Abstract:
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.