Surfactant-controlled light-induced reorientation in dye-doped nematic liquid crystals

We show that a very large optical response is obtained in azo-dyedoped nematic liquid crystals for low input light intensities (of the order of a few tens of µW/cm2 and that this extreme sensitivity of the nematic film results from a combined action of the photoisomerization process of the azo-dye molecules and the light-induced changes of the anchoring energy. The liquid crystal reorientation can be controlled by changing the molecular length of the ionic surfactant which is used as anchoring agent.