Mathias Fink
Langevin Institute, ESPCI ParisTech, CNRS, France

Time-Reversed Waves

Time-reversal invariance can be exploited in wave physics to control wave propagation in complex media. It was first in the field of acoustics and later for microwaves, where antenna array technology was available, that “time-reversal mirrors” have been built. Such mirrors allow to refocuses in space and time an incident wave field at the original source location regardless of the complexity of the propagation medium.

An important concept has emerged from this research: the spatio-temporal degrees of freedom of a broadband wavefield that strongly depends on the dispersive nature of the medium. These degrees of freedom can be controlled very differently depending on the kind of waves that are used and we will compared these approaches from optics to water waves.

Time reversal mirrors are not only unique research tools in the field of fundamentals physics but they have plenty applications including therapy, medical imaging, telecommunications and human-machine interface. An overview of these applications will be presented

Mathias Fink is a professor  of  physics at the Ecole Superieure de Physique et de Chimie Industrielles de la Ville de Paris (ESPCI ParisTech), Paris, France. In 1990 he founded the Laboratory Ondes et Acoustique at ESPCI that became in 2009 the Langevin Institute.  In 2002, he was elected at the French Academy of Engineering, in 2003 at the French Academy of Science and in 2008 at the College de France on the Chair of Technological Innovation.

Mathias Fink’s area of research is concerned with the propagation of waves in complex media and the development of numerous instruments based on this basic research. His current research interests include time-reversal in physics, wave control in complex media, super-resolution, metamaterials, medical ultrasonic imaging, ultrasonic therapy, multiwave imaging, acoustic smart objects, underwater acoustics, geophysics and telecommunications. He has developed different techniques in medical imaging (ultrafast ultrasonic imaging, transient elastography, supersonic shear imaging), wave control and focusing in complex media with time-reversal mirrors. He holds more than 65 patents, and he has published more than 400 peer reviewed papers and book chapters. 4 start-up companies with close to 300 employees have been created from his research (Echosens, Sensitive Object, Supersonic Imagine and Time Reversal Communications).