Observation of edge dislocations in helical smectic liquid crystals

We report the observation of elementary edge dislocations in smectic liquid crystals possessing helical structure. The dislocations were observed in t he entire temperature range of helical phases, including ferroelectric, fer roelectric and antiferroelectric phases. The mechanism for visualizing the dislocations is based on the phenomenon of selective reflection of circular ly polarised light. The performed observations of dislocations deliver not only information on the mechanisms of defect creation in various chiral sme ctic phases, but also on the structure and properties of the investigated s mectics, often inaccessible using standard methods.