Practical considerations for large-area nanoimprinted augmented reality waveguides

Roll-to-Plate (R2P) large-area Nanoimprint Lithography (NIL) is a leading technology to replicate complex textures onto various substrate materials. It combines the accuracy of UV imprinting with large-area display manufacturing methods. This is a significantly cost-effective manner to perform micro and nano surface patterning for a plurality of display optics applications, including emerging technologies, such as Augmented Reality (AR) waveguides. Even though NIL technology is advancing to comply with the strict quality requirements of waveguide manufacturing, many challenges still remain. Hereby, we address different aspects that need to be considered to make R2P-NIL a viable mass manufacturing method for AR optics, focusing on scalability and quality. We discuss the potential for scalable waveguide manufacturing, through waveguide upscaling for large-area NIL (Gen5 size, 1100 mm x 1300 mm), in combination with the usage of square high refractive index glass substrates (in contrast to the usual round wafers). By making optimal use of this combination, we demonstrate that 480 waveguides can be manufactured in one imprint cycle. Additionally, of equal importance to scalability, high waveguide quality is achieved through the use of high refractive index materials, maintaining of imprint fidelity, and control of the residual layer thickness and its variation. We show that, using the R2P-NIL technology of Morphotonics to replicate AR waveguides, imprint fidelity of binary, blazed and slanted gratings are retained over repeating imprint cycles.