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A novel C-band external-cavity wavelength-tunable laser is proposed. The laser consists of a semiconductor gain chip, a collimating lens, a fixed etalon, a liquid-crystal deflector and a diffraction grating in a Littrow configuration. The lasing wavelength of this tunable external-cavity laser can be tuned to 19 wavelength channels of 100 GHz spacing. All channels are within 2.5 GHz of the ITU grids with a side-mode suppression ratio of approximately 35 dB over the whole range. OCIS codes: 140.3600, 140.3570, 140.3410, 140.2020, 230.3720.

Abstract: The Co/SiO2 nanospheres have been prepared by the improved sol–gel method combined with hydrogen reduction. The size, the phase and the shape of the particles varied with the molar ratio of SiO2, reduction temperature and drying temperature. The initial temperature of the phase transformation from hcp-Co to fcc-Co in core–shell structured Co/SiO2 nanospheres is lower than that in the bulk case due to the lower surface energy of nanoscale particles. Result of the thermogravimetric analysis (TGA) indicates that the thermal stability of Co/SiO2 nanoparticles is much better than that of pure Co particles. The value of saturation magnetization decreases with the increase of SiO2 content due to the presence of the nonmagnetic silica coating. [Copyright &y& Elsevier]

A four-electrode liquid crystal cell, featuring a double-side fringe-field switching, has been designed with two-layer electrodes on both glass substrates. The two-layer electrode is the same as that used in fringe-field switching liquid crystal displays. Using a negative dielectric liquid crystal, a homogeneous cell has been fabricated with top and bottom stripe electrodes perpendicular to each other. The fringe fields near top and bottom surfaces drive the homogeneous liquid crystal layer to a twisted structure. The distributions of electric field and molecular director are obtained by theoretical analysis. The double-side fringe-field switching cell shows a much faster response and wider viewing cone compared to traditional fringe-field switching one. The improved electro-optical properties are due to the wider and more symmetric director distribution with respect to the midplane of the liquid crystal cell. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Abstract: Titanium dioxide nanotubes (TiNTs) were fabricated from commercial P25 TiO2 powders via alkali hydrothermal transformation. Dye-sensitized solar cells (DSCs) were constructed by application of TiNTs and P25 nanoparticles with various weight percentages. The influence of the TiNT concentration on the performance of DSCs was investigated systematically. The electrochemical impedance spectroscopy (EIS) technique was employed to quantify the recombination resistance, electron lifetime and time constant in DSCs both under illumination and in the dark. The DSC based on TiNT/P25 hybrids showed a better photovoltaic performance than the cell purely made of TiO2 nanoparticles. The open-voltage (V oc), fill factor (FF) and efficiency (η) continuously increased with the TiO2 nanotube concentration from 0 to 50wt%, which was correlated with the suppression of the electron recombination as found out from EIS studies. Respectable photovoltaic performance of ca. 7.41% under the light intensity of 100mWcm−2 (AM 1.5G) was achieved for DSCs using 90wt% TiO2 nanotubes incorporated in TiO2 electrodes. [Copyright &y& Elsevier]

Abstract: Ambient temperature mechanical properties of Al–8.5Fe–1.3V–1.7Si/15vol.%SiCP composite sheet prepared by a spray deposition (SD)–rolling process were investigated. The experimental results show that the densification method of the as-deposited preforms has an obvious effect on the mechanical properties of the as-rolled sheets. The σ b and δ were 535MPa and 7%, respectively, for the sheet with the preforms extruded at 490°C and then rolled at 490°C. When the preforms were pressed at 450°C and then rolled at 490°C, the obtained σ b and δ were up to 620MPa and 9.5%. The microstructures, density and rigidity are also examined. [Copyright &y& Elsevier]