Investigation of third-order nonlinear optical properties of two azo-nickel chelate compounds

This paper investigates the third-order nonlinear optical properties of two azo-nickel chelate compounds by the optical Kerr gate method at 830 nm wavelength with pulse duration of 120 fs. Both of the two compounds exhibited large third-order optical nonlinearity. The second-order hyperpolarizability, \gamma, of Compound 1 is of 1.0\times 10^ - 31 esu. Due to the charge transfer, the \gamma of Compound 2 with electron donor and acceptor group is 4.9\times10^ - 31 esu, which is a four-time enhancement in comparison with Compound 1. The absorption spectra show that the electron push--pull effect, which induces intramolecular charge transfer, leads to the increased optical nonlinearity.