广义兰姆波的积累二次谐波发生研究

借助色散导波的部分波分析方法、二阳微扰理论及同的声非线性反射处理技术,本文对声波导中广义兰姆波的积累二次谐波发生进行了理论研究。结果表明,在一定条件下,源于声波导介质的体非线性、由文义兰姆波的部分波非线性相互作用所发生的二次谐波具有随传播距离积累增长的性质,文中给出了广义兰姆波的积累二次谐波发生所要满足的条件,并求解出相应的积累二次谐波之解析式。     

复合固体层中兰姆波的积累二次谐波发生与传播研究

文章提出一种分析复合固体层中兰姆波的积累二次谐波发生与传播的方法。基于导波的部分平面波分析理论,建立了复合固体层中非线性兰姆的理论模型。在分析过程中,将非线性作为线性情形的二阶微扰进行处理的方法。尽管复合固体层中兰姆波具有频散性质,分析结果表明,对于一些特定条件,二次谐波的振幅可以随传播距离积累增长。根据边界条件和初始激发条件,得到积累二次谐波的形式解,在此基础上进行了数值分析,给出一些有趣的声场分布。     

活塞聚焦换能器的二次谐波声场

1　引　言　　研究聚焦换能器的非线性声场是非线性声学中受到关注的问题。这是由于聚焦活塞换能器在焦点附近能产生很强的非线性且圆型活塞聚焦换能器由于能有效地提高分辨率而被广泛应用于超声医学诊断及超声显微镜。对于有限振幅的活塞聚焦声场 ,分析时必须同时考虑衍射效应和非线性波型畸变效应 ,因此在数学分析上相当复杂 ,Lucas等人 [1] 在Parabloic近似下 ,导出了活塞聚焦换能器的基波 ,二次谐波积分型式的解 ,尽管这种解的形式是解析的 ,但由于解的形式是多重积分 ,对于实际的声场分析计算不够方便。由于高斯函数的积分具有相对简…     

用二次谐波检测舰船电场的研究

提出一种测量舰船电场的新方法，即用二次谐波方法测量大轴周围磁场，从而确定大轴电流，进而分析由大轴电流带来的舰船电场，理论和实验均表明，该方法结构简单，构思精巧，是检测舰船电场的方法之一。     

电能表试验中奇次谐波和次谐波的频谱分析

对于电能表电流线路中存在的畸变形波、引起误差的情况,为在电能表试验中实现该影响试验项目提出了一种新的方法。该法对试验项目中所施加的试验电流波形进行了频谱分析,为通过试验装置的计算机软件进行检定提供了理论基础。     

二次谐波在二维材料结构表征中的应用

二次谐波作为非线性光学的重要分支,逐渐成为表征晶体结构的重要手段之一。在众多表征方法中,二次谐波因其无损检测、高稳定性、可调谐性、超快响应、偏振敏感性、通用性、操作简单等特点被广泛应用于二维材料结构表征,为二维材料的物性研究和功能应用提供了重要信息,大大推动了二维材料基础研究的快速发展。本文综述了近几年二次谐波在二维材料结构表征中的研究,简述了二次谐波产生原理,介绍了飞秒激光器接入共聚焦拉曼光谱仪产生二次谐波测试装置,分别讨论了二次谐波在二维材料的层间堆垛层数、层间堆垛角度、单层二维材料晶界及晶体取向表征方面的应用。同时,本文还介绍了采用二次谐波强度直接、灵敏地检测晶体中应变幅度以及通过二次谐波信号变化跟踪材料中的缺陷变化,接着讨论了二次谐波与拉曼光谱、光致发光的多维度关联分析在材料全面深度表征方面的重要性。最后展望了二次谐波未来在材料结构表征中的潜在研究方向。     

同步极化聚合及原位二次谐波测试系统的研制

采用同步极化聚合,有效地降低了极化聚合物极化温度。报道了实现这一过程的装置的研制,并结合采用原位二次谐波测试系统实现了对极化过程的实时监测。利用该系统对耐高温聚酰亚胺的极化动力学进行了研究,该聚合物极化膜的ｄ３３值为１５ｐｍ／Ｖ,取向在１９０℃时才开始衰减,具有很好的取向稳定性。     

P91钢高温热损伤的二次谐波评价

P91钢是重要的核电承压钢结构材料,对其进行早期损伤评价具有重要意义。基于非线性超声理论,对P91钢不同温度的热损伤试样进行了非线性超声检测试验,逐级加大激励电压,基波幅度平方和二次谐波幅度呈现出良好线性关系,对基波和二次谐波进行频谱分析得到非线性系数,结果显示随着热处理温度的升高,非线性系数逐渐增大,可用于对这类材料热损伤进行有效评价。     

The elimination of ambiguity when determining cumulative phase shift

Algorithms for eliminating ambiguity when determining the cumulative phase shift between harmonic signals in a time interval less than their period using digital processing are considered. __________ Translated from Izmeritel’naya Tekhnika, No. 9, pp. 57–59, September, 2007.     

