Investigation on Third-Order Optical Nonlinearities of Two Organometallic Dmit2- Complexes Using Z-Scan Technique

The third-order nonlinear optical properties of two dmit organometallic complexes, [(CH3)4N] [Au(C3S5)2] (MeAu) and [(CH3)4N][Ni(C3S5)2] (Me Ni) in acetone solutions, were characterized us- ing a short pulse Z-scan technique at 1064 nm wavelength. Self-defocusing effects were found in both samples and stronger saturable absorp-tion was observed in MeNi solution comparing with that of MeAu. The origins were analyzed for the differences between the results. Two figures of merit W and T were also calculated to evalu-ate the suitability of two materials for all-optical integrated devices. The results of W=22.84 and T≈0 of MeAu make it an excellent candidate for the all-optical applications.

Z-scan analysis of high-order nonlinear refraction effect induced by using elliptic Gaussian beam

The irradiance of an elliptic Gaussian beam that is high enough to excite high-order nonlinear refraction effect is used to calculate the normalized on-axis transmittance function in the z-scan technique by introducing complex beam parameters which make the calculation simpler. The transmittance formula is applied to the first-, first two-, and first three-order nonlinearities. Numerical evaluation shows that the symmetry no longer holds when using an elliptic Gaussian beam instead of a circular Gaussian beam. A distortion is observed in the central part of the curve, which decreases as ellipticity increases. Moreover, the variation of the normalized peak-valley difference decreases as ellipticity decreases.

一种跳转向量的隐性加权分数傅里叶变换通信方法

加权分数傅里叶变换(Weighted fractional Fourier transform,WFRFT)技术可以极大地改变信号的特性,使信号的统计特性多样化,从而有效地保障通信信息安全。为解决单参数WFRFT通信抗扫描能力不足的问题,以单参数WFRFT为切入点,深入研究单参数分数域的形成机理,分析其潜在的微观特征和暗特征,从而提出了一种基于跳转向量的隐性WFRFT通信方法(Implicit WFRFT communication method of jump vector,IWVJ)。利用调制阶数与星座图的关系,建立了跳变矩阵和跳变向量,并以此制定了控制规则。此外,通过跳变向量控制获得动态调制阶数,从而达到安全通信的目的。仿真结果表明,IWVJ方法对授权接收机具有较高的反变换解调相似度和较低的误码率,相比于具有普适扫描能力的非授权接收机性能更优。同时对解调阶数误差、基础调制阶数和跳转频率等参数的设置给出了适用的建议,使IWVJ方法能够更好地应用于通信系统,为具有抗干扰、抗截获和抗欺骗能力的保密通信提供技术依据。

Z-scan分析CdS纳米晶掺杂玻璃的光学非线性

利用溶胶-凝胶方法合成了CdS纳米晶掺杂Na2O-B2O3-SiO2玻璃。通过透射电镜(TEM)以及附带的扫描模式透射(STEM),X射线能量散射谱(EDX)和高分辨透射电镜(HRTEM)分析CdS颗粒的形貌、微结构以及组成。结果显示,在钠硼硅玻璃先驱体中生成了CdS纳米晶,其晶相结构为六方相结构,颗粒尺寸在10～20 nm。此外,利用Z-scan技术在波长为770 nm研究该玻璃的三阶非线性光学性质。结果表明:该玻璃的三阶光学非线性折射率γ,三阶非线性吸收系数β以及三阶非线性磁化率χ(3)分别为-2.16×10-16 m2W-1,6.32×10-11 mW-1和7.32×10-10 esu,优于此前一些关于CdS纳米晶掺杂在不同基体中所得到的三阶非线性光学性质的结果。

基于Krylov子空间降阶的温控算法研究

针对当前常用的散热前馈获取方法存在耗时长、能耗大、步骤繁杂等缺点,文中提出引入模型降阶方法获取散热前馈。通过3组实验获取控制对象响应特性;对在ANSYS Workbench仿真平台建立的控制对象模型进行校正,使仿真模型特性与实际控制对象特性尽可能相同;使用Krylov子空间法对仿真模型进行降阶,降阶后的模型可以通过Matlab计算得出散热前馈;以差示扫描量热仪炉体为控制对象验证散热前馈-PID控制策略的效果。实验结果表明,在环境温度至300℃范围内,扫描模式温控误差小于±5%,恒温模式温控误差小于±0.2℃。

