Light-field modulation and optimization near metal nanostructures utilizing spatial light modulators

Plasmonic modes within metal nanostructures play a pivotal role in various nanophotonic applications.However,a significant challenge arises from the fixed shapes of nanostructures post-fabrication,resulting in limited modes under ordinary illumination.A promising solution lies in far-field control facilitated by spatial light modulators(SLMs),which enable on-site,real-time,and non-destructive manipulation of plasmon excitation.Through the robust modulation of the incident light using SLMs,this approach enables the generation,optimization,and dynamic control of surface plasmon polariton(SPP)and localized surface plasmon(LSP)modes.The versatility of this technique introduces a rich array of tunable degrees of freedom to plasmon-enhanced spectroscopy,offering novel approaches for signal optimization and functional expansion in this field.This paper provides a comprehensive review of the generation and modulation of SPP and LSP modes through far-field control with SLMs and highlights the diverse applications of this optical technology in plasmon-enhanced spectroscopy.

A high-contrast imaging coronagraph for segmented-mirror large aperture telescopes using a spatial light modulator

The primary mirrors of current and future large telescopes always employ a segmented mirror configuration.The small but non-negligible gaps between neighboring segments cause additional diffraction,which restricts the performance of high-contrast coronagraph.To solve this problem,we propose a coronagraph system based on a single liquid crystal spatial light modulator(SLM).This spatial light modulator is used for amplitude apodization,and its feasibility and potential performance are demonstrated using a laboratory setup using the stochastic parallel gradient descent(SPGD)algorithm to control the spatial light modulator,which is based on point spread function(PSF)sensing and evaluation and optimized for maximum contrast in the discovery working area as a merit function.The system delivers a contrast in the order of 10−6,and shows excellent potential to be used in current and future large aperture telescopes,both on the ground and in space.

A review of liquid crystal spatial light modulators:devices and applications

Spatial light modulators,as dynamic flat-panel optical devices,have witnessed rapid development over the past two decades,concomitant with the advancements in micro-and opto-electronic integration technology.In particular,liquid-crystal spatial light modulator(LC-SLM)technologies have been regarded as versatile tools for generating arbitrary optical fields and tailoring all degrees of freedom beyond just phase and amplitude.These devices have gained significant interest in the nascent field of structured light in space and time,facilitated by their ease of use and real-time light manipulation,fueling both fundamental research and practical applications.Here we provide an overview of the key working principles of LC-SLMs and review the significant progress made to date in their deployment for various applications,covering topics as diverse as beam shaping and steering,holography,optical trapping and tweezers,measurement,wavefront coding,optical vortex,and quantum optics.Finally,we conclude with an outlook on the potential opportunities and technical challenges in this rapidly developing field.

Design of Protograph LDPC-Coded MIMO-VLC Systems with Generalized Spatial Modulation

This paper investigates the bit-interleaved coded generalized spatial modulation(BICGSM) with iterative decoding(BICGSM-ID) for multiple-input multiple-output(MIMO) visible light communications(VLC). In the BICGSM-ID scheme, the information bits conveyed by the signal-domain(SiD) symbols and the spatial-domain(SpD) light emitting diode(LED)-index patterns are coded by a protograph low-density parity-check(P-LDPC) code. Specifically, we propose a signal-domain symbol expanding and re-allocating(SSER) method for constructing a type of novel generalized spatial modulation(GSM) constellations, referred to as SSERGSM constellations, so as to boost the performance of the BICGSM-ID MIMO-VLC systems.Moreover, by applying a modified PEXIT(MPEXIT) algorithm, we further design a family of rate-compatible P-LDPC codes, referred to as enhanced accumulate-repeat-accumulate(EARA) codes,which possess both excellent decoding thresholds and linear-minimum-distance-growth property. Both analysis and simulation results illustrate that the proposed SSERGSM constellations and P-LDPC codes can remarkably improve the convergence and decoding performance of MIMO-VLC systems. Therefore, the proposed P-LDPC-coded SSERGSM-mapped BICGSMID configuration is envisioned as a promising transmission solution to satisfy the high-throughput requirement of MIMO-VLC applications.

