Development of a High Frequency Photo-Acoustic Spectrometer for Material Characterization with Nonlinear Surface Acoustic Waves

基于激光的光声方法提供了激发具有极高振幅的短波表面声波（saw）的可能性。这种波为研究固体材料的弹性和力学性能提供了有效的工具。直到最近，表面声波仍然是少数几种没有观察到强烈非线性效应的波现象之一，因为用传统方法不可能激发和探测到它们。这些非线性现象的表现取决于固体的非线性常数，这些常数反映了材料的微观结构和质量以及由于处理、疲劳和磨损而发生的变化。该项目的目标是研制一种基于激光激发和宽带声呐脉冲探测的声呐光谱仪。该方法将用于表征工业和天然材料，如熔融二氧化硅、晶体硅、金属和聚合物。该项目将有助于更好地了解非线性saw在各向同性和各向异性固体材料中的传播，有助于开发其产生和检测的有效技术，以及固体材料表面和体弹性特性的诊断方法。非线性表面声波的研究将对材料科学、声学电子学、非线性声学、非线性波理论和地震学等不同领域产生影响。对这个项目的支持将加强德克萨斯农工大学学生的教育和培训。%%%***

9870143SchuesslerLaser based photo acoustic methods provide the possibility to excite short wavelength surface acoustic waves (SAWs) with extremely high amplitudes. Such waves present an efficient tool for the investigation of elastic and mechanical properties of solid materials. Until recently suface acoustic waves remained among the few wave phenomena for which strong nonlinear effects were not observed, since it was not possible to excite and detect them with traditional methds. The manifestation of these nonlinear phenomena depends on the nonlinear constants of the solid which reflect the microscopic structure and quality of the material and the changes due to treatment, fatigue, and wear. The objective of the project is to develop a SAW spectrometer based on laser excitation and detection of broadband SAW pulses. The method will be applied to characterize industrial and natural materials such as fused silica, crystalline silicon, metals, and polymers.The project will contribute to a better understanding of the propagation of nonlinear SAWs in isotropic and anisotropic solid materials, to the development of efficient techniques for their generation and detection, as well as to diagnostic methods of surface and bulk elastic properties of solid materials. The study of nonlinear surface acoustic waves will provide an impact on different fields such as materials science, acousto electronics, nonlinear acoustics, theory of nonlinear waves, and seismology. Support of this project will enhance the education and training of students at Texas A&M University.%%%***