Scattering-/absorption-mode light shutters based on dye-doped fingerprint chiral textures

Abstract

Scattering-/absorption-mode light shutters based on dye-doped fingerprint chiral textures (DdFCTs) are demonstrated. DdFCTs in a liquid crystal (LC) cell treated with homeotropic alignment are initially stable FCTs due to the vertical surface anchoring force (SAF). The LCs completely rotate to homeotropic orientation from stable FCTs by applying a suitable operation voltage (Vop). Furthermore, when the Vop is switched off, the LCs transform into temporary focal conic textures with lifetimes of few seconds from the homeotropic orientation, the LCs then transform into unstable FCTs. Finally, the unstable FCTs spontaneously return to the initial stable FCTs. The light absorption of DdFCTs in the stable FCTs/unstable FCTs/field-induced multi-domain FCTs is independent of the polarization of the incident light. The operation mechanism of the proposed DdFCTs is also discussed. Most importantly, the response time and the required Vop to rotate all LCs to homeotropic orientation in DdFCTs from stable FCTs in LC cells treated with homeotropic alignment layers are respectively shorter and lower than those in common dye-doped cholesteric LCs (DdCLCs) from stable planar textures in LC cells treated with homogeneous alignment layers. Comparing with DdCLCs, about 20% Vop can be reduced in DdFCTs. The cause can be understood since the Vop applied onto the DdFCTs is fully dedicated to unwind the helical structures.