2ND-HARMONIC-GENERATION STUDIES OF INCLINED THIN-FILMS

The nonlinear surface susceptibility chi(S)(2) is generally referred to the system of Cartesian coordinates of the sample. However, since actual measurements take place with respect to the laboratory system of coordinates, appropriate transformation of chi(S)(2) is necessary to deduce the underlying susceptibility-components. We demonstrate this by analyzing the second-harmonic signal generated by an inclined sample upon rotation around the s-axis of the laboratory system of coordinates. The sample consists of two Langmuir-Blodgett-type monolayers of rotational symmetry around the sample normal, the two layers being separated by a plane-parallel flat of 1 mm thickness. The occurrence of a ''symmetry-forbidden'' I(ss)2omega-signal is discussed in detail.