Fabrication and replication of high efficiency blazed gratings with grayscale electron beam lithography and UV nanoimprint lithography

In a waveguide-type display for augmented reality, the image is injected in the waveguide and extracted in front of the eye appearing superimposed on the real world scene. An elegant and compact way of coupling these images in and out is using blazed gratings, which can achieve high diffraction efficiencies. We report the single step fabrication of blazed gratings (508nm pitch) with grayscale electron beam lithography and the subsequent replication in a polymer material with ultraviolet nanoimprint lithography. We finally show the in and out coupling of an image through two blazed gratings and confirm a throughput efficiency of 17.4%.