氯丁橡胶硫化反应动力学

以1,2-亚乙基硫脲为促进剂、氧化锌和氧化镁为硫化剂对氯丁橡胶进行硫化,采用差示扫描量热法研究了氯丁橡胶的非等温硫化反应动力学,通过Kissinger方程和Crane方程计算了硫化反应的动力学参数,并采用硫化仪法研究了等温硫化反应的动力学,计算了硫化反应热硫化阶段的表观活化能。结果表明,n级动力学模型可以有效描述氯丁橡胶的非等温硫化过程,硫化反应的表观活化能为92.78 kJ/mol,反应级数为0.93;氯丁橡胶的等温硫化过程可以分为焦烧阶段、热硫化阶段和平坦硫化阶段,其中热硫化阶段符合一级反应动力学特征,此时表观活化能为53.38 kJ/mol。

Adsorption behavior of triphenylene on Ru(0001) investigated by scanning tunneling microscopy

As a representative of small aromatic molecules, triphenylene(TP) has markedly high carrier mobility and is an ideal precursor for building graphene nanostructures. We mainly investigated the adsorption behavior of TP molecules on Ru(0001) by using scanning tunneling microscopy(STM). In submonolayer regime, TP molecules are randomly dispersed on Ru(0001) and the TP overlayer can be thoroughly dehydrogenated and converted into graphene islands at 700 K. Due to weak interaction between TP molecules and graphene, the grooves formed among graphene islands have confinement effect on TP molecules. TP adopts a flat-lying adsorption mode and has two adsorption configurations with the 3-fold molecular axis aligned almost parallel or antiparallel to the ■ direction of the substrate. At TP coverages of 0.6 monolayer(ML)and 0.8 ML, the orientational distributions of the two adsorption configurations are equal. At about 1.0 ML, we find the coexistence of locally ordered and disordered phases. The ordered phase includes two sets of different superstructures with the symmetries of ■R23.41° and p(4 × 4), respectively. The adsorption behavior of TP on Ru(0001) can be attributed to the delicate balance between molecule–substrate and molecule–molecule interactions.

Application of Single Scan Differential Scanning Calorimetry Technique for Determination of Kinetic Parameters of Crystallisation in Se-Sb-Ag

A single scan has been performed in Differential Scanning Calorimetry (DSC) at a heating rate of 15oC/min under non-isothermal conditions to investigate the crystallization kinetics of glassy Se90Sb10-xAgx alloys (where x = 2, 4, 6, 8). For this purpose, Handerson’s theory based on non-isothermal method for thermal analysis of single-scan DSC data has been used. The activation energy of crystallization and order parameter has been determined and composition dependence of these parameters has been discussed.

Nonlinear optical properties of [（CH3）4N]Au（dmit）2 using Z-scan technique

The third-order optical nonlinearities of [（CH3）4N]Au（dmit）2 （dmit = 4,5-dithiolate-1,3-dithiole-2-thione） at 532 nm and 1064 nm are investigated using the Z-scan technique with pulses of picoseconds duration. The Z-scan spectra reveal a strong nonlinear absorption （reverse saturable absorption） and a negative nonlinear refraction at 532 nm. No nonlinear absorption is observed at 1064 nm. The molecular second-order hyperpolarizability γ for the [（CH3）4N]Au（dmit）2 molecule at 532nm is estimated to be as high as （2.1 ±0.1） × 10^-31 esu, which is nearly three times larger than that at 1064 nm. The mechanism responsible for the difference between the results is analysed. Nonlinear transmission measurements suggest that this material has potential applications in optical limiting.

