Publications de Karim Achouri | EPFL Graph Search

The Art of Finding the Optimal Scattering Center(s) (Advanced Optical Materials 4/2025)

Wiley2025

Angle-invariant scattering in metasurfaces

Metasurfaces are efficient and versatile electromagnetic structures that have already enabled the implementation of a wide range of microwave and photonic wave shaping applications. Despite the extensive research into metasurfaces, a rigorous and comprehen ...

American Physical Society (APS)2025

A General Susceptibility‐Based Approach for Uniform Metasurface Scattering

Karim Achouri

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

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

Optimal Poloidal Multipole Expansion Centres

Karim Achouri

Resonant optical response is one of the key effects in nanophotonic structures. The characterization of the fundamental resonance metrics, quality factor, electric or magnetic field localization, polarization, and chirality, is often built on a multipolar ...

IEEE Computer Society2024

Pulling force enabled by unlocking the optical phase

Olivier Martin, Karim Achouri, Andrei Kiselev, Siarhei Zavatski

We demonstrate the possibility of achieving an optical pulling force without complex beam-shaping techniques. By using optical pulses detuned from the resonant frequency of the structure, we create conditions in which the spectral maxima of the excited cur ...

Cambridge University Press (CUP)2024

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

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

Roadmap on photonic metasurfaces

Karim Achouri

Here we present a roadmap on Photonic metasurfaces. This document consists of a number of perspective articles on different applications, challenge areas or technologies underlying photonic metasurfaces. Each perspective will introduce the topic, present a ...

AIP American Institute of Physics2024

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

Demonstration of a Plasmonic Nonlinear Pseudodiode

Olivier Martin, Karim Achouri, Andrei Kiselev, Sergejs Boroviks

We demonstrate a nonlinear plasmonic metasurface that exhibits strongly asymmetric second-harmonic generation: nonlinear scattering is efficient upon excitation in one direction, and it is substantially suppressed when the excitation direction is reversed, ...

AMER CHEMICAL SOC2023

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

Bianisotropic metasurface for asymmetric second-sarmonic generation: a nonlinear plasmonic pseudo-diode

Olivier Martin, Karim Achouri, Andrei Kiselev, Sergejs Boroviks

2023

Asymmetric phase modulation of light with parity-symmetry broken metasurfaces

Jean-Yves Duboz, Karim Achouri

The design of wavefront-shaping devices is conventionally approached using real-frequency modeling. However, since these devices interact with light through radiative channels, they are by default non-Hermitian objects having complex eigenvalues (poles and ...

Optica Publishing Group2023

Multipolar Pseudochirality-Induced Optical Torque

Olivier Martin, Karim Achouri, Mintae Chung, Andrei Kiselev

It has been observed that achiral nanoparticles, such as flat helices, may be subjected to an optical torque even when illuminated by normally incident linearly polarized light. However, the origin of this fascinating phenomenon has so far remained mostly ...

Amer Chemical Soc2023

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

Multipolar Modeling of Spatially Dispersive Metasurfaces

Olivier Martin, Karim Achouri, Ville Tuovi Tiukuvaara

There is today a growing need to accurately model the angular scattering response of metasurfaces for optical analog processing applications. However, the current metasurface modeling techniques are not well suited for such a task since they are limited to ...

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

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