Multifunctional Dielectric Metasurfaces Consisting of Color Holograms Encoded into Color Printed Images

A hologram records the wavefront of light from an object, but it is usually not an image itself, and looks unintelligible under diffuse ambient light. Here a new paradigm to encode a color hologram onto a color printed image is experimentally demonstrated. The printed image can be directly viewed under white light illumination, while a low‐crosstalk color holographic image can be seen when the device is illuminated with red (R), green (G), and blue (B) laser beams. The device is a dielectric metasurface that consists of titanium dioxide (TiO₂) cones on a glass substrate. The dimensions of the TiO₂ cones are chosen to allow them to support visible‐wavelength resonances, thereby producing the desired reflection spectra and thus the color printed image. The detour phase method is furthermore used to encode the hologram into the metasurface. The approach is conceptually different from previously demonstrated color printed images or holograms and presents opportunities for optical document security and data storage applications.     

超细颗粒卤化银反射全息图的漂白处理

通过实验优化重铬酸钾、碘化钾和浓硫酸漂白液的配比 ,使其适合于处理用超细颗粒卤化银乳剂SDUF- 1记录的反射全息图。用 SDUF- 1乳剂记录的反射全息光栅经 AAC显影液和优化的漂白液处理后 ,其衍射效率和信噪比分别达 5 0 %和 5 0 ,且乳剂收缩引起的布喇格角偏离小于 3°     

乳胶厚度对卤化银反射全息图衍射特性的影响

实验研究了自制的超细颗粒卤化银乳剂SDUF－1分别在AAC显影、改进的R－10漂白处理及改进的GP－8溶解物理显影处理条件下，其乳胶厚度对反射全息图衍射特性的影响。实验结果表明，在这两种不同处理条件下衍射效率与胶厚的关系有相当大的差别，合适的乳胶厚度分别为12μm和6μm左右。     

基于硅色敏器件的单色光波长测量系统的设计

介绍了基于硅双结型色敏器件的单色光波长测量系统的硬件、软件设计.该系统以微处理器为控制单元、硅双结型色敏器件为探测器,实现了对单色光波长方便、快捷、准确的测量.     

设计激光波长测量实验,有效激发学生学习兴趣

本文探讨了一种测量激光波长的实验设计方法,利用CD光盘片作为反射光栅来测定激光波长。这种方法操作简单实用,而且利用精度为1mm的普通刻度尺可以对激光波长的测量达到10nm量级,具有相对较高的测量精度。该实验设计方法新颖,取材简单,可以有效激发学生的学习兴趣。     

偶氮分子掺杂对蓝相液晶选择性反射波长的影响

偶氮基团(—N=N—)在适当波长光的照射下,会发生可逆的顺反异构反应,这一反应中偶氮分子构型上的变化会影响到蓝相液晶中脆弱的晶格结构,并造成晶格参数的变化,进而影响到选择性反射波长的变化,甚至有时会造成蓝相相态的消失。文章合成并将几种偶氮化合物掺入手性向列相液晶中,再变温至BPI,对比了这几种偶氮化合物对蓝相液晶选择性反射波长的影响,从而得出更有实际使用价值的偶氮分子,在此基础上还从分子结构角度分析了产生差异的原因,为进一步的改进工作提供了方向。     

基于频域滤波的计算机制真彩色彩虹全息图模拟再现

提出了一种计算机制真彩色彩虹全息图模拟再现方法。根据衍射及几何光学的原理,分析了彩色彩虹全息图再现时空间观察窗口与频谱面窗口的对应关系。在计算机中构造照明光(红、绿、蓝三色)的分布,并分别与全息图相乘,采用傅里叶变换对上述结果进行频谱分析,并通过频域滤波获取与特定观察窗口位置对应的频谱信息;然后进行逆傅里叶变换得到全息面上的再现像。将逆傅里叶变换结果衍射一段距离,可得到对应于特定观察窗口、位于不同位置处的再现像。通过计算机模拟得到了与光学再现一致的结果,表明了该方法的可行性。为快速、经济地验证计算机制真彩色彩虹全息图的正确性提供了一种途径。     

