Second-Harmonic Generation in Chiral Liquid Crystals

Abstract

Second-Harmonic Generation (SHG) occurs under special circumstances in chiral liquid crystals, such as Ferroelectric Liquid Crystals and, induced by an external electric field, in Short-Pitch Cholesteric Liquid Crystals. Previously, SHG in FLCs has been studied mainly for the application potential of FLCs as a promising NLO-material. However, with the discovery in the last three years of novel electro-optic effects and liquid crystalline phases - i.e., the high-contrast, analog “V-shaped switching” found to occur in so-called “thresholdless antiferroelectric” liquid crystals; and liquid crystals consisting of bow-shaped molecules - the emphasis is shifting towards SHG becoming a standard tool of investigation in liquid crystal research. In this context symmetry, manifestations of chirality as well as analysis and interpretation issues become more important than ever before.

Key Words:

• Second-harmonic generation
• chirality
• ferroelectric liquid crystal
• cholesteric liquid crystal
• nonlinear optics
• “thresholdless antiferroelectricity”