Synthesis and properties of a new series of low-molar-mass organo-siloxane derivatives

Two series of ferroelectric liquid crystalline organo-siloxanes containing a laterally attached halogen on the phenyl ring have been synthesised and characterised to determine the impact of the siloxane group and the halogen on the mesomorphism and electro-optic switching properties. Both monomesogenic and bimesogenic compounds have been studied. The monomesogenic derivatives were found to be ferroelectric with high tilt and Ps. The tilt angle of 45° and the Ps of 95nC/cm2 are almost temperature independent. The bimesogenic bromo substituted derivatives showed mainly ferroelectric phases about 60°C wide. Maximum values for the spontaneous polarisation and the tilt angle were only slightly influenced by the length of the siloxane spacer. Altering the halogen to a fluorine shifted the liquid cystalline phase slightly to higher temperatures whilst maintaining the mesophase range of 60°C.

Low Molar Mass Organosiloxane Liquid Crystalline Dyes for Dye Guest Host Ferroelectric Display Devices

In low molar mass organosiloxane liquid-crystal materials the siloxane moieties micro-separate and aggregate in planes that could be regarded as an effective or virtual two-dimensional polymer backbone. We show that if a siloxane moiety is attached to a dichroic dye molecule, the micro-segregation of the siloxane moieties makes it possible to include a high concentration of the guest dye (more than 50%) in a host organosiloxane solution. This effect, combined with the temperature independent tilt angles achievable with ferroelectric organosiloxane liquid crystals, provide an ideal material for high-contrast surface-stabilised ferroelectric display devices. We present dyed ferroelectric materials with a temperature independent tilt angle greater than 42 degrees, a wide (room temperature to over 100°C) mesomorphic temperature range and a response time shorter than 500μs in the dye guest host mode.

Step synchronization and third person speed perception in virtual environment locomotion simulators

Human locomotion is known to be influenced by observation of another person's gait. For example, athletes often synchronize their step in long distance races. However, how interaction with a virtual runner affects the gait of a real runner has not been studied. We investigated this by creating an illusion of running behind a virtual model (VM) using a treadmill and large screen virtual environment showing a video of a VM. We looked at step synchronization between the real and virtual runner and at the role of the step frequency (SF) in the real runner's perception of VM speed. We found that subjects match VM SF when asked to match VM speed with their own (Figure 1). This indicates step synchronization may be a strategy of speed matching or speed perception. Subjects chose higher speeds when VMSF was higher (though VM was 12km/h in all videos). This effect was more pronounced when the speed estimate was rated verbally while standing still. (Figure 2). This may due to correlated physical activity affecting the perception of VM speed [Jacobs et al. 2005]; or step synchronization altering the subjects' perception of self speed [Durgin et al. 2007]. Our findings indicate that third person activity in a collaborative virtual locomotive environment can have a pronounced effect on an observer's gait activity and their perceptual judgments of the activity of others: the SF of others (virtual or real) can potentially influence one's perception of self speed and lead to changes in speed and SF. A better understanding of the underlying mechanisms would support the design of more compelling virtual trainers and may be instructive for competitive athletics in the real world. © 2009 ACM.

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 {\sim} 60 dB for binary switching in the SmC* phase and ∼ 55 dB continuous variable attenuation in the SmA* phase. © 2012 IEEE.

Measurement of third-order dispersion in a hong-ou-mandel interferometer

The effect of third-order dispersion in a Hong-Ou-Mandel interferometer is investigated using a ZnSe crystal as a dispersive medium. A value for the TOD coefficient of ZnSe is extracted which is consistent with literature values. © OSA 2013.