Determination of Helical Pitch in Homeotropic Cell of Chiral Smectic C Liquid Crystal Using F-Center Laser

The selective reflection is observed in a monodomain homeotropic cell of chiral smectic C liquid crystal (DOBA MBC). In conjunction with the refractive index, the structural helical pitch is determined as a function of temperature. The results agree well with our previous results obtained by diffraction technique as well as optical microscope observation in a monodomain homogeneous cell. This agreement experimentally confirms that the fringe spacing observed under an optical microscope is ascribed to the full pitch. The large difference in the helical pitches determined by some investigators is also discussed.