Design and fabrication of polygonal grating waveguide display with full-color 2D eye-box expansion

Over the past few decades, the surface relief grating (SRG) based waveguide display technology has attracted significant interest in the augmented reality community due to its light weight, small form factor and ease of mass production. However, the intuition grating structure restricts the optimization freedom which limits the display quality of full-color SRG waveguide. To address this issue the 2D polygonal grating is presented since it has a higher freedom degree in optimizing color uniformity compared to intuition grating structure. By using the 2D polygonal grating we also proposed a design approach of full-color SRG waveguide with hierarchical optimization method. To validate this design, a 2D polygonal grating-based waveguide composed of double layers waveguide was fabricated by using EBL and nanoimprinting technology. The final experimental results show that the 2D eye-box expansion (EPE) waveguide has a field of view (FOV) of 40 degrees, an eye-box of 15 mm x 12 mm, at an eye relief (ERF) of 25 mm, and the overall luminance uniformity is 60 %.