Optical contrast spectroscopy of ferroelectric liquid crystal cells

Abstract

The real and imaginary parts of the optical transmittance following the application of an electric field have been measured for ferroelectric liquid crystal cells (FLC) in the frequency range 0.1–10⁵ Hz. The numerical solution of the dynamic equation of the director motion and analysis of the first harmonic of the optical transmission gives the real and imaginary parts of the optical response in the frequency domain. It is shown that the experimental results are in good agreement with the predicted optical transmittance for both the bookshelf and the layer tilted cell geometry. The optical results are compared to the dielectric spectra and both are shown to identify the same relaxation processes. The optical method yields information about the dynamic processes occurring in FLC's without the sample conductivity affecting the results unlike the dielectric spectroscopy and can also reflect the smectic layer structure.