Some Optical Properties of the Elaidicum Acid in Mesophase

The liquid crystal (smectic C* type) properties of the elaidicum acid, from 28°C to 51°C have been studied and utilised in this paper. The electrical potential, the capacitance and the electric current intensity versus applied voltage on a membrane of liquid crystal were measured. The experimental results of these measurements and the microstructural aspects show that this acid has the dielectric properties of a liquid crystal and is ferroelectric. The dependence of the current on time, when an electric field is applied and removed, were investigated, too, the results confirming the previous conclusions. Taking into account these findings, different liquid crystal cells were realised and utilised for the "nonlinear lens" effect. This is the external self-focusing of laser light in the liquid crystal film. A He-Ne laser (Λ = 6328 Å, P = 16-20 mW) was utilised for the experimental setup. The f NL change with the sample thickness and with the temperature was determined, the optical nonlinearity ϵ 2 versus the liquid crystal thickness was graphically represented, too. The study of the pattern-obtained on a screen in far field-show that the sample have a great optical nonlinearity, even at low optical powers. The different behaviour at heating and cooling confirms the ferro electricity of this substance.