Investigation of transient optical nonlinearity in pyrene-based ferrocene and its optical limiting potential for ultrafast laser absorption

The ultrafast optical nonlinearity of a pyrene-based ferrocene derivative (Py-Fc) is systematically studied via Z-scan, transient absorption spectrum (TAS), and phase object pump probe (POPP). An ultrafast broadband absorption in visible wavelength region is observed via TAS. Based on this finding, nonlinear optical absorption of the material is investigated at various wavelengths. Results indicate that different absorption mechanisms, including reverse saturable absorption and two-photon induced excited state absorption involve in the nonlinear absorption in visible spectrum. The cooperation between the two mechanisms brings strong optical limiting properties. In addition, negative nonlinear optical refraction from the excited state is observed in POPP experiment and its dynamics is discussed. These results demonstrate that the molecular Py-Fc exhibits strong optical limiting, suggesting it is a potential material for ultrafast laser protection.