Fast Electro-Optical Device Based on Chiral Liquid Crystals Encapsulated in Periodic Polymer Channels

The chiral flexo-electro-optic effect produces a sub-millisecond, temperature independent in-plane rotation of the optical axis and is potentially interesting for the display industry. The main drawback in the exploitation of this effect is that it relies on a texture, the Uniform Lying Helix (ULH), which is intrinsically unstable since neither planar nor homeotropic surface conditions are compatible with it. We present a method, based on the use of periodic polymeric micro-channels, to create highly ordered and stable ULH structures. We show that the periodic structure, which is created holographically, naturally aligns the cholesteric helical superstructure along the micro-channels, without requiring any elaborate ad-hoc procedure, even when the size Λ of the micro-channels is much larger than the pitch P (Λ > 20P). Electro-optic measurements performed on the test-device show a large contrast ratio between bright and dark states (better then 100:1), short switching time (200μs) and large optical rotatio...