低频液体表面波激光衍射条纹的特征

用激光衍射法实现了低频液体表面波稳定、清晰、反衬度非常高的条纹,并发现了缺级现象.理论上分析了表面波的光衍射效应,得到了衍射光场和表面波之间的解析表达式,表达式包括衍射因子和干涉因子.通过对衍射因子和干涉因子的分析,得到衍射条纹空间分布与表面波波长的关系、条纹的半角宽度与入射激光光斑覆盖表面波的个数和入射方向的关系、衍射光强度与表面波振幅的关系,并解释了条纹缺级现象.     

多振源低频液体表面波声光效应研究

同时利用两个振源,在液体表面上产生两列低频表面波,实现了多振源条件下表面声光效应,观察到清晰、稳定、反衬度高的声光衍射条纹.当引起两列表面波的两个振源频率具有倍数关系时,声光衍射条纹的极大值位置与较小频率的振源单独存在时所产生表面波的极大值位置相同,与较大频率的振源单独存在时所产生表面波的极大值位置部分相同.当引起两列表面波的两个振源频率不具备倍数关系时,不仅观察到单振源的衍射条纹,而且也观察到了双振源的干涉条纹.理论上得到多振源衍射光场和表面波波长、振幅之间的解析表达式,理论规律与实验结果吻合较好.     

声表面波垂直入射于声栅时的衍射

本文分析了声表面波垂直入射于声栅时的衍射现象。理论上,应用唯象理论分析了声表面波垂直入射于声栅时,在“薄栅”和“厚栅”条件下的衍射特性。实验上,我们用光学法观察和测量了相应于“薄栅”和“厚栅”两种条件下的声栅衍射现象,得到了一些有意义的结果。例如,衍射声场近场的强度分布、正一级和负一级声的干涉场的强度分布,声栅内及透射后近场的声波波阵面等。还测量了各级衍射声波传播角度随频率而变化的情形,测量了零级和一级衍射声强度随频率而变化的情形。最后,将上述实验结果与应用唯象方法所分析的结果作了比较。     

干涉法测量低频表面波的衰减系数

对于频率为几十赫兹的低频衰减液体表面波，结合激光干涉法和激光扫描法，实验得到反衬度很高的调制干涉图样，理论上给出了干涉图样的条纹宽度，条纹分布范围与表面声波振幅之间的解析关系，实时测量了液体表面波的衰减系数.     

超声光栅测声速的方法运用到液体表面波波速的测量

理论上分析了超声光栅衍射和液体表面波光栅衍射,得到了表面波光栅衍射图样与表面波参数的解析关系.实验上得到清晰的衍射图样,利用表面波光栅衍射法测量了液体表面波波速,实验结果与理论值误差不超过1%.     

基于衍射条纹非对称性的表面波衰减系数的测量

通过采用将入射光掠入射到频率为几百赫兹的衰减低频液体表面波上,观察到了清晰的间距分布具有明显非对称性的衍射条纹。当入射光掠入射到低频液体表面上时,衍射图样非对称分布具有普遍性。理论上得到了考虑表面波衰减影响后观察屏处衍射光强分布的解析表达式。理论结果表明:衍射图样的这种非对称分布与衍射级次、入射光波波长、液体表面波波长及表面波衰减系数有关;正负级次衍射亮条纹距离中央零级亮条纹的间距体现表面波衰减信息;正衍射级次之间以及负衍射级次之间的条纹间距体现表面波波长信息。利用所提出的方法实现了对几百赫兹液体表面波的衰减系数的实时便捷测量。     

用光的干涉和衍射测量金属的线胀系数

在光的干涉实验中只要测出干涉条纹随金属温度变化的个数,进而求出金属长度随温度的变化量,在光的衍射实验中则利用衍射条纹的间距与缝宽之间的关系,通过测量衍射条纹的间距求出温度变化时待测金属的长度变化量,从而计算出待测金属的线胀系数。     

凝视光电成像系统猫眼回波特性的理论与实验研究

以惠更斯-菲涅尔衍射公式为基础,推导了猫眼系统的回波光场,并以二维光栅作为凝视光电成像系统的焦平面器件进行理论计算和实验验证.分析了光阑孔径对回波图像与焦平面器件调制之间相关性及空间截止频率对猫眼回波的影响.结果表明:随着光阑孔径的减小,回波图像信息减少,与焦平面上光斑的相关性降低;随着光阑孔径的增大,光栅干涉形成的次级光斑逐渐出现在回波图像中,回波图像也由于各级光斑的干涉变得复杂,对应的空间频谱变化反映了各级光斑的交叠情况.该研究对利用回波特征用于凝视光电成像侦察设备实施激光主动探测具有实际应用价值.     

