空气包层大模场面积掺镱光子晶体光纤研究

采用改进的化学气相沉积法和气相液相混合掺杂技术制备大芯径掺镱石英光纤预制棒, 以此作为有源纤芯制备了纤芯直径约90 μm的掺镱双包层光子晶体光纤, 纤芯组分为镱铝磷共掺.双包层光子晶体光纤的模场面积约1330 μm², 纤芯数值孔径0.065,包层数值孔径0.5.首次实现了国产掺镱光子晶体光纤的高功率高效率激光输出, 1 m长的光子晶体光纤激光器实现102 W 激光输出,斜率效率76%.     

Stark位移对热环境下双Jaynes-Cummings模型中原子纠缠的影响

研究双光子跃迁的双Jaynes-Cummings模型中, 两原子初始处于最大纠缠态、光场初始处于单模热态时的原子纠缠动力学, 考虑双光子过程中的Stark位移、热光场的平均光子数对原子纠缠的影响. 结果表明: 不考虑Stark位移时, 两原子在系统演化过程中周期性地出现退纠缠现象, 而考虑Stark位移时, 两原子长时间地纠缠. 特别是当Stark位移参数取值较大且热光场的平均光子数值比较小时, 两原子能保持 稳定地纠缠. 这些结果表明, 可以利用Stark位移对热环境下双Jaynes-Cummings模型中的原子纠缠进行调控.     

140GHz大功率交错双栅行波管的设计和模拟研究

采用交错双栅结构,结合带状电子注,研究了一种工作在140 GHz频段的大功率行波管. 本振模数值计算表明该结构具有良好的色散特性和耦合阻抗.针对所采用的慢波结构, 提出了慢波过渡结构、输入输出耦合器和集中衰减器,保证了行波管的良好工作. 利用三维大信号模拟计算的方法得到的结果显示,当电子注直流功率为5.115 kW,输入信号功率为0.1 W时, 所研究的行波管能在132-152 GHz范围内提供大于300 W的峰值功率,其中在138 GHz时得到最大功率546 W, 对应增益为37.37 dB.当在0.027-0.46 W内调节输入信号功率,可以保持该行波管在128-152 GHz 频带内得到大于440 W的峰值功率,对应的电子效率大于8.6%. 结果显示该行波管将在大功率短毫米波领域具有重要意义和潜在应用价值.     

Effects of divalent alkaline earth ions on the magnetic and transport features of La0.65A0.35Mn0.95Fe0.05O3 (A = Ca, Sr, Pb, Ba) compounds

We have studied the magnetic and transport properties of Fe doped La_0.65A_0.35Mn_0.95Fe_0.05O₃ (A = Ca, Sr, Pb, Ba) manganites. All the compositions show ferromagnetic/metal to paramagnetic/insulator transition (T_C) except the Pb doped sample which is insulating and ferromagnetic (FM) in the entire temperature range. The magnetization and T_C are decreased by decreasing the cation size on La site. The transition temperature and magnetic moment at 77 K is a maximum for Sr doped sample and is decreasing if we increase or decrease the cation size from Sr size. The maximum value of T_C and magnetic moment for Sr based sample is most likely due to the closer ionic sizes of La and Sr as compared to the other dopants (Ca, Pb, and Ba). We observed a spin freezing type effect in the Pb doped sample below 120 K in resistivity, ac susceptibility and in magnetization. This suggests that the AFM interactions introduced by the Fe are most effective in the Pb doped composition leading to increased competition between the FM and AFM interactions. This FM and AFM interaction generates some degree of frustration leading to the appearance of spin glass like phase whose typical magnetic behavior is studied for small ion when the metallic like behavior is lost.     

