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Modeling

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  • People involved :
    • Permanent Researchers : Julien Cardin, Christian Dufour.
    • Invited Researcher : Vladimir Khomenkov.
    • Young Researchers : Roy Aad (Post-Doc), Nicolas Guth (Post-Doc), Pratibha Nalini Ramesh Sundar (PhD), Alexandre Fafin (PhD), Lucile Dumont (PhD).
  • Projects : ANR PNANO DAPHNES (2009-2012),
    • ANR Blanc SHAMAN (2010-2012)),
    • Interreg IVA – MEET (2012-2015),
    • Labex EMC3 – ASAP (2012-2015),
    • Project Emergent SOLAIRE (2012-2014),
    • ANR Blanc GENESE (2014-2017).

This thematic is a new one begun in 2009 initiated by the DAPHNES and SHAMAN ANR projects with the aims to develop tools for understanding, managing and optimizing the light propagation in systems for photonic, photovoltaic and/or plasmonic applications.
For the former, a new algorithm based on auxiliary differential equations (ADE) and finite difference time domain method (FDTD) has been developed in the CIMAP NIMPH team.
This method allows calculating the propagation of electromagnetic fields in a structure described by its refractive index distribution. More originally, it permits to describe in 3 dimensions the steady state electronic population of all the considered electronic levels of a physical system described by a set of rate equations.
From this description, it is possible to estimate the gross gain distribution in the studied structure. We significantly improved the convergence speed of our algorithm compared to the classical ADE-FDTD method by splitting the main ADE-FDTD loop in a fast and slow coupled two loops algorithm. This algorithm is stable and applicable to a wide range of optical gain materials which are described by characteristic lifetimes ranging from 1ps to some ms.
By means of an auxiliary differential equations and finite difference time domain (ADE-FDTD) approach that we developed, we investigated the steady states regime of both rare earths ions and silicon nanograins levels populations in a Si-based waveguide.
The Nd3+ doped waveguide showed a higher gross gain per unit length at 1064 nm (up to 30 dB/cm) than the one with Er3+ doped active layer at 1532 nm (up to 2 dB/cm).
Taking into account the experimental background losses, we have demonstrated that a significant positive net gain can only be achieved with the Nd3+ doped waveguide.

In the framework of the SHAMAN ANR project, we realized the theoretical studies of metallic nanoparticles (NPs) embedded in an amorphous silica host matrix irradiated by swift heavy ions irradiation.
The electromagnetic response of gold shaped NPs has been investigated analytically and numerically by several methods. The near field response of nanoparticles was investigated experimentally through nanometer-scale Electron Energy Loss Spectroscopy (EELS) analysis for different kinds of ion-shaped objects. We confirmed the near field distribution and the identification of LSPR modes of nanoparticles by modeling with a home developed Auxiliary Differential Equations-Finite Difference Time Domain (ADE-FDTD) code.
Moreover, the dispersion of a class of ion-shaped gold nano-objects with cylindrical symmetry has been studied successfully by combined surface modes and Fabry-Pérot theoretical approach.
The modal dispersion of modes observed experimentally and numerically has been explained by this model.

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