Screw Dislocations Decorated by Disclinations of C-Directors Observed in Thin Ferroelectric Smectic Liquid Crystal Cells

Characteristic defect lines, frequently observed in surface stabilized ferroelectric liquid crystal cells, are studied. They typically consist of thin lines perpendicular to the smectic layers and rather thick lines connecting them at their alternate ends. The neighboring parallel thin lines appear different from each other. The alternate appearance interchanges by reversal of the C -director field. The thin and thick lines are assigned to the screw and edge dislocations decorated with the singularity of C -directors. The difference in appearance of the thin lines is attributed to the relation of handedness between the screw dislocations and the s =+1 disclinations.