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

Abstract

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.