title: Azo-azulene derivatives as second-order nonlinear optical chromophores
abstract: The molecular and solid state nonlinear optical (NLO) properties of several (phenylazo)-azulenes are investigated. In particular, (4-nitrophenylazo)-azulene (2b) exhibits a quadratic hyperpolarizability (beta(vec)) of 80 x 10(-30) cm5esu recorded at 1.907 microm by the electric field-induced second-harmonic (EFISH) technique. This molecular material, which crystallizes in the monoclinic noncentrosymmetric space group Pc, exhibits an efficiency 420 times that of urea in second-harmonic generation. The origin of the optical nonlinearity in azo-azulene is discussed in relation with crystal structures and semiempirical calculations within the INDO/SOS formalism, and compared with that of the well known disperse red one (DR1) organic dye.
authors.affiliation: Laboratoire de Chimie de Coordination (CNRS), Toulouse, France. pascal@lcc-toulouse.fr
authors.initials: PG
authors.lastname: Lacroix
authors.initials: I
authors.lastname: Malfant
authors.initials: G
authors.lastname: Iftime
authors.initials: AC
authors.lastname: Razus
authors.initials: K
authors.lastname: Nakatani
authors.initials: JA
authors.lastname: Delaire