Publications de Karim Achouri | EPFL Graph Search

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Analog optical signal processing has dramatically transcended the speed and energy limitations accompanied with its digital microelectronic counterparts. Motivated by recent metasurface?s evolution, the angular scattering diversity of a reciprocal passive ...

Bianisotropic metasurfaces empower planarized optical components with subwavelength thicknesses that are not amenable to conventional optics. In particular, bianisotropy gives control over the spatial dispersion and allows engineering of both spectral and ...

Optical metasurfaces rely on subwavelength scale nanostructures, which puts significant constraints on nanofabrication accuracies. These constraints are becoming increasingly important, as metasurfaces are maturing toward real applications that require the ...

The truncated spatial multipolar spectra enable efficient approximate solutions to acoustic, quantum-mechanical, and electromagnetic problems. In photonics, the efficient multipole description of a general emitter or scatterer with controlled accuracy is c ...

The transition matrix, frequently abbreviated as T-matrix, contains the complete information in a linear approximation of how a spatially localized object scatters an incident field. The T-matrix is used to study the scattering response of an isolated obje ...

We review three different approaches for the calculation of electromagnetic multipoles, namely, the Cartesian primitive multipoles, the Cartesian irreducible multipoles, and the spherical multipoles. We identify the latter as the best suited to describe th ...

We propose a theoretical study on the electromagnetic forces resulting from the superposition of TE and TM plane waves interacting with a sphere. Specifically, we first show that, under such an illumination condition, the sphere is subjected to a force tra ...

In this paper, we aim at unveiling the underlying physical mechanism for transversal optical forces, appearing due to the simultaneous illumination of a spherical object with two plane waves possessing different polarizations. The appearance of such a tran ...

Metasurfaces have opened the way for gaining control over the frequency and the polarization responses of electromagnetic waves. However, it is still challenging to control their electromagnetic angular response. Here, the potential of diffractive surfaces ...

While metasurfaces (MSs) are constructed from deeply subwavelength unit cells, they are generally electrically large and full-wave simulations of the complete structure are computationally expensive. Thus, to reduce this high computational cost, nonuniform ...

We look beyond the standard time-average approach and investigate optical forces in the time domain. The formalism is developed for both the Abraham and Minkowski momenta, which appear to converge in the time domain. We unveil an extremely rich - and by fa ...

We aim at providing a global perspective on electromagnetic nonreciprocity and clarifying confusions that arose in recent developments of the field. We provide a general definition of nonreciprocity and classify nonreciprocal systems according to their lin ...

Full wavefront control by photonic components requires that the spatial phase modulation on an incoming optical beam ranges from 0 to 2 pi. Because of their radiative coupling to the environment, all optical components are intrinsically non-Hermitian syste ...

We propose a framework that connects the spatial symmetries of a metasurface to its material parameter tensors and its scattering matrix. This provides a simple and universal way to effortlessly determine the properties of a metasurface scattering response ...

We propose an extensive discussion on the homogenization and scattering analysis of the second-order nonlinear metasurfaces. Our developments are based on the generalized sheet transition conditions (GSTCs) that are used to model the electromagnetic respon ...

The general approach in metasurface design is to find the unit‐cell properties required to achieve a given functionality. This is usually done by modeling the metasurface as a combination of surface electric and magnetic polarization densities, whose param ...

We derive generalized sheet transition conditions (GSTCs) including dipoles and quadrupoles, using generalized functions (distributions). This derivation verifies that the GSTCs are valid for metasurfaces in non-homogeneous environments, such as for practi ...

This article aims at studying the angular scattering properties of bianisotropic metasurfaces and clarifying the different roles played by tangential and normal polarization densities. Different types of metasurfaces are considered for this study and are c ...

We provide a detailed discussion on the electromagnetic modeling and classification of polarization converting bianisotropic metasurfaces. To do so, we first present a general approach to compute the scattering response of suchmetasurfaces, which relies on ...

We provide a self-consistent extension of the Lorentz reciprocity theorem and the Poynting theorem for media possessing electric and magnetic dipolar and quadrupolar responses related to electric and magnetic fields and field gradients thus corresponding t ...

Karim Achouri

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Parallel integro-differential equation solving via multi-channel reciprocal bianisotropic metasurface augmented by normal susceptibilities

Bianisotropic metasurface enables a nonlinear pseudo-diode: asymmetric second-harmonic generation

Robustness Analysis of Metasurfaces: Perfect Structures Are Not Always the Best

The Art of Finding the Optimal Scattering Center(s)

T-matrix representation of optical scattering response: Suggestion for a data format

Multipolar expansions for scattering and optical force calculations beyond the long wavelength approximation

Multipolar origin of electromagnetic transverse force resulting from two-wave interference

Multipolar origin of electromagnetic transverse force resulting from TE/TM wave interference

Symmetry breaking of the angular transmittance by a metagrating

Surface Susceptibilities as Characteristic Models of Reflective Metasurfaces

Electromagnetic forces in the time domain

Electromagnetic Nonreciprocity

Crossing of the Branch Cut: The Topological Origin of a Universal 2 pi-Phase Retardation in Non-Hermitian Metasurfaces

Spatial symmetries in nonlocal multipolar metasurfaces

Homogenization and Scattering Analysis of Second-Harmonic Generation in Nonlinear Metasurfaces

A General Susceptibility‐Based Approach for Uniform Metasurface Scattering

Quadrupolar susceptibility modeling of substrated metasurfaces with application to the generalized Brewster effect

Angular Scattering Properties of Metasurfaces

Fundamental Properties and Classification of Polarization Converting Bianisotropic Metasurfaces

Extension of Lorentz reciprocity and Poynting theorems for spatially dispersive media with quadrupolar responses