Diffractive characteristics of the liquid crystal spatial light modulator

The liquid crystal spatial light modulator （LC SLM） is very suitable for wavefront correction and optical testing and can produce a wavefront with large phase change and high accuracy. The LC SLM is composed of thousands of pixels and the pixel size and shape have effects on the diffractive characteristics of the LC SLM. This paper investigates the pixel effect on the phase of the wavefront with the scalar diffractive theory. The results show that the maximum optical path difference modulation is 41μm to produce the paraboloid wavefront with the peak to valley accuracy better than λ/10. Effects of the mismatch between the pixel and the period, and black matrix on the diffraction efficiency of the LC SLM are also analysed with the Fresnel phase lens model. The ability of the LC SLM is discussed for optical testing and wavefront correction based on the calculated results. It shows that the LC SLM can be used as a wavefront corrector and a compensator.

Fast generation of controllable equal-intensity four beams based on isosceles triangle multilevel phase grating realized by liquid crystal spatial light modulator

Liquid crystal spatial light modulator （LCSLM） realizing equal-intensity multiple beams often has some features, i.e., phase valley between two adjacent pixels, flybaek region when phase decreases immediately from 2~r to 0, and inevitable backplane curvature, which are different from those of most conventional diffractive optical elements （DOEs）, such as static DOEs. For optimal intensity uniformity, equal-intensity multi-beam generation must be considered for these artifacts. We present a tunable-grating method in which the intensity uniformity can be improved by considering the LCSLM artifacts. For instance, tuning phase modulation depth of the grating, called isosceles triangle multilevel phase grating （ITMPG）, can be used not only to improve the intensity uniformity, but also to fast steer four beams with narrow beamwidths, determined by the same effective aperture of ITMPG. Improved intensity uniformity and high relative diffraction efficiency are demonstrated through experiments with phase-only LCSLM.

3D fluorescence emission difference microscopy based on spatial light modulator

We report three-dimensional fluorescence emission difference(3D-FED)microscopy using a spatial light modulator(SLM).Zero phase,0–2
vortex phase and binary 0-pi phase are loaded on the SLM to generate the corresponding solid,doughnut and z-axis hollow excitation spot,respectively.Our technique achieves super-resolved image by subtracting three di®erently acquired images with proper subtractive factors.Detailed theoretical analysis and simulation tests are proceeded to testify the performance of 3D-FED.Also,the improvement of lateral and axial resolution is demonstrated by imaging 100 nm°uorescent beads.The experiment yields lateral resolution of 140 nm and axial resolution of approximate 380 nm.

Low insertion loss silicon-based spatial light modulator with high reflective materials outside Fabry–Perot cavity

The extinction ratio and insertion loss of spatial light modulator are subject to the material problem, thus limiting its applications. One reflection-type silicon-based spatial light modulator with high reflective materials outside the Fabry-Perot cavity is demonstrated in this paper. The reflectivity values of the outside-cavity materials with different film layer numbers are simulated. The reflectivity values of 6-pair Ta2O5/SiO2 films at 1550 nm are experimentally verified to be as high as 99.9%. The surfaces of 6-pair Ta2O5/SiO2 films are smooth: their root-mean-square roughness values are as small as 0.53 nm. The insertion loss of the device at 1550 nm is only 1.2 dB. The high extinction ratio of the device at 1550 nm and 11 V is achieved to be 29.7 dB. The spatial light modulator has a high extinction ratio and low insertion loss for applications.

Spatial Light Modulator with BSO Crystal and Its Application in Holography

The combined use of the photoelectric and electro-optic properties of BSO crystal (Bi 12 SiO 20 ) leads to realize spatial light modulation.Under some condition,BSO crystal can become birefringent depending on a local illuminance.The relationship between the distributions of an illuminance and a birefringence will be discussed.This spatial light modulator can work in real-time. The experiment shows,in order to increase the sensitivity of BSO crystal,an electric field of 6 kV/cm at an atmosphere pressure of 15×10 5 Pa should be applied to BSO crystal.With BSO we have measured 3-dimensional deformation by means of real-time holography.

