Kinetics of third-order nonlinear optical susceptibilities in alkynyl ruthenium complexes

Kinetics of third-order optical susceptibilities obtained for a new series of alkynyl ruthenium complexes was investigated in using pump-dependent transmission experiment and the degenerate four-wave mixing (DFWM) technique. We investigate electron rich σ-acetylide ruthenium complexes in which the d-transition metal is incorporated in the same plane as the π-system of formyl alkynyl ligands. The obtained results show that the presence of a bilaterally ligands leads to substantial increase of the χ〈3〉. The maximally achieved third optical susceptibility was χ〈3〉 = 0.9 × 10−20 m2 V−2 at λ = 0.53 μm for chloroform solution concentration 0.4 mol l−1. The value of second-order optical hyperpolarizabilities γ for the investigated compounds were four orders of magnitude larger compared to the known values of CS2. The quasi-periodic relaxation time kinetics of the DFWM with period about 7 ns was found after switching off the pumping beams. Such kinetics of the DFWM is explained by tunnelling between the occupied d-transition metal levels and electron-phonon trapping levels after interruption of the pumping signals.