Multiphoton fluorescence free hyperpolarizabilities of subphthalocyanines

Subphthalocyanines have potential applications in the field of second-order nonlinear optics. However, multiphoton fluorescence has seriously complica ted the accurate retrieval of their molecular first hyperpolarizability bet a by hyper-Rayleigh scattering. We report here hyper-Rayleigh scattering re sults on subphthalocyanines with experimental evidence of effective multiph oton fluorescence suppression. It is demonstrated that multiphoton fluoresc ence does indeed contribute to the scattering signal but that accurate valu es for the first hyperpolarizabilities can be deduced when taking this prop erly into account. More generally, this shows that experimental evidence of the absence of a multiphoton fluorescence contribution to hyper-Rayleigh s cattering should be included whenever hyperpolarizability values of fluores cent compounds are reported. (C) 1999 Elsevier Science B.V. All rights rese rved.