Composite Liquid Crystalline Mixtures for Guided Wave Electro–Optic Applications

Abstract

A low refractive index multifunctional composite liquid crystalline mixture is proposed to address the issues of in-guide tuning of optical properties. As the standard optical telecommunication line is made of fused silica, signal phase and amplitude modulation using liquid crystal requires that its refractive indices match the refractive index of silica, which is low compared to the majority of commercially available mixtures. In the present work, low molecular mass liquid crystals are mixed with fluorinated additives to adjust refractive index below a critical limit (n < 1.4584 at D-line) without impacting significantly on the nematic temperature range (T CN ¼ À24 C and T NI ¼ 68 C). A method of reducing the surface anchoring energy of liquid crystals to glass surface is also proposed as a non contact alignment method around the reduced diameter optical fibers. The bulk elastic energy around the fiber acts as an alignment mechanism when LC-fused silica molecular interactions are minimized. The combination of these two properties makes possible the in-guide modulation of the light phase and amplitude with the liquid crystal used as an outer-cladding electro-controllable medium, significantly improving insertion losses.