2D exit pupil expansion in near-eye display by using surface-relief-grating lightguide and volume-holographic-grating lightguide

A two-dimensional eye-pupil expander (2D-EPE) architecture is proposed based on a hybrid combination of a surface relief grating (SRG) lightguide and a volume holographic grating (VHG) lightguide. The fabrication methods of the lightguides were illustrated, and the performance was measured and simulated individually. The SRG lightguide demonstrated a vertical field of view (FOV) of 20.4°, and the VHG lightguide exhibited a horizontal FOV of 20.4°. The proposed dual-element architecture leverages the broadband coupling capability of SRGs to capture all diffractable light within the Bragg selectivity of VHGs. As a result, the guidable FOV is significantly enhanced compared with conventional VHG-based 2D EPEs, enabling see-through functionality while preserving image privacy. This provides high potential for future applications in compact and efficient augmented/mixed reality display systems.