Micro-Scanning Error Correction Technique for an Optical Micro-Scanning Thermal Microscope Imaging System

An error correction technique for the micro-scanning instrument of the optical micro-scanning thermal microscope imaging system is proposed. The technique is based on micro-scanning technology combined with the proposed second-order oversampling reconstruction algorithm and local gradient image reconstruction algorithm. In this paper, we describe the local gradient image reconstruction model, the error correction technique, down-sampling model and the error correction principle. In this paper, we use a Lena original image and four low-resolution images obtained from the standard half-pixel displacement to simulate and verify the effectiveness of the proposed technique. In order to verify the effectiveness of the proposed technique, two groups of low-resolution thermal microscope images are collected by the actual thermal microscope imaging system for experimental study. Simulations and experiments show that the proposed technique can reduce the optical micro-scanning errors, improve the imaging effect of the system and improve the system's spatial resolution. It can be applied to other electro-optical imaging systems to improve their resolution.

Growth, Crystal Structure and Characterization of a New Single Crystal: Lithium Sodium Acid Phthalate (LiNaP), for Third Order Nonlinear Optical Applications

A new alkali metallo-organic single crystal of Lithium Sodium Acid Phthlate (LiNaP) complex has been synthesized from aqueous solution in the equimolar ratio 3:1:2. Transparent and bulk single crystals of dimension 9 × 4 ×2 mm3 have been grown from the conventional slow-cooling technique. The crystal structure of the compound has been solved from single crystal X-ray diffraction. The compound 2[C8H4O3]4-Li3+Na+ crystallizes in triclinic system with a space group of Pī having cell dimensions a = 7.5451(2) ? b = 9.8422(3) ? c = 25.2209(7) ? α = 80.299(2);β = 89.204(2);γ = 82.7770(10). FTIR measurement was carried out fo? LiNaP to study the vibrational structure of the compound. The various functional groups present in the molecule and the role of H-bonds in stabilizing the crystal structure of the compound have been explained. Optical absorption properties were studied for the grown crystal using UV-Vis-NIR spectrum. Thermal measurements were carried out for LiNaP to determine the thermal strength as well as to ascertain the hydrated nature of the crystal. Third order nonliner optical studies have also studied by Z-scan techniques. Nonlinear absorption and nonlinear refractive index were found out and the third order bulk susceptibility of compound was also estimated. The results of all studies have been discussed in detail.

Synthesis, Characterization and Third Order Non Linear Optical Properties of Metallo Organic Chromophores

The organic imine and their metal complexes were synthesized and characterized by IR, UV and NMR. The third order non linear optical properties of the compounds were investigated. The measurements of second hyperpolarizabilites were performed using single beam Z-scan technique with 8 ns laser pulses. Ligand and its Copper, Zinc and Nickel complexes show good third order non linearity whereas Manganese complex did not show any activity.

含圆孔平板结构的连续扫描激光测振方法

提出一种基于扫描路径规划和工作变形归一化的激光连续扫描多普勒测振的方法,用以测量含任意圆孔平板结构的振型。通过构造边界函数等进行规划,获取对被测区域连续域范围内的遍历式路径方案;针对边界条件变化导致的同一阶内振幅比例不一致的问题,借助重合的规则区域振型结果进行归一化处理;将其结果与逐点扫描激光测振结果进行对比,MAC值均高于0.94,验证了该方法的有效性,对进一步提高其工程应用范围,具有重要作用。

基于共面波导的全角度频率波束扫描天线

为满足平面集成系统、雷达等领域对宽角度频率波束扫描天线的需求,提出了一种低剖面、小型化、全角度频扫天线的设计方案.天线通过在共面波导上刻蚀周期性孔阵列,形成人工表面等离子体激元结构,利用其高次模辐射的特性产生频率扫描波束.通过在共面波导一侧金属地上刻蚀周期性的梳状结构,并由共面波导为其馈电,产生低频反向端射波.仿真结果表明,天线在9.1~53 GHz频带内平均增益为12.75 dBi,频率波束扫描范围为180°.由于矢量网络分析仪频率量程限制,实测结果在9.1~40 GHz与仿真结果具有较好的一致性.该天线具有加工易、剖面低、成本低、全角度扫描的特点,为平面集成系统、雷达等领域宽角度频扫天线提供了一种新的设计思路.

