Zou Ying-hua

Heterodyned Femtosecond Optical Kerr Effect of Substituted Conjugated Polymers

The femtosecond optical heterodyne detected optical Kerr effect is described. The real and the imaginary parts of complex third-order optical nonlinearity can be effectively separated and their values and signs can be determined. Using this method, we have thoroughly investigated the substitution effect by adding side-groups on the -(-C=N-)- conjugated system, a new class of nonlinear optical material, and find that the polybenzonitrile (γr = -1.59 × 10-31 esu, m = 6) is an order of magnitude superior to poly-amino-nitrile. But when we further add substituents on benzoid rings, the enhancement is limited. We can say that for the series of polybenzonitrile, the benzoid ring can improve the χ(3) value more effectively than other substitutions.

FEMTOSECOND TIME-RESOLVED NEAR-FIELD SPECTROSCOPY OF CDSE NANOCLUSTER FILMS

By using scanning near-field optical microscopy in the femtosecond time-resolved pump-probe experiments, we have studied the time-resolved near-field spectroscopy of CdSe nanocluster films. The submicrometer space dependence of electron dynamics was observed, which is attributed to the non-uniform distributions of interstitial defects in the films.

Coherent Phonons in Ag-BaO Thin Films

Coherent acoustic phonons have been observed in Ag nanoscale particles (NSPs) embedded in BaO thin film by means of the femtosecond time-resolved pump-probe technique. The oscillatory component in the signal corresponds to a very low-frequency acoustic phonon mode of Ag NSPs. The generation of coherent acoustic phonons is attributed to the resonant excitation of localized surface plasmon.

Ultrafast Time-Resolved Optical Kerr Effect in Phthalocyanine Langmuir-Blodegett Film

The resonant optical Kerr effect in the Langmuir-Blodegett film of 2, 9, 16, 23-tetraheptadecylamido substituted vanadyl phthalocyanine was measured with femtosecond laser pulses to determine the relaxation time, and meanwhile slow decay components were observed. The ultrafast nonlinearity of the molecule was also measured.

Measurement of Third Order Hyperpolarizability of Some Dyes

A degenerate four-wave mixing experiment with the solutions of some dyes has been performed using 10 ns pulses at 530 nm. Large resonant and off-resonant third order hyperpolarizabilities were obtained.

Transarterial chemoembolization plus multi-imaging–guided radiofrequency ablation for elimination of hepatocellular carcinoma nodules measuring 3.1 to 5.0 cm: a single-center study

Objective This study was performed to determine whether transarterial chemoembolization (TACE) plus multi-imaging–guided radiofrequency ablation (MIG-RFA) can completely eliminate 3.1- to 5.0-cm hepatocellular carcinoma (HCC) nodules and identify factors that may influence the complete elimination rate (CER) of this therapy. Methods Patients who underwent TACE+MIG-RFA for initial treatment of HCC from January 2008 to January 2016 were retrospectively reviewed. In total, 162 patients with 216 HCC nodules (3.1–5.0 cm) were enrolled. TACE was performed first; MIG-RFA was performed 2 to 4 weeks later. Contrast-enhanced computed tomography was performed 1, 3, 6, and 12 months after TACE+MIG-RFA. If tumor enhancement was not detected by the end of the 12-month follow-up, the lesion was considered completely eliminated. Additional TACE+MIG-RFA was performed for residual lesions. The CER was calculated 12 months after the last therapy. Factors that may influence the CER were analyzed. Results In total, 207 (95.8%) nodules showed no residual lesions and were completely eliminated after one or more TACE+MIG-RFA sessions. Nine (4.2%) nodules were incompletely eliminated even with repeated TACE+MIG-RFA. Tumor location was the only significant prognostic factor influencing the CER. Conclusions TACE+MIG-RFA can eliminate 3.1- to 5.0-cm HCC nodules; the tumor location may affect the treatment outcome.

Ultrafast Optical Properties of C70 Thin Film

The relaxation of optically excited carrier in C70 thin film fabricated by physical jet deposition was investigated by femtosecond pump-probe measurements. A transient decrease in transmission was observed indicating induced absorption. In comparison to C60 thin film the initial response of C70 film is laser pulse limited and the long lived component has smaller magnitude. The third order optical nonlinear susceptibility of C70 thin film was determined to be χ(3) = 3.3 × 10-11 esu by femtosecond time-resolved optical Kerr effect. From the primarily pulse limited response the dephasing time of C70 thin film has been proved to be shorter than the laser pulse width.

Ultrafast Optical Response of Phthalocyanine Langmuir-Blodegett Film

The mechanism of 2, 9, 16, 23- tetra-heptadecylamido substituted vanadyl phthalocyanine Langmuir-Blodegett film was studied with femtosecond laser pulses. An ultrafast decay due to phonon-exciton coupling greatly affected by temperature, and exciton-exciton annihilation leading to the recovery of the ground state (T similar 10 ps) and an even slower relaxation were observed.

Femtosecond Spectroscopy Studies on YBa2Cu3O7-x and PrBa2Cu3O7-x Epitaxial Thin Films

We report the results of femtosecond spectroscopy studies on YBa2Cu3O7-x (x=0.1, 0.4, 0.8) and PrBa2Cu3O7-x (x=0.1) epitaxial thin films at room temperature. The transient reflectivity signals ΔR(t) in the samples are consistent with a band filling model. The relaxation times of ΔR(t) in YBa2Cu3O7-x increase from less than 100 fs to more than 1 ps with increasing x and with substitution of Pr for Y. These results reveal that in high Tc superconductors decrease of carrier concentration slows down the carrier-phonon coupling.

Optical field induced refractive index change due to collision-enhanced zeeman coherence

The collision-enhanced Zeeman coherence ?(w1-w2)(2) has been demonstrated by the effect of optical field induced index of refraction change, which is described by the real part of the nonlinear susceptibility ?(-w1,w1,-w2,w2)(3). The experiments are performed in sodium vapor by a Mach-Zehnder interferometer. The dependences of the effect on the magnetic field, pump beam intensity, and Ar pressure are consistent with the theory.