| Autor: |
Monika Ritsch-Marte, Alex Meyer, Stefan Bernet, Stefan Gspan |
| Rok vydání: |
2004 |
| Předmět: |
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| Zdroj: |
The Journal of the Acoustical Society of America. 115:1142-1146 |
| ISSN: |
0001-4966 |
| DOI: |
10.1121/1.1643367 |
| Popis: |
The optoacoustic generation of a helicoidal ultrasonic beam is demonstrated. Such an ultrasonic “doughnut” beam has a pressure amplitude minimum in the center along its entire longitudinal extension, and it carries orbital angular momentum. It is produced by illuminating a specially structured absorbing surface in a water tank with pulsed laser light. The absorbing surface has a profile with a screw dislocation, similar to the transverse cross-sectional surface of a helix. Upon illumination with modulated light, a correspondingly prepared absorber generates an ultrasonic wave with the desired phase discontinuity in its wave front, which propagates through the water tank and is detected with spatial resolution using a scanning needle hydrophone. This situation can be viewed as the optoacoustic realization of a diffractive acoustical element. The method can be extended to tailor optoacoustically generated ultrasonic waves in a customized way. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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