Liquid Crystal Television Spatial Light Modulator

The liquid crystal television spatial light modulator (LCTVSLM) characterized is usable in optical processing applications,e.g.,optical pattern recognition,associative memory, optical computing,correlation detection and optical data processing systems.The array performance and real-time optical correlation applications are reviewed.

Experimental implementation of phase triplicator gratings in a spatial light modulator

In this work,we compare different methods for implementing a triplicator,a phase grating that generates three equiintense diffraction orders.The design with optimal efficiency features a continuous phase profile,which cannot be easily reproduced,and is typically affected by quantization.We compare its performance with binary and sinusoidal phase profiles.We also analyze the effect of quantizing the phase levels.Finally,a random approach is adopted to eliminate the additional harmonic orders.In all cases,a liquid-crystal-on-silicon spatial light modulator is employed to experimentally verify and compare the different approaches.

Spatial light modulation for femtosecond laser manufacturing:Current developments and challenges

Since the invention of lasers,spatial-light-modulated laser processing has become a powerful tool for various applications.It enables multidimensional and dynamic modulation of the laser beam,which significantly improves the processing efficiency,accuracy,and flexibility,and presents wider prospects over traditional mechanical technologies for machining three-dimensional,hard,brittle,or transparent materials.In this review,we introduce:(1)The role of spatial light modulation technology in the development of femtosecond laser manufacturing;(2)the structured light generated by spatial light modulation and its generation methods;and(3)representative applications of spatial-light-modulated femtosecond laser manufacturing,including aberration correction,parallel processing,focal field engineering,and polarization control.Finally,we summarize the present challenges in the field and possible future research.

基于SLM的几何稳相法光束整形影响因素分析

基于几何稳相法求解调制相位,使用傅里叶透镜进行傅里叶变换,在后焦面处聚焦,得到对应的平顶光束,从而将圆形高斯光束整形为方形平顶光束,其中光路参数对整形质量将产生较大影响。实验中发现,方形平顶光束受零级光影响均匀性较差,因此详细分析了零级光产生的原因,提出了有效的解决方法,并对实验结果中出现的零级光通过叠加闪耀光栅直接移除。实验结果表明:移除零级光后方形平顶光束的能量利用率为72.3%,光束均匀性高达97.2%,优于传统整形方法。最后进一步分析了全息图与入射光束偏移量、离焦以及入射光束束腰半径对几何稳相法整形质量的影响,为几何法光束整形的应用提供了便利。

一种基于SAM-MSFF网络的低照度目标检测方法

由于低照度图像具有对比度低、细节丢失严重、噪声大等缺点,现有的目标检测算法对低照度图像的检测效果不理想.为此,本文提出一种结合空间感知注意力机制和多尺度特征融合(Spatial-aware Attention Mechanism and Multi-Scale Feature Fusion,SAM-MSFF)的低照度目标检测方法 .该方法首先通过多尺度交互内存金字塔融合多尺度特征,增强低照度图像特征中的有效信息,并设置内存向量存储样本的特征,捕获样本之间的潜在关联性;然后,引入空间感知注意力机制获取特征在空间域的长距离上下文信息和局部信息,从而增强低照度图像中的目标特征,抑制背景信息和噪声的干扰;最后,利用多感受野增强模块扩张特征的感受野,对具有不同感受野的特征进行分组重加权计算,使检测网络根据输入的多尺度信息自适应地调整感受野的大小.在ExDark数据集上进行实验,本文方法的平均精度(mean Average Precision,mAP)达到77.04%,比现有的主流目标检测方法提高2.6%~14.34%.

基于空间光调制器的艾里光束能量调制方法

艾里光束由于具有无衍射、自加速和自愈合等特性,具有重要的应用前景。本文基于空间光调制器可编程特性,提出了一种可调谐的艾里光束能量调制新方法。从理论上深入分析通过在相位图中引入一个可控的调制相位而实现了艾里光束能量调控的方法,并且量化了调制参数与能量调制范围的关系。仿真和实验结果表明通过改变调制相位可以灵活地调节光束能量分布,本文的研究有助于进一步推动艾里光束的应用。

