Dr. Kofi Edee

Innovation in nanophotonics currently relies on human experts who synergize specialized knowledge in photonics and coding with simulation and optimization algorithms, entailing design cycles that are time-consuming, computationally demanding, and frequently suboptimal. We introduce MetaChat, a multi-agentic design framework that can translate semantically described photonic design goals into high-performance, freeform device layouts in an automated, nearly real-time manner. Multistep reasoning is enabled by our Agentic Iterative Monologue paradigm, which coherently interfaces agents with code-based tools, other specialized agents, and human designers. Design acceleration is facilitated by Feature-wise Linear Modulation–conditioned Maxwell surrogate solvers that support the generalized evaluation of metasurface structures. We use freeform dielectric metasurfaces as a model system and demonstrate with MetaChat the design of multiobjective, multiwavelength metasurfaces orders of magnitude faster than conventional methods. These concepts present a scientific computing blueprint for using specialist design agents, surrogate solvers, and human interactions to drive multiphysics innovation and discovery.

10 May 2022 in Optics Continuum

Journal Article

Semi-analytical model for the analysis of a magnetically biased 1D subwavelength graphene-strip-grating

Maha Ben Rhouma

Brahim Guizal

Pierre Bonnet

Françoise Paladian

Kofi Edee

We propose a simple semi analytical model that allows to compute the transmittance and reflectance of a one dimensional subwavelength graphene strip grating under an external static magnetic field. In this model graphene is treated as an anisotropic layer with atomic thickness and a frequency dependent complex permittivity tensor. The model is based on an effective medium approach (EMA) and a rigorous phase correction. The scattering matrix approach is also used to take into account the different resonant phenomena occurring in the structure. The approach is validated against the Polynomial Modal Method (PMM) through numerical examples.

5 February 2019 in OSA Continuum

Journal Article

Understanding the plane wave excitation of the metal-insulator-metal gap plasmon mode of a nanoribbons periodic array: role of insulator-metal-insulator lattice mode

Kofi Edee

A simple semi-analytical single mode model describing the mechanism of metal-insulator-metal gap plasmon mode excitation by a plane wave is proposed. The role of the insulator-metal-insulator (IMI) lattice mode is highlighted. Although many other works addressed this issue, the crucial role of this mode has never been demonstrated before. This mode appears as the missing link that ensures energy transfer between the incident plane wave and the metal-insulator-metal (MIM) gap plasmon mode. In this single mode model, the grating layer, the host layer of the IMI lattice mode, is viewed as an effective homogeneous medium, and the scattering matrix characterizing the interaction between the IMI lattice mode and the MIM gap plasmon mode is easily computed. The proposed simplified model allows us to grasp the physical origin of the modes of the system and to predict accurately the resonance frequencies of the 1D structure. These modes are classified in symmetric and antisymmetric modes. The incident field, by its symmetry properties, acts on the system as a selection rule, activating a class of modes with the same symmetry properties as itself.

1 October 2018 in OSA Continuum

Journal Article

Single mode approach with versatile surface wave phase correction for the extraordinary optical transmission comprehension of 1D period nano-slits arrays

Kofi Edee

A simple semi-analytical model for the comprehension of the extraordinary optical transmission of a 1D array of periodic subwavelength slit is proposed. In this single mode model, the mono layer of the perforated metal film is considered as a homogeneous medium. Therefore, the electromagnetic response of this structure to a plane wave excitation is equivalent to that of a slab with homogeneous equivalent permittivity. A versatile phase correction is added to this model in order to handle the contribution of surface waves in the EOT phenomenon. The proposed model leads to a cavity-like dispersion relation that allows accurate prediction of the resonance frequencies of the 1D structure.

22 March 2018 in Journal of the Optical Society of America A

Journal Article

Matched coordinates in the framework of polynomial modal methods for complex metasurface modeling

Kofi Edee

J.-P. Plumey

A. Moreau

B. Guizal

The polynomial modal method (PMM) is one of the most powerful methods for modeling diffraction from lamellar gratings. In the present work, we show that applying it to the so-called matched coordinates leads to important improvement of convergence for crossed lamellar gratings with patterns that are not parallel to the coordinates’ axes. After giving the new formulation of the PMM under matched coordinates in the general framework of biperiodic structures, we provide numerical examples to demonstrate the effectiveness of the proposed approach.

19 March 2019 in OSA Continuum

Journal Article

Coupling between subwavelength nano-slit lattice modes and metal-insulator-graphene cavity modes: a semi-analytical model

Kofi Edee

Maha Benrhouma

Mauro Antezza

Jonathan Albert Fan

Brahim Guizal

We present a semi-analytical model of the resonance phenomena occurring in a hybrid system made of a 1D array of periodic subwavelength slits deposited on an insulator/graphene layer. We show that the spectral response of this hybrid system can be fully explained by a simple semi-analytical model based on weak and strong couplings between two elementary sub-systems. The first elementary sub-system consists of a 1D array of periodic subwavelength slits viewed as a homogeneous medium. In this medium lives a metal-insulator-metal lattice mode interacting with surface and cavity plasmon modes. A weak coupling with surface plasmon modes on both faces of the perforated metal film leads to a broadband spectrum while a strong coupling between this first sub-system and a second one made of a graphene-insulator-metal gap leads to a narrow band spectrum. We provide a semi-analytical model based on these two interactions thus allowing efficient access of the full spectrum of the hybrid system.

About Me

Prof. Dr. Kofi Edee is a renowned researcher in the field of computational physics, with a particular focus on mathematical and computational physics. He received his Ph.D. in computational physics for electromagnetic modelling from Clermont Auvergne University and completed his postdoctoral training at the Microelectronics Technology Laboratory in Grenoble before returning to Clermont-Ferrand. Currently, Dr. Edee serves as an Associate Professor and researcher at the Institute Pascal. Dr. Edee's research interests primarily revolve around developing advanced and accurate electromagnetic modal methods and optimization methods for treating optics and electromagnetic problems related to modern nanophotonic devices, such as plasmonic lenses, waveguides, gratings, and more. He has introduced a new polynomial modal method based on Gegenbauer polynomial expansion that has the potential to significantly improve the accuracy of computational simulations in this field. The main advantage of this new method is that the continuity relations of the electromagnetic field can be written in an exact manner. His research has significant implications for the advancement of computational physics and the development of cutting-edge technologies. His contributions have been instrumental in expanding the understanding of the physical principles underlying modern nanophotonic devices.

Dr. Kofi Edee

Dr. Kofi Edee

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