Electric-field-induced nematic-cholesteric transition and 3-D director   structures in homeotropic cells
  We study the phase diagram of director structures in cholesteric liquid crystals of negative dielectric anisotropy in homeotropic cells of thickness d which is smaller than the cholesteric pitch p. The basic control parameters are the frustration ratio d/p and the applied voltage U. Fluorescence Confocal Polarising Microscopy allows us to directly and unambiguously determine the 3-D director structures. The results are of importance for potential applications of the cholesteric structures, such as switchable gratings and eyewear with tunable transparency based. 
I.I. Smalyukh, B.I. Senyuk, P. Palffy-Muhoray, O.D. Lavrentovich, H.   Huang, E.C. Gartland, Jr., V.H. Bodnar, T. Kosa, and ...