In this Letter, we demonstrate polarization volume grating (PVG)-based couplers for a double-layer waveguide display to realize a full-color near-eye display. The polarized interference exposure with photo-alignment methods was employed to generate a birefringent spiral configuration with two-dimensional periodicity in a chiral-dopant reactive mesogen material. Such a structure presents a unique highly efficient single-order Bragg diffraction with polarized selectivity. The prepared PVG couplers exhibited over 80% diffraction efficiency with large diffraction angles at spectra of blue (457 nm), green (532 nm), and red (630 nm). The demonstrated waveguide prototype showed a full-color display with a diagonal field of view of around 35°. The overall optical efficiency was measured as high as $118.3\mathrm{cd}/{\mathrm{m}}^2$ per lumen with a transparency of 72% for ambient light.

We propose a polarization multiplexing structure based on multilayer reflective polarized volume holographic gratings(PVGs) to improve the field of view and brightness of the augmented reality waveguide display. The multilayer structure forms the splicing of different response bandwidths by stacking PVGs with different periodic components, and realizes the expansion of the wavelength (angle) bandwidth. The polarization multiplexing structure controls the polarization of the diffracted light by controlling the rotation direction of the liquid crystal pitch in the liquid crystal material, so that both left-hand and right-hand circularly polarized light are diffracted to enhance efficiency. Based on these two structures, the wavelength bandwidth of PVG is increased by 40 nm, the angular bandwidth is increased by 10° and the diffraction efficiency is nearly doubled. In order to verify the feasibility of these two structures, we use the holographic waveguide display with OLED as the image source. The demonstrated waveguide prototype shows a complete display with a diagonal field of view of 55°. The brightness of virtual image was measured as high as 1100 cd/m ² with a transparency of 72% for ambient light.

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.

The paper presents the characterization of the field of view (FOV) in a holographic waveguide display (HWD) with a broadband spectrum image source. The influences of parameters such as grating slanted angle of volume holographic grating (VHG), grating period, and effective refractive index are systematically analyzed. We optimized the parameters and calculated the maximum FOV of monochromatic and chromatic HWD. A multilayered VHGs structure is proposed to enlarge the FOV effectively without additional cost and optical design. We also build a rigorous simulation model to verify the feasibility of the multilayered structure. The theoretical maximum FOV of monochromatic and chromatic HWD are presented after optimization.

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.