Publications de Karim Achouri | EPFL Graph Search

Publications associées (51)

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

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 ...

2019

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

Olivier Martin, Karim Achouri, Andrei Kiselev, Sergejs Boroviks

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 ...

2024

Dynamics of optical forces and torques in plasmonic systems: a surface integral equation

Olivier Martin, Karim Achouri, Andrei Kiselev

A novel approach is introduced to determine the time evolution of optical forces and torques on arbitrary shape nanostructures by combining Maxwell's stress tensor with the surface integral equation method (SIE). Conventional time averaging of Maxwell’s st ...

SPIEDigitalLibrary2020

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

Olivier Martin, Karim Achouri, Hsiang-Chu Wang

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 ...

AMER CHEMICAL SOC2022

The Art of Finding the Optimal Scattering Center(s)

Karim Achouri

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 ...

WILEY-V C H VERLAG GMBH2024

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

Karim Achouri

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 ...

2025

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

Olivier Martin, Karim Achouri, Andrei Kiselev, Marco Riccardi

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 ...

AMER PHYSICAL SOC2022

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

Olivier Martin, Karim Achouri, Andrei Kiselev

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 ...

AMER PHYSICAL SOC2020

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

Olivier Martin, Karim Achouri, Andrei Kiselev

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 ...

2021

Symmetry breaking of the angular transmittance by a metagrating

Olivier Martin, Karim Achouri

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 ...

SPIE2024

Surface Susceptibilities as Characteristic Models of Reflective Metasurfaces

Karim Achouri, Shourya Dutta Gupta, Ville Tuovi Tiukuvaara

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 ...

IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC2022

Electromagnetic forces in the time domain

Olivier Martin, Karim Achouri, Andrei Kiselev

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 ...

Optica Publishing Group2022

Electromagnetic Nonreciprocity

Karim Achouri, Christophe Caloz

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 ...

American Physical Society (APS)2018

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

Olivier Martin, Karim Achouri

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 ...

WILEY-V C H VERLAG GMBH2023

Spatial symmetries in nonlocal multipolar metasurfaces

Olivier Martin, Karim Achouri, Ville Tuovi Tiukuvaara

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 ...

SPIE-SOC PHOTO-OPTICAL INSTRUMENTATION ENGINEERS2023

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

Olivier Martin, Karim Achouri, Jérémy Butet, Gabriel David Bernasconi

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 ...

2018

A General Susceptibility‐Based Approach for Uniform Metasurface Scattering

Karim Achouri, Francisco Sebastian Cuesta Soto

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 ...

Wiley2025

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

Olivier Martin, Karim Achouri, Ville Tuovi Tiukuvaara

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 ...

Optica Publishing Group2023

Optical Force Control Using Phase-Gradient Metasurfaces

Olivier Martin, Karim Achouri, Hsiang-Chu Wang

We propose to control the motion of nanoparticles using phase-gradient metasurfaces. The latter are used to generate surface waves, which put the particles into motion, when illuminated by a normally incident plane wave. We present an initial study of the ...

IEEE2018

Angular Scattering Properties of Metasurfaces

Olivier Martin, Karim Achouri

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 ...

2020