Anisotropy detection in sapphire by acoustic microscope using line-focus beam

Nonscanning reflection acoustic microscopes can be satisfactorily applied to detect the anisotropy of acoustic properties of solid materials using a line-focus beam. As a demonstration, the anisotropic dependence of leaky surfac-acoustic-wave velocities on the propagation directions are measured on the water/Z-cut-sapphire boundary at a frequency of 200 MHz. The measured values are in good agreement with the calculated results within a difference of about 1%.     

Visualisation of acoustic beames using liquid crystals

A sound visualisation technique has been developed using the light-scattering properties of cholesteric liquid crystals. An acoustic wave propagating in these materials produces a local colour change, rendering the sound beam visible to the eye.     

Contrast in reflection acoustic microscopy

Although the reflection acoustic microscope has long been used to study solid surfaces, the contrast that has been observed in images of complex i.c. devices were not well understood until fairly recently. Our recent article where we calculated the acoustic response of different materials suggested that the observed contrast was a strong function of the elastic properties of the surface being investigated. This letter is devoted to explaining the analysis used in our calculations.     

Leaky SAW velocity on water/silicon boundary measured by acoustic line-focus beam

Propagation characteristics of leaky SAWs at the boundary of water/silicon are investigated by the nonscanning reflection acoustic microscope using a line-focus beam. Experiments are performed for typical crystalline planes of silicon such as (111), (110), (001) and slightly inclined (111). These results obtained by the line-focus beam are compared to the experimental results obtained by the conventional point-focus beam.     

Electrically controlled acoustic beam deflection

A method is described for deflecting a microwave acoustic beam by controlling the group-velocity deviation in an anisotropic medium. The basic principle is presented in terms of a general wave-vector surface. A detailed treatment is then given for the special case of anisotropy due to the spin-acoustic-wave interaction in magnetic insulators. Experimental beam deflection observations in yttrium iron garnet are discussed. A brief discussion of beam deflection in current-carrying piezoelectric semiconductors is also given. Possible applications of this method of beam deflection are suggested.     

Multimode interference mechanism in V(z) curves obtained by acoustic line-focus beam

The multimode interference mechanism in the acoustic material signatures of V(z) curves, which generally deforms the dip intervals and the shape, is investigated theoretically and experimentally for the acoustic line-focus beam. It is shown, taking a (111)-Si substrate as an example, that V(z) curves associated with multiple leaky waves are represented as a superposition of elemental V(z) curves with different characteristic dip intervals corresponding to the respective velocities of the leaky waves.     

中低频水下声信号的激光干涉法探测

基于迈克尔逊干涉仪原理,提出了在非平静水面情况下探测中低频水下声信号的激光干涉方法。利用携带声波信息的散射光和参考光的干涉结果提取水下声信号的频率信息,并进行了理论分析和实验验证,结果表明,激光干涉法可以准确探测出中低频水下声信号的频率信息。     

Optimizing fiber coatings for interferometric acoustic sensors

The pressure sensitivity of the phase of light propagating in an optical fiber is studied both analytically and experimentally. The analysis, which takes into account the exact composition and geometry of multilayer fibers, is utilized to identify coating properties which optimize the fiber acoustic sensitivity. In order to predict the fiber acoustic sensitivity, the elastic parameters of commonly used coating materials, thermoplastics, and UV curable elastomers have been studied in bulk samples as a function of frequency (10^{2}-10^{4}Hz) and temperature (0-35degC). The analytically predicted frequency dependence of the acoustic sensitivity is found to be in agreement with that obtained experimentally from fibers with coatings of various materials.     

水下声信号光电探测技术的实验研究

为了实现水下声信号的遥感探测,针对水下声信号光电探测技术的强度调制理论,提出了光线分析理论模型,并进行了初步的理论分析和实验验证,取得了频率为65Hz和100Hz的水下声信号的探测数据,验证了水下声信号光电探测技术的强度调制理论.实验结果表明,在空气中利用激光,在水中利用声波,通过这两种信号载体来探测水下声信号技术是可行的,这一结果对于水下声信号光电探测技术的研究具有一定的参考价值.     

Optical probing of surface acoustic waves

Light diffraction by surface acoustic waves is used in studying the propagation characteristics of Rayleigh waves on y-cut z-oriented LiNbO3. In reflection, only the surface deformation contributes to the diffracted light. In transmission, the photoelastic effect, which is incident beam polarization dependent, must also be considered. Such optical probing has been used to study the Fresnel diffraction radiation pattern of an interdigital transducer, to measure beam steering effects related to transducer misalignment on an anisotropic substrate, and to measure reflection and transmission coefficients of an electrically loaded transducer. Attenuation measurements have been made over frequencies as high as 3.5 GHz. The power dependence of attenuation and harmonic generation is also examined.     

扫描探针声显微镜原理及其应用

将声学检测技术与扫描探针显微术相结合,构成的扫描探针声显微镜,不仅可以检测材料表面、亚表面和内部的微小缺陷,还可以分析样品的弹性特性、电特性等物理性能,同时还具有分辨率高的特点,在材料科学和生命科学等领域具有很高的应用价值.目前,得到实际应用的扫描探针声显微镜主要有扫描隧道声显微镜和原子力声显微镜.本文介绍了这两类显微镜的基本工作原理,并对扫描探针声显微镜今后的发展方向进行了探讨.     

