Incoherent optical second harmonic (SH) generation, or hyper-Rayleigh scattering (HRS), is used to study the structure and properties of multilayer Langmuir–Blodgett (LB) films. SH reflection spectra (in combination with linear absorption spectra), HRS indicatrices, thickness dependence, and wave polarization diagrams are measured for s-polarized fundamental radiation. The SH radiation is entirely diffuse but predominantly s polarized, with the maximum of the HRS indicatrix shifted by 8° relative to the specular direction, which is interpreted as being due to the contribution of a fluctuating quadrupole to the nonlinear-optical response of the films. The estimated correlation length of spatial fluctuations of the nonlinear-optical polarization in the film is ∼400 nm. These properties are associated with an islandlike structure formed by Gd ions inside LB structural units.
© 2000 Optical Society of America