Faraday Rotation in Discotic Liquid Crystals by Long-Range Electron Movement

Faraday rotation (FR), a magneto-optic (MO) property of a material, is the rotation of the plane of polarization of light by a magnetic field in the direction of the propagation of the light. Being able to use this effect for measuring very small magnetic fields requires efficient Faraday-active materials, which combine high activity with low losses of light intensity. In search of such materials, we examined the FR of a room temperature discotic liquid crystal. When homeotropically aligned, a large MO response was observed, which only occurred when the magnetic field was perpendicular and the electric field was parallel to the liquid crystal director. The MO response could be further enhanced by changing the intermolecular distance by mixing in another compound to relief sterical hindrance. Combined with the excellent optical transparency in the visible part of the spectrum, we have identified a new MO material that shows great potential for use in demanding applications