Wave Control with “Time Materials”

by Prof. Mathias Fink
Langevin Institute, ESPCI Paris
HKUST IAS Senior Visiting Fellow

 :  11 Dec 2018 (Tue)
 :  10:30am - 11:30am
Venue  :  Classroom 2504 (via lifts 25/26)

Phononic crystals and Metamaterials are made from assemblies of multiple elements usually arranged in repeating patterns at scales of the order or smaller than the wavelengths of the phenomena they influence. 
Because time and space play a similar role in wave propagation, wave propagation is affected by spatial modulation or by time modulation of the refractive index.  Here we emphasize the role of time modulation. We show that sudden changes of the medium properties generate instant wave sources that emerge instantaneously from the entire wavefield and can be used to control wavefield and to revisit the way to create time-reversed waves. Experimental demonstrations of this approach will be presented. More sophisticated time manipulations can also be studied in order to extend the concept of phononic crystals in the time domain. 
Mathias Fink is the George Charpak Professor at the Ecole Superieure de Physique et de Chimie Industrielles de la Ville de Paris (ESPCI Paris) where he founded in 1990 the Laboratory “Ondes et Acoustique” that became in 2009 the Langevin Institute. He is member of the French Academy of Science and of the National Academy of Technologies of France. In 2008, he was elected at the College de France on the Chair of Technological Innovation. He has received several scientific awards as the CNRS Medal of innovation, the Helmholtz-Rayleigh Award of the Acoustical Society of America, the Rayleigh Award of the IEEE Ultrasonics Society and the Edwin H. Land Medal of the Optical Society of America. 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). He holds more than 70 patents, and he has published more than 400 peer reviewed papers and book chapters. 6 start-up companies with more than 350 employees have been created from his research (Echosens, Sensitive Object, Supersonic Imagine, Time Reversal Communications, CardiaWave and GreenerWave).