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In this study, linear absorption, single-photon excited fluorescence, fluorescence quantum yields, fluorescence lifetime and two-photon excited fluorescence of a series of triphenylamine derivatives (L1, L2, L3 and L4) have been measured. L1and L3are D-p-A type dyes, while L2and L4are D-p-D-p-A type dyes (D = donor, A = acceptor). The investigated compounds consist of triphenylamine-bearing donor-substituted and/or systematically extended p-conjugated length, which are designed to gain insight into the effect of the ethoxyl unit and p-linkage length on the linear and nonlinear optical properties. The influence of solvent polarity on the photophysical properties was investigated. Employing time-dependent density functional theory (TD-DFT) calculations, the structure-property relationships are discussed.

The linear and nonlinear optical properties of a new organic dye, trans-4-[p-(N-ethyl-N-ethylamino)-styryl]-N-methyl-pyridinium tris(thiocyanato) cadmates (II), are reported in this paper. When pumped with a picosecond laser at the wavelength range of 850–1200 nm, intense upconversion fluorescence can be obtained. The upconversion efficiencies at different pump energies were measured when pumped with a 1064-nm laser beam from a mode-locked Nd:YAG laser. The highest upconversion efficiencies were measured to be 5.8% and 7.6% in dimethyl formamide (DMF) and methanol. The lifetime of the dye in DMF was measured to be 75 ps. The strongest nonlinear absorption was at the wavelength of 940 nm, and the highest upconversion efficiency was at the wavelength of 1030 nm. The difference of the two wavelengths was caused by excited state absorption in the dye at wavelengths shorter than 1000 nm. The dye solution in DMF and methanol show a clear optical power limiting effect.