A Kind of New Three-Mode Coherent-Entangled State and Its Application

A kind of new continuous variable three-mode coherent-entangled state (CV-CES) is proposed in Fock space by the technique of integration within an ordered product (IWOP), which exhibits both the properties of coherent state and entangled state, and spans a complete and orthonormal representation. The conjugate state of CV-CES is derived by Fourier transformation. Moreover, the simple experimental protocol of generating a CV-CES is proposed by beam-splitters. As applications of this CV-CES, a three-mode entangled state and a three-mode squeezing-Fresnel operator are constructed.     

The multi-dimensional limiters for solving hyperbolic conservation laws on unstructured grids

Novel limiters based on the weighted average procedure are developed for finite volume methods solving multi-dimensional hyperbolic conservation laws on unstructured grids. The development of these limiters is inspired by the biased averaging procedure of Choi and Liu [10]. The remarkable features of the present limiters are the new biased functions and the weighted average procedure, which enable the present limiter to capture strong shock waves and achieve excellent convergence for steady state computations. The mechanism of the developed limiters for eliminating spurious oscillations in the vicinity of discontinuities is revealed by studying the asymptotic behavior of the limiters. Numerical experiments for a variety of test cases are presented to demonstrate the superior performance of the proposed limiters.     

Solvothermal synthesis, cubic structure and multicolor upconversion emission of ultrasmall monodisperse lanthanide-doped BaYF5 nanocrystals

Lanthanide (Ln³⁺) doped BaYF₅ (Ln=Yb³⁺, Er³⁺, Tm³⁺) nanocrystals (NCs) with a mean size of approximately 10 nm are synthesized by a solvothermal method using oleic acid as a stabilizing agent at 210 °C. The size of BaYF₅ NCs can be controlled by simply tuning the reaction parameters such as reaction temperature, reaction time and the molar ratio of F⁻/Y³⁺. The detailed structure investigation reveals that the as-synthesized BaYF₅ NCs are in the cubic structure with space group Fm3¯m instead of the reported tetragonal structure. Ln³⁺ cations occupy crystal lattice positions with lower point symmetry, which may lead to high upconversion efficiency under the excitation of a 980 nm diode laser. By adjusting the dopant concentrations of Yb³⁺, Er³⁺ and Tm³⁺, intense near-infrared, blue, yellow and white upconversion emissions are readily realized, respectively. The desirable property of the ultrasmall monodisperse NCs makes it the promising material for the applications in miniaturized solid-state light sources, multicolor three-dimensional display devices and fluorescent labels for biomedicine imaging.     

Surface plasmon resonance sensors based on Ag-metalized nanolayer in microstructured optical fibers

Surface plasmon resonance sensors based on Ag-metalized nanolayer in microstructured optical fibers are theoretically analyzed by using finite element method (FEM). In our simulations we use Drude-Lorentz model to describe the metal dielectric constant. The numerical results show that the sensitivity of Ag-metalized SPR sensor could reach 1167 nm/RIU and corresponding resolution is 8.57×10⁻⁵ RIU. Compared to conventional Au-metalized SPR sensors the performance of our device is obviously better.     

Study on inverse taper based mode transformer for low loss coupling between silicon wire waveguide and lensed fiber

We have simulated the coupling loss of three types of Inverse Taper and taper-lensed fiber using three dimensional (3D) semi-vectorial beam propagation methods (BPM) respectively. Our results showed that the performances of exponential inverse taper and quadratic inverse taper were better than the commonly used linear inverse taper. Especially, for TM mode the improvement in the reduction of devices size is 53% and 136% for exponential and quadratic inverse taper compared with the linear inverse taper.     

Multi-wavelength operation of LD side-pumped Nd:YAG laser

A dual-wavelength laser at 1064 nm and 1319 nm is obtained by a single Nd:YAG crystal rod. On the basis of 1064 nm and 1319 nm dual-wavelength laser installation, the second harmonic waves at 532 nm and 660 nm can be achieved by using non-linear frequency conversion technology. When 1064 nm and 1319 nm lasers oscillate simultaneously, the maximum output power is 30.5 W and 8.78 W, respectively. When the 1319 nm laser is restrained, we obtain a 35.6 W maximum output power at 1064 nm and by contrary 11.2 W at 1319 nm. The maximum output powers of 532 nm and 660 nm lasers are 5.34 W and 1.353 W when oscillating simultaneously. With one of them restrained, the maximum output power is 6.72 W at 532 nm and 1.90 W at 660 nm. The optimum repetition rate of the acousto-optic Q-switch is 10.5 KHz and 20.5 KHz for 532 nm and 660 nm lasers, respectively. The optical-to-optical conversion efficiency from the fundamental waves to the harmonic waves is 17.5% and 15.4%. The instability is less than 2%.     

Coulomb forces on DNA polymers in charged fluidic nanoslits

We investigate the repulsive electrostatic interactions between a DNA polyelectrolyte and the charged walls of a fluidic nanoslit. The scaling of the DNA coil size with the physical slit height revealed electrostatic depletion regions that reduced the effective slit height. These regions exceeded the Debye screening length of the buffer, λ(D)(buffer), and saturated at ≈ 50 nm when λ(D)(buffer) reached 10 nm. We explain these results by modeling a semiflexible charged rod near a charged wall and the electrostatic screening by the polyelectrolyte. These results demonstrate the surprisingly long range over which a nanofluidic device can exert field-effect control over confined molecules.     

图形处理器并行计算用于离子发动机粒子模拟

 为了研究离子发动机羽流对航天器的影响,采用质点网格-蒙特卡罗碰撞方法对离子发动机羽流中的交换电荷离子进行了模拟。利用计算设备统一架构技术,开发出一套基于图形处理器的并行粒子模拟程序。随机数生成采用并行MT19937伪随机数生成器算法,电场方程使用完全近似存储格式的代数多重网格法求解。r-z轴对称坐标系中,在z=0 m处获得的电流密度均值为4.5×10^-5 A/m²,图形处理器所得结果与中央处理器模拟结果吻合。在16核心的NVIDIA GeForce 9400 GT图形显示卡上,取得相对于Intel Core 2 E6300中央处理器4.5~10.0倍的加速比。     

强流二极管绝缘体滑闪监测及其影响

 以闪光二号加速器为研究平台, 建立了微分环阵列和Rogowski线圈同时监测二极管电流的方法,监测了二极管绝缘体表面的滑闪现象。根据电流探头测量结果的差异,分析了绝缘体滑闪对电子束流参数的影响。二极管绝缘体出现滑闪,位置附近的微分环波形严重畸变,其它位置的微分环和Rogowski线圈测量结果基本一致。采用距离滑闪位置较远的微分环结果处理二极管束流参数,相对于不出现滑闪时的结果,束流强度和总能量没有明显的变化。绝缘体滑闪沿面局部放电,能量损失较小,尚未对电子束流造成较大影响。     

被动谐波锁模Er3+/Yb3+共掺双包层光纤环形腔激光器

 为了实现高重复频率和高功率的光脉冲,实验采用Er³⁺/Yb³⁺共掺双包层光纤作为增益介质,稳定的中心波长为976 nm的高功率半导体激光器作为泵浦源,利用非线性偏振旋转锁模技术,得到稳定的自起振锁模光脉冲。当泵浦功率为2.4 W时,激光器输出重复频率为8.829 MHz的连续锁模光脉冲,平均输出功率为52.5 mW,自起振锁模泵浦阈值功率为0.6 W,并观测到了稳定的高阶谐波锁模、调Q和调Q-锁模光脉冲输出。