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  1. Article ; Online: On the scattering directionality of a dielectric particle dimer of High Refractive Index.

    Barreda, Ángela I / Saleh, Hassan / Litman, Amélie / González, Francisco / Geffrin, Jean-Michel / Moreno, Fernando

    Scientific reports

    2018  Volume 8, Issue 1, Page(s) 7976

    Abstract: Low-losses and directionality effects exhibited by High Refractive Index Dielectric particles make them attractive for applications where radiation direction control is relevant. For instance, isolated metallo-dielectric core-shell particles or ... ...

    Abstract Low-losses and directionality effects exhibited by High Refractive Index Dielectric particles make them attractive for applications where radiation direction control is relevant. For instance, isolated metallo-dielectric core-shell particles or aggregates (dimers) of High Refractive Index Dielectric particles have been proposed for building operational switching devices. Also, the possibility of using isolated High Refractive Index Dielectric particles for optimizing solar cells performance has been explored. Here, we present experimental evidence in the microwave range, that a High Refractive Index Dielectric dimer of spherical particles is more efficient for redirecting the incident radiation in the forward direction than the isolated case. In fact, we report two spectral regions in the dipolar spectral range where the incident intensity is mostly scattered in the forward direction. They correspond to the Zero-Backward condition (also observed for isolated particles) and to a new condition, denoted as "near Zero-Backward" condition, which comes from the interaction effects between the particles. The proposed configuration has implications in solar energy harvesting devices and in radiation guiding.
    Language English
    Publishing date 2018-05-22
    Publishing country England
    Document type Journal Article
    ZDB-ID 2615211-3
    ISSN 2045-2322 ; 2045-2322
    ISSN (online) 2045-2322
    ISSN 2045-2322
    DOI 10.1038/s41598-018-26359-8
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  2. Article ; Online: Electromagnetic polarization-controlled perfect switching effect with high-refractive-index dimers and the beam-splitter configuration.

    Barreda, Ángela I / Saleh, Hassan / Litman, Amelie / González, Francisco / Geffrin, Jean-Michel / Moreno, Fernando

    Nature communications

    2017  Volume 8, Page(s) 13910

    Abstract: Sub-wavelength particles made from high-index dielectrics, either individual or as ensembles, are ideal candidates for multifunctional elements in optical devices. Their directionality effects are traditionally analysed through forward and backward ... ...

    Abstract Sub-wavelength particles made from high-index dielectrics, either individual or as ensembles, are ideal candidates for multifunctional elements in optical devices. Their directionality effects are traditionally analysed through forward and backward measurements, even if these directions are not convenient for in-plane scattering practical purposes. Here we present unambiguous experimental evidence in the microwave range that for a dimer of HRI spherical particles, a perfect switching effect is observed out of those directions as a consequence of the mutual particle electric/magnetic interaction. The binary state depends on the excitation polarization. Its analysis is performed through the linear polarization degree of scattered radiation at a detection direction perpendicular to the incident direction: the beam-splitter configuration. The scaling property of Maxwell's equations allows the generalization of our results to other frequency ranges and dimension scales, for instance, the visible and the nanometric scale.
    Language English
    Publishing date 2017-01-04
    Publishing country England
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ISSN 2041-1723
    ISSN (online) 2041-1723
    DOI 10.1038/ncomms13910
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  3. Article ; Online: Brewster quasi bound states in the continuum in all-dielectric metasurfaces from single magnetic-dipole resonance meta-atoms.

    Abujetas, Diego R / Barreda, Ángela / Moreno, Fernando / Sáenz, Juan J / Litman, Amelie / Geffrin, Jean-Michel / Sánchez-Gil, José A

    Scientific reports

    2019  Volume 9, Issue 1, Page(s) 16048

    Abstract: Bound states in the continuum (BICs) are ubiquitous in many areas of physics, attracting special interest for their ability to confine waves with infinite lifetimes. Metasurfaces provide a suitable platform to realize them in photonics; such BICs are ... ...

