Enhanced wave absorption through irregular interfaces

¹  Physique de la Matière Condensée, Ecole Polytechnique, CNRS - 91128 Palaiseau, France, EU
²  CMLA, ENS Cachan, CNRS, UniverSud - 61 Avenue du President Wilson, F-94230 Cachan, France, EU
³  LAMFA, Université de Picardie Jules Vernes CNRS - 80039 Amiens, France, EU

Corresponding author: marcel.filoche@polytechnique.edu

Received: 16 September 2008
Accepted: 26 November 2008

Abstract

The diffraction and absorption of waves by a system with both absorbing properties and irregular geometry is an open physical problem. A more reachable and closely related question is the understanding of wave oscillations in confined systems containing an absorbing material with an irregular shape. This has to be solved to understand why anechoic chambers (electromagnetic or acoustic) do work better with irregular absorbing walls. The answer to this question could also be used in other fields such as light or microwave absorption, or also to improve the performances of break-waters in order to damp sea-waves. It is found here that, in resonators containing an irregular shaped absorbent material, there appears a new type of mode localization. This phenomemon, that we call “astride” localization, describes the fact that these modes exist in both the lossless and the lossy regions. It is these modes that are particularly efficient in dissipating the energy of waves excited in the non-absorbing region.