Depth-Resolved Analysis of Ferroelectric Domain Structures in Ti:PPLN Waveguides by Nonlinear Confocal Laser Scanning Microscopy

Abstract

We have analyzed the ferroelectric domain structure of periodically poled LiNbO ₃ by nonlinear confocal laser scanning microscopy. Annealed samples exhibit domain wall width below 300 nm, which more or less corresponds to the diffraction limit. In contrast, domain walls in “as poled” samples appear considerably broader and tentatively structured. In periodically poled Ti:LiNbO ₃ waveguide structures we find a pronounced enhancement of the nonlinear signal from the domain walls, which appears within the Ti-diffused range of the waveguide including the surface region.

Keywords:

• Ferroelectric domain structures
• nonlinear microscopy
• Ti:LiNbO₃ waveguides

Acknowledgment

We express thanks to Dr. H. Suche, Dr. H. Herrmann, Dipl. Phys. S. Orlov (Universität of Paderborn, Germany) and V. Gopalan (Pennsylvania State University, USA) for useful discussions on ferroelectric materials. The authors would also like to acknowledge financial support by the DFG research unit 295.