An Approach to the Design of Ferroelectric Liquid Crystals with Large Second Order Electronic Nonlinear Optical Susceptibility

Abstract

Ferroelectric liquid crystal thin films in the Clark-Lagerwall surface-stabilized geometry exhibit well known spontaneous polar orientation of functional groups. The symmetry of the system thus allows the existence of bulk electronic second order nonlinear hyperpolarizability x⁽²⁾ within thc context of the simple dipolar model. For all FLC materials examined to date, however, the magnitude of x⁽²⁾ is small, presumably since the particular functional group arrays oriented along the polar axis possess small molecular hyperpolarizdbility β.

Using the Boulder Model for the molecular origins of the polar order occurring in FLC films, it is possible to design materials with functionalized aromatic rings oriented along the polar axis of the film. Since such functional arrays may show respectable values of β, it should be possible to obtain FIX films (both low molecular weight and polymeric) with useful magnitude of x⁽²⁾ using this approach. Results of initial experiments aimed at design of FLC materials with large x⁽²⁾ will be described.