Wide-angle, high-efficiency dot array projection based on particle swarm optimized metasurface with high degrees of freedom

Diffractive optical elements (DOEs) are typical components for splitting the incident laser beam into multiple beams with equal intensity. However, their conversion efficiency and uniformity are limited when working at a wide angle. Here, we propose metasurfaces with high degrees of freedom to overcome this limitation. The width, center position, and height of the nanopillar array in a supercell of the metasurface are collectively optimized using a particle swarm optimization algorithm. To illustrate the feasibility of the proposed method, several transmitted and reflected metasurfaces are inversely designed to project vertically incident light into dot array with a field of view (FOV) angle in the range of 115.6° to 151.6° at a working wavelength of 850 nm. The transmitted metasurfaces with a conversion efficiency higher than 85.3% and a uniformity error lower than 3.1% have been demonstrated. By integrating multilayer film with nanopillar array, the reflected metasurfaces can achieve a conversion efficiency higher than 94.2% and a uniformity error lower than 5.1%. The proposed method provides an idea that can be readily applied to the design of other high-performance metasurfaces.