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(R) Blue) accepters have been synthesized and investigated for their nonlinear optical properties. Very large quadratic hyperpolarizabilities beta(-2 omega; omega, omega) have been found, up to 25,700 x 10(-48) esu at lambda = 1.91 mu m. In a guest-host polymer very high electro-optic (EO) coefficients, of up to 55 pm/V, have been determined at lambda = 1.31 mu m 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 mu and hyperpolarizability beta quickly and reliably at the wavelength of interest for EO applications without the complications associated with EFISH measurements. (C) 1996 Optical Society of America.