计算全息综合性光电教学实验设计

基于傅里叶光学原理实现对目标光场进行精确重建,设计了从显示目标绘制,相应计算全息图生成到光学重建的综合性教学实验。具体的实验流程包含基于Visio的显示目标设计,基于MATLAB的相位型计算全息图生成算法编写和基于相位型液晶空间光调制器的目标重建光路搭建。实验设计结合了光学、数字电路和计算机软件技术,具有流程清晰、易于教学、学生参与度高和获得感强的优势,可有效增强学生对计算全息技术与光电信息技术的理论理解与实操能力。

基于反射式空间光调制器的非球面面形干涉检测方法设计

目前光学系统中非球面数量多,针对各个非球面单独做补偿器检测面形加工成本高、通用性不好、加工难度大,为解决对多个参数不同的非球面需要不同的补偿器的问题,提出了一种基于空间光调制器(spatial light modulator,SLM)作为补偿器的干涉面形检测方法,该干涉检测法采用反射式空间光调制器作为零位补偿器,结合偏振分光镜和波片建立检测光路,可以实现对非球面面形误差的测量。通过在ZEMAX上模拟一个两表面皆为凹非球面的场镜的检测光路,对该干涉检测方法进行了验证,并在MATLAB中仿真分析了SLM的波前调制误差。仿真结果表明,该方法可以实现对不同非球面面形的检测,设计光路中的波前调制精度可达0.0083λ。

液晶调控下的亚波长金光栅反射相位

空间光调制器(Spatial Light Modulator,SLM)是实现光场调控的关键器件。本文研究了一种将亚波长金光栅嵌入硅基液晶(Liquid Crystal on Silicon,LCoS)构成的SLM(G-LCoS)器件模型的反射相位特性,该器件模型以ITO透明导电层和液晶构成G-LCoS中亚波长金光栅的非对称边界。首先运用散射矩阵原理给出了亚波长金光栅反射相位的计算表达式,其次给出了下表面液晶的有效折射率计算公式。在此基础上,利用TechWiz 3D软件模拟加电情况下金光栅下表面液晶指向矢的变化,给出金光栅下表面液晶有效折射率的变化值。将得到的有效折射率数据导入到FDTD Solutions软件,对该器件结构开展了相关的仿真实验和结果分析。综合考虑了上表面的ITO色散情况、金光栅高度变化以及不同电压下液晶有效折射率值,实现了可见光范围内多波长的近2π相位调制。本文研究的器件也为AR/VR显示系统以及全息视频显示的优化提供了一种新思路。

基于HOE的全息显示双目视差构建方法

全息光学元件(Holographic Optical Element,HOE)是全息三维显示的重要器件之一。为了解决HOE用于双目全息显示时视差不匹配的问题,本文提出并实现了一种基于HOE的全息显示双目视差构建方法,同时对元件成像时的像差进行了分析校正。通过对HOE的制作原理和成像规律分析,结合光线跟踪技术渲染的虚拟模型和现实场景模型,设计了基于HOE的全息双目显示系统,提出了双目视差构建方法,即在获取人眼坐标位置时为观察者实时提供包含双目视差关系的视点图像。通过进一步分析全息显示系统内部的图像畸变产生原因及过程,提出了去畸变的优化处理算法。实验结果表明,提出的方法不仅能够实现HOE实时显示全息三维图像,而且解决了HOE在全息双目显示中视差不匹配以及成像畸变的问题。

基于光强传输方程与SLM的快速相位恢复（英文）

基于光强传输方程(TIE)的相位恢复技术,可以通过测量一系列垂直于光轴分布的散焦强度图,直接求解得到光场的相位信息。传统的基于TIE的强度图像采集系统在获得散焦图像时需要机械移动。通过在空间光调制器(SLM)上加载透镜相位图,使其实现可编程透镜的功能,任意改变此透镜的焦距值,可以实现不同的散焦距离,从而避免采集图像过程中CCD的移动。根据不同的算法理论,设计了两种光强图像采集系统。由于日常生活中使用相机拍照时,透镜的相位调制作用不可忽略,使用SLM代替含透镜的光传播模型中透镜的作用,设计了第一种实验装置。此外,通过在4f系统的频率域位置放置SLM,设计了第二种实验装置。真实实验的结果验证了这两种方法的有效性和正确性。