Abstract : This PhD thesis concerns the modelizing of scattering in the harmonic regime in two dimensional domains with thin slots. We first introduce and analyse an approximate model, which consideres a 1D approximation inside the slot. This approximate model is
based on two new "brute" coupling conditions at each end of the slot. As the accuracy of this technique is limited, we then use the technique of matching asymptotic expansions to obtain and justify the asymptotic expansion of the solution to any order with respect to the width of the slot. The results are totally different if the
slot length is a multiple of half of the wave length. In this case a phenomena of resonance can be observed. New 1D-2D matching procedures can be deduced from this study.