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Title: Low molar mass organosiloxane ferroelectric liquid crystals for telecommunication applications
Author: Hu, X.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2010
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The alignment quality of FLCs could be significantly improved by mixing two low molar mass (LMM) organosiloxane FLCs. The electro-optic properties such as spontaneous polarisation Ps, tilt angle αtilt and response time Tres were tailored by the mixing. Ps was reduced from 225 to 75 nC cm-2. Optimum αtilt of around 22.5° was achieved with a wide temperature range from 21 to 45 °C. Fast Tres in the FLC test call at moderate electric fields of ±13.3 V μm-1 were ~70 and ~7 μs for ferroelectric and electroclinic switching, respectively. These characteristics are suitable for telecommunication applications. The FLC test cells were characterised at 1550 nm, i.e. the third window of telecommunication, a large extinction ratio of > 60 dB was obtained. A quantitative model for assessing the alignment quality in the FLC test cells found very small angle deviations of the FLC directors in the well-aligned test cells i.e. ~0.0172° and ~0.0229° for the 13 and 16.6 wt% samples, respectively. The best aligned 13wt% sample was successfully integrated into single mode silica optical waveguide structures. The FLC mixture exhibited a very good alignment quality in the waveguide gap where there were no alignment layers deposited on the inside walls of the gap. As a result, a good extinction ratio of up to 33 dB and a low insertion loss of < 4 dB at λ = 1550 nm were observed in the waveguide structures with the operating temperature range from 30 to 60 °C. Tres in the waveguide structures was < 100 μs at electric fields of ±7.59 V μm-1.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available