Low Molar Mass Organosiloxane Liquid Crystals for Telecommunication Applications

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 V μm^-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.