title: Tricritical-like behavior of the nonlinear optical refraction at the nematic-isotropic transition in the E7 thermotropic liquid crystal.
abstract: We use Z-scan technique to investigate the nonlinear optical response of the thermotropic liquid crystal E7 in the neighborhood of the nematic-isotropic phase transition. The analysis of the data for the nonlinear optical birefringence is compatible with an effective critical exponent of the order parameter, β = 0.28 ± 0.03, which is close to the classical value, β = 0.25 , for a tricritical point. The nonlinear optical absorption in the nematic range depends on the geometrical configuration of the nematic director with respect to the polarization beam, and vanishes in the isotropic phase.
authors.affiliation: Departamento de Física, Universidade Estadual de Ponta Grossa, PR, Brazil.
authors.forename: V M
authors.initials: VM
authors.lastname: Lenart
authors.forename: S L
authors.initials: SL
authors.lastname: Gómez
authors.forename: I H
authors.initials: IH
authors.lastname: Bechtold
authors.forename: A M
authors.initials: AM
authors.lastname: Figueiredo Neto
authors.forename: S R
authors.initials: SR
authors.lastname: Salinas
mesh_terms: D001718:Birefringence; D050866:Liquid Crystals / Q000737:chemistry*; D008956:Models, Chemical; D044367:Phase Transition