Publications by Karim Achouri | EPFL Graph Search

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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

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

Asymmetric phase modulation of light with parity-symmetry broken metasurfaces

Karim Achouri, Jean-Yves Duboz

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 ...

Washington2023

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

Modeling of second-order nonlinear metasurfaces

Olivier Martin, Karim Achouri, Andrei Kiselev

We present a frequency-domain modeling technique for second-order nonlinear metasurfaces. The technique is derived from the generalized sheet transition conditions (GSTCs), which have been so far mostly used for modeling linear metasurfaces. In this work, ...

IOP Publishing Ltd2022

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

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