Benjamin Vial

Benjamin Vial
Imperial College London | Imperial · Department of Mathematics

PhD

About

34
Publications
7,796
Reads
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376
Citations
Introduction
My research interests include metamaterials, Transformation Optics, homogenization techniques, topology optimization, resonant phenomena in Electromagnetics, light-matter interaction, Numerical modelling (FEM, FDTD, RCWA) and modal analysis, for applications in Optics, Photonics and microwave engineering.
Additional affiliations
July 2014 - present
Queen Mary, University of London
Position
  • PostDoc Position
May 2013 - January 2014
Institut Fresnel
Position
  • PostDoc Position
October 2009 - April 2013
Aix-Marseille Université
Position
  • PhD Student

Publications

Publications (34)
Article
The design of photonic devices is usually done through analytical modeling or variation in geometry and material parameters to obtain the required functionalities. Here, we report the use of topology optimization to obtain a bi-focal lens that concentrates the electromagnetic field at different spatial positions depending on the wavelength. Numeric...
Article
Composites with subwavelength features exhibit effective properties that depend on microstructure morphology and materials, which can be adjusted to obtain enhanced characteristics. We detail the systematic design of electromagnetic metamaterials composed of dielectric inclusions in a ferroelectric matrix that, under an applied voltage, present an...
Article
We investigate numerically the homogenized permittivities of composites made of low-index dielectric inclusions in a ferroelectric matrix under a static electric field. A refined model is used to take into account the coupling between the electrostatic problem and the electric field dependent permittivity of the ferroelectric material, leading to a...
Preprint
We investigate the homogenized permittivity of ferroelectric-dielectric mixtures under a static electric field. A refined model is used to take into account the coupling between the electrostatic problem and the electric field dependent permittivity of the ferroelectric material. Periodic and random structures in one and two dimensions are investig...
Article
Full-text available
The beam-steering capabilities of a simplified flat Luneburg lens are reported at 60 GHz. The design of the lens is first described, using transformation electromagnetics, before discussion of the fabrication of the lens using casting of ceramic composites. The simulated beam-steering performance is shown, demonstrating that the lens, with only six...
Article
Full-text available
In this article we propose a new design methodology to control both amplitude and phase of electromagnetic waves from cylindrical incidence, which utilizes engineered media that does not resort to transformation optics or its quasi-conformal approximations. This method can lead to two-dimensional isotropic, inhomogeneous material profiles of permit...
Article
Full-text available
We report the design, fabrication and experimental verification of an illusion device working at microwave frequencies. A two dimensional topology optimization procedure is employed to find the binary layout of a dielectric coating that, when wrapped around a metallic cylinder, mimics the scattering from a predefined, arbitrarily-shaped dielectric...
Article
Full-text available
We propose a general method to arbitrarily manipulate an electromagnetic wave propagating in a two-dimensional medium, without introducing any scattering. This leads to a whole class of isotropic spatially varying permittivity and permeability profiles that are invisible while shaping the field magnitude and/or phase. In addition, we propose a meta...
Article
Full-text available
We develop a model for the coupling of quasi-normal modes in open photonic systems consisting of two resonators. By expressing the modes of the coupled system as a linear combination of the modes of the individual particles, we obtain a generalized eigenvalue problem involving small size dense matrices. We apply this technique to a 2D problem of a...
Article
Full-text available
We present the design of an all-dielectric cloaking device at microwave frequencies. A gradient based topology optimization is employed to find a dielectric permittivity distribution that minimizes the diffracted field in free space. The layout is binary, i.e. made either of standard ABS plastic or air and is designed to reduce the scattering from...
Article
Full-text available
We present the design of infrared filters for multispectral imaging applications, based on square annular aperture arrays in a thin gold film. These structures function as band pass filters with large bandwidth and high transmission at resonance. A modal analysis based on the Finite Element Method (FEM) is performed to obtain quickly the features o...
Article
Full-text available
