Physique sublongueur d’onde (SWAP)

Réseau de résonateurs acoustiques de Helmoltz

Coordinateurs

Sébastien BIDAULT

Tél. : 01 80 96 30 49

Yannick DE WILDE

Tél. : 01 80 96 30 84

Actualités

Topology optimization for microwave control with reconfigurable intelligent metasurfaces in complex media Karamanos, T. D., M. Fink, and F. Lemoult Physical Review Applied 21, no. 4 (2024) Résumé: Reconfigurable intelligent metasurfaces have been proposed as an efficient solution for improving wireless telecommunication systems in multiple-scattering or reverberating media. Concurrently, topology optimization has been successfully used as an inverse-design technique in many fields, and particularly in electromagnetics. In this work, we apply a gradient-based topology optimization for tuning the binary elements of a metasurface for a focusing goal in a complex environment. First, the metasurface unit cells are approximated as point sources and, then, the optimization problem is formulated. Afterwards, the proposed method is applied to find the optimal parameter sets for three distinct environments of increasing complexity, and the resulting focus for each case is demonstrated via numerical simulations. The combination of a reverberating cavity and a metasurface inside the latter is very powerful since everything can be solved analytically for focusing outside the cavity.
Dynamic structured illumination for confocal microscopy Nœtinger, G., F. Lemoult, and S. M. Popoff Optics Letters 49, no. 5, 1177-1180 (2024) Résumé: Structured illumination enables the tailoring of an imaging device’s optical transfer function to enhance resolution. We propose the incorporation of a temporal periodic modulation, specifically a rotating mask, to encode multiple transfer functions in the temporal domain. This approach is demonstrated using a confocal microscope configuration. At each scanning position, a temporal periodic signal is recorded. By filtering around each harmonic of the rotation frequency, multiple images of the same object can be constructed. The image carried by the nth harmonic is a convolution of the object with a phase vortex of topological charge n, similar to the outcome when using a vortex phase plate as an illumination. This enables the collection of chosen high spatial frequencies from the sample, thereby enhancing the spatial resolution of the confocal microscope.
Viscoelastic dynamics of a soft strip subject to a large deformation Delory, A., D. A. Kiefer, M. Lanoy, A. Eddi, Prada C., and F. Lemoult Soft Matter (2024) Résumé: To produce sounds, we adjust the tension of our vocal folds to shape their properties and control the pitch. This efficient mechanism offers inspiration for designing reconfigurable materials and adaptable soft robots. However, understanding how flexible structures respond to a significant static strain is not straightforward. This complexity also limits the precision of medical imaging when applied to tensioned organs like muscles, tendons, ligaments and blood vessels among others. In this article, we experimentally and theoretically explore the dynamics of a soft strip subject to a substantial static extension, up to 180%. Our observations reveal a few intriguing effects, such as the resilience of certain vibrational modes to a static deformation. These observations are supported by a model based on the incremental displacement theory. This has promising practical implications for characterizing soft materials but also for scenarios where external actions can be used to tune properties.

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Présentation du thème

Le thème SWAP étudie les interactions onde-matière aux échelles sub-longueur d’onde (sub-𝜆) afin, non seulement, d’optimiser ces interactions mais aussi d’ouvrir de nouveaux degrés de liberté pour la manipulation des ondes (par le développement de métasurfaces et de métamatériaux) ou pour imager la matière à des échelles inférieures à la limite de diffraction (imagerie super-résolue). Les briques élémentaires, que ce soit pour des ondes électromagnétiques ou mécaniques, avec des longueurs d’onde nanométriques, micrométriques ou centimétriques, sont des résonateurs sub-𝜆. Ces morceaux de matière peuvent aussi bien être des émetteurs quantiques et des nanoparticules métalliques ou diélectriques en optique, des antennes en micro-ondes que des bulles ou certains résonateurs de Helmholtz en acoustique. Le thème SWAP s’intéresse à la conception et à l’étude de ces résonateurs à l’échelle individuelle, à la conception de métasurfaces et de métamatériaux en organisant ces derniers de manière régulière ou désordonnée, et à l’utilisation de résonateurs comme agents de contraste en imagerie super-résolue.

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