PROCEEDINGS ARTICLE | November 10, 2003
Proc. SPIE. 5212, Linear and Nonlinear Optics of Organic Materials III
KEYWORDS: Sensors, Polymers, Metals, Tungsten, Nonlinear optics, Picosecond phenomena, Optical limiting, Molybdenum, Laser beam diagnostics, Absorption
Transition metal carbonyl clusters incorporating group 6 (molybdenum, tungsten) and iridium atoms in a tetrahedral or butterfly-shaped four-atom cluster core, together with carbonyl, cyclopentadienyl and alkyne ligands, have been synthesized and incorporated into oligourethanes, and their optical limiting properties assessed by open-aperture Z-scan (ns pulses, 523 nm) and time-resolved pump-probe studies (ps pulses, 527 nm). The Z-scan studies reveal that the tetrahedral [M2Ir2] cluster cores (M = Mo, W) displayed a greater effective nonlinear absorption coefficent β2 than the [MoIr3] cores; the tungsten example, W2Ir2(CO)10(η-C5H5)2, exhibited the highest response. Substitution at the cyclopentadienyl group (including incorporation into a polymer backbone) had little effect on the response measured. A time-resolved investigation of the alkyne-adduct Mo2Ir2(μ4-η2-MeC2Ph)(CO)8(η-C5H4Me)2 using picosecond pulses at 527 nm reveals optical-power-limiting behaviour that results from electronic processes [specifically, a fast nonlinear absorption process followed by reverse saturable absorption involving long-lived (>1000 ps) metastable excited states].
