On nonlinear effects in holographic-modulated ultrasound
On nonlinear effects in holographic-modulated ultrasound
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DOI：
10.1063/5.0123271
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发表时间：
2022-11
影响因子：
4
通讯作者：
A. Sallam;S. Shahab
中科院分区：
文献类型：
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作者：
A. Sallam;S. Shahab
全息声透镜（HAL），也称为声全息图，用于产生前所未有的复杂聚焦超声（FU）场。HAL存储所需波前的相位分布，其用于在被单个声源照射时重建声压场。随着声强的增加，非线性效应发生，导致波形失真和不对称。在这里，k空间伪谱方法被用来执行均匀的三维非线性声学模拟与幂律吸收。进行了深入的分析，以研究全息调制的FU字段所产生的HAL作为激励振幅的增加的演变。结果表明，非线性波形失真显着影响重建的压力模式相比，线性条件。衍射和非线性效应导致在目标平面处具有不同的正压力和负压力图案的非对称波形。峰值正压力分布变得更加局部化的区域周围的最高非线性失真。目标平面的峰值信号失真比（PSDR）下降，而不均匀性指数（NUI）上升。福尔斯。作为谐波产生的结果，热沉积分布变得高度局部化，NUI显著增加。非线性效应也被证明可以使峰值负压分布变平，同时对PSDR或NUI的影响最小。然而，非线性效应被证明是准确预测空化区的关键。研究结果将为HAL在高强度应用中的实现铺平道路，并促使将非线性声学纳入计算机生成全息的概念。
Holographic acoustic lenses (HALs), also known as acoustic holograms, are used for generating unprecedented complex focused ultrasound (FU) fields. HALs store the phase profile of the desired wavefront, which is used to reconstruct the acoustic pressure field when illuminated by a single acoustic source. Nonlinear effects occur as the sound intensity increases, leading to distorted and asymmetric waveforms. Here, the k-space pseudospectral method is used to perform homogeneous three-dimensional nonlinear acoustic simulations with power law absorption. An in-depth analysis is performed to study the evolution of holographic-modulated FU fields produced by HALs as the excitation amplitude increases. It is shown that nonlinear waveform distortion significantly affects the reconstruction of the pressure pattern when compared to the linear condition. Diffraction and nonlinear effects result in an asymmetric waveform with distinct positive and negative pressure patterns at the target plane. Peak positive pressure distribution becomes more localized around the areas with the highest nonlinear distortion. The peak signal-to-distortion ratio (PSDR) at the target plane falls while the nonuniformity index (NUI) rises. As a result of harmonic generation, the heat deposition distribution becomes highly localized with a significant increase in the NUI. Nonlinear effects have also been shown to flatten the peak negative pressure distribution while having minimal effect on the PSDR or NUI. However, nonlinear effects are shown to be critical for accurately predicting cavitation zones. Findings will pave the way for HALs implementation in high-intensity applications and prompt the incorporation of nonlinear acoustics into the notion of computer-generated holography.