Time-sequential color code division multiplexing holographic display with metasurface

Color metasurface holograms are powerful and versatile platforms for modulating the amplitude,phase,polarization,and other properties of light at multiple operating wavelengths.However,the current color metasurface holography can only realize static manipulation.In this study,we propose and demonstrate a multiplexing metasurface technique combined with multiwavelength code-division multiplexing(CDM)to realize dynamic manipulation.Multicolor code references are utilized to record information within a single metasurface and increase the information capacity and security for anticracks.A total of 48 monochrome images consisting of pure color characters and multilevel color video frames were reconstructed in dual polarization channels of the birefringent metasurface to exhibit high information density,and a video was displayed via sequential illumination of the corresponding code patterns to verify the ability of dynamic manipulation.Our approach demonstrates significant application potential in optical data storage,optical encryption,multiwavelengthversatile diffractive optical elements,and stimulated emission depletion microscopy.

Reconstruction resolution enhancement of EPISM based holographic stereogram with hogel spatial multiplexing

We investigate how the splicing mode of a holographic element(hogel)affects the reconstruction of a 3 D scene to improve the reconstruction resolution of a holographic stereogram fabricated using the effective perspective image segmentation and mosaicking method(EPISM).First,the effect of hogel spatial multiplexing on holographic recording and reconstruction is studied based on the mechanism of recording interference fringes in the holographic recording medium.Second,combined with the influence of multiple exposures on the hologram's diffraction efficiency,the diffraction efficiency of the holographic stereogram is analyzed in the spatial multiplexing mode.The holographic stereogram is then regarded as a special optical imaging system.The theory of spatial bandwidth product is adopted to describe the comprehensive resolution of the holographic stereogram,which explains why hogel spatial multiplexing can significantly improve the reconstruction resolution of a holographic stereogram.Compared with the traditional printing method under the same parameters in optical experiments,hogel spatial multiplexing has a lower diffraction efficiency but a higher quality of reconstructed image,consistent with the theoretical analysis.

100 Hertz frame-rate switching threedimensional orbital angular momentum multiplexing holography via cross convolution

The orbital angular momentum(OAM)of light has been implemented as an information carrier in OAM holography.Holographic information can be multiplexed in theoretical unbounded OAM channels,promoting the applications of optically addressable dynamic display and high-security optical encryption.However,the frame-rate of the dynamic extraction of the information reconstruction process in OAM holography is physically determined by the switching speed of the incident OAM states,which is currently below 30 Hz limited by refreshing rate of the phase-modulation spatial light modulator(SLM).Here,based on a cross convolution with the spatial frequency of the OAM-multiplexing hologram,the spatial frequencies of an elaborately-designed amplitude distribution,namely amplitude decoding key,has been adopted for the extraction of three-dimensional holographic information encoded in a specific OAM information channel.We experimentally demonstrated a dynamic extraction frame rate of 100 Hz from an OAM multiplexing hologram with 10 information channels indicated by individual OAM values from-50 to 50.The new concept of cross convolution theorem can even provide the potential of parallel reproduction and distribution of information encoded in many OAM channels at various positions which boosts the capacity of information processing far beyond the traditional decoding methods.Thus,our results provide a holographic paradigm for high-speed 3D information processing,paving an unprecedented way to achieve the high-capacity short-range optical communication system.

Flat multifunctional liquid crystal elements through multi-dimensional information multiplexing

Flat optical elements have attracted enormous attentions and act as promising candidates for the next generation of optical components.As one of the most outstanding representatives,liquid crystal(LC)has been widely applied in flat panel display industries and inspires the wavefront modulation with the development of LC alignment techniques.However,most LC elements perform only one type of optical manipulation and are difficult to realize the multifunctionality and light integration.Here,flat multifunctional liquid crystal elements(FMLCEs),merely composed of anisotropic LC molecules with space-variant orientations,are presented for multichannel information manipulation by means of polarization,space and wavelength multiplexing.Specifically,benefiting from the unique light response with the change of the incident polarization,observation plane,and working wavelength,a series of FMLCEs are demonstrated to achieve distinct near-and far-field display functions.The proposed strategy takes full advantage of basic optical parameters as the decrypted keys to improve the information capacity and security,and we expect it to find potential applications in information encryption,optical anti-counterfeiting,virtual/augmented reality,etc.

