在非线性光学薄膜内以长程表面电磁激元波为泵波实现简并四波混频的理论研究

本文提出一种以长程表面电磁激元波作为泵波,在非线性介质膜中实现简并四波混频的新方案。我们借助于将介质膜内曲折光线在一个方向上展开,获得系统的一维耦合方程,并得到了方程的解及共轭波转换效率的表达式。估计应用这种方案,采用波长合适、功率为1W量级的连续激光可有效地研究一些有机薄膜的三次非线性光学性质。     

非均匀交换各向异性铁磁介质的非线性表面自旋波

利用Landau-Lifshitz 方程，研究了具有非均匀交换各向异性的半无限大铁磁体的非线性表 面自旋波理论。导出了部分钉扎纯交换铁磁介质的磁化强度所满足的边界条件和非线性表面 自旋波的色散关系，并获得了自旋波振幅沿z方向驻波的一维非线性Schrdinger方程和包 络振幅沿平面传播的二维非线性Schrdinger方程，结果表明铁磁体磁化强度的包络振幅随时空变化的性质是由二维非线性Schrdinger方程决定的。因此预言铁磁介质的表面非线性激发应是二维孤波的形式。对于弱非线性表面自旋波，对非线性Schrdinger方程存在孤子形式解的可能性作了讨论. 关键词： 表面自旋波 Landau-Lifshitz方程 非线性Schrdinger方程 孤子     

具5次强非线性项的波方程新的孤波解

提出一种新的函数变换法，并与直接积分法相结合简便地求出了Lienard方程、广义PC方程以及力学中重要的一类非线性波方程等几类具5次强非线性项的波方程的四类显示精确孤波解.本方法同样适用于求解其他具有更高次非线性项的非线性方程. 关键词： 函数变换法 孤波解 直接积分法 非线性波方程     

近简并四波混频相位共轭介质中的光强分布

从求解耦合波方程出发，详细研究了非线性光学介质中由近简并四波混频所产生的相位共轭过程。以上述波方程的解为基础，给出作为混频结果的反射传播相位共轭波沿介质轴向的光强分布，得到比以往文献中所报道的更为精确的结果，从而为选择工作物质的最佳尺寸提供了理论依据。     

大尺度浅水波方程中相互调制的非线性波

基于一般的浅水波方程, 根据大尺度正压大气的特点, 得到无量纲的控制大尺度大气的动力学非线性方程组. 利用多尺度法, 由无量纲的动力学方程组导出了扰动位势的非线性控制方程. 采用椭圆方程构造该扰动位势控制方程的解, 获得了扰动位势和速度的多周期波与冲击波(爆炸波) 并存的解析解. 扰动位势的解表明经向和纬向具有不同周期和波长的周期波, 且都受纬向孤波的调制; 速度的解表明大尺度大气流动存在气旋和反气旋周期性分布的现象. 关键词： 浅水波方程 大尺度正压大气 解析解 非线性波     

负折射介质中孤波间相互作用

以描述负折射介质中超短脉冲传输的归一化非线性薛定谔方程为模型,采用对称分步傅里叶算法研究了负折射介质中亮、暗孤波间的相互作用.数值模拟发现:当孤波的初始频移为零时,亮孤波间的相互作用与常规介质中类似;当孤波的初始频移不为零时,其传输速度和相互作用明显受三阶色散和自陡峭效应的影响,主要表现为相互排斥.而负折射介质中暗孤波间的相互作用与常规介质中的相互作用类似,无论暗孤波是否存在初始频移,暗孤波间的相互作用在三阶色散和自陡峭的影响下都表现为相互排斥.结果表明,通过调节三阶色散和自陡峭系数可以在一定程度上抑制负折射介质中亮、暗孤波间的相互作用.该研究结果为负折射介质在未来高速通信中的应用提供了理论依据.     

