A8-a1 - Sixty-Seven Years in Nonlinear Acousto-Optics
- Event
- 2025 ICU PADERBORN - 9th International Congress on Ultrasonics
2025-09-21 - 2025-09-25
Paderborn - Band
- Lectures
- Chapter
- A8-a - Nonlinear Acoustics and Ultrasonics
- Author(s)
- L. Adler - Ohio State University, Clearwater (USA)
- Pages
- 69 - 77
- DOI
- 10.5162/Ultrasonic2025/A8-a1
- ISBN
- 978-3-910600-08-9
- Price
- free
Abstract
In the late 1950s the Ultrasonic Group at Michigan State University introduced light diffraction to study distortion of ultrasonic waves in liquids under the direction of Professor Egon Hiedemann. In this paper, some results of these studies will be presented (with a detailed description of the author’s measurements of B/A). The rate at which the harmonics are developed (the wave distortion is an indication of the harmonics present) during the propagation of the initially sinusoidal ultrasonic wave depends on the nonlinearity of the medium. The light which is diffracted by the distorted wave results in an asymmetric pattern contrary to Raman–Nath theoretical prediction. From the light intensity measurements due to the generated second harmonics—filtered out by a metal plate—the Nonlinearity Parameter B/A was determined. In the 1970s at the University of Tennessee, a similar filtering technique was also applied to study imaging mechanisms in the Bragg diffraction region of finite amplitude waves. Developments in studying finite amplitude standing ultrasonic waves in a liquid filled cavity will be also discussed. Using light diffraction measurements, it was observed that above a threshold amplitude, fractional harmonics of the driver transducer are also generated in addition to the generated harmonics. Some of these fractional harmonics are lower and some of them are higher frequencies than the frequency of the driver. The generation mechanism of the fractional harmonics is explained based on parametric resonance. It was recently observed that above a second threshold value of the driver’s amplitude, the system undergoes chaotic behavior. Further increase of the driver’s amplitude returns the system from chaos to stable oscillation.