三种金属酞菁配合物的非线性光学性质研究

用YAG皮秒激光器 ,利用“Z scan”方法测量了三种金属钛菁配合物苯硫基钛菁锌 (C56H3 2 N8S4Zn) ,苯硫基铝钛菁 (C56H3 2 AlClN8S4) ,烷氧基铝钛菁 (C56H3 2 AlClN8O4)二甲基甲酰胺 (DMF)溶液的非线性折射率 ,并计算了三阶非线性光学极化率Χ(3 ) 。比较发现 ,不同中心离子 ,不同取代基的金属钛菁配合物的三阶非线性系数不同。文章对引起三阶非线性光学效应的机制做了初步的探讨和分析 。

C_(60)-吡咯烷衍生物的合成及非线性光学性质的研究

通过富勒烯C60与肌氨酸和有机醛化合物的1,3-偶极环加成反应,获得了九种含不同有机功能基团的C60吡咯烷衍生物1～9,用1HNMR,13CNMR,FTIR,UV-vis和FAB-MS进行了结构表征;利用皮秒激光光源,采用z扫描技术测定了分子的三阶非线性超极化率γ(3),结果显示:化合物3(γ(3)=4.14×10-33esu)具有最大的三阶非线性光学系数,说明增加噻吩共轭链的长度,使三阶非线性活性增加;对具有相同共轭链的C60-噻吩吡咯烷衍生物(2,5,1和4),吸电子取代基减小了三阶光学非线性活性,给电子基增大了三阶光学非线性活性;同时发现喹啉环2-位键联(7)比4-位(8)有更好的三阶光学非线性活性.

数字半色调技术中的误差扩散算法的研究

误差扩散是一种非常优秀的调频半色调技术,但这种方法在图像高光和暗调以及阶调平滑区域会产生"蠕虫",同时噪声较多,导致半色调图像的边缘不清晰。在Floyd和Steinberg的误差扩散算法的基础上,设计一种新的基于平均阈值和改变扫描路径的误差扩散算法——阈值采用平均值法,通过优化平均阈值方法中的γ值得到最优的半色调图像,同时扫描路径采用"蛇型"路径。实验结果表明该算法可以减少"蠕虫",增强图像的边缘,提高半色调图像的主观视觉效果。

系列羟基苯基卟啉化合物三阶非线性光学特性

用Z扫描方法测量了系列羟基苯基卟啉化合物的非线性折射率n2和反饱和吸收系数β,由此算出了三阶非线性极化率(χ3),并分析了分子结构对其三阶非线性光学性质的影响.实验结果表明,它们具有大的反饱和系数和三阶非线性折射率,并且取代基数目和取代位置对实验结果有明显的影响.

具有鲁棒性与数据嵌入能力的JPEG压缩图像加密算法

针对JPEG图像加密算法引起的比特流大小增加与鲁棒性较差的问题,提出了一种具有鲁棒性与数据嵌入能力的JPEG图像格式兼容的加密算法。利用AC系数抓取纹理信息并生成部分区域,基于该区域将DC系数编码,使用八个不同的顺序扫描AC系数,选择其中比特流大小最小的顺序,并提取每块的AC系数,操作AC系数来增加置换的范围。算法的主要过程均具有可逆性,可成功提取嵌入信息并且完美地重建原图像。基于真实JPEG照片的实验结果表明,本算法对素描攻击具有鲁棒性,可抑制比特流大小增加且具有数据嵌入的能力。

二氧化钛薄膜的三阶非线性光学特性

采用脉冲激光沉积技术在熔石英基片上制备了c轴取向的锐钛矿相TiO2薄膜.通过X射线衍射和原子力显微镜对薄膜的结构、结晶性和表面特性进行了表征.通过透射光谱计算得到TiO2薄膜折射率约为2.1,光学带隙约为3.18eV.结合飞秒激光和Z扫描方法测量了薄膜的超快非线性光学特性,结果表明:锐钛矿TiO2薄膜具有负的非线性吸收系数和负的非线性折射率,其大小分别为-6.2×10-11m/W和-6.32×10-17m2/W,对应的三阶非线性极化率的实部和虚部分别为-7.1×10-11esu和-4.42×10-12esu.并计算薄膜的优值比T=βλ/n2≈0.8,表明锐钛矿相的TiO2在非线性光学器件方面具有潜在的应用前景.