Wavelength Dependence and Figures of Merit of Ultrafast Third-Order Optical Nonlinearity of a Conjugated 3,3 -Bipyridine Derivative

The wavelength dependence and figures of merit of the third-order optical nonlinearity of a conjugated 3,3 ʹ-bipyridine derivative, a designed nondipolar structure of the donor-acceptor-acceptor-donor type, are reported. Z scans reveal positive nonlinear refractive-index changes for wavelengths longer than the one-photon absorption wavelength. Although the value of nonlinear Kerr coefficient n2 decreases from 6.0( +/-0.2) x 10^-6 cm^2 /GW at 750 nm to 4.6( +/-0.7) x 10^-6 cm^2 /GW at 1550 nm, the value of nonlinear absorption ? decreases from 0.084 cm /GW at 750 nm to a negligible value at 1550 nm, giving rise to excellent nonlinearity-to-loss figures of merit at telecommunications wavelengths.