Polarization-modulated Raman scattering measurements of nematic liquid crystal orientation

This article presents a new, automated Raman scattering experiment to measure the orientation in nematic liquid crystals. The automated experiment utilizes phase modulation to alter the polarization state of light unlike conventional, polarized Raman experiments which require the manual manipulation of polarizers and multiple measurements. Polarization modulation imparts the ability to quantify the second and fourth moments of the orientation distribution function with a single measurement. The feasibility of the new experiment is demonstrated through orientation measurements of a well characterized nematic liquid crystal, 4-pentyl-(4-cyanophenyl)-cyclohexane. Additionally, since the results of the polarization-modulated technique are in excellent agreement with conventional Raman measurements, this study supports the validity of the theory describing Raman scattering from birefringent materials. (C) 1996 American Institute of Physics.