周期结构介质中Floquet－Bloch波的波矢量图

利用波矢量图分析了周期结构介质中Ｆｉｏｑｕｅｔ－Ｂｌｏｃｈ波的色散规律．实例计算结果表明，波矢量图中的波矢禁带的产生和变化强烈地依赖于光波长和结构参量，随着周期长度的增大或光波长的减小，波矢量图将变得更加复杂，并将产生更多的波矢禁带．     

声表面波在声栅上的Bragg衍射

本工作揭示了声表面波在声栅上的Bragg型衍射效应。应用简正波理论近似处理了在强Bragg条件下,声表面波在声栅上衍射的一些规律:栅阵内简正模式,偏转角和偏转效率与入射声波工作频率和声栅参数的关系。实验上,我们在y切割LiNbO₃压电晶体表面,用金属栅阵构成声栅,用光学法观察了声表面波(Rayleigh波)在上述声栅上的Bragg型衍射现象,并测量了偏转角和偏转效率随工作频率的关系。实验与理论结果比较表明,二者基本上是符合的。 关键词：     

Experimental measurement of variations in the optical reflection coefficient of water-magnetic liquid interface in an electric field,wave motion,and surface instability

A variation in the reflection coefficient of an interface of two liquids (water and magnetic liquid) in the presence of an electric field is experimentally studied. An increase in the reflection coefficient of the interface is demonstrated. A surface instability of the water-magnetic liquid interface, the wave motion at the interface, and wave interference are observed.     

Theoretical analysis and experimental results of interference striation pattern of underwater target radiated noise in shallow water waveguide

Waveguide invariant in shallow water is an attractive topic in recent three decades. The interference phenomena of direct wave of radiated noise of underwater target and reflection wave from sea surface and sea bottom can be considered as a typical case of shallow water waveguide.The interference striation pattern of direct wave and its reflection is the effective and comprehensive figure for better understanding the essence of shallow water waveguide invariant.The theoretical analysis of interference phenomena generated by direct wave of radiated noise of underwater target and its reflection wave from sea surface and sea bottom is presented in this paper.It is shown that the interference wave resulted by sea surface reflection will produce striation pattern centered at high frequency band.But the interference of nulling frequency resulted by sea bottom reflection may be at low frequency or high frequency, it strongly depends on the acoustic behavior of sea bottom.The relationship between main parameters of interference striation pattern and target,receiver,and environment is derived.It is shown that the interference striation have the shape of hyperbolic curve.The equation set of the hyperbolic curve and its asymptotic line is presented.The at sea experiment carried out in South China sea shows some interesting results.A part of data processing results are illustrated in this paper.The results expressed in this paper show that the interference striation pattern can be used,in some conditions,as a potential means for target recognition.     

Interference acoustical method for measuring velocity,attenuation and reflection of acoustic surface waves

An interference acoustical method for measuring velocity, attenuation and reflection of acoustic surface waves was developed. Applications to diagnostics and nondestructive testing of acoustic surface wave devices are discussed.     

圆形活塞声源的有限振幅反射波

本文研究了圆形活塞声源的有限振幅声波的反射。应用像源法计算已产生的谐波本身在边界上的反射,将它们看成是反射边界上振动的新声源所产生的辐射场,再应用弱冲击理论来计算这部分场自己产生的谐波场。在水池中作了二阶谐波的反射实验,反射界面是水池壁。结果表明,谐波声压随距离的平均衰减规律与理论符合得很好。实验还表明,反射谐波场沿纵向距离以及与它相垂直的横断面上有强烈的干涉现象,而纵向相干长度比横向相干长度大一个数量级。通过理论估计,认为这种现象是由于反射壁的有限厚度、它的两个平面之间有一个很小的角度以及发射波束有一定的宽度所造成的。这样估算出来的两个相干长度与实验符合。 关键词：     

