Whitepaper - Optimizing manufacturing of augmented reality waveguides by combination of precision inkjetting and nanoimprinting

Augmented Reality (AR) smart glasses and headsets enable users to merge the real world with virtual environments by projecting images onto transparent displays.

The effectiveness of AR devices relies on providing high-quality visuals with a wide field of view (FOV) while being lightweight and compact. A key technology in augmented visualization is the waveguide combiner, which includes input, output, and exit pupil expansion (EPE) gratings.

Here, we discuss the fabrication of these couplers using diffractive gratings that are modulated by duty cycle, depth, and structure. The primary challenge is to achieve a minimal and uniform residual layer thickness, ideally using a high refractive index resist, across gratings with different fill factors to maximize efficiency and FOV. Our method involves creating a waveguide combiner with modulated duty cycle, depth, and structure using high-performing high-refractive-index nanoimprint materials from INKRON and inkjet printers and nanoimprint equipment from SUSS. Using interference imaging and scanning electron microscopy (SEM), we highlight the benefits of inkjet-printing the nanoimprint resin over traditional spin-coating processes. We focus on precise control of the residual layer, achieving thicknesses as low as 50 nm with excellent uniformity throughout the waveguide combiner.