Birefringence and order parameter studies in ferroelectric liquid crystals using laser transmission technique

Birefringence of the ferro electric liquid crystals (FLCs): (S)-(−)-2-methylbutyl 4′-(4ʺ-n-alkanoyloxybenzoyloxy) biphenyl-4-carboxylates (S-MB-nB-BC) where<i>n</i> = 16 and 18 is determined experimentally using laser transmission technique. In this experimental technique, the light coming out from the laser source (of wavelength 633 nm) passes through the polarizer and analyzer via FLC sample under crossed position. Optical intensities transmitted from the sample fall on the phototransistor through the analyzer. Phototransistor is a photo detector in which the transmitted light from the analyzer is converted into the electric response and measured in terms of voltage. These voltage measurements are used to determine the birefringence values of the samples. Further, order parameter is also determined. The results are compared with image analysis technique values along with phase transition temperatures, which are in good agreement.