Figure 2
From: Uncovering different states of topological defects in schlieren textures of a nematic liquid crystal
Positive and negative fluorescent dichroic properties of dyes in NLC. (a) Analyser-angle-dependence of relative fluorescence intensities of dye-doped NLCs in a planar cell with the thickness of 2 μm collected using the fluorescence microscopy setup. The analyser at 0 degree is parallel to the director n without an electric field. An AC electric field (peak-to-peak 10 V at 100 Hz) is applied in the surface normal direction to orient n perpendicularly. The relative fluorescence intensities are values normalized by those at the angle of ±90 degree without electric field. (b) and (c), Schematics of the average configurations of transition dipole moments, t, of the dyes in NLCs (blue ellipsoids), along with their chemical structures. t of pyrromethene 597 (PMN) (shown by green colour) aligns along n, indicating that PMN in NLC has positive dichroic property. t of C-Naphox (CNX) (shown by red colour) is distributed perpendicularly to n with rotational freedom in the plane normal to n, indicating that CNX has negative dichroic property.
