Single-layer waveguide with compound metasurfaces for highly efficient and chromatic-aberration-free augmented reality near-eye displays

Augmented reality (AR) near-eye displays seamlessly integrate virtual information with real world, in which the optical waveguide is the key component functioned as a coupler. Due to strong chromatic aberration, independent waveguides are always indispensable to separate the three primary colors that inevitably brings larger and thicker appearance. To address this, this paper proposes a new chromatic-aberration-free single-layer waveguide for AR displays by integrating a double-layer grating metasurface (MS) and the covered cylindrical MSs. The double-layer grating MS breaks through the limitations on a narrow wavelength band, enabling high diffraction efficiency for incident light deflection across the entire visible spectrum. Further, the cylindrical MSs provide accurate control over incident angles, not only overcoming the challenge of total reflection but also effectively eliminating chromatic aberration. Design results show that the proposed structure achieves an impressive diffraction efficiency of over 80 % for blue and green light and over 90 % for red light with an outstanding diffraction angular difference lower than 2.5 deg. Real-time ray tracing simulation demonstrates the capability of the designed AR engine to achieve high-resolution full-color imaging. The compound MSs enable precise light and color control for a single-layer waveguide coupler with exceptional diffraction efficiency and minimal chromatic aberration, which show great potential for cutting-edge AR applications.