Dynamic 3D Metasurface Holography via Cascaded Polymer Dispersed Liquid Crystal

Academic Background

Metasurfaces, as two-dimensional subwavelength structures, enable local modulation of the phase and amplitude of light fields, offering novel solutions for the design of miniaturized optical devices. However, most existing metasurface holographic display technologies are limited to static characteristics, unable to achieve real-time dynamic modulation, which restricts their application in intelligent display systems. To meet the demands of dynamic 3D holographic displays, researchers have explored various active metasurface technologies, including multiplexing metasurfaces, structural modification metasurfaces, and integrated metasurfaces. Among these, liquid crystals (LCs), as a typical light field modulation material, are widely used in the design of active metasurfaces. However, traditional LC devices often suffer from low degrees of freedom, limited information capacity, slow response speeds, and severe crosstalk.

To address these issues, Sun et al. proposed for the first time a cascaded device based on polymer-dispersed liquid crystal (PDLC) and broadband metasurfaces, achieving dynamic 3D holographic displays with ultra-high contrast, rapid response, and continuous modulation. This research provides a new perspective on dynamic metasurface holographic display technology, with significant scientific and application value.

Source of the Paper

The paper was co-authored by Shuo Sun, Jin Li, Xiaoxun Li, Xianyu Zhao, Kun Li, and Liang Chen, affiliated with the College of Optical and Electronic Technology at China Jiliang University, the School of Instrumentation and Optoelectronic Engineering at Beihang University, the National Institute of Extremely-Weak Magnetic Field Infrastructure Quantum Biology Science and Technology Center, the School of Electronic Science and Engineering at Southeast University, and Camoptics (Suzhou) Co., Ltd. The paper was published in 2024 in the journal Microsystems & Nanoengineering.

Research Process and Results

1. Preparation and Characterization of PDLC Devices

The study first prepared PDLC devices with high contrast and rapid response capabilities. PDLC is composed of low-molecular-weight liquid crystals and high-molecular-weight polymers, forming liquid crystal droplets through phase separation. In the absence of an external electric field, the liquid crystal droplets are randomly distributed, causing light scattering. When a sufficiently strong electric field is applied, the liquid crystal droplets align along the field direction, allowing light to pass through the PDLC completely. By precisely controlling the thickness of the PDLC (7 μm to 18 μm), the researchers optimized its driving voltage and saturation voltage. Experiments showed that a 13 μm-thick PDLC device exhibited optimal performance under 635 nm laser illumination, with a minimum transmittance below 5%, a maximum transmittance exceeding 80%, and a response time of less than 10 ms.

2. Optimization of Broadband and High-Efficiency Metasurfaces

To integrate with broadband PDLC devices, the researchers designed and optimized a metasurface based on amorphous silicon (α-Si). Using the finite-difference time-domain (FDTD) method, the dimensions of the nanopillars were optimized to achieve cross-polarization transmittance (CR-Transmittance) exceeding 40% across the entire visible spectrum. The metasurface’s nanopillars were fabricated using photolithography and etching techniques, with a period of 500 nm and a height of 600 nm. By rotating the nanopillars, the metasurface covered a complete phase range of 0-360°, ensuring uniform holographic image generation across the full spectrum.

3. Continuously Modulated Holographic Display Based on PDLC-Metasurface

The researchers cascaded PDLC with the metasurface to construct a dynamic 3D holographic display system. By adjusting the voltage to modulate the transmittance of the PDLC, continuous modulation of the holographic image intensity was achieved. Experiments showed that as the voltage increased from 10 V to 30 V, the intensity of the holographic image gradually increased, exhibiting ultra-high contrast. Additionally, the researchers developed a 3D holographic display algorithm based on holographic lenses, generating holographic images of different depths and colors through multi-layer virtual holographic lenses.

4. Broadband and Low-Crosstalk Multi-Channel Dynamic PDLC-Metasurface Holographic Display

The study further prepared a four-channel dynamic addressing 3D holographic display device. Each channel was controlled by independent ITO electrodes, enabling high-contrast holographic image switching. Experiments showed that when a single channel was activated, its transmittance exceeded 80%, while the transmittance of other channels was below 0.06%, demonstrating extremely low crosstalk. Moreover, by combining 473 nm, 532 nm, and 635 nm lasers, the researchers achieved broadband dynamic 3D holographic display, with holographic images dynamically switching between red, green, and blue.

Conclusion and Significance

This study experimentally demonstrated for the first time a cascaded device based on PDLC and broadband metasurfaces, achieving dynamic 3D holographic displays with ultra-high contrast, rapid response, and continuous modulation. By optimizing the thickness of the PDLC and the dimensions of the metasurface nanopillars, the researchers successfully constructed a self-addressing, rapid-response, and multi-channel PDLC-metasurface device, showcasing the effects of monochromatic holographic image switching and color holographic display. This method provides new insights into dynamic 3D holographic display technology, with broad application prospects in fields such as optical communication, optical encryption, optical storage, and laser manufacturing.

Research Highlights

1. Innovation: First-time integration of PDLC with broadband metasurfaces to achieve dynamic 3D holographic display.
2. High Performance: PDLC devices exhibit high contrast (>80%) and rapid response (<10 ms), while the metasurface demonstrates high transmittance (>40%) across the entire visible spectrum.
3. Multi-Channel Low Crosstalk: The four-channel dynamic addressing holographic display device shows extremely low crosstalk, with activated channel transmittance exceeding 80% and other channels below 0.06%.
4. Broadband Display: By combining lasers of different wavelengths, dynamic switching of red, green, and blue holographic images was achieved, demonstrating the potential of broadband dynamic 3D holographic display.

Additional Valuable Information

The research was supported by the Zhejiang Provincial Science and Technology Plan Project, the National Natural Science Foundation of China Excellent Young Scientists Fund (Overseas), the Fundamental Research Funds for the Provincial Universities of Zhejiang, and the 27th Student Research Project of China Jiliang University. The research team also detailed the preparation methods for PDLC and metasurface devices, including the phase separation polymerization process of PDLC and the photolithography and etching techniques for metasurfaces, providing a technical foundation for future large-scale production and commercialization.