Variations of the organometallic cluster known as King's complex, [ (CsH~)Fe(C0)14, have been synthesized to study the excited-state transition responsible for reverse saturable absorption observed at 532 nm in this molecule. Picosecond pumpprobe measurements have been used to measure the excited-state cross sections and lifetimes in King's complex and the analogs methyl-King's complex, [CH3(C5H4)Fe(C0)I4, and triethylaluminum King's complex, [ (CsH5)Fe(COAl(C2H5)3)]4. Within experimental error, the excited-state parameters are unaffected by alterations to either the carbonyl or the cyclopentadienyl ligand of the King's complex. These results are consistent with an excited-state absorption resulting from a second d to d transition within the singlet states of the metal core.

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We present a modification of the beam-propagation algorithm that avoids computer-intensive processing of the sound carrier and instead deals with the slowly varying complex sound profile only. Our three test cases of Gaussian beams with different waists, strongly interacting with a two-dimensional sound column, show excellent agreement with the analytical treatment and with physical experiments performed in our laboratory.

Picosecond time-resolved pump-probe and Z-scan measurements are used to investigate the nonlinear refraction and absorption associated with intense picosecond excitation above the indirect band edge of GaP. The pump-probe results reveal both an instantaneous absorption feature, which is consistent with two-photon absorption, and a long-lived feature that is associated with the generation of free carriers by linear indirect absorption. Z scans conducted with pulses of 25- and 95-ps duration indicate that, for these pulse widths, the nonlinear refraction in GaP is dominated by the linear generation of free carriers and that the role of the electronic Kerr effect is negligible. The measured free-carrier refraction is compared with the value predicted from a simple model based on band filling. This model predicts that the primary contribution to the index change at the applied optical frequency arises from holes blocking direct transitions near the zone center and that similar blocking of indirect transitions has a negligible effect on the index.

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