Tandem achromatic metasurface for waveguide coupling in full-color AR displays.

Waveguide coupling design is one of the most challenging topics in augmented reality (AR) near-eye displays (NED). The primary challenge stems from the necessity to simultaneously address two competing factors: the overall volume of the AR system and the occurrence of chromatic aberration. To address this issue, what we believe to be a novel tandem trilayer achromatic metasurface is specifically designed for waveguide coupling in AR NEDs, capable of achieving an achromatic effect in a nanometer-thin layer. By analyzing the influence of unit structure parameters on the phase delay of input electromagnetic waves, the optimal parameters are determined and the tandem trilayer achromatic metasurface structure is established. Simulation results show that the incident light can be deflected by 45°, 46°, and 45° at wavelengths of 440 nm ∼ 470 nm, 520 nm ∼ 550 nm, and 620 nm ∼ 660 nm, respectively. The angular deviation error of the three primary colors is maintained lower than 1° in the AR waveguide, ensuring a satisfactory achromatic effect. This design provides a new solution for developing ultra-thin and compact optical systems for full-color AR NEDs.