Light Scattering by Deformation of the Plane Texture of Smectic and Cholesteric Liquid Crystals

Distortions of the plane texture of smectic-$A$ and cholesteric liquid crystals are shown to combine with the uniaxial birefringence of the plane texture to produce a strong characteristic light-scattering effect. We have observed static deformations, arising from surface defects, as well as dynamic deformations arising from thermal or mechanical stress. An immediate application of this effect is to confirm theoretical speculations on the elasticity of smectic-$A$ phases.