Hannover 2010 – wissenschaftliches Programm

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Q: Fachverband Quantenoptik und Photonik

Q 47: Photonics I

Q 47.1: Vortrag

Donnerstag, 11. März 2010, 11:15–11:30, F 128

Electrooptical properties of clear point modified liquid-crystal-based mixtures — •Martin Blasl, Kirstin Bornhorst, and Florenta Costache — Fraunhofer Institute for Photonic Microsystems, Maria-Reiche-Str. 2, 01109 Dresden, Germany

We investigate electro-optically active materials, such as the thermotropic liquid crystals of n-CB type to be used in active waveguide devices.

The n-CB exhibit in their isotropic phase high Kerr coefficients, being therefore well-suited for such devices. In addition, as opposed to their nematic or smectic phases, in their isotropic phase n-CB give rise to low scattering of the guided light.

However, to get n-CB in their isotropic phase they must be heated above their nematic-isotropic transition temperature (clear point). This means that the waveguide device should be kept at a temperature above the clear point. Our aim is to minimize the required heat power consumption of the device by lowering the clear point.

We observed that the clear point can be manipulated by embedding n-CB in different mixtures. For instance a 6-CB-oil mixture appeared in its isotropic-phase already at room temperature. DSC measurements revealed that the clear point changes with changing the oil concentration in the mixture. For instance in 6-CB the clear point shifts towards lower temperatures with increasing concentration of oil. On the other side critical angle measurements show that the Kerr effect in the mixtures remains nearly unchanged, which is of significant importance for active liquid crystals based waveguide devices.