Superlentille | EPFL Graph Search

Une superlentille est une lentille optique élaborée avec des métamatériaux et permettant de distinguer des détails jusqu'à vingt fois inférieurs à la longueur d'onde d'utilisation. Une lentille classique est dite « limitée par la diffraction », c'est-à-dire que l'image la plus petite que l'on pourra obtenir sera toujours une tache d'Airy et donc possède un diamètre dépendant du diamètre de la lentille et de la longueur d'onde d'utilisation, limitant l'utilisation de lentilles classiques en verre optique à l'observation d'objet de quelques centaines de nanomètres. De manière à distinguer des objets de l'ordre du nanomètre, il est nécessaire d'utiliser un microscope électronique à balayage. Historique La possibilité de réaliser des superlentilles avait été prédite en 2000 par le physicien John Pendry qui avait expliqué que les métamatériaux dont l'indice de réfraction est négatif pourraient amplifier et focaliser les ondes dites évanescentes. Une première expérience en 200

Chiral Metamaterials for a Robust Waveguiding Scheme

Romain Christophe Rémy Fleury, Nadège Sihame Kaïna, Bakhtiyar Orazbayev

Recent advances in the field of metamaterials have shown that waves can be efficiently manipulated at the subwavelength scale through the interactions with an ensemble of resonant inclusions, opening new horizons in overcoming the size limits of devices which are often tied to the wavelength of operation [1]. Such size limit is crucial for many applications where the overall dimensions are required to be as small as possible, for instance cost-eﬃcient devices for satellite communications. Unfortunately, the resonant inclusions of these artificial media result in a large sensitivity of the propagation to geometrical imperfections and disorder-induced backscattering, reducing their performance. More recently, it has been demonstrated that the topological concepts which originated in solid-state physics can be transferred to not only to photonic crystals [3,4], which still scale with the operating wavelength, but also to locally-resonant crystalline metamaterials, which can have a deeply subwavelength structure [5]. However, since the topological properties in such time-reversal invariant designs heavily rely on the lattice structure of the media and frequency dispersion of the metamaterial, they are inevitably sensitive to any disruption of the lattice symmetries that can couple time-reversed modes. Moreover, since most of disorders (in the location or in resonance frequency of the resonant inclusions) will most likely break the lattice symmetry and disrupt the wave propagation, these time-reversal invariant topological designs are also in principle sensitive to defects. In this talk, we will show that a chiral metamaterial [6,7] can be exploited to create a robust-to-disorder subwavelength waveguide and we will demonstrate this possibility experimentally in the microwave regime. Moreover, we will quantitatively demonstrate the superior robustness of the proposed design to both spatial or frequency disorders by performing ensemble averages on disorder realizations along the path of the guided wave, and comparing them with previously proposed subwavelength waveguide designs: frequency defect lines, symmetry-based topological edge modes and valley interface states. [1] J. D. Joannopoulos, S. G. Johnson, J. N. Winn, and R. D. Meade, Photonic Crystals: Molding the Flow of Light (Princeton University Press, Princeton, 2008), 2nd ed. [2] N. Kaina, F. Lemoult, M. Fink, and G. Lerosey, Negative Refractive Index and Acoustic Superlens from Multiple Scattering in Single Negative Metamaterials, Nature, 525, 77 (2015). [3] S. Raghu and F. D. M. Haldane, Analogs of Quantum-Hall-Effect Edge States in Photonic Crystals, Phys. Rev. A - At. Mol. Opt. Phys., 78, 1 (2008). [4] Z. Wang, Y. Chong, J. D. Joannopoulos, and M. Soljacić, Observation of Unidirectional Backscattering-Immune Topological Electromagnetic States., Nature, 461, 772 (2009). [5] S. Yves, R. Fleury, T. Berthelot, M. Fink, F. Lemoult, and G. Lerosey, Crystalline Metamaterials for Topological Properties at Subwavelength Scales, Nat. Commun., 8, 16023 (2017). [6] M. Goryachev and M. E. Tobar, Reconfigurable Microwave Photonic Topological Insulator, Phys. Rev. Appl., 6, 1 (2016). [7] J. E. Vázquez-Lozano and A. Martínez, Optical Chirality in Dispersive and Lossy Media, Phys. Rev. Lett., 121, 43901 (2018).

2019

Enhancing subwavelength image recognition with resonant metamaterial lenses

Romain Christophe Rémy Fleury, Bakhtiyar Orazbayev

In this work, we discuss our recent research advances in the field of subwavelength image recognition using deep learning tools. We show that combining locally-resonant metamaterial lenses with a deep learning technique that uses a multi-layered artiﬁcial neural network allows for direct recognition of subwavelength objects from an observer in the far-field, without complex calibration procedures. We will discuss the physics of deeply subwavelength image recognition, and the possibility to tailor the metamaterial lens to increase the conversion of evanescent fields to propagating fields that can reach the far field enhance the image recognition to 80% accuracy for objects as small as λ/10.

2019

Tetradymites as Natural Hyperbolic Materials for the Near-Infrared to Visible

Moritz Esslinger, Pascal Gehring, Klaus Kern

Hyperbolic media exhibit unparalleld properties, e.g, as light absorbers in photovoltaics and photonics, as superlenses in far-field imaging, as subwavelength light concentrators in nanolithography, or as novel materials in emission engineering. With the advent of optical metamaterials, deliberate design of material properties became possible. However, inadvertent variability in fabrication techniques and other factors limit performance characteristics of man-made hyperbolic materials. Here, we draw attention to a class of natural hyperbolic materials, the tetradymites. From generalized spectroscopic ellipsometry we extract the dielectric tensor components and find hyperbolic behavior in Bi2Se3 and Bi2Te3 in the near-infrared to visible spectrum. Previously, natural hyperbolic media were known only in the far-infrared spectral range. As possible applications of tetradymites we discuss superlenses for near-field microscopy and far-field isoindex filters. Solid solutions of tetradymites are likely tunable in operational wavelength from the infrared to the visible, complementing hyperbolic metamaterials.

Amer Chemical Soc2014

Chiral Metamaterials for a Robust Waveguiding Scheme

Romain Christophe Rémy Fleury, Nadège Sihame Kaïna, Bakhtiyar Orazbayev

2019