Nonlinear Optical Effects at Ferroelectric Domain Walls

Ferroelectric materials tend to form macroscopic domains of electric polarization. These domains have different orientations and coexist in the medium being separated by domain walls. In general, symmetry and structure of ferroelectric domain walls differ from their parent materials and consequently lead to abundant physical properties. In this book chapter, we review the nonlinear optical effects which are bundled with ferroelectric domain walls or whose properties can be significantly enhanced by the presence of domain walls. In particular, we have reviewed Google Scholar articles from 2008 to 2018 using the keywords “nonlinear Čerenkov radiation from ferroelectrics”. We show that the spatially steep modulation of the second-order nonlinear optical coefficient across the domain wall leads to strong emission of the Čerenkov second harmonic in bulk materials. This feature also enables an effective nondestructive method for three-dimensional visualization and diagnostics of ferroelectric domain structures with very high resolution and high contrast.