Dresden 2009 – wissenschaftliches Programm

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DY: Fachverband Dynamik und Statistische Physik

DY 15: Quantum chaos I

DY 15.1: Hauptvortrag

Mittwoch, 25. März 2009, 14:00–14:30, HÜL 386

Time-reversed waves and super-resolution — •Mathias Fink — Ecole Supérieure de Physique et Chimie Industrielles de la Ville de Paris, University Denis Diderot, UMR CNRS 7587, 10 rue Vauquelin, 75005, Paris, France

Time-reversal invariance is a very powerful concept in classical and quantum mechanics. In the field of classical waves (acoustics and electromagnetism), where time reversal invariance also occurs, time-reversal mirrors (TRMs) may be made simply with arrays of transmit-receive antenna, allowing an incident broadband wave field to be sampled, recorded, time-reversed and re-emitted. TRMs refocus an incident wave field to the position of the original source regardless of the complexity of the propagation medium. TRMs have now been implemented in a variety of physical scenarios from GHz Microwaves to MHz Common to this broad range of scales is a remarkable robustness exemplified by observations at all scales that the more complex the medium (random or chaotic), the sharper the focus. A TRM acts as an antenna that uses complex environments to appear wider than it is, resulting for a broadband pulse, in a refocusing quality that does not depend of the TRM aperture. Time reversal focusing opens also completely new approaches to super-resolution. We will show that in random metamaterials, a time-reversed wave field interacts with the random medium to regenerate not only the propagating but also the evanescent waves required to refocus below the diffraction limit. Focal spots as small as λ/30 are demonstrated with microwaves. This results in a large increase of the information transfer rate.