Inversion in the change of the refractive index and memory effect near the nematic-isotropic phase transition in a lyotropic liquid crystal

This work demonstrates the occurrence of dn/dT inversion from negative to positive near the nematic-isotropic phase transition in a lyotropic liquid crystal. It is suggested that this effect can he attributed to a sudden increase of the electronic polarizability due to a change in the micelle shape near this phase transition. Formation of a long lasting lenslike element within the sample when it is irradiated at moderately high laser powers is also reported. This permanent lens is erasable by increasing the temperature above the nematicisotropic transition temperature.