增益调制型波长转换中信号光波长的选择

增益调制型波长转换中 ,为得到转换后信号最大的消光比 (ER) ,信号光波长应该比半导体光放大器 (SOA)的小信号增益峰值波长长。采用分段模型 ,考虑了SOA中增益谱的不对称性以及增益峰值波长随载流子密度的漂移 ,深入研究了信号光功率 ,ER ,参考光功率 ,波长以及SOA注入电流对选择信号光波长λpk ,s 以及消光比改善量的影响。模拟计算表明 ,信号光功率每增加 3dB ,λpk ,s 就需向长波长移动约 7nm。信号光ER增加、参考光功率增加以及SOA注入电流的增加 ,λpk ,s 需向短波长移动。消光比改善量随信号光功率和电流的增加而显著增加 ,随信号ER的增加而降低 ,但是参考光功率和波长变化时影响不大     

大气痕量气体浓度反演中的谱对准偏差研究

在大气痕量气体浓度反演中,对测量光谱和计算得到的参考光谱做最小二乘拟合是常用的方法之一。但在获取光谱过程中,由于仪器光栅位置的不准确、温度等环境因素的变化、以及二者光谱分辨率的不同,均会导致在现场工作的监测设备所测得的光谱与计算的参考光谱之间存在谱对准偏差,即存在光谱在波长上的漂移、拉伸或压缩。这种不对准会给浓度反演带来很大的影响,介绍了在反演过程中校正谱对准偏差的算法,计算了不同光谱分辨率下由谱漂移造成的浓度反演误差。     

颜色迁移算法在古建筑虚拟色彩修复中的应用

分析了彩色图像间色彩传递算法和灰度图像彩色化算法的优缺点和应用特点,描述了两种典型颜色迁移算法在古建筑虚拟色彩修复中的应用,实验结果表明颜色迁移算法可成为古建筑虚拟色彩修复的有效工具.     

Wavelength Assignment to Minimize the Number of SONET ADMs in WDM Rings*†

Optical wavelength division multiplexing (WDM) rings are being deployed to support SONET/SDH self-healing rings. In such systems, multiple SONET/SDH self-healing rings are realized over a single physical optical ring through wavelength division multiplexing. The cost of such a system is dominated by the SONET add/drop multiplexers (ADMs). To minimize the system cost, algorithms must be developed to assign wavelengths to lightpaths in the system so that the number of ADMs required is minimized. This problem of optimal wavelength assignment to minimize the number of SONET ADMs is known to be NP-hard. Existing heuristic algorithms for this problem include the assign first heuristic, the iterative matching heuristic and the iterative merging heuristic. In this paper, we develop an integer linear programming (ILP) formulation for this problem, propose a new wavelength assignment heuristic, and evaluate the existing and the newly proposed heuristic using the ILP formulation. We conclude that the performance of the newly proposed heuristic is very close to optimal.     

Wavelength Conversion in WDM Optical Networks: Strategies and Algorithms for Limiting the Number of Converters in the Optical Cross-Connects

This paper considers the problem of wavelength conversion in optical networks using wavelength division multiplexing technique. In the previous literature, two main wavelength routing and assignment strategies have been introduced: wavelength path (WP) and virtual wavelength path (VWP), depending on whether the signal stays on the same wavelength or is converted to another during its travel throughout the network. While the former method does not require any wavelength conversion, the latter needs wavelength conversion in each optical node and, in particular, a wavelength converter per each signal handled by the node itself. From the previous literature emerged that the VWP leads to optical cross-connect (OXC) with lower dimensions compared to the ones required by the WP scheme, and that the difference between the WP and VWP schemes increases as the number of wavelengths carried by each fiber increases. In this paper a new strategy is introduced, named partial virtual wavelength path (PVWP), with the related wavelength routing and assignment algorithm, which makes limited use of wavelength conversion compared to the VWP scheme, and allows the same advantages of VWP to be attained with lower OXC dimensions. The paper reports a comparative analysis among the different strategies, considering both the cases of a network without failures and a network with the possibility of failure restoration. The main result is that the proposed PVWP strategy allows the same advantages of the VWP scheme with a strongly reduced number of wavelength converters (around 5% of the number required by VWP scheme). This figure does not vary appreciably if failure restoration is considered. The new strategy can be adopted by using an opportune OXC architecture, as illustrated in the paper, which allow a limited number of converters to be shared among all the channels as a common pool.     

