Observations of the Ferroelectric Deformed Helix Mode in a Large Pitch Smectic C* Sample

Abstract

Display devices making use of the deformed helix mode normally employ a smectic C* phase whose pitch is smaller than a wavelength of visible light. Here we study the opposite case, where the pitch is large. Our samples are aligned in the usual bookshelf geometry and the electric field is applied perpendicular to the helix. When the sample is viewed between crossed polarizers with the helix parallel to one of the polarization axes, we observe two stages of response to the application of the electric field. Initially, the transmitted intensity decreases quadratically with the field. This is then followed by a discontinuous jump to a high transmission state at some threshold field. We present evidence that the initial decrease in intensity is due to a diffraction phenomenon.