Nonlinear optical properties of push–pull polyenes for electro-optics

Improved nonlinear organic chromophores of varying conjugation length with either thiobarbituric acid or 3-dicyanomethylene-2,3-dihydrobenzothiophene-1,1-dioxide (FORON® Blue) acceptors have been synthesized and investigated for their nonlinear optical properties. Very large quadratic hyperpolarizabilities b(22v; v, v) have been found, up to 25,700 3 10248 esu at l 5 1.91 mm. In a guest–host polymer very high electro-optic (EO) coefficients, of up to 55 pm/V, have been determined at l 5 1.31 mm with 20-wt % chromophore loading. We find good agreement between molecular parameters evaluated by electric-field-induced second-harmonic generation (EFISH) and the measurements of guest–host solid–solid solutions. The latter method is well suited to the determination of the product of dipole moment m and hyperpolarizability b quickly and reliably at the wavelength of interest for EO applications without the complications associated with EFISH measurements. © 1996 Optical Society of America.