Planar peristrophic multiplexing metasurfaces

As a promising counterpart of two-dimensional metamaterials,metasurfaces enable to arbitrarily control the wavefront of light at subwavelength scale and hold promise for planar holography and applicable multiplexing devices.Nevertheless,the degrees of freedom(DoF)to orthogonally multiplex data have been almost exhausted.Compared with state-of-theart methods that extensively employ the orthogonal basis such as wavelength,polarization or orbital angular momentum,we propose an unprecedented method of peristrophic multiplexing by combining the spatial frequency orthogonality with the subwavelength detour phase principle.The orthogonal relationship between the spatial frequency of incident light and the locally shifted building blocks of metasurfaces can be regarded as an additional DoF.We experimentally demonstrate the viability of the multiplexed holograms.Moreover,this newly-explored orthogonality is compatible with conventional DoFs.Our findings will contribute to the development of multiplexing metasurfaces and provide a novel solution to nanophotonics,such as large-capacity chip-scale devices and highly integrated communication.

Active metasurface via magnetic control for tri-channel polarization multiplexing holography

Active metasurfaces have recently attracted more attention since they can make the light manipulation be versatile and real-time. Metasurfaces-based holography possesses the advantages of high spatial resolution and enormous information capacity for applications in optical displays and encryption. In this work, a tunable polarization multiplexing holographic metasurface controlled by an external magnetic field is proposed. The elaborately designed nanoantennas are arranged on the magneto-optical intermediate layer, which is placed on the metallic reflecting layer. Since the non-diagonal elements of the dielectric tensor of the magneto-optical material become non-zero values once the external magnetic field is applied,the differential absorption for the left and right circularly polarized light can be generated. Meanwhile, the amplitude and phase can be flexibly modulated by changing the sizes of the nanoantennas. Based on this, the dynamic multichannel holographic display of metasurface in the linear and circular polarization channels is realized via magnetic control, and it can provide enhanced security for optical information storage. This work paves the way for the realization of magnetically controllable phase modulation, which is promising in dynamic wavefront control and optical information encryption.

基于全介质超表面的太赫兹波段偏振复用计算全息成像

提出利用全介质超表面实现太赫兹波段计算全息成像技术方案,采用基于几何相位调控的全介质超表面实现了频率0.95 THz~1.2 THz的宽带全息成像。在此基础上,设计了基于几何相位和传输相位同时调控的全介质超表面并实现了偏振复用全息成像。该研究提高了超表面的复用能力和工作效率,有望解决金属超表面存在的固有欧姆损耗和低极化转换效率等问题。同时可以激发Mie型电共振和磁共振实现波前调制,为开发高效、轻便、低成本的太赫兹功能器件提供了一种新途径。

Mode division multiplexed holography by out-of-plane scattering of plasmon/guided modes

We design and demonstrate a type of multiplexed hologram by nanoscatterers inside a dielectric-loaded plasmonic waveguide with guided-wave illuminations. The mode division multiplexed hologram（MDMH） is fulfilled by the scattering of guided waves to free space with respect to different modes. According to different mode numbers, these guided modes have different responses to the multiplexed hologram, and then give rise to different holographic images in reconstructions. In experiments, we show two kinds of MDMHs based on TM0∕TE0 and TE0∕TE1 modes as examples. Our approach could enrich the holography method that favors on-chip integration.

一种新的多通道全息干涉计量术

旋转光楔多重全息术,是利用置于平面参考光波光路上的旋转光楔,调制其传播方向,实现多参考光编码记录获得多重全息图。当用平面波垂直入射再现时,就能从理论上分析出再现像的分布、分离条件及估算的通道数等。这种技术用在全息干涉计量上,就是一种新的多通道全息干涉计量术。 本文给出这种新技术在时间平均和双曝光全息干涉计量上的应用,并讨论了在单次曝光全息干涉计量(实时法)上的应用。实验结果说明,这种新技术是完全可行的。

旋转光楔多重一步彩虹全息术

根据旋转光楔多重全息术和一步彩虹全息术基本原理 ,讨论了采用旋转光楔实现多重一步彩虹全息术的原理 ,进而用He Ne激光光源 ,获得了在同一块干版上记录的多个彩虹全息图 ,并可在白光下同时再现的多重一步彩虹全息像。理论分析和实验结果基本吻合。结果表明 ,该技术简单易行 ,有广泛的应用价值。

多重一步彩虹全息的理论探究

讨论的多重全息技术是在一步彩虹全息的基础上 ,在物光的成像光路中加入一块可旋转的光楔 ,在同一块干板上多次曝光记录多个彩虹全息图像 ,并且可在白光下同时再现 .本文给出了理论分析和光路设计 .

