Observation of the Orientational Fluctuation in a Nematic Liquid Crystal by Focusing a Laser Beam

Abstract

The orientational fluctuations in a nematic liquid crystal were successfully observed by focusing a laser beam on the liquid crystal in a homogeneous cell. The transmitted intensity was traced by a digitizing oscilloscope, and the average intensity and the mean square were obtained. From the Maxwell equations, we theoretically derived the expressions for above quantities. It was found that the mean square of the transmitted intensity is inversely proportional to the square of the beam radius, which was experimentally confirmed. In addition, by using the theoretical results we have succeeded in obtaining the twist elastic constant from the experimental results.