Multifunctional metasurface image display enabled by merging spatial frequency multiplexing and near- and far-field multiplexing

Metasurface can precisely modulate the fundamental properties such as polarization, amplitude, frequency, and phase of optical waves at the subwavelength scale. Based on this background, we propose and experimentally verify a multifunctional metasurface image display technology enabled by merging spatial frequency multiplexing and near- and far-field multiplexing. In near- and far-field multiplexing, the orientation degeneracy of nanostructures is introduced to combine geometric phase modulation and light intensity modulation, which leads to independent coding of near-field grayscale image and far-field holographic image displays by using simulated annealing algorithm. In spatial frequency multiplexing, different spatial frequency components of two images are added together to generate a hybrid image for hologram design. Since people receive different spatial frequency parts when the observation position changes, both high-frequency and low-frequency images can be easily distinguished. In our experiment, three independent images (a grayscale image, a high-frequency image and a low-frequency image) can be displayed simultaneously at different distances, which explains that our multifunctional metasurface has enhanced information storage capacity. This work provides a new path for multifunctional metasurface design, and possesses broad applications in optical encryption, optical anti-counterfeiting, and many other related fields.