Colloquium: Wave Control and Antenna Radiation Mechanism in “Time Materials”

ABSTRACT

Photonic 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 as well 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.

Periodic time manipulations can also be studied in order to extend the concept of photonic crystals in the time domain. The difference between periodic time modulation and periodic spatial modulation will be emphasized and the way an antenna radiates in these two kind of situation will be discussed.

BIOGRAPHY

Prof Mathias Fink received his PhD in Solid State Physics from the University of Paris in 1970. Then he moved to ultrasonic medical imaging and received his Doctorat és Sciences degree in Acoustics. He is currently the George Charpak Professor and Professor of Physics at the École Supérieure de Physique et de Chimie Industrielles de la Ville de Paris (ESPCI ParisTech), where he founded in 1990 the Wave and Acoustics Laboratory that became in 2009 the Langevin Institute, where he formerly served as the Director. The Institute today brings together over 110 scientists engaged in research on waves and imaging. 

Prof 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. He pioneered the development of time-reversal mirrors and time reversal signal processing. He developed many of these concepts into applications like medical imaging, ultrasound therapy, telecommunications, seismic imaging and tactile objects. He also pioneered several innovative medical imaging methods - transient elastography, supersonic shear imaging and multi-wave imaging - that are now implemented by several companies. He holds more than 60 patents, and has published more than 350 peer reviewed papers. 

Prof Fink is a Member of the French Academy of Sciences and of the French Academy of Technologies. He was elected Chair of Technological Innovation at the College de France in 2008.