Z-Scan Studies of Dispersion of the Complex Third-Order Nonlinearity of Nonlinear Absorbing Chromophores

We have studied dispersion of the cubic nonlinear optical properties of organic and organometallic nonlinear absorbers. The results indicate that a multitude of excited states may be contributing to the resonances seen in the real and imaginary part of the complex hyperpolarizability. Attempts to understand the relation between the real and imaginary part of the hyperpolarizability in terms of a Kramers-Kronig transform are undertaken.