    Abstract Bound states in the continuum (BICs) are ubiquitous in many areas of physics, attracting special interest for their ability to confine waves with infinite lifetimes. Metasurfaces provide a suitable platform to realize them in photonics; such BICs are remarkably robust, being however complex to tune in frequency-wavevector space. Here we propose a scheme to engineer BICs and quasi-BICs with single magnetic-dipole resonance meta-atoms. Upon changing the orientation of the magnetic-dipole resonances, we show that the resulting quasi-BICs, emerging from the symmetry-protected BIC at normal incidence, become transparent for plane-wave illumination exactly at the magnetic-dipole angle, due to a Brewster-like effect. While yielding infinite Q-factors at normal incidence (canonical BIC), these are termed Brewster quasi-BICs since a transmission channel is always allowed that slightly widens resonances at oblique incidences. This is demonstrated experimentally through reflectance measurements in the microwave regime with high-refractive-index mm-disk metasurfaces. Such Brewster-inspired configuration is a plausible scenario to achieve quasi-BICs throughout the electromagnetic spectrum inaccessible through plane-wave illumination at given angles, which could be extrapolated to other kind of waves.
    Language English
    Publishing date 2019-11-05
    Publishing country England
    Document type Journal Article
    ZDB-ID 2615211-3
    ISSN 2045-2322 ; 2045-2322
    ISSN (online) 2045-2322
    ISSN 2045-2322
    DOI 10.1038/s41598-019-52223-4
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  4. Article: Two-dimensional inverse profiling problem using phaseless data.

    Litman, Amélie / Belkebir, Kamal

    Journal of the Optical Society of America. A, Optics, image science, and vision

    2006  Volume 23, Issue 11, Page(s) 2737–2746

    Abstract: We discuss the characterization of two-dimensional targets based on their diffracted intensity. The target characterization is performed by minimizing an adequate cost functional, combined with a level-set representation if the target is homogeneous. One ...

    Abstract We discuss the characterization of two-dimensional targets based on their diffracted intensity. The target characterization is performed by minimizing an adequate cost functional, combined with a level-set representation if the target is homogeneous. One key issue in this minimization is the choice of an updating direction, which involves the gradient of the cost functional. This gradient can be evaluated using a fictitious field, the solution of an adjoint problem in which receivers act as sources with a specific amplitude. We explore the Born approximation for the adjoint field and compare various approaches for a wide variety of objects.
    Language English
    Publishing date 2006-09-01
    Publishing country United States
    Document type Journal Article
    ZDB-ID 283633-6
    ISSN 1520-8532 ; 1084-7529 ; 0740-3232
    ISSN (online) 1520-8532
    ISSN 1084-7529 ; 0740-3232
    DOI 10.1364/josaa.23.002737
    Database MEDical Literature Analysis and Retrieval System OnLINE

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    In stock of ZB MED Cologne/Königswinter

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  5. Article ; Online: Small Dielectric Spheres with High Refractive Index as New Multifunctional Elements for Optical Devices.

    Tribelsky, Michael I / Geffrin, Jean-Michel / Litman, Amelie / Eyraud, Christelle / Moreno, Fernando

    Scientific reports

    2015  Volume 5, Page(s) 12288

    Abstract: The future of ultra-fast optical communication systems is inevitably connected with progress in optical circuits and nanoantennas. One of the key points of this progress is the creation of elementary components of optical devices with scattering diagrams ...

    Abstract The future of ultra-fast optical communication systems is inevitably connected with progress in optical circuits and nanoantennas. One of the key points of this progress is the creation of elementary components of optical devices with scattering diagrams tailored for redirecting the incident light in a desired manner. Here we demonstrate theoretically and experimentally that a small, simple, spatially homogeneous dielectric subwavelength sphere with a high refractive index and low losses (as some semiconductors in the visible or near infrared region) exhibits properties allowing to utilize it as a new multifunctional element for the mentioned devices. This can be achieved by taking advantage of the coherent effects between dipolar and multipolar modes, which produce anomalous scattering effects. The effects open a new way to control the directionality of the scattered light. The directional tuning can be obtained in a practical way just by a change in the frequency of the incident wave, and/or by a well-chosen diameter of the sphere. Dielectric nanoparticles with the required optical properties in the VIS-NIR may be now readily fabricated. These particles could be an efficient alternative to the widely discussed scattering units with a more complicated design.
    Language English
    Publishing date 2015-07-23
    Publishing country England
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 2615211-3
    ISSN 2045-2322 ; 2045-2322
    ISSN (online) 2045-2322
    ISSN 2045-2322
    DOI 10.1038/srep12288
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  6. Article ; Online: Polarization effects in 3D vectorial-induced current reconstructions.

