Two‐Dimensional Angular Bandwidth Broadening of Metasurface Grating

Abstract

Waveguide‐type near‐eye displays (NED) have attracted increasing attention in the market of augmented reality (AR) and virtual reality (VR) devices, thanks to their outstanding performance within ultra‐compact size. The performance of waveguide‐type NED mainly depends on the waveguide coupler that transmits the incident image to the user's eye through the total internal reflection (TIR) inside the waveguide. However, the waveguide couplers, that have been widely used, exhibit nonuniform diffraction efficiency within the transferable angular range, i.e., field of view (FoV) of waveguide‐type NED, so that the image intensity distribution distortion is induced. Thus, it is needed that many researchers focus on broadening angular bandwidth to overcome the non‐uniformity of the diffraction efficiency. Herein, the 2D angular bandwidth broadening metasurface grating that exhibits uniform and high diffraction efficiency for the 2D FoV range is proposed. Specifically, the proposed device is designed specifically, and the diffraction efficiency of this device shows uniform efficiency of about 75% with a variance of 0.25% for the FoV range, and it is demonstrated both numerically and experimentally. Consequently, it is expected that the proposed device can be a game‐changer in the market for waveguide‐type NED for the enhancement of image uniformity.

Keywords

• adjoint variable method
• grating
• inverse design
• metasurfaces
• waveguide combiners