基于时分复用方法的真彩色全息显示

提出了一种改进的时分复用方法,采用同步控制电路控制两段式彩色滤光轮的转动速度与全息图的切换速度一致,通过两次切换全息图,即可实现傅里叶计算全息图的真彩色显示。该方法通过缩放处理来消除再现像的色差,并采用迭代傅里叶算法制作了两幅包含有彩色信息的合成相位全息图,使记录着单一颜色场景信息的全息图再现时只占用空间光调制器(SLM)的1/2区域。此方法实现了白光LED真彩色全息显示,减少了传统时分复用方法加载全息图的次数,对SLM刷新率的要求也降低了1/3。实验验证了此方法的可行性。

抗水性光致聚合物的体全息存储研究

提出了基于酞菁染料的全息记录材料,与目前已报道的基于丙烯酞胺基单体光聚合型全息记录介质相比,该聚合体系显示了优良的全息特性:全"干"热后处理,良好的抗水性和环境稳定性,制备过程简单和低毒性,并可制备成较厚的感光膜层。针对存储过程的页间和页内串扰做了理论分析和MTALAB仿真,采用自主研制的抗水性光致聚合物材料记录多幅不同图像的实验方案,分析了本抗水性全息材料的角度复用性能。

一种简易的多重全息术

在全息照相实验光路的基础上,通过调换扩束镜与反射镜的位置,改变反射镜角度可以得到多重全息图.实验结果与理论分析基本吻合.

多路角度复用体全息三维显示技术

为满足高分辨率真三维大数据显示的空间带宽积要求,提出一种基于多通道角度复用模式的体全息三维显示技术。通过对三维场景进行波前编码,获得相位计算全息图,并将计算全息图依次按照不同角度复用记录到掺杂金纳米颗粒体全息光致聚合物材料的同一区域,获得复用体全息图,再现时可以在不同角度观察三维场景。在体全息三维显示实验系统中,实现体全息材料记录区域的单点像素总数为120×1 920×1 080,显示的空间带宽积达到了2.5×10~8,相对于空间光调制器显示提升了120倍。

全息照相实验的拓展

在大学物理普通全息照相实验的基础上，不外加其他光学元件、仅适当改进光路，从而得到了2种简易的实验方法。分别从参考光、物光两个方面人手拍摄多重全息图，使学生加强对全息照相多重性的理解，从而更进一步理解与普通照相的区别。

基于空间角度复用和双随机相位的多图像光学加密方法

提出了基于空间角度复用和双随机相位的多图像光学加密新方法.加密过程中,首先将原始图像进行随机相位调制和不同距离的菲涅耳衍射;其次,将携带调制后图像的参考光与携带随机相位且具有不同立体角的参考光相干叠加,产生干涉条纹;最后,将不同方向的干涉条纹叠加形成复合加密图像.解密为加密的逆过程,将复合加密图像置于空间滤波和菲涅耳衍射系统中,经过不同相位密钥解调和正确距离的菲涅耳衍射完成解密,得到多幅解密图像.该方法可以同时对多幅图像进行高效的加密,计算简单、安全可靠、抗噪声能力强.利用相关系数评估了该方法的加密效果,并通过仿真实验验证了该方法的有效性和安全性.

频域光存储和全息术

本文通过分析光谱烧孔的全息探测法,提出了全息频域光存储系统,并分析了系统的特性指标。计算机模拟分析结果表明,全息频域光存储技术是一种大容量并行光存储新技术。

面向高通量的多通道复用数字全息成像技术

光学成像已成为跨尺度表征生物系统信息的主要方法之一,近年来生物样本的快速、无损且全面表征对成像系统的可解析量提出了更高的要求。数字全息通过干涉成像方式,可准确重构光波前的振幅和相位信息,具有快速、无损、三维成像等优势,在数字病理诊断、细胞无标记观察和实时监测等方面得到了广泛的研究和应用。本文首先介绍了实现高通量成像的主要方式,并分析了数字全息的优势及空间带宽变化,展示了基于希尔伯特变换的面向高通量多通道复用数字全息技术的理论框架,并介绍了基于该理论框架设计的拓展视场双通道复用数字全息显微成像系统。该系统在不牺牲空间和时间分辨率的情况下,可实现超越传统离轴全息显微镜8倍的空间带宽积。所介绍的数字全息复用技术可充分利用单幅强度图像的冗余空间带宽,可用于高通量多通道复用数字全息成像。

High-dimensional orbital angular momentum multiplexing nonlinear holography

Nonlinear holography has been identified as a vital platform for optical multiplexing holography because of the appearance of new optical frequencies.However,due to nonlinear wave coupling in nonlinear optical processes,the nonlinear harmonic field is coupled with the input field,laying a fundamental barrier to independent control of the interacting fields for holography.We propose and experimentally demonstrate high-dimensional orbital angular momentum(OAM)multiplexing nonlinear holography to overcome this problem.By dividing the wavefront of the fundamental wave into different orthogonal OAM channels,multiple OAM and polarization-dependent holographic images in both the fundamental wave and second-harmonic wave have been reconstructed independently in the spatial frequency domain through a type-II second harmonic generation process.Moreover,this method can be easily extended to cascadedχ2 nonlinear optical processes for multiplexing in more wavelength channels,leading to potential applications in multicasting in optical communications,multiwavelength display,multidimensional optical storage,anticounterfeiting,and optical encryption.