Seeing is believing: Nonlinear optics on ferroic materials

Presently, a large variety of ferroic, that is, spontaneous and switchable types of long-range order is discussed. All of these all have one property in common: The ferroic ordering breaks the symmetry of the host material. Nonlinear optical processes are very sensitive to these symmetry changes. Even its simplest representative, doubling of the frequency of the light or "second harmonic generation" (SHG), therefore couples to the ferroic order parameter and accesses important features of the ferroic state that are often inaccessible to non-optical techniques. In my talk I will give an overview of the most important milestones in the classification of (multi-)ferroic materials by nonlinear optics. I will discuss basic questions such as the search for yet unknown types of ferroic order as well as application-relevant issues such as the use of SHG for tracking the emergence of ferroic order in thin films. A not-too-serious concept for "magnetoelectric teleportation" will conclude the lecture.