We propose a two-dimensional exit pupil expansion (2D-EPE) design of a diffractive waveguide (DW) based on polarization volume grating (PVG). The designed waveguide structure and pupil expansion principle are introduced in this paper. The light propagation behavior and available field of view (FoV) of the proposed waveguide are investigated by simulations. In addition, the waveguide sample based on the proposed design is prepared, and an imaging system based on a monochromatic MicroLED projector is built for AR imaging experiments. The experimental results show that the prepared waveguide system can achieve a clear AR display with a diagonal FoV of 30° and obtain an exit pupil magnification of nearly 20 times compared to the entrance pupil size. The optical imaging efficiency was measured to be 3.85%, and the backward light leakage rate was as low as 8.7%. This work further enhances the feasibility and practicality of the PVG-waveguide technology and provides a promising candidate for AR-DW applications.

We present a volume holographic waveguide display by dispersing gold nanoparticles (Au-NPs) in acrylate-based photopolymer. The diffractive bandwidth and diffraction efficiency (DE) of the volume holographic grating (VHG) applied for waveguide displays are characterized and analyzed through both the simulations and experiments. The results show that the wavelength bandwidth of the VHG can be enlarged to 30 nm with a corresponding refractive index modulation (RIM) increased to around 0.08 by dispersing the Au-NPs with a concentration of 0.012 g/ml into the acrylate-based photopolymer. Finally, the green monochromatic waveguide display system with 30° horizontal field of view (FOV) is realized.

Planar waveguide structure has benefits to expand the exit pupil of the near-eye display. To achieve a uniform output luminance within the expanded exit pupil, a specific distribution of diffractive efficiency (DE) should be set for the out-coupling grating. In this paper, a physical model is built to study the DE distribution of out-coupling grating with consideration of the whole field-of-view. Compared to the previous works which only considered the central view angle, this model is more consistent with the actual situations to realize a uniform imaging output for a waveguide-based near-eye display system. Also a planar waveguide with two holographic volume gratings as the in and out-coupling gratings is fabricated to verify the proposed DE distribution. In experiments, a spatial light modulator (SLM) is applied as the spatial luminance modulator, and the coupling grating with proposed DE distribution is fabricated by the holographic interference exposure setup. The results shows a high consistency between the simulation and the experiment.

This work proposes a green light-sensitive acrylate-based photopolymer. The effects of the preparation conditions for the waveguide applied volume holographic gratings (VHGs) were experimentally investigated. The optimum preparation conditions for holographic recording were revealed. After optimization, the peak of VHG diffraction efficiency reached 99%, the diffractive wavelength bandwidth increased from 13 nm to 22 nm, and the corresponding RIM was 0.06. To prove the wide application prospect of the acrylate-based photopolymer in head-mounted augmented reality (AR) displays, green monochromatic volume holographic waveguides were fabricated. The display results showed that the prototype was able to achieve a 28° diagonal FOV and possessed a system luminance of 300 cd/m².

Near-eye holographic waveguide display system using novel reflective polarized volume gratings (RPVG) have lately gotten a lot of interest. However, from polarization characteristics to imaging simulation, there is no systematic approach based on RPVG. Here, a full methodology for solving this problem using the rigorous coupled wave analysis (RCWA) model is presented. This self-built RCWA model is used to examine the optical behavior of RPVG. This excellent portability of the RCWA model makes it possible for RPVG as a diffractive optical element, which is integrated into the commercial optical software Zemax via a self-compiled dynamic link library (DLL), and a full-color imaging simulation of the based-RPVG waveguide display system is obtained. Our work provides an instructive imaging analysis method using the RPVG for holographic waveguide display.

A ray-tracing model is developed based on coupled wave theory for a volume holographic grating, which is the most important element of the holographic waveguide display but not accessibly integrated in current optical design software. The model fully and faithfully represents the angular selectivity, wavelength selectivity, polarization, and other properties for the in-coupling, out-coupling, and expansion gratings. It is especially important that the model is compatible with the current optical design software. In this paper, combining with other mature optical simulation functions of Zemax, integrated models are built for typical holographic waveguide display configurations, including image source, collimation element, gratings, waveguide plates, and approximate eye. It could provide the retina image at different viewing positions, based on which the main performance characteristics of a holographic waveguide display, such as field of view, color uniformity, eye box, and light efficiency, could be easily derived. Consequently, it provides a valuable guiding approach for the design and optimization of holographic waveguide displays.