Quantum mechanics in space-time: The Feynman path amplitude description of physical optics, de Broglie matter waves and quark and neutrino flavour oscillations

Feynman’s laws of quantum dynamics are concisely stated, discussed in comparison with other formulations of quantum mechanics and applied to selected problems in the physical optics of photons and massive particles as well as flavour oscillations. The classical wave theory of light is derived from these laws for the case in which temporal variation of path amplitudes may be neglected, whereas specific experiments, sensitive to the temporal properties of path amplitudes, are suggested. The reflection coefficient of light from the surface of a transparent medium is found to be markedly different to that predicted by the classical Fresnel formula. Except for neutrino oscillations, good agreement is otherwise found with previous calculations of spatially dependent quantum interference effects.     

Nonlinear regime of the excitation of a surface electromagnetic wave on the silicon surface by an intense femtosecond laser pulse

A surface electromagnetic wave has been excited on an atomically smooth silicon surface by an intense infrared femtosecond laser pulse as a result of its self-diffraction on a microscale short-lived optical inhomogeneity of the excitation region rather than on the roughness of its surface relief. This wave has been visualized in the form of the pattern of its interference with the same incident infrared ultrashort pulse, which corresponds to the instantaneous surface dielectric constant grating (reflection), as well as the resulting surface relief grating, using time-resolved far-field optical reflection microscopy.     

Electrooptic reflection with surface plasmons

Electrooptic reflection with surface plasmons is studied both experimentally and theoretically. An attenuated total reflection (ATR) geometry is used in which a quartz electrooptic crystal onto which a thin Ag film has been evaporated is contacted to the hypotenuse face of a high-index prism. Modulation in the ATR of an He–Ne beam near the angle for surface plasmon excitation is observed when a low-frequency electric field is applied to the quartz crystal. Experiments have been done with both single and multiple boundary surface waves. The angular spectra show phase reversal structure due to the interference of the modulated reflected wave with the ATR wave. The modulated reflectance is calculated directly from a well-known solution to the boundary value problem in nonlinear optics. Good quantitative agreement with the observations is obtained.     

半导体激光Fabry-Perot干涉波长的微位移测量仪

摘要设计了一种基于Fabry-Perot干涉波长测量仪.这种测量仪使用两个Fabry-Perot干涉腔,其中一个作为测量腔、另一个作为参考腔,测量腔的一个反射面与被测对象安装在一起,参考腔的一个反射面与压电陶瓷安装在一起.根据透射光谱中心波长与其干涉腔长之间的关系,当参考腔与测量腔的透射光谱中心波长完全重合时,对纳米级微位移实现实时测量.光源采用半导体激光器,可获得所需要的波长值和波长变化范围.实验结果表明,这种测量仪测量误差不大于1.5 nm,该精度可以满足精密机械加工、光电子和微电子加工以及纳米级测量技术等领域的精度要求.     

半无限深势阱中自旋相关玻色-爱因斯坦凝聚体的量子反射与干涉

玻色-爱因斯坦凝聚体与势垒或势阱的量子反射及干涉是考察宏观物质波奇特物性的最有效途径之一.利用传播子方法和基于冷原子实验广泛采用的飞行时间吸收成像方案,研究自旋相关玻色-爱因斯坦凝聚体在半无限深势阱中的反射和干涉演化动力学,得到了自旋相关的凝聚体波函数的严格解析解.结果表明,当自旋相关光晶格关闭后,非局域于不同格点中相同自旋态的物质波在自由膨胀过程中发生量子干涉,形成了对比度明显的干涉条纹.与此同时,扩张的自旋相关物质波包与半无限深势阱壁相遇发生量子反射,反射波与入射波产生二重干涉,在密度分布两边对称的局部位置出现剧烈的振荡,干涉条纹表现出显著的调制效应.分析讨论了自旋态、相干输运距离和相对相位等因素对干涉条纹的影响.该研究有助于促进对自旋相关凝聚体宏观量子特性的认识,为深入检验自旋相关光晶格中凝聚体干涉的理论模型和物理机理提供依据和新方案.     

强脉冲CO2激光与靶材在空气中的相互作用

用高速干涉摄影诊断手段对激光作用在固体靶材上的表面效应,冲击波的传播、反射及绕射机制进行了实验观察,拍摄了各种现象的干涉及阴影照片,并进行了简要的分析。 关键词：