The electroclinic response in a network-stabilized cholesteric phase

The electroclinic effect is a very fast response of the optic axis in chira l orthogonal smectics (like SmA*) on the application of an electric field. In smectic systems it represents a soft mode which takes on a high amplitud e near the A* --> C* transition but otherwise is limited to a tilt of typic ally 2-5 degrees. This response can also be found in chiral nematics, altho ugh its origin here is still obscure and so small-typically 0.1 degrees or less-that it has been of academic interest only. In two cases investigated of a cholesteric phase which has a direct transition to SmC*, the electrocl inic effect could be enhanced to the same level as in SmA* materials by pho toreticulation without slowing down the response speed. Remarkably, the tem peratures at which this high amplitude/high speed response is measured are actually lower than in the corresponding measurements on the basic mixtures .