融合空频复用和近远场复用的多功能超表面图像显示

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

超表面可以在亚波长尺度上对光波的偏振、振幅、频率、相位等基本参量进行精确调控。基于此背景,本文提出并实验验证了一种融合空间频率复用和近远场复用的多功能超表面图像显示技术。其中,近远场复用是利用纳米结构的转角简并性将超表面几何相位调控与光波强度调控相融合,基于模拟退火算法实现近场灰度图像与远场全息图像的独立编码;空间频率复用是将两幅图像的不同空间频率成分叠加作为远场全息图像,可以在不同观察位置分别接收到不同的空间频率信息,对应高频图像和低频图像。实验结果表明,通过优化超表面可以同时在不同工作距离实现三幅独立图像(灰度图像、高频图像及低频图像)的显示,这提升了超表面的信息存储容量。本工作将为超表面多功能复用及其在光学加密、光学防伪等领域的应用提供新思路。

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 lowfrequency 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.