Mixtures of two proprietary low molar mass organosiloxane liquid crystals were studied in order to improve their alignment and optimize their electro-optic properties for telecommunication applications. Over a certain concentration range, mixtures exhibited an isotropic–chiral smectic A–chiral smectic C (Iso–SmA*–SmC*) phase sequence leading to exceptionally good alignment. At room temperature, the spontaneous polarization of these samples was reduced from 225 nC cm-2 in the pure SmC* liquid crystal to as low as 75 nC cm-2 in the mixture. Within this concentration range, the ferroelectric tilt angle could be varied between 35° and 15°, while the rise time decreased by 69.4%. The rise times were < 45 μs for moderate electric fields of ±10 Vμm-1 in the SmC* phase and ~4 μs, independent of electric field, in the SmA* phase. At λ = 1550 nm, these mixtures exhibited very large extinction ratios of ~60 dB for binary switching in the SmC* phase and ~55 dB continuous variable attenuation in the SmA* phase.
© 2012 IEEE
Xuesong Hu, Oliver Hadeler, and Harry J. Coles, "Low Molar Mass Organosiloxane Liquid Crystals for Telecommunication Applications," J. Lightwave Technol. 30, 2525-2531 (2012)