Calculations of nonlinear optical properties of model Langmuir‐Blodgett films

Abstract

Calculations have been performed on models of Langmuir‐Blodgett LB films to explore how molecular nonlinear response expresses itself in film response. The molecules are treated as a string of s beads initially arranged normal to the film with their long axes forming a close‐packed hexagonal array, but they are then allowed to tilt away from the vertical. The molecular polarizability α and first hyperpolarizability β are represented by one‐dimensional models in which the axial components are s times the perpendicular ones. Because of the layer structure of the films, the dipolar interactions are calculated as planewise sums between one molecule and all the molecules in a given layer. The sums have been calculated for various values of s as a function of tilt; they are negligible except for interactions of a molecule with its own layer. They have been used to calculate the local electric field, refractive index and …