TWO-DIMENSIONAL ARRAY OF ION TRAPS ON A PLANAR CHIP

We investigate a planar ion chip design with a two-dimensional array of linear ion traps for the scalable quantum information processor. The segmented electrodes reside in a single plane on a substrate and a grounded metal plate, a combination of appropriate rf and DC potentials are applied to them for stable ion confinement, and the trap axes are located above the surface at a distance controlled by the electrodes' lateral extent and the substrate's height as discussed. The potential distributions are calculated using static electric field qualitatively. This architecture is conceptually simple and many current microfabrication techniques are feasible for the basic structure. It may provide a promising route for scalable quantum computers.

基于同步移相技术的1/4波片快轴方位角的实时测量

提出了一种基于同步移相技术的1/4波片快轴方位角的实时测量方法。由正交光栅、光阑、检偏器组和四象限探测器实现同步移相功能。检偏器组由4个不同方位角的检偏器组成。通过检偏器组的四束光束的光强由四象限探测器同时测量。1/4波片的快轴方位角由这四光束的光强得到。由于该方法不需旋转偏振器件，从而实现的1/4波片的快轴方位角的实时测量。

基于同步移相技术的1/4波片相位延迟量的快速测量

提出了一种基于同步移相技术的1/4波片相位延迟量的快速测量方法。由正交光栅、光阑、检偏器组和四象限探测器实现同步移相功能。检偏器组由4个不同方位角的检偏器组成。通过检偏器组的四束光束的光强由四象限探测器同时测量。1/4波片的相位延迟量由这四光束的光强得到。该方法中波片的快轴不需被事先确定。另外光源光强的波动对测量结果没有影响。通过实验验证了该方法的有效性。

Even aberration measurement of lithographic projection system based on optimized phase-shifting marks

In the present paper, we propose a novel method for measuring the even aberrations of lithographic projection optics by use of optimized phase-shifting marks on the test mask. The line/space ratio of the phase-shifting marks is optimized to obtain the maximum sensitivities of Zernike coefficients corresponding to even aberrations. Spherical aberration and astigmatism can be calculated from the focus shifts of phase-shifting gratings oriented at 0 degrees, 45 degrees, 90 degrees and 135 degrees at multiple illumination settings. The PROLITH simulation results show that, the measurement accuracy of spherical aberration and astigmatism obviously increase, after the optimization of the measurement mark. (C) 2008 Elsevier B.V. All rights reserved.

Design guidelines and characteristics for a kind of four-layer large flattened mode fibers

A theoretical method to analyze a kind of four-layer large flattened mode (LFM) fibers is presented. The properties of the fiber, including the fundamental and higher-order modal fields, effective area and bending loss are discussed by comparison. At the same time, the reasons for the different characteristics are considered. The obtained results indicate that the effective area of the four-layer LFM fiber is about 1.3 times larger than that of the conventional standard step-index fiber and the fiber can suppress the higher-order modes via bending effectively. The four-layer LFM fiber has less efficient bend-induced filtering ability than the conventional step-index fiber; however, it has more efficient filtering ability than the three-layer LFM fiber. (C) 2007 Elsevier GmbH. All rights reserved.

Electromagnetic fields and transmission properties in tapered hollow metallic waveguides

We analyze the electromagnetic spatital distributions and address an important issue of the transmission properties of spherical transverse-electric (TE) and transverse-magnetic (TM) eigenmodes within a tapered hollow metallic waveguide in detail. Explicit analytical expressions for the spatital distributions of electromagnetic field components, attenuation constant, phase constant and wave impedance are derived. Accurate eigenvalues obtained numerically are used to study the dependences of the transmission properties on the taper angle, the mode as well as the length of the waveguide. It is shown that all modes run continuously from a propagating through a transition to an evanescent region and the value of the attenuation increases as the distance from the cone vertex and the cone angle decrease. A strict distinction between pure propagating and pure evanescent modes cannot be achieved. One mode after the other reaches cutoff in the tapered hollow metallic waveguide as the distance from the cone vertex desreases. (C) 2008 Optical Society of America

A Z-scan model for optical nonlinear nanometric films

The Z-scan technique is useful for measuring the nonlinear refractive index of thin films. In conventional Z-scan theories, two effects are often ignored, namely the losses due to the internal multi-interference and the nonlinear absorption inside the sample. Therefore, the theories are restricted to relatively thick films. For films thinner than about 100 nm, the two effects become significant, and thus cannot be ignored. In the present work, we present a Z-scan theory that takes both effects into account. The proposed model calculation is suitable for optical nonlinear films of nanometric thickness. With numerical simulations, we demonstrate dramatic deviations from the conventional Z-scan calculations.

