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Light-induced instabilities driven by competing helical patterns in long-pitch cholesterics
E Brasselet1, D O Krimer, L Kramer
1Laboratoire de Physique UMR 5672, Ecole Normale Supérieure de Lyon, 46 Allée d'Italie, 69364 Lyon Cedex 07, France. ebrassel@ens-lyon.fr
The European Physical Journal. E, Soft Matter
|July 27, 2005
Summary
We theoretically investigate light-induced reorientation in long-pitch cholesteric liquid crystals. A threshold light intensity triggers structural changes, with dynamics influenced by the cholesteric pitch and competing helical patterns.
Area of Science:
- Materials Science
- Optics
- Soft Matter Physics
Background:
- Cholesteric liquid crystals exhibit helical structures.
- Long-pitch cholesterics have pitch comparable to film thickness.
- Boundary conditions can frustrate the helical structure.
Purpose of the Study:
- To theoretically study dynamical reorientation in long-pitch cholesteric liquid crystal films under circularly polarized light.
- To analyze the influence of natural cholesteric pitch on reorientation dynamics.
- To explore the competition between intrinsic and extrinsic helical patterns.
Main Methods:
- Theoretical analysis of dynamical reorientation phenomena.
- Investigation of light-induced structural changes in liquid crystal films.
- Modeling of helical pattern competition.
Main Results:
- A light intensity threshold was identified for reorientation.
- The bifurcation scenario strongly depends on the natural cholesteric pitch.
- Competition between intrinsic (dopant-induced) and extrinsic (light-induced) helical patterns was observed.
Conclusions:
- Light can induce significant dynamical reorientation in frustrated cholesteric liquid crystals.
- The interplay between material chirality and light-induced chirality governs the observed phenomena.
- All-optical analogs in pure nematics were also considered.