Exploring the softening of smectic layer dynamics to defect control in high tilt angle ferroelectric liquid crystal for optical device applications

High-tilt-angle ferroelectric liquid crystal (FLC) in its surface stabilised geometry (6.5 μm) has been used for the investigation of the smectic layer softening and their role in defects formation. Dielectric spectroscopy and optical observations have been employed for the analysis of samples. The alignment of the sample was achieved in two ways: first, the cell is cooled in a sample holder connected with a temperature controller (slow cooled) and second, it is allowed to cool naturally in an oven (fast cooled). The different stripe defects have been observed in both samples having distinct dielectric behaviour at 30°C. The twisted structure is also observed within stripe structure and aligned along the orientation of the stripe. It has also been observed that for higher bias field, near transition temperature (Tc) in the SmC* phase, the smectic layers are observed to rearrange their orientation and grow into focal conic defects (FCDs) in both the stripe structures near Tc. This behaviour suggests the softening of smectic layers near Tc, whereas, at 30°C or lower temperatures, they are relatively rigid. The study is highly significant for understanding the defect geometry and smectic layer reorientation configuration in high tilt angle FLCs.