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Organometallic iridium(III) complexes have seen widespread use over the past two decades, particularly as phosphorescent dopants in organic light emitting diodes (OLEDs) due to their large spin-orbit coupling and metal-toligand charge transfer (MLCT) excited states. Interest in the non-linear optical (NLO) applications of these materials has increased recently with reports of both two-photon absorption (2PA) and reverse saturable absorption (RSA). A family of materials of the form [IrIII(NO2piq)2(acac)] were synthesized and characterized, where acac is acetylacetonate and NO2piq is a nitrophenylisoquinoline ligand. In order to assess structure-property relationships for the photophysics of these complexes, the placement of the nitro group was altered on the phenyl ring. Systematic control over the maxima of the absorption and photoluminescence bands attributed to the MLCT excited states was achieved through the ligand variation. The photophysical properties of this family of materials are discussed in detail and include their linear absorption spectra, photoluminescence measurements at 298 and 77K, excited state lifetimes, and CIE color chromaticity coordinates.

We exploit the strong spin-orbit coupling in iridium to modify the linear absorption spectrum of a novel iridium(III) complex so as to broaden the spectral region over which it exhibits reverse saturable absorption. We discuss the design of the new chromophore, present its ground-state absorption spectrum, and report values of its singlet excited-state lifetime and singlet and triplet excited-state absorption cross sections, determined from femtosecond transient difference absorption measurements and nanosecond and picosecond open-aperture Z scans.

Experimental measurements were performed to completely characterize the linear and nonlinear optical properties in butyl salicylate solution of a novel bipyridyl platinum(II) complex bearing benzothiazolylethynylfluorene ligands. This paper describes the analysis of the resulting experimental data and reports the values of the ground- and excited-state absorption cross sections and of the other photophysical parameters characterizing the chromophore/solvent system.

In top -hat Z scans that employ tunable sources such as optical parametric generators without line- narrowing gratings, the size of the aperture used to clip the beam may exceed the coherence length, and the variation with of the transverse z profile of the resulting partially coherent beam may differ significantly from that of a perfect top-hat beam. After a careful validation of our experimental set-up, we perform picosecond open -aperture Z scans with a top-hat beam at selected wavelengths in the visible and nanosecond open- aperture Z scans with a spatially Gaussian beam at 532-nm wavelength on a toluene solution of a particular platinum(II) -bipyridyl complex bearing  naphthalimidylethynyl-substituted fluo renylacetylide ligands . We report values of the singlet and triplet excited -state absorption cross sections of the complex. Keywords: Z scan, reverse saturable absorption 1. INTRODUCTION Thanks both to their intriguing photophysical properties and to the relative ease with which they can be synthesized and modified, platinum diimine complexes containing bis(arylacetylide) ligands have been the subject of considerable study in recent years.

We report the results of measurements performed on a particular platinum(II) 4,4'-bis[3-ethyl-1-(2-ethylhexyl)heptyl]-2,2'-bipyridyl complex bearing 2-(benzothiazol-2'-yl)-7-ethynyl-9,9-dihexadecyl-fluorenyl units. A similar complex, identical except for the presence of ethyl groups at the 9-position of the fluorenes and tert-butyl groups at the 4- and 4'- positions of the bipyridine, was recently reported to possess a very high ratio of triplet excited-state absorption to ground-state absorption, a quantity that has long been used as a figure of merit for reverse saturable absorbers; in addition, femtosecond transient difference absorption experiments and picosecond open-aperture Z-scans have shown it to display broad nonlinear absorption throughout the visible spectrum. In this work, we measured the triplet excitedstate absorption cross section at several representative wavelengths between 450 nanometers and 660 nanometers in an open-aperture top-hat Z-scan experiment employing a nanosecond-pulsed tunable optical parametric oscillator (OPO). The open-aperture Z-scan is a highly sensitive single-beam experiment used to measure nonlinear absorption. Since the spatial profile of the OPO beam resembled a cross-pattern, we closed an adjustable iris on the beam to create a top-hat profile. A dynamic five-level model was used to fit the Z-scan data.

Nonlinear transmission and optical limiting of picosecond and nanosecond laser pulses in an organic fiber core liquid are investigated. The measured effective absorption coefficients and other limiting characteristics are analyzed using a model that accounts for linear, two-photon, intermediate, and excited-state absorptions. In the picosecond regime, two-photon absorption process is the dominant mechanism. On the other hand, in the nanosecond and longer time scale, other processes such as excited state absorption and nonlinear scattering contribute significantly, giving rise to an effective nonlinear absorption coefficient that can be two orders of magnitude larger than the picosecond counterpart.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.