Optical studies of thin layers of smectic-C materials

Abstract

The optical behaviour of surface-stabilized ferroelectric liquid crystal samples cannot be described using a uniform director profile. The simplest model based on the chevron layer structure and the surface alignment is a triangular director profile. Analytical expressions for the resulting transmitted light were calculated using the Jones matrix formalism and fitted to experimental data results of a smectic-C host made using an optical multichannel analyser (OMA). This simple model gives an excellent fit, with results that are consistent with X-ray measurements of the chevron structure.

An investigation into the director structure in the electroclinic effect at the SA-SC* transition

“…Further methods exist which rely on the fact that the wavelength dependence of light transmission through a liquid crystal cell is influenced by the liquid crystal refractive indices and director profile. Wavelength dependent extinction angle microscopy is one such method [4]. The experimental method used in this work also utilises the wavelength dependence of light transmission through a cell.…”

On the biaxiality of smectic C and ferroelectric liquid crystals

“…The chevron interface lies in the central plane of the cell and the two surfaces are equivalent, so the profile has mirror symmetry and forms a triangular director profile (TDP) [17]. Typically, δ C ≈ θ C , and so the in-plane component of the director β C follows the triangular profile from β S to β i and back to β S , where the azimuthal angle at the chevron interface β i is given by equation (8).…”

“…The starting configuration for ε p used a triangular director profile [17], and again it was assumed that the field was insufficient to cause change in θ C , δ C or the layer structure. This latter assumption was justified by restricting the voltages to those below the formation of "needle" defects in the sample, and by checking that the permittivity was free from hysteresis with reducing field.…”

Physical Properties: Optical Properties

“…As an example of the application of the Jones matrices, the director configuration in a thin liquid crystal film of a SmC material has been investigated [34] by measuring the transmission of polarized light as a function of wavelength. Knowing the refractive indices of the material, the experimental results can be fitted to a model for the director configuration, as illustrated in the Fig.…”