Regensburg 2019 – wissenschaftliches Programm
KFM 14.8: Poster
Mittwoch, 3. April 2019, 16:00–18:30, Poster C
PSF-analysis of ferroelectric domain-walls in tightly focused regimes — •Peter Mackwitz, Kai Spychala, Alex Widhalm, Christof Eigner, Christine Silberhorn, Gerhard Berth, and Artur Zrenner — Department Physik, Universität Paderborn, 33098 Paderborn, Germany
A combined experimental and numerical approach is applied to unravel the second-harmonic generation contrast mechanism of ferroelectric domain structures. The numerical calculation comprises a vectorial model of the imaging process. Experimentally we use a direct imaging technique which records the spatial distribution of the second-harmonic signal in the back focal plane. As the model depends on the optical properties of the material different scenarios of contrast mechanisms can be simulated and compared to the experimental data. With lithium niobate and potassium titanyl phosphate as model systems it turns out that many features of the nonlinear signatures of ferroelectric domain boundaries arise from destructive interference of phase-shifted wavelets. The phase is acquired due to the interaction of the focus with differentially poled domains, whose susceptibility tensor appears rotated by 180°. Another ingredient for the contrast are new tensor elements which do only occur at the domain walls. Furthermore, incoherence due to wall roughness plays an important role. Considering those three phenomena the contrast mechanism can be well described and predictions for other material systems become possible.