In the present paper, we show that it is possible to use a periodic structure of disconnected elements (e.g. a line of rods) to guide electromagnetic waves, in the direction of the periodicity. To study such segmented waveguides, we use the concept of quasimodes associated to complex frequencies. The numerical determination of quasimodes is based o...
Article
Subwavelength sized dielectric Mie resonators have recently emerged as a promising photonic platform as they combine the advantages of dielectric microstructures and metallic nanoparticles supporting surface plasmon polaritons. Here, we report the capabilities of a dewetting-based process, independent on the sample size, to fabricate Si-based reson...
Article
Full-text available
We consider arrays of square coaxial apertures in a gold layer and study their diffractive behavior in the far infrared region. These structures exhibit a resonant transmission enhancement that is used to design tunable bandpass filters. We provide a study of their spectral features and show by a modal analysis that the resonance peak is due to the...
Article
Full-text available
We present a modal analysis of metal-insulator-metal (MIM) based metamaterials in the far infrared region. These structures can be used as resonant reflection bandcut spectral filters that are independent of the polarization and direction of incidence because of the excitation of quasimodes (modes associated with a complex frequency) leading to qua...
Article
Full-text available
A quasimodal expansion method (QMEM) is developed to model and understand the scattering properties of arbitrary shaped two-dimensional (2-D) open structures. In contrast with the bounded case which have only discrete spectrum (real in the lossless media case), open resonators show a continuous spectrum composed of radiation modes and may also be c...
Article
Full-text available
Infrared imaging is nowadays growing rapidly due to large-scale production of uncooled detectors. One of the potential evolution of these sensors is to integrate optical filtering capabilities to realize images on several spectral bands, allowing to extract information such as the chemical composition of the observed scene. In this thesis, we discu...
Article
Full-text available
In this chapter, we demonstrate a general formulation of the Finite Element Method allowing to calculate the diffraction efficiencies from the electromagnetic field diffracted by arbitrarily shaped gratings embedded in a multilayered stack lightened by a plane wave of arbitrary incidence and polarization angle. It relies on a rigorous treatment of...
Article
Full-text available
We describe the absorption by the walls of a quantum electrodynamics cavity as a process during which the elementary excitations (photons) of an internal mode of the cavity exit by tunneling through the cavity walls. We estimate by classical methods the survival time of a photon inside the cavity and the quality factor of its mirrors.
Article
Full-text available
We propose an Adaptive Perfectly Matched Layer (APML) to be used in diffraction grating modeling. With a properly tailored co-ordinate stretching depending both on the incident field and on grating parameters, the APML may efficiently absorb diffracted orders near grazing angles (the so-called Wood's anomalies). The new design is implemented in a f...
Conference Paper
Full-text available
This paper presents the Perfectly Matched Layers (PMLs) in the framework of transformation optics as a complex-valued change of coordinates. PMLs provide the suitable operator extensions required for the quasi-mode analysis of open problems. Leaky modes in open dielectric waveguides and spectral analysis of diffraction gratings are considered here.
Conference Paper
Full-text available
This paper presents the Perfectly Matched Layers (PMLs) in the framework of transformation optics as a complex-valued change of coordinates. PMLs provide the suitable operator extensions required for the leaky mode computation of open waveguides and the quasi-mode computation of scattering problems. Quasi-modes of diffraction gratings are considere...
Article
Full-text available
We analyze diffraction gratings via their resonances by a direct determination of the eigenmodes and the complex eigenfrequencies using a finite element method (FEM), that allows to study mono‐ or bi‐periodic gratings with a maximum versatility : complex shaped patterns, with anisotropic and graded index material, under oblique incidence and arbi...
Article
Full-text available
Our approach consists in finding the eigenmodes and the complex eigenfrequencies of structures using a finite element method (FEM), that allows us to study mono- or bi-periodic gratings with a maximum versatility : complex shaped patterns, with anisotropic and graded index material, under oblique incidence and arbitrary polarization. In order to va...

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