Smectic C* layer directional instabilities in cells with twist geometry

We have investigated the formation and structure of horizontal chevrons, as well as the reorientation dynamics of smectic layers under applied asymmetric electric fields in cells with a twist geometry. The tilted layer structure of horizontal chevron domains is found to be rotated by an angle approximately equal to the twist angle α, as compared with parallel rubbed substrates, α = 0°. The time of horizontal chevron formation decreases slightly with increasing twist angle. The smectic layer reorientation under application of time-asymmetric electric fields is found to be enhanced for reorientation into the direction of twist, while it is hindered for reorientation out of the direction of layer twist. Increasing the twist angle results in a basically linear increase/decrease in the reorientation velocity, depending on field asymmetry direction. The electro-optic behaviour of twist cells with inclined smectic layers is outlined and compared with measurements performed on cells with monostable, parallel anchoring conditions.