Lengths of ferroelectric domains: The role of defects and random fields

Abstract

Using noncollinear optical second-harmonic generation, the characteristic lengths of ferroelectric domains in strontium-barium niobate are determined. The role of the domain geometry in the random quasiphase matching process involved is elucidated by model calculations on different domain arrangements. The calculations prove that the domain geometries—especially the domain lengths—strongly affect the angular distribution of the generated second-harmonic light. The evaluation of the measured angular distributions in crystals with different doping concentrations shows that the domain lengths are distinctly albeit not drastically influenced by the dopant-induced random electric or strain fields.