Enhancement of third-order nonlinear optical susceptibility of Alq in polar aprotic solvents.

The influence of solvent polarity on nonlinear optical properties of tris-(8-hydroxyquinoline)-aluminum (Alq) was investigated by the degenerate four-wave mixing method at the 532 nm. It was obtained that the effective values of the third-order nonlinear optical susceptibility (χeff⟨3⟩) and the second-order hyperpolarizability (γ) of Alq depend on the solvent polarity. Additionally, it was found that Alq dissolved in dimethyl sulfoxide has the highest values of χeff⟨3⟩ and γ. Furthermore, two Stegeman's figures of merit were also calculated. The obtained results suggest that Alq is also promising material for application in all-optical signal processing devices.