Two-photon-absorption and upconverted superradiance properties of organic dye HEASPS-doped linear homogeneous polymer at several wavelengths

The spectral and temporal properties of single- and two-photon fluorescence of a dye-doped linear homogeneous polymer are reported. The dopant is a new organic dye, trans-4-p-(N-hydroxyethyl-N-ethylamino)styryl-N-methylpyridinium p-toluene sulfonate (HEASPS), synthesized by researchers at the State Key Laboratory, Jinan China. When the dye is excited by near-infrared laser radiation, strong upcoverted fluorescence and superradiance can be observed. The difference in the blueshift of two-photon superradiance compared with that of two-photon fluorescence is explained by the use of different reabsorption coefficients under different conditions. The lifetime of two-photon fluorescence in a solid was measured to be 4.14 ns, which was much longer than that in solution. Two-photon transmittance and upconversion efficiencies at different wavelengths were measured with an optical parameter amplifier as the pump source. The strongest two-photon absorption occurred at 930 nm. The highest upconversion efficiency was 4.05% at 1030 nm. A possible mechanism is discussed.