Surface-induced orientational phase transition in a lyotropic liquid crystal observed by nonlinear optical techniques.

Contains fulltext : 59342.pdf (publisher's version ) (Open Access)We have observed a phase transition from a uniaxial to a biaxial nematic phase in a lyotropic liquid crystal as a function of decreasing film thickness. The results, obtained by optical second-harmonic generation experiments in a wedged cell geometry, are supported by additional Z -scan measurements and can be interpreted by wall-induced ordering effects