简并四波混频相位共轭介质中的光强分布

相位共轭现象在很多领域有着广阔的应用前景。本文对非线性介质中所发生的简并四波混频相位共轭过程进行了较详细的分析，以耦合波动方程的解为基础，研究了介质中正向探测波和反向相位共轭波的光强分布，得到比迄今文献报导的更为确切的结果。     

负折射介质中孤波间相互作用

以描述负折射介质中超短脉冲传输的归一化非线性薛定谔方程为模型,采用对称分步傅里叶算法研究了负折射介质中亮、暗孤波间的相互作用.数值模拟发现:当孤波的初始频移为零时,亮孤波间的相互作用与常规介质中类似;当孤波的初始频移不为零时,其传输速度和相互作用明显受三阶色散和自陡峭效应的影响,主要表现为相互排斥.而负折射介质中暗孤波间的相互作用与常规介质中的相互作用类似,无论暗孤波是否存在初始频移,暗孤波间的相互作用在三阶色散和自陡峭的影响下都表现为相互排斥.结果表明,通过调节三阶色散和自陡峭系数可以在一定程度上抑制负折射介质中亮、暗孤波间的相互作用.该研究结果为负折射介质在未来高速通信中的应用提供了理论依据.     

生长及耗散波色-爱因斯坦凝聚中的怪波

利用达布变换法(Darboux transformation),解析的研究了生长及耗散波色-爱因斯坦凝聚(BEC)中的怪波.通过降维和无量纲化,将描述BEC的Gross-Pitaevskii (GP)方程转化成一维无量纲非线性薛定谔方程.利用达布变换,得到了一维非线性薛定谔方程的怪波解析解.根据解析结果,数值模拟了生长及耗散BEC中怪波的性质.结果表明,BEC中出现了一种典型的双洞怪波,并且BEC生长会延缓怪波的消失,而BEC的耗散会加速怪波的消失.     

光纤放大器中非自治光畸波的传播控制研究

本文采用一个通用的理论,即用相似变换的方法,研究构建了(1+1)维变系数非线性薛定谔方程的精确畸形波解,首先讨论了一阶光畸波在光纤放大器中的传播问题.发现光学畸波的特性,如宽度、振幅和位置,可通过非线性光学介质特性和光脉冲的初始参量进行控制;然后在选择可控参数条件下,讨论了可控光畸波在非线性介质的传播行为,包括延迟激发、抑制、以及保持.这在理论和实际应用上具有启迪价值.     

Laser spectroscopic investigation of a new precursor-type polyparaphenylenevinylene

Optical, structural and morphological properties of thin films of polyparaphenylenevinylene (PPV) formed by an alkyl sulfinyl precursor route have been studied. Thin films were fabricated on an optical glass and on quartz glass either by spin-coating of the precursor solution or by layer-by-layer deposition using Langmuir–Blodgett technique. PPV precursor films were also spin-coated on gold-coated glass in order to study thin-film optical parameters by surface plasmon spectroscopy. We have been successful in forming about 40 precursor mono layers on quartz glass by Langmuir–Blodgett technique using optimized surface pressure and dipping conditions. After thermal conversion of the precursor layers good quality fluorescent PPV films of yellow colour have been obtained. Optical characterization of the films was carried out by linear absorption and emission spectroscopy, ellipsometry, and surface plasmon spectroscopy. Structural and morphological studies on the thin films were carried out by using X-ray scattering and atomic force microscopy. Wave-guided travelling-wave laser action has been achieved in a PPV film on quartz glass. The sample was transversally pumped with picosecond laser pulses (wavelength 347.15 nm, duration 35 ps). Laser emission occurred at 550 nm for pump pulse energy densities above .     