Structural change of laser-irradiated Ge2Sb2Te5 films studied by electrical property measurement

Sheet resistance of laser-irradiated Ge2Sb2Te5 thin films prepared by magnetron sputtering was measured by the four-point probe method. With increasing laser power the sheet resistance undergoes an abrupt drop from 10(7) to 10(3) Omega/square at about 580 mW. The abrupt drop in resistance is due to the structural change from amorphous to crystalline state as revealed by X-ray diffraction (XRD) study of the samples around the abrupt change point. Crystallized dots were also formed in the amorphous Ge2Sb2Te5 films by focused short pulse laser-irradiated, the resistivities at the crystallized dots and the non-crystallized area are 3.375 x 10(-3) and 2.725 Omega m, sheet resistance is 3.37 x 10(4) and 2.725 x 10(7) Omega/square respectively, deduced from the I-V Curves that is obtained by conductive atomic force microscope (C-AFM). (C) 2008 Elsevier B.V. All rights reserved.

Laser tunable Toraldo superresolution with a uniform nonlinear pupil filter

We demonstrate that it is possible to reduce the focal spot size by inserting a uniform nonlinear thin film at the aperture of a focusing lens. The reduction of spot size is tunable by adjusting the incoming laser power. In comparison with the original diffraction spot, the transverse spot size can be reduced 0.65 times. The nonlinear thin film acts effectively as a Toraldo filter, and the phase and amplitude modulation stems from the laser-induced variances in the transmission of the thin film. The proposed technique removes the need of fabricating annular pupil filters. (C) 2008 Optical Society of America.

Reversible Resistance Switching Effect in Amorphous Ge1Sb4Te7 Thin Films without Phase Transformation

We demonstrate a reversible resistance switching effect that does not rely on amorphous-crystalline phase transformation in a nanoscale capacitor-like cell using Ge1Sb4Te7 films as the working material. The polarity and amplitude of the applied electric voltage switches the cell resistance between low- and high-resistance states, as revealed in the current-voltage characteristics of the film by conductive atomic force microscopy (CAFM). This reversible SET/RESET switching effect is induced by voltage pulses and their polarity. The change of electrical resistance due to the switching effect is approximately two orders of magnitude.

Temperature dependence of thermal properties of Ag8In14Sb55Te23 phase-change memory materials

The dependence of thermal properties of Ag8In14Sb55Te23 phase-change memory materials in crystalline and amorphous states on temperature was measured and analyzed. The results show that in the crystalline state, the thermal properties monotonically decrease with the temperature and present obvious crystalline semiconductor characteristics. The heat capacity, thermal diffusivity, and thermal conductivity decrease from 0.35 J/g K, 1.85 mm(2)/s, and 4.0 W/m K at 300 K to 0.025 J/g K, 1.475 mm(2)/s, and 0.25 W/m K at 600 K, respectively. In the amorphous state, while the dependence of thermal properties on temperature does not present significant changes, the materials retain the glass-like thermal characteristics. Within the temperature range from 320 K to 440 K, the heat capacity fluctuates between 0.27 J/g K and 0.075 J/g K, the thermal diffusivity basically maintains at 0.525 mm(2)/s, and the thermal conductivity decreases from 1.02 W/m K at 320 K to 0.2 W/m K at 440 K. Whether in the crystalline or amorphous state, Ag8In14Sb55Te23 are more thermally active than Ge2Sb2Te5, that is, the Ag8In14Sb55Te23 composites bear stronger thermal conduction and diffusion than the Ge2Sb2Te5 phase-change memory materials.

Spectral anomalies of focused hollow Gaussian beams at the geometrical focal plane

On the basis of diffraction integral and the expansion of the hard-aperture function into a finite series of complex Gaussian functions, an approximate expression for spatially fully coherent polychromatic hollow Gaussian beams passing through aperture lens is obtained. Detailed numerical results indicate that remarkable spectral changes always occurs near the points where the field amplitude has zero value. The effects of truncation parameter, Fresnel number and the beam order on spectral shifts and spectral switches are investigated numerically. (C) 2008 Elsevier B.V. All rights reserved.

Beam conditions for radiation generated by an electromagnetic J 0-correlated Schell-model source

Based on the 2 x 2 (electric field) cross-spectral density matrix, a model for an electromagnetic J(0)-correlated Schell-model beam is given that is a generalization of the scalar J(0)-correlated Schell-model beam. The conditions that the matrix for the source to generate an electromagnetic J(0)-correlated Schell-model beam are obtained. The condition for the source to generate a scalar J(0)-correlated Schell-model beam can be considered as a special case. (C) 2008 Optical Society of America

Transparent Ni2+-doped silicate glass ceramics for broadband near-infrared emission

Transparent Ni2+-doped MgO-Al2O3-Ga2O3-SiO2-TiO2 glass ceramics were fabricated. The precipitated nanocrystal phase in the glass ceramics was identified by X-ray diffraction and transmission electron microscope. Broadband near-infrared emission centered at 1220 nm with full width at half maximum of about 240 nm and lifetime of about 250 mu s was observed with 980 nm excitation. The longer wavelength emission compared with Ni2+-doped MgAl2O4 crystal was attributed to the low crystal field occupied by Ni2+ in the glass ceramics. The present Ni2+-doped transparent glass ceramics may have potential applications in broadband optical amplifiers. (c) 2007 Elsevier B.V. All rights reserved.