Abstract : In this thesis we were interested in studying different nonlinear phenomena of the radiation-matter interaction and in particular the generation of gap solitons in nonlinear media presenting forbidden band gaps. In the first part we used a semi-classical model of Maxwell- Bloch to describe the interaction of a quantum two-level medium with charges and a classical electromagnetic field, by mediation of the population density, which is actually at the very origin of nonlinearity. The resulting nonlinear coupling possesses particularly interesting consequences (generation of slow-light solitons and effective scattering with charges) at the resonance, when the frequency of the excitation is close to the transition frequency of the two-level medium. The nonlinear dynamic observed numerically is understood by means of a nonlinear Schrödinger model in an external potential related to the charges. The second part of this thesis is focused on the theoretical study of the dynamics of quadratic gap solitons in optical parametric amplifiers (OPA). The equations describing the degenerate three-wave interaction in a nonlinear birefringent crystal are established in presence of transverse diffraction and spatial walk-off. We proposed a method for solving the challenging problem of determining the nonlinear supratransmission threshold in OPA which was generalised to any multicomponent nonintegrable nonlinear systems.