A new hexagonal prism shaped metal cluster compound Mo2Ag4S8(dppy)4 was synthesized and structurally characterized by single crystal X-ray diffraction measurement. Its third-order nonlinear optical (NLO) properties were investigated by using a Z-scan technique under nanosecond laser pulses at 532 nm. Optical nonlinear response of the metal cluster was researched by using a time-resolved pump-probe experiment under picosecond laser pulses at 532 nm. The experimental results show that the metal cluster exhibits both optical self-focusing effect and optical nonlinear absorption. The nonlinear refractive index n2, the nonlinear absorption coefficient β, and the third-order nonlinear susceptibility χ(3) of Mo2Ag4S8(dppy)4 are 1.45×10－10 esu, 6.2×10－10 m/W, and 2.1×10－11 esu, respectively. The experimental results indicate that the optical nonlinear response for Mo2Ag4S8(dppy)4 originates from the combination of nonlinear absorption and nonlinear scattering.

Key words: metal cluster, optical nonlinearity, Z-scan, pump-probe