Mathias FINK - Institut d'études scientifiques de Cargèse (IESC)

performing any calculations.
Pr. John H. Page
Anderson Localization of Ultrasound in Three-Dimensional Mesoglasses
The question of whether or not the Anderson localization of classical waves can really occur in
three-dimensional disordered materials has intrigued physicists for many years. Recently there has
been considerable progress in answering this question, with the most direct demonstration of 3D
Anderson localization being first established in acoustics, through measurements of the dynamic
transverse confinement of energy in a “mesoglass” consisting of a disordered elastic network of
aluminum beads [1]. In this approach, an incident ultrasonic point source is used, and the spatial
extent of the transmitted intensity is measured as a function of time on the opposite side of the
sample. For diffuse waves, the spatial intensity profile on the sample surface is Gaussian, and the
width squared grows linearly with time. For localized waves, the transverse spreading of the
intensity is cut off, and the width saturates at long propagation times, giving information on the
localization length. Thus, measurements of this dynamic transverse width provide a very direct way,
which is independent of absorption, of distinguishing between diffusive and localized states [1].
After reviewing our initial experiments and their successful interpretation using the self-consistent
theory of localization [2], I will show how the transverse width evolves with time as frequency is
varied, and a mobility edge, separating extended from localized waves, is crossed. This work is
enabling us to study aspects of classical wave localization near the Anderson transition that have
not been amenable to experimental investigation previously, such as the multifractal spatial
structure of localized wavefunctions [3], long-range and even infinite-range correlations of the
intensity with position and frequency [4], and dynamic backscattering phenomena that reveal, in
addition to the effects of localization on time-dependent coherent backscattering, a surprisingly
large recurrent scattering contribution.
[1] H. Hu, A. Strybulevych, J.H. Page, S.E. Skipetrov and B.A. van Tiggelen, Nature Phys. 4, 945-8
(2008).
[2] N. Cherroret, S.E Skipetrov, and B.A van Tiggelen, Phys. Rev. E 82, 056603 (2010).
[3] S. Faez, Anatoliy Strybulevych, J.H. Page, A. Lagendijk and B.A. van Tiggelen, Phys. Rev. Lett.
103, 155703 (2009).
[4] W.K. Hildebrand, A. Strybulevych, S.E. Skipetrov, B.A. van Tiggelen, and J.H. Page,
arXiv:1303.7042.
Pr. Morchedaï Segev
Anderson Localization of Light and Beyond
Anderson Localization is one of the most basic concepts in solid-state physics. However,
experiments with electronic systems have eluded scientists for many decades. Three decades after
Anderson’s prediction, the concept has been extended to optics, and in 2007, our group has made
the first demonstration of Anderson localization in its original context, where random fluctuations
superimposed upon a periodic structure bring transport to a halt. Many experimental works have
followed, in optics and matter-waves. But can disorder work to increase transport beyond diffusion,
and perhaps even beyond ballistic transport ? The talk will review the recent progress on Anderson
localization of light, and will describe experiments and theory demonstrating disordered–enhanced
transport in photonic quasicrystals, and hyper-transport of light in photonic media with evolving
disorder : a new regime of transport in which an arbitrary wavepacket expands at a rate faster than
ballistic.
Pr. Lihong Wang
Synergy between light and sound : photoacoustic tomography and TRUE optical focusing