letters, the top journal of the Optical Society of America Optica, and the authoritative optical journal Advanced Optical Materials. Wuhan University is the first signatory unit.


 Figure 1. Relevant achievements were selected as cover articles of Laser & Photonics Reviews and Advanced Optical Materials.

        Focusing on the key direction of nanophotonic research “AR holographic display of on-chip meta-optics”, the research titled “Augmented Reality Enabled by On-Chip Meta-Holography Multiplexing” was published in Laser & Photonics Reviews and selected as Inside Front Cover. As shown in Figure 1, through the integration of judiciously engineered meta-atoms onto the waveguide, a triple-channel hologram with independent-encoding freedom is demonstrated to simultaneously manipulate both the on-chip guided and the free-space light waves. Eventually, a new type of miniaturized AR hologram free from zero-order diffraction with holography-multiplexing functionality is realized. The first authors are Shi Yangyang and Wan Chengwei, Ph.D. students from School of Electronic Information. The corresponding author is Prof. Li Zhongyang. The co-authors also include Prof. Zheng Guoxing from Wuhan University and Prof. Zhang Shuang from the University of Hong Kong.


Figure 2. On-chip and free-space multiplexed holography and AR holographic projection.

        As shown in Figure 2, utilizing the spatial degrees of freedom of the antennas to induce the two-dimensional detour phase, a dual-channel meta-holography with independent-encoding freedom is realized and experimentally captured as a colorful AR hologram by a mobile phone. By further hybridizing detour phase and free-space Pancharatnam-Berry (PB) phase, the on-chip metasurface simultaneously manipulates both the on-chip guided and the free space light waves, thus extending the multiplexing functionalities for both in-plane and out-of-plane modes. It expands the AR multiplexing to triple-channel to independently exhibit RGB-coloring images, which goes beyond the state-of-art of meta-holography based only on waveguide. Compared with free-space holography, the projected images here are free from the zero-order diffraction interference to the observer due to the optical on-chip propagation scheme. The proposed on-chip meta-optics AR strategy is compatible with current photonic integrated circuit (PIC) technology and hence it can be readily integrated with wearable photonic devices, such as eyeglasses or contact lens.

        In the direction of dynamic AR display, the group proposed a “folding” metasurface design method and integrated electrically driven liquid crystal devices to realize dynamic and controllable AR display. The research titled “Dynamic Augmented Reality Display by Layer-Folded Metasurface via Electrical-Driven Liquid Crystal” was published in Advanced Optical Materials and selected as Front Cover. As shown in Figure 1, by ingeniously folding the optical path between meta-device vertical space, the research successfully cascaded a beam-steering metasurface in parallel with the other two holographic metasurfaces placed on a single surface. Such a layer-folded scheme enjoys single-time lithography processing for multi-patterning with nanoscale alignment accuracy and avoids any vertical alignment issue. The first authors are Ph.D. students Tang Jiao and Wan Shuai, and the corresponding author is Prof. Li Zhongyang.

        To enrich on-chip optical functionalities and information capacity, the research group further explores the large-area tunable dynamic holography. The paper entitled “Immersive Tuning the Guided Waves for Multi-Functional On-Chip Meta-Optics” was published in the journal Laser & Photonics Reviews. This research is based on a large-scale easy-accessible immersion switch scheme, which achieves new functions such as on-chip 3D sliced holography and liquid immersion dynamic holography. These functions have great potential in numerous practical applications in the next generation dynamic display, optical sensing, optical communication and optical computing. The first authors are Ph.D. students Yang Rui, Wan Shuai and Shi Yangyang, and the corresponding author is Prof. Li Zhongyang.


Figure 3. On-chip meta-optics for semi-transparent screen display in sync with AR projection.

        Regarding the breakthrough of new multi-dimensional display technology, the research titled “On-chip meta-optics for semi-transparent screen display in sync with AR projection” was published In Optica, the top journal of the Optical Society of America. In this study, through judicious engineering of on-chip meta-diatom displacement and interference at the nanoscale, the on-chip optical scattering intensities can be modulated to create a semi-transparent screen display with independent-encoding freedom and eventually realized a multiplexing screen display in sync with an AR holographic display for human eyes (Figure 3). This on-chip meta-optic display configurations with the merit of miniaturization and multi-functionality can be widely applicable to next-generation wearable AR devices, intelligent dynamic display, visual aesthetics, multi-dimensional optical information storage/encryption and other application fields. The first author is Ph.D. student Shi Yangyang, and the corresponding author is Prof. Li Zhongyang.

        Additionally, in terms of free-space beam steering, a paper entitled “Free-Space Optical Merging via Meta-Grating Inverse-Design” was published in the authoritative journal Nano Letters. Research revolves around a fundamental function in optics steering—beam merging. As is widely known, a transflective beam splitter would be typically utilized to achieve the function of beam merging based on geometric optics. However, the two incident beams are required to be input from both sides of the device, which leads to a bulky system with stray light. On the contrast, in this work, the inversely designed meta-gratings were used to impact distinct wavevectors for different incident angles, realizing beam merging only by single-time reflection. Overall, the proposed creation of free-space merging facilitates the miniature optical device with little stray light and paves a promising path to the future optical system integration. The first authors are M. student Wang Zejing and Ph.D. student Dai Chenjie, and the corresponding author is Prof. Li Zhongyang.

        In recent years, NEAL research group (https://whuneal.wordpress.com/) has acquired a series of new research achievements in the field of metasurface optical devices, and published many high-level papers in renowned and authoritative journals, including Advanced Functional Materials (IF=19.9), Small (IF=15.1), Nano Letters (IF=12.2), Laser & Photonics Reviews (IF=10.9), Optica (IF=10.6), etc. The NEAL group will continue to be dedicated to promoting the innovation and research of micro-nano optical devices in practical applications including dynamic intelligent display and multi-dimensional light field multiplexing.

        Link to the papers:
1) https://doi.org/10.1002/lpor.202100638
2) https://doi.org/10.1002/adom.202200418
3) https://doi.org/10.1002/lpor.202200127
4) https://doi.org/10.1364/OPTICA.456463
5) https://doi.org/10.1021/acs.nanolett.1c05026