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Zhang J.,China Jiliang University | Zhang J.,Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology | Liu J.,China Jiliang University | Huang X.,China Jiliang University | And 2 more authors.
Physica Status Solidi (A) Applications and Materials Science | Year: 2012

Ba0.4Sr0.6Ti1-yCoyO3 ceramics show a diphase of Ba1-xSrxTiO3 and 6H-hexagonal BaTi1-yCoyO3. As y increases, Ba0.4Sr0.6Ti1-yCoyO3 ceramics experience a transformation from ferroelectric to relaxor-like behavior. For the samples with y ≥ 0.10, the dielectric constant exhibits relaxor-like behavior with the frequency-dependent temperature of the dielectric peak Tm following an Arrhenius law, accompanying a giant dielectric response. The dielectric relaxation with an extremely high dielectric peak is attributed to charge ordering and defects. The samples with low Co levels (y ≤ 0.05) exhibit dielectric nonlinear behavior, whereas those with high Co levels (y ≥ 0.10) have ferromagnetic properties. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Wu C.,Tongji University | Wu C.,Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology | Li H.,Tongji University | Wei Z.,Tongji University | And 4 more authors.
Physical Review Letters | Year: 2010

We developed a theory to compute and interpret the photonic band structure of a periodic array of metallic helices. Interesting features of the band structure include longitudinal and circularly polarized eigenmodes and wide polarization gap. The helical symmetry also implies unusual features such as negative group velocity bands at both sides of the polarization gap and band crossings pinned at the zone boundary. A direct proof of negative refraction via a chiral route is achieved for the first time by measuring the spatial beam shift through a slab of the three-dimensional helices. © 2010 The American Physical Society. Source


Gao W.,Hong Kong University of Science and Technology | Leung H.M.,Hong Kong University of Science and Technology | Li Y.,Hong Kong University of Science and Technology | Li Y.,Tongji University | And 4 more authors.
Journal of Optics | Year: 2011

We report on the fabrication of double-layer gold crossed-gratings consisting of a convoluted top gold grating superposed on a bottom gold grating by using an e-beam direct write technique together with a lift-off process. The crossed-gratings exhibit, in the visible range, strong circular dichroism which is dependent upon the incident direction due to the convoluted top gold grating and also the substrate. Resonance dips in the transmittance of circularly polarized light are also observed. The experimental results are explained qualitatively by simulations using a finite-integration technique. The simulations confirm that the dips in the transmittance are electromagnetic resonances corresponding to parallel and anti-parallel current flows in the crossed-gratings. © 2011 IOP Publishing Ltd. Source


Wang X.,Tongji University | Wang X.,Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology | Zheng H.,Tongji University | Zheng H.,Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology
Journal of Solution Chemistry | Year: 2011

In order to obtain the electronic structure of leucine (Leu) in aqueous solution, we studied three systems: Leu+7H2O, Leu+8H2O and Leu+9H2O. The results indicated that the system Leu +8H2O was the only choice which was both acceptable and doable: its computational effort was affordable, and it could simulate a main part of the solvent effect on the electronic structure of Leu in solution. Based on the system Leu+8H 2O, all-electron, ab initio calculations were performed to construct an equivalent potential of water for the electronic structure of Leu with dipoles. The results showed that the main effect of water on the electronic structure of Leu was raising the occupied states about 0.0824 Ry on average, and broadening the energy gap by 11%. The water effect on the electronic structure of Leu could be well simulated by the dipole potential. The obtained equivalent potential can be applied directly to the electronic structure calculation of proteins in solution. © Springer Science+Business Media, LLC 2011. Source


Li X.,Tongji University | Li X.,Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology | Shen J.,Tongji University | Shen J.,Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology
Qiangjiguang Yu Lizishu/High Power Laser and Particle Beams | Year: 2010

The mechanism of laser induced damage on optical films, and the methods to improve the laser-induced damage threshold(LIDT) were reviewed in two respects including theory and experiment. We summarized the existing theory models and their applicable scope, and also discussed the problems about defects from various aspects. The characteristics of different coating technics and after-treatment ways were compared in detail. By gathering the achievements of our own and peer institutions at home and abroad, we generalized the sol-gel technics which could be used to improve the LIDT. We also pointed out the direction of future work considering some newly emerging problems such as contamination in vacuum and the subsurface damage. Source

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