Tieqiao Zhang

Third-order nonlinear optical properties of didodecyldimethylammonium–Au(dmit)2

The third-order optical nonlinearity of metal(dmit)2 was investigated with femtosecond optical Kerr effect at 830 nm wavelength. The nonresonant second-order hyperpolarizability for the didodecyldimethylammonium–Au(dmit)2 (2C12–Au) molecule was estimated to be as large as 2.2×10−32 esu.

Measurement on the third-order optical nonlinearity of C70 and its poly-aminonitrile derivative by using the femtosecond optical Kerr effect

Abstract We have measured the second-order hyperpolarizability γ for C 70 and its poly-aminonitrile derivative by using the femtosecond optical Kerr effect at 810 nm. The result showed that C 70 exhibited a low optical nonlinearity. For the derivative C 70 –poly-aminonitrile a magnitude as high as 1.6×10 −32 esu was measured for the second-order hyperpolarizability. The origin of this extreme enhancement of the nonlinearity of fullerene was assigned to the formation of a charge-transfer complex.

Time-resolved excited state dynamics of a cyanine dye

Abstract The photophysics and isomerization dynamics in the excited state of a cyanine dye, 3,3′-di(3-sulfopropyl)-thiacyanine triethylaminium salt was investigated. Using the femotosecond time-resolved fluorescence up-conversion technique, wavelength-dependent fluorescence dynamics was observed and the theoretical prediction of the dual fluorescence behavior was vindicated. The results were explained using a barrierless isomerization reaction model. The origins of two decay components were assigned to the relaxation within the excited state and the S 1 → S 0 transition, respectively, and the time constants were obtained.

Ultrafast third-order optical nonlinearity of polybenzonitriles

Abstract The second-order hyperpolarizabilities γ of two novel substituted polynitriles: poly( p -methyl-benzonitrile) and poly( p -hydroxylbenzonitrile) (PHBN) were measured by using femtosecond time-resolved optical Kerr effect at 820 nm. The results show that these polynitriles have large non-resonant third-order optical non-linearities. Non-resonant γ as large as 4.8×10 −32 esu has been obtained for PHBN with only eight conjugated bonds. Compared with structurally similar materials, these polynitriles have larger γ at the same conjugation length. The dependence of γ on the substitution groups and the conjugation length was also studied.

Blocking effect of TiO2 colloids on the excited state isomerization of a cyanine dye

Abstract Fluorescence dynamics of a cyanine dye 3,3′-di(3-sulfopropyl)-thiacyanine triethylaminium salt in water with and without doping TiO 2 colloids has been investigated using the femtosecond time-resolved fluorescence up-conversion technique. A new component with a decay time larger than 30 ps for the dye molecules associated with TiO 2 was observed and a blocking effect of TiO 2 on the conformational isomerization process of the cyanine dye is suggested.

Ultrafast excited state dynamics of polybenzonitrile investigated by using femtosecond time-resolved fluorescence up-conversion

Abstract The photoluminescence dynamics of a new polymer, (–CN–) conjugated polybenzonitrile, was investigated with a femtosecond time-resolved fluorescence up-conversion technique. The experimental results revealed a bi-exponential relaxation dynamics for excited state and it was explained with the photo-generated excitons’ migration model.