Nonlinear optical properties of a new two-photon-absorption organic dye: HEASPS

Trans-4- [p-(N-hydroxyethyl-N-ethylamino)styryl] N-methylpyridinium p-tolue ne sulfonate (abbreviated as HEASPS) is a two-photon-absorption (TPA) dye n ewly synthesized by our research group. It possesses a much larger TPA cros s-section and much stronger upconversion fluorescence emission than those o f common organic dyes (such as rhodamine) when excited with near-infrared ( IR) radiation. TPA spectrum and upconversion efficiency spectrum of HEASPS solution at different wavelengths have been measured. The largest molecular TPA cross-section sigma'(2) is measured to be 2.06 x 10(-47) cm(4) s/photo n at 930 nm. At 1064 nm, sigma'(2) is 2.71 x 10(-48) cm(4)s/photon, which i s only one-ninth of that at 930 nm. The upconverted lasing efficiency spect rum has been measured at different wavelengths. The highest efficiency is 5 .1% at 1020 nm, whereas it is 3.5% at 1064 nm. Its optical-power-limiting p roperties at 930 nm have also been illustrated.