Improved Polarization Retention of BiFeO_3 Thin Films Using GdScO_3 (110) Substrates

Epitaxial ferroelectric thin films on single-crystal substrates generally show a preferred domain orientation in one direction over the other in demonstration of a poor polarization retention. This behavior will affect their application in nonvolatile ferroelectric random access memories where bipolar polarization states are used to store the logic 0 and 1 data. Here the retention characteristics of BiFeO_3 thin films with SrRuO_3 bottom electrodes on both GdScO_3(110) and SrTiO_3(100) substrates are studied and compared, and the results of piezoresponse force microscopy provide a long time retention property of the films on two substrates. It is found that bismuth ferrite thin films grown on GdScO_3 substrates show no preferred domain variants in comparison with the preferred downward polarization orientation toward bottom electrodes on SrTiO_3 substrates. The retention test from a positive-up domain to a negative-down domain using a signal generator and an oscilloscope coincidentally shows bistable polarization states on the GdScO_3 substrate over a measuring time of 500 s, unlike the preferred domain orientation on SrTiO_3, where more than 65% of upward domains disappear after 1 s. In addition, different sizes of domains have been written and read by using the scanning tip of piezoresponse force microscopy; where the polarization can stabilize over one month. This study paves one route to improve the polarization retention property through the optimization of the lattice-mismatched stresses between films and substrates.     

掺杂和未掺杂氧化锌薄膜的拉曼光谱

利用拉曼光谱分别对不同衬底上,未掺杂和掺杂以及掺杂浓度不同的ZnO薄膜进行了系统的分析研究。其中ZnO薄膜均由溶胶-凝胶法制得,掺杂源为LiCl。测得的拉曼光谱显示,Pt/Ti/SiO2/Si衬底上生长的ZnO薄膜的拉曼特征峰(437cm-1)的强度明显高于SiO2/Si衬底上ZnO薄膜的拉曼特征峰的强度,说明Pt/Ti/SiO2/Si衬底上ZnO的晶化程度比SiO2/Si上ZnO的晶化程度高;但ZnO拉曼特征峰的位置和半高宽并没有发生变化,说明两种衬底上ZnO薄膜中应力大小没有发生变化。掺Li+后,580cm-1处的峰位向高频方向移动,且掺杂浓度越大频移量越大,说明掺杂已经在不同程度上引起了ZnO晶体中自由载流子浓度的变化。此外,还分析了掺Li+未在很大程度上引起ZnO晶格畸变的原因。     

SiNx薄膜热物性参数实验测量与分析研究

采用一种新的实验测量方案，将金属加热单元与温度探测单元合二为一，间接获得了在半导体和微电子学MEMS领域内有重要用途的SiN_x薄膜的导热系数、发射率、比热容和热扩散系数，并对实验结果进行了不确定度分析，为微电子电路设计和掩模成型工艺等提供了可靠的热物性数据. 实验结果表明，薄膜的导热系数、发射率、热扩散系数远比相应体材质低，而且还与温度、厚度有关，尺寸效应显著，而比热容则与体材质相差不大. 关键词： 微尺度传热 热物性参数 x薄膜')" href="#">SiN_x薄膜 测量技术     

Mechanical properties of sol-gel derived lead zirconate titanate thin films by nanoindentation

Lead zirconate titanate (PZT) thin films are deposited on platinized silicon substrate by sol-gel process. The crystal structure and surface morphology of PZT thin films are characterized by X-ray diffraction and atomic force microscopy. Depth-sensing nanoindentation system is used to measure mechanical characteristics of PZT thin films. X-ray diffraction analyses confirm the single-phase perovskite structures of all PZT thin films. Nanoindentation measurements reveal that the indentation modulus and hardness of PZT thin films are related with the grain size and crystalline orientation. The increases of the indentation modulus and hardness with grain size are observed, indicating the reverse Hall-Petch effect. Furthermore, the indentation modulus of (1 1 1)-oriented PZT thin film is higher than those of (1 0 0)- and random-oriented films. The consistency between experimental data and numerical results of the effective indentation moduli for fiber-textured PZT thin films using Voigt-Reuss-Hill model is obtained.     

