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Origin of Gouy Phase Shift Identified by Laser-Generated Focused Ultrasound
ACS Photonics ( IF 6.5 ) Pub Date : 2020-10-19 , DOI: 10.1021/acsphotonics.0c01313
Taehwa Lee 1 , Yeonjoon Cheong 1 , Hyoung Won Baac 2 , L. Jay Guo 1, 3
Affiliation  

The Gouy phase shift, the phase change of a converging wave passing through a focus, is a general characteristic of waves of any kind, including light and sound. Direct observation of the phase shift has been typically limited to high-frequency short pulses, e.g., terahertz light pulses and picosecond sound pulses. We demonstrate the Gouy phase shift of relatively low-frequency, megahertz ultrasound, widely implemented for ultrasound imaging and sensing. This demonstration is experimentally enabled with monopolar ultrasound pulses generated by nanosecond laser excitation of a light-absorbing concave film, which undergoes polarity reversal from before to after focusing. Moreover, our simulation results for various input pressure profiles show that the Gouy phase shift is observed for beams with significant diffractions. The physical origin of the phase anomaly is intuitively explained based on Huygens’ principle and the acoustic interference of secondary waves, providing further understanding of the Gouy phase shift in optics as well.

中文翻译:

激光聚焦聚焦超声识别Gouy相移的起源

古伊相移是通过焦点的会聚波的相变,是任何类型的波的总体特征,包括光和声。直接观察相移通常限于高频短脉冲,例如太赫兹光脉冲和皮秒声音脉冲。我们证明了相对低频的兆赫超声的Gouy相移,已广泛用于超声成像和传感。该演示可以通过纳秒激光激发吸光凹膜产生的单极超声脉冲进行实验,该吸光凹膜在聚焦之前和之后都会发生极性反转。此外,我们对各种输入压力曲线的仿真结果表明,对于具有明显衍射的光束,可以观察到Gouy相移。
更新日期:2020-11-18
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