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

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