Nonlinear absorption and upconversion properties of two-photon absorption dye: ASPI

Two-photon absorption (TPA) cross sections of an organic dye, trans-4-[p-(N-hydroxyethyl-N-methylamino)tyryl]-N-methylpyridinium iodide (abbreviated as ASPI), from 720 to 1100 nm have been measured by using nonlinear transmittance method, which reflect the TPA degrees of the dye at different wavelengths. The maximum TPA wavelength is located at 930 nm. The upconversion efficiencies of ASPI in dimethyl formamide and benzyl alcohol at different pump wavelengths have also been measured. There is 90 nm red shift for the highest upconversion wavelength as comparing with the strongest TPA wavelength. The influences of the solvents on the TPA-induced emission spectrum and the conversion efficiencies have also been given.