Probing and modeling of carrier motion in organic devices by optical second harmonic generation

We here report a novel optical second harmonic generation (SHG) measurement that allows an electric field formed in organic solid to be probed. We examined the SHG intensity profile that changes depending on a space charge field caused by carrier injection. Experiments making use of time-resolved SHG technique has revealed dynamic changes of SHG intensity profiles arising from pentacene, and that carrier transport in OFET was diffusion-like. Calculations using drift-diffusion equation well accounted for the visualized carrier motion probed by time-resolved SHG. That is, interface charge propagation process dominates the carrier transport, which is regulated by applied gate-source voltage.     

Transient charge accumulation in pentacene field effect transistor with silver electrode

Time-resolved microscopic optical second harmonic generation (TRM-SHG) imaging was employed to study a transient charge accumulation in top-contact pentacene field effect transistor (FET) with Ag electrodes. It was demonstrated that the SHG signal at the edge of the Ag electrode decayed but remained in a steady state depending on biasing condition. An electric field formed in pentacene layer below Ag electrode activates the SHG, indicating the insufficient accumulation of injected carriers in the FET channel. By using the TRM-SHG technique transient change of the carrier density in the OFET is obtained.     

PREPARATlON AND OPTICAL PROPERTIES OF a-AXIS ORIENTED β-BaB_2O_4 SURFACE CRYSTALLIZED GLASS

采用传统熔融方法制备了透明ＢａＯ－Ｂ２Ｏ３玻璃。经受控热处理后,由ＸＲＤ谱发现存在ａ轴取向ＢＢＯ结构的微晶薄膜层。由Ｓｃｈｅｒｒｅｒ公式计算得出晶粒尺寸约２０ｎｍ。在１．０６４μｍＱ开关Ｎｄ：ＹＡＧ强激光作用下,观察到了倍频效应的产生（ＳＨＧ）。     

α轴取向β-BaB_2O_4表面析晶玻璃的制备及光学性质

采用传统熔融方法制备了透明BaO-B2O3玻璃.经受控热处理后，由XRD谱发现表面存在a轴取向BBO结构的微晶薄膜层,由Soberrer公式计算得出晶粒尺寸约20nm.在1.064μmQ开关Nd：YAG强激光作用下，观察到了倍频效应的产生（SHG）。     

Large enhancement of second harmonic generation in highly cerium doped lead-phosphate glass

The influence of lead and cerium concentration on photoinduced second harmonic generation (SHG) in lead-phosphate glasses has been studied. It has been shown that SHG can be considerably enhanced by increasing of lead and cerium concentration. We also have found that cerium greatly extends the induced nonlinearity lifetime. Physical mechanism of the phenomenon is discussed.     

Optical second harmonic generation measurements for investigating electron injection into a pentacene field effect transistor with Au source and drain electrodes

The pentacene field effect transistors (FETs)' operation for the injection carrier was revealed by means of the drain current-elapsed time (I_ds-t) and optical second harmonic generation (SHG) measurements. The charge carriers forming the conducting channel of pentacene FETs were mainly holes injected from the Au source electrode. Carrier injection from source and drain electrodes was followed by the carrier trapping, and the SHG signal modulated by the change in the electric field distribution between Au the source and drain electrodes was shown. In particular, at the off state of the FET, electron injection and succeeding trapping were suggested. Furthermore, hole injection assisted by trapped electrons was also suggested.     

Squeezing and photon antibunching in second harmonic generation: an analytical approach

With the help of second-order nonlinear interactions and hence Hamiltonian, we construct the equations of motion corresponding to pump and signal (second harmonic) fields in a second harmonic generation. The corresponding coupled differential equations involving the non-commuting field operators are not solvable in closed analytical forms. With the help of a perturbation method, we obtain analytical solutions of these field operators up to cubic orders in the interaction constant. In an appropriate limit (truncating the solution up to the second order in the interaction constant), these solutions lead to the existing solutions under the short-time approximation. The present analytical solutions are exploited to investigate the squeezing and the antibunching of photons of the input coherent light coupled to the said second-order nonlinear medium. We report the squeezing and antibunching effects of the pump field even for solutions up to the second order and hence the present results are consistent with earlier results. However, for the second harmonic mode, we report the squeezing involving the leading cubic term in the interaction constant.