INFLUENCE OF DOMAINS ON NONLINEAR-OPTICAL PROPERTIES OF SOLIDS

The investigations of an influence of different macroscopic domain str uctures on nonlinear optical susceptibilities of several solids were p erformed. We have chosen a semi-empirical tight-binding calculational method in order to calculate nonlinear optical third rank polar tensor components. The domain walls of different nature (magnetic, ferroelec tric, superconducting twins and incommensurate phase) were considered by means of breaking the translational symmetry in the first order per turbation approach. We have predicted an appearance of an oscillatory behaviour of the nonlinear optical susceptibilities as the functions o f the domain sizes. The above mentioned theoretical results are in goo d agreement with our experimental measurements of optical second harmo nic generation.