Multi-wavelength achromatic metacoupler for augmented reality display using adjoint method

Diffractive waveguides are a promising optical combiner technology for augmented reality (AR) as they provide the potential for the slimmest geometry and lightest weight. However, their severe chromatic aberration imposes a big challenge for full-color display applications. In this study, we propose multi-wavelength achromatic metacouplers to overcome the longstanding chromatic aberration issue. The metacouplers were inverse-designed to realize a true achromatic behavior in an ultra-thin silicon nitride surface (160 nm) with only binary nanostructures. We achieved a horizontal field of view (FOV) of 45 ° using a single waveguide with high exit-pupil uniformity across the entire FOV range. We will report our simulation results along with our experimental validation of these. This initial study will be used to inform the future direction of the research to perfect the techniques developed.