On s'intéresse au calcul du champélectromagnétique diffracté par un obstacle conducteur recouvert d'un matériau hétérogène. Onétudie une méthode numérique consistantà coupler une approximation paŕ eléments finis de volumes avec des potentiels retardés de surface. Plusieurs formulations variationnelles espace-temps sont présentées. Onétablit des résultats de stabilité et de convergence pour la méthode proposée.

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We have performed simulations of laser energy deposit in sub-micrometric spherical defects and the surrounding fused silica. We have studied crater generation produced by the absorber explosion with a 2D/3D Lagrange-Euler code taking into account crack formation and propagation in the brittle material. The comparison of the 2D simulations with experiment shows quite good agreement for shallow defects (depth < 2 µm). We have observed experimentally that the explosion of deeper absorbers results in a more complex crater morphology. Therefore we have begun performing 3D simulations in order to reproduce these features.Depending on the defect depth, the cracks may not reach the surface and a crater doesn't appear. Nevertheless, those cracks or pre-existing cracks can contribute to efficient electric field enhancement and breakdown on the surface. Different types of cracks (size, inclination, filled with a material or not) were investigated and the 2D or 3D electromagnetic field distributions were computed using a finite element code.

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