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′–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) × 10^–6 cm²/GW at 750 nm to 4.6(±0.7) × 10^–6 c²/GW at 1550 nm, the value of nonlinear absorption β 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.