Investigation of the coercive force of thin magnetic films obtained by vacuum sputtering

The investigation of the magnetic properties of thin magnetic films is of great scientific as well as practical interest for two reasons. First, thin magnetic films, being two dimensional (one of the dimensions is much smaller than the others) show novel properties; their study can solve various problems in the theory of ferromagnetism which are difficult to solve using only data obtained from bulk materials [1,2]. Second, scientific and practical interest with respect to thin magnetic films has increased due to their possible practical applications for logic and memory elements in computer technology [3–7].Their coercive force, which is relatively increased with respect to bulk magnetic materials, is one of the basic properties of thin magnetic films. As is known, the coercive force of thin magnetic films is one of the most important design parameters for memory and logic elements in computer technology, since the coercive force defines the current necessary for the reversal of the magnetic polarity. Although this parameter is of great importance and intensive investigations of it have been carried out, precise data do not yet exist. As a matter of fact, the existing data are often contradictory, because basic technological factors were not taken into account in the investigations.To illustrate the above we give the results of a number of experimental studies in which attempts were made to establish the dependence of the coercive force upon the thickness of the magnetic film as shown in Fig. 1 (curves 2,3,4,7,15,17). Curve 16 is a calculated curve, the other curves refer to thin magnetic films obtained by various authors using the electrolytic depositing method.From this data it is evident that the magnitude of the coercive force for a certain thickness of thin magnetic film, prepared from the same magnetic material according to the same method, assumes different values with different authors. This is explained by the fact that the investigation of the dependence of the coercive force upon the film thickness is extremely complex because it is difficult to control the basic technological factors and also because various additional factors come into play which were not taken into account by the authors.     

Full field and microregion deformation measurement of thin films using electronic speckle pattern interferometry and array microindentation marker method

Thin films now are widely used in micro devices and structures, such as MEMS, electronic packaging, micro sensors, and so on. Their performances highly affect the reliability of the devices. Therefore, it is important to investigate the deformation and the failure mechanism of thin films. In this paper, we present two experimental methods to measure the mechanical properties of thin films. In the first method, a double-field-of-view electronic speckle pattern interferometry system (ESPI) and an integrated deformation and load measurement system are employed, which allows in situ and real-time measurements of full-field deformations of the thin films and microforces under uniaxial tensile test. In the second method, the array microindentation markers were indented on the surface of the thin film using a nanoindenter and the microregion deformations of the tested thin films were measured. In the proposed methods, the tested thin films can be made of metals, oxide ceramics, and multi-layer composites of thickness from several tens micrometers to less than a micron, and the tensile loads from 88 μN to 15 N for the first method or up to 100 N to the second one. The underlying principle of the methods and the experimental set-ups are presented. The deformations of Au and Au/Cr multi-layer films, and the pure Ni films are measured. The performance of the methods and the testing systems are also discussed.     

Thermal Conductivity Measurement of Submicron-Thick Aluminium Oxide Thin Films by a Transient Thermo-Reflectance Technique

Thermal conductivity of submicron-thick aluminium oxide thin films prepared by middle frequency magnetron sputtering is measured using a transient thermo-reflectance technique. A three-layer model based on transmission line theory and the genetic algorithm optimization method are employed to obtain the thermal conductivity of thin films and the interracial thermal resistance. The results show that the average thermal conductivity of 330- 1000nm aluminium oxide thin films is 3.3 Wm^-1K^-1 at room temperature. No significant thickness dependence is found. The uncertainty of the measurement is less than 10%.     

Properties of NiO thin films deposited by intermittent spray pyrolysis process

NiO thin films have been grown on glass substrates by intermittent spray pyrolysis deposition of NiCl₂·6H₂O diluted in distilled water, using a simple “perfume atomizer”. The effect of the solution molarity on their properties was studied and compared to those of NiO thin films deposited with a classical spray system. It is shown that NiO thin films crystallized in the NiO structure are achieved after deposition. Whatever the precursor molarity, the grain size is around 25-30 nm. The crystallites are preferentially oriented along the (1 1 1) direction. All the films are p-type. However, the thickness and the conductivity of the NiO films depend on the precursor contraction. By comparison with the properties of films deposited by classical spray technique, it is shown that the critical precursor concentration, which induces strong thin films properties perturbations, is higher when a perfume atomizer is used. This broader stability domain can be attributed to better chlorides decomposition during the rest time used in the perfume atomizer technique.