Jun Mi

Excited-state dynamics of magnesium phthalocyanine thin film

Abstract Ultrafast excitation relaxation dynamics of magnesium phthalocyanine (MgPc) thin film were investigated by femtosecond pump-probe spectroscopy. The excited state dynamics of MgPcs Q-band were found to be strongly dependent on the probe wavelength. Ultrafast exciton–exciton annihilation with a t −1/2 time dependence of the excited-state population was observed.

Femtosecond nonlinear optical response of metallophthalocyanine films

The third-order nonlinear optical properties of copper phthalocyanine (CuPc) and magnesium phthalocyanine (MgPc) films were investigated by femtosecond optical Kerr effect (OKE) and pump-probe techniques. For both CuPc and MgPc, the third-order nonlinear optical susceptibility was enhanced at least by one order of magnitude in comparison with that of the metal-free Pc, and the enhancement effect arises from different mechanisms for both films. From pump-probe measurement, quite different transmittance and decay behavior between CuPc and MgPc films were observed. The CuPc films show an ultrafast decay, while the decay behavior of MgPc film is complicated with several temporal components, which could be explained by the relaxation of singlet excited state.

Ultrafast optical nonlinearity of titanylphthalocyanine films

Abstract The optical properties of titanylphthalocyanine (TiOPc) thin film fabricated by physical jet deposition technique were investigated by using absorption, femtosecond (fs) optical Kerr effect (OKE) and fs pump–probe techniques. The third-order nonlinear optical susceptibility of TiOPc film was measured to be 3×10 −10 esu. The OKE response of TiOPc films shows a decay process with subpicosecond time constant, demonstrating that the excited state of TiOPc molecule has little contribution to the photo-induced birefringence. From the fs pump–probe experiment, a complicated decay behavior with three decay components was observed, which originates from the contribution of exciton–exciton annihilation process, the enhanced intersystem crossing process and the relaxation of the triplet state.

The observation of excited-state dynamical evolution in light-harvesting complex LH2 from Rhodobacter sphaeroides 601

With selective excitation around BChl–B800 and BChl–B850 absorption bands, we observed the evolution of excited‐state dynamics in LH2 from Rhodobacter sphaeroides 601. The dynamical traces demonstrate a dominant excited‐state absorption (ESA) followed concomitantly by an ultrafast transmission increase and decay with pulse‐width limited time scale at 818 nm and 828 nm excitation. The ESA occurring prior to excitonic thermalization or ground‐state bleach was observed at 840 nm as well. These experimental results indicate the competition between the transition from excitonic states to higher‐lying excited states and interexciton relaxation, which are of physical significance for understanding excitation transfer and related mechanisms in LH2.

Synthesis and optical properties of PbS/ZnO composite films

Pure ZnO films and PbS/ZnO nanocomposite films of optical quality were prepared with a sol–gel method. The particle size, optical absorption, and linear refractive index of the PbS/ZnO films were measured by TEM (transmission electron microscopy), UV-Vis absorption, and ellipsometry techniques, respectively. For high Pb/Zn ratios, PbS particles of size 5–8 nm are observed in TEM, and a large refractive nonlinearity of 10−7 esu with a saturable absorption was measured in picosecond Z-scan experiments.

Excited-state enhancement of third-order optical nonlinearity in a PPV derivative

By using two-color femtosecond optically heterodyned optical Kerr effect experiment, we studied the real components of third-order nonlinearity of 2,5-dioctyloxy poly(p-phenylene vinylene) (DO-PPV). As pump wavelength was set near the absorption region of the material, the value of x(3) of DO-PPV was improved by one order of the magnitude comparing with that of nonresonant condition. We suggest that this enhancement result from the contribution of the excited state.