Second harmonic generation in photonic crystals and nonlinear reflection in microcavities

Second-order nonlinear optical processes in spatially modulated material structures are investigated. In a first part, second harmonic generation in photonic crystals is considered, experimentally and theoretically, in two cases: first, when the nonlinear material is located within a "defect" in a single-dimensional periodic structure; and, second, when the nonlinear material is distributed all along a regular three-dimensional structure. It is also shown in this part that for narrow layers of second-order nonlinear material "momentum non-conserving" interactions can be as important as momentum conserving interactions. Finally, in a second part it is investigated how, in a microcavity, cascading effects induced by an intense second harmonic field can modify the reflectance properties of the structure at the fundamental frequency (nonlinear reflection).