Smectic C* local layer structure within texture lines studied with a (sub)micrometer optical measuring spot

Abstract

The smectic layer structure within texture lines is investigated with a (sub)micrometer optical measuring spot. The property that the SmC-cone is perpendicular to the smectic layer is used to measure the in-plane rotation angle of the local smectic layers. From the measurements and observations it is concluded that texture lines, either spontaneously present or field induced, which run parallel to the rubbing direction in a virgin area, consist of two parts which are equivalent to zig-zag lines. These texture lines can be removed with a small low-frequency electric field, indicating that the smectic layers at the FLC-solid interfaces are not rotated or displaced. The texture which results after a prolonged treatment with a large low-frequency field consists of a dense structure of parallel texture lines, modified in such a way that the in-plane smectic layer rotation is extended from the bulk to the FLC-solid interfaces. Texture lines from DC electric fields, running obliquely to the rubbing direction, show an in-plane smectic layer rotation of a few degrees, which reasonably agrees with the layer rotation calculated from existing theory. Oblique lines created with a low frequency field exhibit an internal fine-structure which originates from the two polarities of the AC field. From this structure the electro-optical properties can be understood.