Surface morphology of doped nematic liquid crystals: role of dye concentration

Abstract

We report on laser-induced ripple structures in dye-doped nematic liquid crystals for different dye concentrations varying between 0.5% and 2% wt. The surface morphology was studied by atomic force microscopy. For dye concentrations smaller than 0.56% the ripple structure was not obtained. The depth of the ripple structure depends on both the laser power and the dye concentration. Using the Berreman formula for periodic structure, the azimuthal anchoring energy was evaluated. An increase of the anchoring energy with the dye concentration and with the pump power was noted.

Keywords:

• nematic liquid crystal
• azo dye
• ripple structure
• atomic force microscopy

Acknowledgements

The authors thank Professor Anca-Luiza Alexe-Ionescu for fruitful discussions. This work was supported by CNCSIS Romania, IDEI nr.109/5.10.2011.