Nonlinear optical absorption of a metal dithiolene complex irradiated by different laser pulses at near-infrared wavelengths

Abstract

Nonlinear optical (NLO) absorption of a metal dithiolene complex, [(C 2H 5) 4N][Ni(dmit) 2] has been studied by open-aperture (OA) Z-scan technique under irradiation with 15 ns and 1 ns laser pulses at 1053 nm and 40 ps laser pulses at 1064 nm. Distinct excited-state absorption behaviors were observed: a reverse saturable absorption (RSA) for 15 ns while a saturable absorption (SA) for 1 ns and 40 ps laser pulses, and the SA for 1 ns laser pulses was stronger than that for the latter. The mechanism responsible for the results with different laser pulses is analyzed using a five energy-level diagram.