Two-photon absorption and nonlinear optical properties of a new organic dye trans-4-[p-(N-hydroxyethyl-N-methylamino)styryl]-N-methylpyridinium p-toluene sulfonate

Trans-4-[p-(N-hydroxyethyl-N-methylamino)styryl]-N-methylpyridinium p-tolue ne sulfonate (abbreviated as HMASPS) is a newly synthesized dye that posses ses a much greater two-photon-absorption (TPA) cross-section and much stron ger upconversion fluorescence emission than common dyes (such as rhodamine) when excited with near infrared laser radiation. TPA induced upconverted l asing has been obtained in HMASPS solution in dim ethylformamide (abbreviat ed as DMF) pumped by near infrared laser beam from 900 to 1150 nm. The cent ral wavelength and bandwidth of the lasing are 626 nm and 26 nm. The upconv ersion efficiencies of 1cm-path HMASPS solution in DMF at 0.05 mol/l concen tration at different wavelengths from 900 to 1150 nm were measured. The net upconversion efficiency from the absorbed pump energy to the upconverted l asing output was 14% at the pump energy level of 2.04 mJ when the pump lase r beam was provided by Nd:YAG laser. The molecular TPA cross-section at 106 4 nm was sigma (2) = 6.0 x 10(-48) cm(4).s/photon measured by using an open aperture Z-scan system. The linear absorption, single-photon induced fluor escence, two-photon induced fluorescence and two-photon induced upconverted lasing properties have also been studied in this paper.