We report an experimental investigation of absorption, fluorescence, and nonlinear absorption in a platinum-ethynyl complex. We have observed strong singlet absorption at 355 nm, and a weaker triplet absorption at 520 nm. Photoluminescence measurements show a fluorescence band at 400 nm and a phosphorescence band at 520 nm. Pump–probe nonlinear absorption measurements confirmed that S0→T1 followed by excited triplet-state absorption corresponds to the dominant excitation path in the region between 513 and 532 nm.

The Z-scan technique is a popular method for measuring degenerate (single frequency) optical nonlinearities using a single laser beam. In order to perform reliable measurements, it is necessary to carefully characterize and control a number of experimental parameters, such as the beam quality, the power and temporal characteristics of the laser, the collection aperture size and position, the sample reflectivity, sample thickness and imperfections in the sample. Failure to control these parameters leads to inaccurate determinations of the nonlinearities. In this paper, we review the theory of Z-scan and examine each of these issues from experimental and theoretical viewpoints. This work will be of interest to anyone who performs Z-scan experiments and to those interested in optical power limiting and nonlinear optical propagation.

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Analytical, numerical, and experimental studies of the nonlinear transmission of a Pt:ethynyl compound have been carried out. Based on a model for the electronic transitions derived from earlier work, optical limiting behavior that is both broadband across the visible and effective over a range of pulse lengths, is predicted. Detailed experimental results are presented which exhibit many of the theoretically predicted characteristics, including a broadband nonlinear response from 450 to 700 nm.

We report pulsed laser studies of nonlinear luminescence in a platinum ethynyl complex which, from 560 to 700 nm, shows strong two-photon absorption from the ground singlet state to an excited singlet state. The spectral dependence of the photoluminescence peaks indicates that in the region from 560 to 700 nm the two-photon absorption cross section is independent of excitation wavelength. Through the use of a simple calibration we have been able to estimate the number of states (NS1) formed from two-photon absorption, and have found good agreement with theory using the value of β=0.34 cm/GW measured previously.