Nikahood' Dr. Hu Dejiao: "Volume Holography-Based Augmented Reality Waveguide Technology"

On October 20, 2024, the 15th sub-forum "Stereoscopic Imaging Technology and Applications" of the 32nd Annual Scientific Conference of the China Society for Imaging Science and Technology, organized by the Stereoscopic Imaging Technology Professional Committee, was successfully held at the Peking University Shenzhen Graduate School in Shenzhen University Town.

The event focused on multi-dimensional discussions covering new stereoscopic imaging technologies, materials, and devices, as well as creative applications, content production, and demonstrations of stereoscopic imaging. Twelve speakers from research institutions and enterprises, including Peking University, Sichuan University, the China Academy of Engineering Physics, the Technical Institute of Physics and Chemistry of CAS, the Institute of Optics and Electronics of CAS, and Nikahood (Tianjin) Co., Ltd., engaged in lively exchanges and discussions on topics such as augmented reality (AR) glasses technology, holography, and stereoscopic display technology.

Dr. Hu Dejiao, Optical Director of Nikahood, delivered a keynote presentation titled "Volume Holography-Based Augmented Reality Waveguide Technology" to the attendees.

In his presentation, Dr. Hu reviewed the evolution of augmented reality (AR) display technology—from the bulky "Sword of Damocles" systems to today's compact, lightweight, and cost-effective waveguide solutions. He highlighted the inherent advantages of volume holographic grating (VHG) waveguides, including low light leakage, minimal rainbow artifacts, and simplified manufacturing processes.

Dr. Hu explained that VHGs are Bragg gratings whose diffraction behavior follows Bragg matching principles, which underpin all these advantages. The Bragg condition dictates that for maximum diffraction efficiency, the diffracted wave vector equals the incident wave vector minus the VHG's 3D grating vector. This principle inherently restricts permissible wavelengths and angles for both incident and diffracted light, eliminating stray diffraction orders and thus preventing light leakage.

He further noted that when incident light angles deviate from Bragg matching, coupled-wave theory can quantify diffraction angles and efficiency. The diffraction efficiency decreases with angular deviation, giving VHGs angular selectivity—a critical feature for mitigating rainbow effects caused by ambient light. Conventional waveguides disperse ambient light into red-to-blue chromatic glare when it strikes internal gratings, severely degrading user experience. VHGs' angular selectivity confines such diffraction to narrow angular ranges, dramatically reducing rainbow artifacts.

Dr. Hu detailed VHG waveguide design principles, combining k-space analysis and diffraction efficiency optimization to finalize grating parameters. For fabrication, he introduced core components of exposure systems and emphasized the importance of wavefront quality, beam uniformity, and precise incident angle control.

Additionally, Dr. Hu shared Nikahood' latest advancements in photosensitive materials. As a core foundational technology for VHG waveguides, the polymer-dispersed liquid crystal (PDLC) material developed by Nikahood achieved a refractive index modulation (Δn) exceeding 0.1 and haze below 0.3%, laying a robust foundation for high-quality waveguide product development.

Nikahood is committed to developing China's premier VHG waveguide products by overcoming technical limitations of existing solutions and reducing production costs from raw materials to manufacturing. This will help transform AR waveguide glasses into consumer-ready devices that people truly want to use.