    Eyraud, Christelle / Vaillon, Rodolphe / Litman, Amélie / Geffrin, Jean-Michel / Merchiers, Olivier

    Journal of the Optical Society of America. A, Optics, image science, and vision

    2013  Volume 30, Issue 10, Page(s) 1967–1974

    Abstract: In tomography algorithms, the complex amplitude scattering matrix corresponds to the input parameter. When considering 3D targets, the scattering matrix now contains vectorial information. Thus, this scattering matrix might be calculated with various ... ...

    Abstract In tomography algorithms, the complex amplitude scattering matrix corresponds to the input parameter. When considering 3D targets, the scattering matrix now contains vectorial information. Thus, this scattering matrix might be calculated with various polarization projections. Moreover, when dealing with experimental data, we are almost every time faced with truncated data. We focus here on the impact of selecting parts of the amplitude scattering matrix elements versus others and in particular on the influence of the polarization choices on the imaging results. In order to better apprehend the physical content associated to each polarization term, the study is conducted with a simple vectorial-induced current reconstruction algorithm allowing reconstruction of qualitative maps of the scene. This algorithm is applied on scaled models of aggregates combined with experimental scattered fields acquired in the microwave frequency range.
    Language English
    Publishing date 2013-10-01
    Publishing country United States
    Document type Journal Article
    ZDB-ID 283633-6
    ISSN 1520-8532 ; 1084-7529 ; 0740-3232
    ISSN (online) 1520-8532
    ISSN 1084-7529 ; 0740-3232
    DOI 10.1364/JOSAA.30.001967
    Database MEDical Literature Analysis and Retrieval System OnLINE

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    In stock of ZB MED Cologne/Königswinter

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  7. Article: Phaseless imaging with experimental data: facts and challenges.

    D'Urso, Michele / Belkebir, Kamal / Crocco, Lorenzo / Isernia, Tommaso / Litman, Amélie

    Journal of the Optical Society of America. A, Optics, image science, and vision

    2007  Volume 25, Issue 1, Page(s) 271–281

    Abstract: Two-dimensional target characterization using inverse profiling approaches with total-field phaseless data is discussed. Two different inversion schemes are compared. In the first one, the intensity-only data are exploited in a minimization scheme, ... ...

    Abstract Two-dimensional target characterization using inverse profiling approaches with total-field phaseless data is discussed. Two different inversion schemes are compared. In the first one, the intensity-only data are exploited in a minimization scheme, thanks to a proper definition of the cost functional. Specific normalization and starting guess are introduced to avoid the need for global optimization methods. In the second scheme [J. Opt. Soc. Am. A21, 622 (2004)], one exploits the field properties and the theoretical results on the inversion of quadratic operators to derive a two-step solution strategy, wherein the (complex) scattered fields embedded in the available data are retrieved first and then a traditional inverse scattering problem is solved. In both cases, the analytical properties of the fields allow one to properly fix the measurement setup and identify the more convenient strategy to adopt. Also, indications on the number and types of sources and receivers to be used are given. Results from experimental data show the efficiency of these approaches and the tools introduced.
    Language English
    Publishing date 2007-11-06
    Publishing country United States
    Document type Journal Article
    ZDB-ID 283633-6
    ISSN 1520-8532 ; 1084-7529 ; 0740-3232
    ISSN (online) 1520-8532
    ISSN 1084-7529 ; 0740-3232
    DOI 10.1364/josaa.25.000271
    Database MEDical Literature Analysis and Retrieval System OnLINE

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    In stock of ZB MED Cologne/Königswinter

    Zs.B 2689: Show issues Location:
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