Title：
Fast-switching Electro-Optical Devices Based on Bimesogen-doped Liquid Crystals
Abstract：
In recently discovered Twist-Bend Nematic (NTB) phase based on bent-core or bimesogen liquid crystals, the nematic director is spontaneously distorted and twisted along a conical helix with an extremely short pitch, ~10 nm [1-5]. Due to the periodic NTB structure, many investigations have shown the electro-optic effects are not nematic-like but are close analogs to those in the chiral smectic A and cholesteric phases. In particular, these studies have shown fast (sub-microsecond) flexoelectrically-induced rotation of the optic axis, which is similar to the electroclinic effect in the SmA* phase and the flexoelectric response of short-pitch cholesterics [6-10].
A linear electro-optic effect in a cholesteric liquid crystal is described and attributed to the flexoelectric effect. An electric field applied perpendicular to the helix axis rotates the director about an axis parallel to the field. This produces a periodic splay-bend pattern in the helix, which couples flexoelectrically to the field. By using a small concentration of photoreactive liquid crystal monomer sless than 5 wt. %d and selecting the illumination conditions, we were able to create a nonuniform polymeric network in the liquid crystal bulk slocalized essentially at both substrate surfacesd which stabilized efficiently the amplitude and the phase modulation modes of the device. This presentation will discuss the possible applications of the fast electro-optic effects based on bimesogenic nematics and their cholesteric mixtures.
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