Seminar:Time Reversal of waves in scattering media: from smart sonar to medical imaging
Date: 30 October 2018 (Tuesday), 9:00 AM to 12:00 AM
Venue: 复旦大学科学楼5楼530会议室
Invited Speakers:Prof. Arnaud Tourin
Institut Langevin, ESPCI Paris, CNRS UMR, 1 rue Jussieu, 75005 Paris, France. Arnaud.Tourin@espci.psl.eu
Invited by: 许凯亮，他得安
Abstract:
Time reversal is an efficient way for focusing waves deeply inside heterogeneous media. In a typical time-reversal focusing experiment, the wave field radiated by a broadband source is recorded with a set of detectors located on a surface named a “Time Reversal Mirror”. The detectors then become sources sending back the time-reversed sequence of the recorded field. The result is a time-reversed field that focuses at the source location as if time were going backwards. Surprisingly, the more scattering the medium is, the thinner the focal spot is. This rather counterintuitive result has contributed to creating a new paradigm for the manipulation of waves in complex media: contrary to long-held beliefs, disorder is not only an impediment to focusing and imaging but can be turned into an ally for controlling waves. In this talk, I will be discussing some applications of time-reversal focusing to various fields ranging from underwater acoustics, wireless communications and non-destructive testing to medical imaging.
Bio-sketch: Arnaud Tourin
Professor Tourin is the Head of the Langevin Institute, a joint research unit between ESPCI Paris and CNRS. His research focuses on wave propagation in complex media. Especially, he led some pioneering experiments on time reversal focusing of ultrasound in multiple scattering media and worked to extend this concept to wireless communications and geophysics. Using ultrasound, he has also studied spectacular effects that find their analogue in condensed matter physics: the coherent backscattering cone, which is similar to weak localization, the transverse localisation, which is the 2D version of Anderson localization, or the resonant tunnelling effect. His recent work has focused on the design of locally resonant acoustic materials for super absorption and subwavelength focusing. In close collaboration with Prof. Jia, he is currently working on acoustic wave propagation in granular media. He has 73 publications in peer-reviewed journals, books and conference proceedings. He is co-inventor of 5 patents and co-founded a company.