Advanced acoustic microimaging using sparse signal representation for the evaluation of microelectronic packages

Acoustic microimaging (AMI) has been widely used to nondestructively evaluate microelectronic packages for the presence of internal defects. To detect defects in small devices such as /spl mu/BGA, flip-chip, and chip-scale packages, high acoustic frequencies are required for the conventional AMI systems. The acoustic frequency used in practice, however, is limited by its penetration through materials. In this paper, a novel acoustic microimaging technique, which utilizes nonlinear signal processing techniques to improve the resolution and robustness of conventional AMI, is proposed and investigated. The technique is based on the concept of sparse signal representations in overcomplete time-frequency dictionaries. Simulation and experimental results show its super resolution and high robustness.     

声像分析在系统级封装和多芯片模块检测中的应用

用反射模式的超声波显微镜对系统级封装SIP和多芯片MCM封装模块的品质进行了研究。探测封装内部的分层、裂纹和气泡等间隙类缺陷。用超声探测转换器把脉冲超声波送入样品,同一个转换器把接收到的回声转换成像点。最大的反射振幅是从固体与气体间的界面产生的。在固体材料内部,分层、孔洞及裂纹会造成最大振幅的回声并可以成像。超声波显微镜可发现SIP和MCM样品内间隙类的缺陷分层裂纹和气泡。     

Simplified model for effect of Ge doping on silica fibre acoustic properties

A simplified model for the effect of Ge doping on the longitudinal acoustic modulus and acoustic damping coefficient of silica fibres is presented. The model provides the longitudinal acoustic velocity, Brillouin spectral width, and Brillouin gain coefficient as a function of the Ge concentration. The model only requires knowledge of high-level, easily-measurable physical properties of the bulk fictive materials. The model and experimental data were found to be in excellent agreement.     

非本征光纤F-P干涉声传感器的研究

为研究不同材料对法布里-珀罗(F-P)干涉声传感器性能的影响。采用几种不同金属材料,设计制作了基于光纤端面—膜片非本征型F-P干涉声传感器,利用有限元方法对圆形振动膜片进行模态分析,得到了一阶固有频率。实验结果表明:由金、锌合金材料制作的传感器可探测较低声压,且传感器灵敏度较高、对外界声波信号响应成良好的线性关系。     

基于声发射技术的金刚石单晶生长机理研究

作为一种动态无损检测技术,声发射在研究材料的变化机理和特殊性能表征等方面具有重要作用.本文采用声发射检测技术对高温高压下人造金刚石单晶的生长过程进行了检测与分析.并结合金刚石/金属包膜界面微观形貌的观察,讨论了声发射信号能量、幅度、振铃等参数的变化规律.实验结果表明,声发射信号的特征参数能客观反映金刚石单晶在高温高压下...     

Acousto-optic interaction in the lithium niobate crystal upon the surface excitation of the bulk acoustic wave

The interaction of light with the bulk acoustic wave that is excited from the surface of the lithium niobate crystal is experimentally studied. A prototype of the acousto-optic device that employs the XY-cut crystal and the optimized (Y-13°)-cut crystal is presented. Diffraction efficiencies of 1 and 2 %/W are obtained for the first and second prototypes, respectively. It is demonstrated that the polarization characteristics of the device differ from the conventional characteristics by the dependence on the structure of the acoustic beam. An original method for the excitation of the ultrasonic beam can be used in the acousto-optic devices for light control.     

Theoretical analysis for V(z) curves obtained by acoustic microscope with line-focus beam

A theoretical analysis is developed for V(z) curves obtained by a nonscanning reflection acoustic microscope system using a line-focus beam which is formed by an acoustic lens with a cylindrical concave surface. Numerical calculations are made for a ZY-sapphire and compared with the experimental results at 179 MHz. From the comparison, it is confirmed that the shape and the dip interval in the V(z) curves can be explained well by the theory developed here.     

Ion bombardment-induced high orientation of Al/Ti films for surface acoustic wave device applications

Al/Ti films were deposited on 128° Y-X LiNbO₃ substrates by electron-beam (e-beam) deposition. Low-energy Ar ion beam bombardment was employed during the Ti underlayer deposition. Influence of low-energy beam bombardment on the texture of Al/Ti films was investigated by x-ray diffraction (XRD) analysis. It was found that Al films deposited on Ar-ion bombarded Ti underlayers possessed excellent (111) texture. With the textured Al/Ti films, a 2.3-GHz range image-impedance connection surface acoustic wave (SAW) filter was successfully fabricated.     

Microwave acoustic materials, devices, and applications

This paper surveys applications of acoustic waves in microwave devices. After a general and historical introduction to bulk acoustic waves (BAWs), surface acoustic waves (SAWs), practical wave types, and acoustoelectric transducers, a review is given of technologically important materials for microwave acoustic applications. Following this, we discuss BAW and SAW microwave devices and their technologies. Specifically reviewed are thin-film resonators and filters, transversal filters, and filters for correlative analog signal processing. Finally, an overview of the most important microwave applications is given, along with manufacturing and packaging issues