Hyper-Rayleigh scattering of polymers with orientationally correlated chromophores

Conjugated organic chromophores capped with electron donor and acceptor groups are known to have good electro-optical (E-O) properties such as large second order susceptibility. Much research activity has been focused on these molecules to search for possible applications in second harmonic generation, frequency conversion, and E-O modulation. Organic chromophores used in second order nonlinear devices must be noncentrosymmetric such that their first hyperpolarizabilities (β) are nonvanishing. Furthermore, in macroscopic scale organic chromophores should be arranged into a noncentrosymmetric distribution with a nonzero second order susceptibility. This is usually achieved by poling organic chromophores with a static electric field Recently, Kauranen et al. (1995) have shown that organic chromophores can be organized as orientationally correlated side groups of the polymers with a rigid backbone. In such organization, each chromophore contributes coherently to both μ (permanent dipole moment) and β of the polymers and hence the second order nonlinear responses of the polymers are enhanced. In the paper, the hyperpolarizabilities of the push-pull chromophores and the polynorbornenes that contain the push-pull chromophores as side groups are measured and compared using the long wavelength hyper-Rayleigh scattering (HRS) technique