From nanostructured liquid crystals to electro-optic devices and lasers

摘要

We have recently shown that bimesogenic liquid crystals exhibiting chiral nematic and smectic (SmA, SmA* or C*) phases have macroscopic electro-optic properties that make them very interesting for both display and non-display applications. Since materials have been synthesised where the optical effect observed could be due to scattering power, birefringence, dichroism, fluorescence and optical-nonlinearity (SHG and THG), and where the principle optical axis can be rotated in any direction through 90° in times of the order of micrpseconds at moderate fields, i.e., 1-10V per micron, then this suggests an exciting variety of new optoelectronic applications. In this paper we will describe nanoscopic design protocols, molecular templating effects and the molecular properties important for these systems. Specifically we will consider bimesogenic SmC* incorporating siloxane linking groups that exhibit either ferroelectric or anti-ferroelectric phases depending on the number of silicon atoms in the siloxane moiety using the same mesogens. The siloxane configuration leads to a molecular template effect observed on the macroscopic scale as synclinic or anticlinic phases. Unusually these materials have cone angles of up to and including 90° which makes them ideal for high contrast displays, phase elements, photonics transducers and lasers.