Jonathan Paul Hannington

Fast electro-optic liquid crystal switch and attenuator with large extinction ratio at 1550 nm

We demonstrate an electro-optic switch and a variable attenuator for telecommunication applications at λ=1550nm by employing the ferroelectric and electroclinic properties of an organosiloxane liquid crystal. In the ferroelectric SmC* phase an optical switch has been realised with an extinction ratio of 36dB between crossed polarisers. The switching time was ~200microseconds. In the SmA* phase the analogue nature of the electroclinic effect was employed to obtain a variable attenuator. The maximum attenuation range between crossed polarisers was 35dB for an applied electric field of +-9V/micron. The response time of the device was about 100microseconds, independent of the applied electric field. Both devices where demonstrated in the same 21.5micron thick cell which provided a retardance of λ/2 at λ=1550nm.

Hybrid integration of silicone PDLC into a planar light circuit

Silicone polymeric materials are being developed that will allow the hybrid integration of tunable functionality provided by polymer dispersed liquid crystal, PDLC, and continuous phase liquid crystal materials on planar silica-on-silicon and planar polymer light circuits. The advantages of this approach are ease of integration, the possibility for reduced power consumption, and therefore a reduction of the overall cost for component manufacturing and operation. A successful demonstration of a low loss approach to hybrid integration of polymers and liquid crystals is presented. The challenges for successful integration and acceptance will be discussed. New liquid crystal materials are being developed specifically for this application.

Effects of Electric-Field Shape and Frequency on Smectic Layer Rotation of Siloxane Ferroelectric Liquid Crystals

Smectic layer rotations in ferroelectric liquid crystals (FLC) upon application of electric fields have been observed only in chiral smectic phases and believed to be related to the electroclinic effect. In this article, effects of electric field shape and frequency on smectic layer rotations in siloxane-based FLCs were investigated by applying various kinds of asymmetric ac waveforms for a range of frequencies and temperatures. For a given peak voltage, we have found that the asymmetry was one of the most important parameters and demonstrated that the modified step form showed the best efficiency for smectic layer rotations.

A new class of bookshelf bistable siloxane modified ferroelectric LC materials with electrical repairability in an LCoS configuration

Investigation of siloxane-based ferroelectric liquid crystals (Si-FLCs) has revealed chevron- free long-term bistable behavior and, unusually, an easy regeneration of bistable performance after damage (e.g., by mechanical shock). The properties are intrinsically related to the chemical structure of the oligosiloxane materials. The phenomena result from the coupling of siloxane and organic moieties that causes nano-phase segregation, which essentially reduces the correlation of tilting from adjacent layers and also generates weak anchoring by decoupling the bulk structure from the strong surface anchoring. A method of regenerating a condition with bistable performance by an electric field (without mechanical and heat treatment) is established. An in-house Si-FLC over a silicon (Si- FLCoS) device is demonstrated, which exhibits good memory effects without chevron defects and a repair function for regenerating bistability in case of damage.