Effects of Composition and Polymerization Conditions on the Electro-Optic Performance of Liquid Crystal-Polymer Composites Doped with Ferroelectric Nanoparticles.

The presence of a polymer network and/or the addition of ferroelectric nanoparticles to a nematic liquid crystal are found to lower transition temperatures and birefringence, which indicates reduced orientational order. In addition, the electro-optic switching voltage is considerably increased when a polymer network is formed by in situ polymerization in the nematic state. However, the resulting polymer network liquid crystal switches at similar voltages as the neat liquid crystal when polymerization is performed at an elevated temperature in the isotropic state.

Unraveling the electrochemical and spectroscopic properties of neutral and negatively charged perylene tetraethylesters.

A detailed investigation of the energy levels of perylene-3,4,9,10-tetracarboxylic tetraethylester as a representative compound for the whole family of perylene esters was performed. It was revealed via electrochemical measurements that one oxidation and two reductions take place. The bandgaps determined via the electrochemical approach are in good agreement with the optical bandgap obtained from the absorption spectra via a Tauc plot.

Two-dimensional switchable blue phase gratings manufactured by nanosphere lithography.

Switchable two dimensional liquid crystal diffraction gratings are promising candidates in beam steering devices, multiplexers and holographic displays. For these areas of applications a high degree of integration in optical systems is much sought-after. In the context of diffraction gratings this means that the angle of diffraction should be rather high, which typically poses a problem as the fabrication of small grating periods is challenging.

Switchable waveguiding in two liquid-crystal-filled photonic crystal fibers.

Switchable waveguiding is investigated in two liquid-crystal-filled photonic crystal fibers with a solid core using the nematic liquid-crystal mixture E7 under planar and homeotropic anchoring conditions. Addressing experiments using ac voltages show polarization-dependent and -independent effects with response times down to a few ms. It is shown that the attenuation spectra of the two liquid-crystal-filled photonic crystal fibers can be changed dramatically by just varying the boundary conditions.

Infiltrated photonic crystal fiber: experiments and liquid crystal scattering model.

Experimental results obtained by means of a cut-back technique indicate low attenuations (< 1 dB x cm(-1)) for a solid core photonic crystal fiber filled with the nematic liquid crystal E7. These results observed in the visible wavelength range are compared with electromagnetic field simulations. The latter are carried out with a full vectorial finite element algorithm.

Color-Tuned Electroluminescence from Columnar Liquid Crystalline Alkyl Arenecarboxylates.

Simple ester derivatives of polycyclic arenes offer access to light-emitting diodes of nearly any visible color by making use of the good charge-transport properties of the columnar liquid crystals of these derivatives. The picture shows the orange-red electroluminescence of a light-emitting diode containing the perylene 3,4,9,10-tetracarboxylic acid ethyl ester (structure shown, R=Et). Through use of multiple layers of different esters light-emitting diodes with almost white luminescence can be obtained.