脊槽波导主模截止波长研究

为了满足微波传输系统性能的某些需求,各种结构形状的新型波导应运而生。采用有限差分法,利用MATLAB计算了脊槽波导中脊和槽的几何尺寸在中间位置连续变化时的主模截止波长,并对计算结果进行了对比分析,得出了主模截止波长随着脊的高度、宽度、槽的宽度等变化而变化的一些相关结论,为设计脊波导器件提供了参数。     

Dimensioning of the Wavelength Converters in a WDM Optical Packet Switch

This paper analyzes the performances of a WDM optical packet switch making use of fiber delay lines to resolve output packet contentions; the optical packet switch is equipped with tunable wavelength converters which can shift optical packets to any wavelength of the output link which they are directed to. As not all packets need conversion, we propose a dimensioning technique allowing to reduce the number of converters and to improve the signal quality by reducing unnecessary conversions. The obtained results show that a remarkable reduction of the number of converters is obtained with respect to that needed by other switches described in literature. Such a saving is achieved by maintaining the packet loss probability below a prefixed threshold.     

采用动态波长分插复用器的光突发交换环网中的控制协议研究

提出了一种光突发交换(OBS)环网控制协议——延迟光突发固定周期(DBFP)协议。它采用动态波长分插复用器(WADM)。即采用波长可调发送可调接收(TTTR)机制．通过提前的光突发控制分组(BCP)．为光突发数据分组(BDP)预留资源，并利用固定长度的光纤延迟线(FDL)将突发数据包延迟同定的时间，以便等待所有已经预留的突发数据包发送完毕，从而完全避免突发数据包冲突问题。仿真结果表明。延迟光突发固定周期协议能完全避免突发数据包冲突。同时有效地实现了波长统计复用、按需分配和空间重用，波长重用效率高达160％。从而提高链路利用率．特别适合于突发性的业务；并且延迟光突发固定周期协议所引入的时延为1ms左右．对业务的影响不大。     

基于颜色识别的食堂结算系统的设计

本文完成了基于颜色识别的食堂结算系统的设计,在食堂购餐时能通过识别餐盘的颜色实现智能化自助结算.该系统由微控制器模块、红外检测模块、颜色识别模块、显示模块、系统电源模块构成.当餐盘放入结算区域时,红外检测传感器向微处理器发出启动信号,系统通过识别餐盘的颜色来统计不同菜品的种类和数量,然后根据对应的单价计算用餐者应支付的总价,并通过液晶屏显示出来,从而完成自助结算.该系统通过了自助结算测试,对实现食堂现代化、科学化管理具有一定的参考价值.     

脊的变化对对称双脊波导主模截止波长的影响

关于双脊波导的研究报道很多,但对双脊波导的研究都集中于脊中心对称情况,对于脊偏离中心位置的情况则没有涉及.采用对亥姆霍兹方程有限元方法分析了脊的变化对双脊波导主模截止波长的影响,数值结果与文献结果对比,计算方法精确有效,从而可以通过改变脊尺寸和位置调节截止波长.     

利用光栅实时测量被动入射激光波长

从理论上分析了利用光栅实时测量被动入射激光波长的能量分布及信噪比，给出了计算公式及误差分析。最后给出了实验结果数据表格并进行了讨论。     

基于半导体光放大器中交叉偏振调制效应的波长转换器

了改善基于半导体光放大器(SOA)中交叉偏振调制效应(CPM)的波长转换器的转换信号码型效应，对交叉偏振调制一半导体光放大器波长转换器的工作原理进行了分析；通过讨论交叉偏振调制一半导体光放大器波长转换脉冲的上升沿和下降沿的频率啁啾，结合滤波器的透过谱特性，提出了一种利用滤波器的波长正斜率边和波长负斜率边分别对正相转换信号和反相转换信号进行码型优化的方案，并进行了实验验证。在信号码率为10Gb／s的交叉偏振调制一半导体光放大器波长转换实验中，采用光带宽为0．3nm的JDS滤波器优化转换信号的波形，基本消除了转换信号中长“1”码和长“0”码的码型效应，并将正相转换信号和反相转换信号的功率代价分别改善了3dB以上。     

反射及发射率对光纤测温仪精度的影响及抑制

在简要介绍一种利用钽酸锂热释电探测器实现的实用化双波长光纤测温仪的基础上,着重讨论了待测面对背景目标辐射的反射（反射辐射）及待测面的光谱发射率对仪器测温精度的影响,并提出了相应的抑制措施.结果表明,在采取相应的抗干扰措施后,在仪器要求的测温范围400～1360℃内,其测温精度符合设计要求.