Generation and storage of double slow light pulses in a solid

We experimentally study the generation and storage of double slow light pulses in a Pr³⁺:Y₂SiO₅ crystal. Under electromagnetically induced transparency, a single signal pulse is stored in the spin coherence of the crystal. By simultaneously switching on two control fields to recall the stored information, the spin coherence is converted into two slow light pulses with distinct frequencies. Furthermore, the storage and controlled retrieval of double slow light pulses are obtained by manipulating the control fields. This study of double slow light pulses may have practical applications in information processing and all-optical networks. vspace2mm     

组合透镜法测量透镜焦距方法研究及数值分析

为了解决神光系列装置所需长焦透镜焦距的检测问题,在现有斐索干涉仪的基础上,对常规组合透镜方法进行了拓展,提出了双探头光栅尺法。对两种方法的工作原理及检测方法进行了分析,同时计算分析了测量数据误差对测量结果的影响,得出测量数据测量误差的上限要求。这两种方法具有测量精度高、重复性好、测量过程简单的优点,对于各类透镜焦距的检测具有重要的实用价值。     

Low-voltage antimony-doped SnO2 nanowire transparent transistors gated by microporous SiO2-based proton conductors

A battery drivable low-voltage transparent lightly antimony（Sb）-doped SnO2 nanowire electric-double-layer （EDL） field-effect transistor （FET） is fabricated on an ITO glass substrate at room temperature. An ultralow operation voltage of 1 V is obtained on account of an untralarge specific gate capacitance （- 2.14 μF/cm2） directly bound up with mobile ions-induced EDL （sandwiched between the top and bottom electrodes） effect. The transparent FET shows excellent electric characteristics with a field-effect mobility of 54.43 cm2/V. s, current on/off ration of 2 × 104, and subthreshold gate voltage swing （S = dVgs/d（logIds）） of 140 mV/decade. The threshold voltage Yth （0.1 V） is estimated which indicates that the SnO2 namowire transistor operates in an n-type enhanced mode. Such a low-voltage transparent nanowire transistor gated by a microporous SiO2-based solid electrolyte is very promising for battery-powered portable nanoscale sensors.     

Quantum correlations between two non-interacting atoms under the influence of a thermal environment

By considering a double Jaynes-Cummings model,we investigate the dynamics of quantum correlations,such as the quantum discord and the entanglement,for two atoms in their respective noisy environments,and study the effect of the purity and the cavity temperature on the quantum correlations.The results show that the entanglement suffers sudden death and revival,however the quantum discord can still reveal the quantum correlations between the two atoms in the region where the entanglement is zero.Moreover,when the temperature of each cavity is high the entanglement dies out in a short time,but the quantum discord still survives for quite a long time.It means that the quantum discord is more resistant to environmental disturbance than the entanglement at higher temperatures.     

Spin-dependent thermoelectric transport through double quantum dots

We study the thermoelectric transport through a double-quantum-dot system with spin-dependent interdot coupling and ferromagnetic electrodes by means of the non-equilibrium Green’s function in the linear response regime.It is found that the thermoelectric coefficients are strongly dependent on the splitting of the interdot coupling,the relative magnetic configurations,and the spin polarization of leads.In particular,the thermoelectric efficiency can reach a considerable value in the parallel configuration when the effective interdot coupling and the tunnel coupling between the quantum dots and the leads for the spin-down electrons are small.Moreover,the thermoelectric efficiency increases with the intradot Coulomb interaction increasing and can reach very high values at appropriate temperatures.In the presence of the magnetic field,the spin accumulation in the leads strongly suppresses the thermoelectric efficiency,and a pure spin thermopower can be obtained.     

Time evolution of information entropy for a stochastic system with double singularities driven by quasimonochromatic noise

<正>This paper deals with the time evolution of information entropy for a stochastic system with double singularities driven by quasimonochromatic noise.The dimension of the Fokker-Planck equation is reduced by the linear transformation. The exact expression of the time dependence of information entropy is obtained based on the definition of Shannon’s information entropy.The relationships between the properties of dissipative parameters,system singularity strength parameter,quasimonochromatic noise,and their effects on information entropy are discussed.