Photo-induced birefringence in a nematic liquid crystal mixture doped with light-switchable mesogenic azobenzene derivatives

Abstract We report on photoinduced effects observed in azo-mesogene doped nematic liquid crystal mixture using birefringence measurement method. In Optical Kerr Effect configuration the photoinduced birefringence observed in the studied planarly aligned liquid crystal cell is equivalent to very high n 2  ≈ 13 cm 2 /W nonlinear optical coefficient. Experimental results are explained on a basis of light-induced modification of the surface conditions due to trans-cis isomerizations that affect the bulk effective electric field acting on molecules. The measurements are supported by a simple model of the phenomenon and Jones matrix calculus. The response of the system is composed of two dynamically different contributions: the fast and the slow one.