Near-eye display technology plays a crucial role in realizing the vision of the metaverse. However, the current bottleneck of near-eye display technology is the "impossible triangle", where it is challenging to simultaneously achieve optimal levels of display performance, appearance (form factor), and cost. This challenge is particularly pronounced in augmented reality (AR) technology. The key to solving this problem lies in finding suitable optical solutions. Among the current optical solutions for AR displays, prism solutions, freeform solutions, and birdbath solutions are limited by their bulky glasses thickness, compromising the appearance factor, while geometrical waveguide solutions are limited by complex manufacturing processes, compromising the cost factor. Diffractive waveguides are considered the most promising future mainstream solution to overcome the "impossible triangle". They can achieve a more traditional eyeglass-like appearance, and can leverage semiconductor fabrication techniques such as nano-imprint lithography to reduce costs. However, the main obstacles preventing further commercialization of diffractive waveguides are inadequate image uniformity, and the color non-uniformity caused by chromatic dispersion issues. This project proposes the use of the metasurface as a replacement for traditional diffractive gratings to develop a novel metasurface diffractive waveguide that can address the key bottlenecks faced by current diffractive waveguide technology. Unlike the aforementioned solutions based on traditional optics, the metasurface employs the design concept of micro-/nano- optics, allowing for precise control of light phase and amplitude, and providing higher design freedom. This project will utilize metasurface diffractive waveguides to achieve the following objectives: (1) improve luminance uniformity for multi-color displays, (2) reduce chromatic dispersion to enhance color display capabilities, and (3) simultaneously optimize image uniformity in terms of spatial and angular factors (EPE uniformity and FOV uniformity).
