FAR-FIELD AND NEAR-FIELD 2ND-HARMONIC IMAGING OF FERROELECTRIC DOMAIN-WALLS

Domain walls in periodically poled ferroelectric LiNbO3 crystals are o bserved with both far- and near-field imaging techniques that make use of second harmonic generation in the transition regions between neigh bouring domains, Second harmonic images of domain walls represent brig ht lines of similar to 0.5 mu m in width (as measured with a near-fiel d microscope) for the polarization of the second harmonic radiation pe rpendicular to the domain walls. Origin and selection rules for the co ntrast in second harmonic images of domain walls are discussed. (C) 19 98 Elsevier Science B.V. All rights reserved.