EAGER: Understanding and Leveraging Nonlinear Effects in Acoustic Holograms

可以穿过人体组织和流体的超声波已经用于声学感测、超声治疗和成像。对超声波传播的空间控制可以显着改善无创超声技术。这个早期概念探索性研究资助（EAGER）项目将探索在高强度场中塑造超声波的声学全息图。最近的研究表明，被动声全息图可以用于投影任意的声学图案时，只有一个单一的声源照明。然而，对于高强度的超声波操纵，其中非线性效应设置，全息技术是在其早期阶段的未经测试的方法。本项目将体声全息的新技术应用于非线性领域，并为波前工程的新领域所需的关键要素做出贡献。EAGER项目的研究目标是了解非线性效应如何影响声全息图中的反射和透射现象的一般图像，其特征在于目标平面中的构造声场。在较高的激励振幅下，非线性效应表现为谐波的产生、声波波形的失真以及可能的激波阵面的形成。这些效应可能是造成初级干扰波的幅度和相位失真的原因，初级干扰波的幅度和相位失真引起重建声场的额外声学图像和模糊函数。该奖项将探索一种基于实验测量和建模的未经测试的非线性体全息方法。该方法将有助于回答波前工程研究中的基本科学问题，包括：（1）声全息图中非线性的主要来源是什么？(2)非线性效应的增强和工程化是否可以提高控制声波的效率？(3)声波的强度和频率以及非线性谐波对重建的声场有什么影响？该奖项反映了NSF的法定使命，并被认为是值得通过使用基金会的知识价值和更广泛的影响审查标准进行评估的支持。

Ultrasound waves, which can travel through human tissues and fluids, have been used in acoustic sensing, ultrasound therapy, and imaging. The spatial control over the propagation of ultrasound waves can significantly improve noninvasive ultrasound techniques. This EArly-concept Grant for Exploratory Research (EAGER) project will explore acoustic holograms for shaping ultrasound waves in high-intensity fields. Recent studies suggest that passive acoustic holograms can be used for projecting an arbitrary acoustic pattern when illuminated with only a single acoustic source. However, for high-intensity ultrasonic manipulations, where nonlinear effects set in, the hologram technology is in its early stage on untested approaches. This project applies new expertise in volume acoustic holography in nonlinear regimes and contributes to the key elements needed for the novel field of wavefront engineering.The research goal of this EAGER project is to understand how the nonlinear effects influence the general picture of the reflection and transmission phenomena in acoustic holograms, which are characterized by the constructed acoustic fields in the target plane. At higher excitation amplitudes, the nonlinear effects are exhibited by the generation of harmonics, distortion of the acoustic waveform, and possibly the formation of shock fronts. These effects can be responsible for amplitude as well as phase distortions of the primary interfering waves that give rise to extra acoustic images and ambiguity functions of the reconstructed acoustic field. This award will explore an untested nonlinear volume holography approach based on experimental measurements and modeling. The method will help to answer fundamental scientific questions in wavefront engineering research including: (1) What are the dominant origins of nonlinearity in acoustic holograms? (2) Is the enhancement and engineering of nonlinear effects can increase the efficiency of controlling sound waves? (3) What are the effects of the intensity level and frequency of the sound wave as well as nonlinear harmonics on reconstructed acoustic fields?This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.