Investigation of the nonlinear absorption and optical limiting properties of two [Q]2[Cu(C3S5)2] compounds

The nonlinear absorption properties of two organometallic compounds, (C₂H₅)₄N]₂Cu(C₃S₅)₂] (DCu1) and (C₄H₉)₄N]₂Cu(C₃S₅)₂] (DCu2), have been investigated using an open-aperture Z-scan technique at 1064 nm with 40 ps pulse width and at 1053 nm with 18 ns pulse width. The reverse saturable absorption (RSA) which was observed in both samples with nanosecond pulse excitation was much larger than that observed with picosecond pulse excitation. The nonlinear absorption properties were analyzed theoretically by a five-level model. Optical limiting based on RSA was performed and limiting thresholds were evaluated for both samples under three conditions. DCu1 exhibited the better limiting characteristics because of its stronger RSA response.