带状电子注的聚焦和传输

 采用单粒子模型,对有限宽矩形带状电子注在周期会切磁场(PCM)、带偏移磁极的周期会切磁场(offset-pole PCM)和周期会切周期四极磁铁混合磁场(PCM-PQM)聚焦结构中传输的双平面聚焦,进行了详细的理论和数值分析研究。结果表明:PCM和offset-pole PCM聚焦结构对于实现带状电子注的双平面边缘聚焦比较困难,原因在于它们无法独立控制电子注水平和垂直两个方向的聚焦。PCM-PQM聚焦结构则非常有效地改善了聚焦,可以很好地实现带状电子注边缘的聚焦和均匀稳定的传输。     

Measurements of a periodically driving qubit using a quantum point contact

Using the method developed by Gurvitz [1996 Phys. Rev. B 53 15932], we obtained the Bloch-type rate equations describing the entire system of a periodically driving qubit monitored by a quantum point contact detector. The results demonstrate that the isolated qubit can be kept in its initial state with a large driving frequency due to more difficult electron tunneling in qubit, and this initial state can always be measured at a small measurement-induced decoherence rate during a short time.     

Continuous-wave mid-infrared intracavity singly resonant optical parametric oscillator based on periodically poled lithium niobate

This paper reports a continuous-wave (CW) mid-infrared intracavity singly resonant optical parametric oscillator based on periodically poled lithium niobate (PPLN) pumped by a diode-end-pumped CW Nd:YVO$_{4}$ laser. Considering the thermal lens effects, it adopted an optical ballast lens and the near-concentric cavity for better operation. At the PPLN's grating period of 28.5\,$\mu$m and the temperature of 140\du, the maximum idler output power of 155\,mW at 3.86\,$\mu$m has been achieved when the 808\,nm pump power is 8.5\,W, leading to an optical-to-optical conversion efficiency of 1.82{\%}.     

Three-wavelength generation from cascaded wavelength conversion in monolithic periodically poled lithium niobate

Tunable coherent emission is generated in a single-pass,cascaded wavelength conversion process from mode-locked laser-pumped monolithic periodically poled lithium niobate(PPLN).Three ranges of wavelength,including visible output from 628 nm to 639 nm,near-infrared output from 797 nm to 816 nm,and mid-infrared output from 3167 nm to 3459 nm,were obtained from the monolithic PPLN,which consists of a 10-mm section for 532-nm-pumped optical parametric generation(OPG)and a 7-mm section for 1064-nm-pumped sum frequency generation(SFG).A pump-to-signal conversion efficiency of 23.4%for OPG at 50°C and a quantum efficiency of 26.2%for SFG at 200°C were obtained.     

Spatial shapes of magnetoelastic shear body waves at the transmission edges in a periodically inhomogeneous magnetostrictive medium

The spatial shapes of magnetoelastic shear body waves at the transmission edges in a periodically inhomogeneous magnetostrictive medium are studied. Numerical results are obtained for a two-component composition of ferrite and nonmagnetic dielectric __________ Translated from Prikladnaya Mekhanika, Vol. 42, No. 3, pp. 61–69, March 2006.     

Weak law of large numbers for almost periodically correlated processes

This note contains two simple observations concerning the weak law of large numbers for almost periodically correlated processes.

     

Asymptotics of the reduced logarithmic capacity of a narrow cylinder

We consider the Dirichlet problem for the Laplace operator in the exterior of a narrow infinite cylinder with periodically varying directrix. The solution is sought in the class of functions logarithmically increasing as the distance from the cylinder is increased. The reduced logarithmic capacity is defined as a generalization of the logarithmic capacity (of the outer conformal radius).We construct and justify the asymptotics of the solution of the problem as the ratio of the diameter of the cross-section of the cylinder to its period tends to zero.Translated from Matematicheskie Zametki, vol. 77, no. 1, 2005, pp. 16–27.Original Russian Text Copyright © 2005 by I. I. Argatov.This revised version was published online in April 2005 with a corrected issue number.     

Diode-pumped Actively Q-switched Nd:GdVO<Subscript>4</Subscript> Green Laser with Periodically Poled KTP

A diode-pumped actively Q-switched Nd:GdVO₄ green laser with periodically poled KTP (PPKTP) and Acoustic-optic (AO) modulator has been realized. The dependences of pulse energy, pulse width, and peak power on incident pump power are measured. At the pump power of 4.1 W and repetition rate of 10 kHZ, we can obtain a 19.2 ns pulse with pulse energy of 0.11 mJ and peak power of 5.8 kW, which are almost three times of that in the conventional KTP green laser, respectively. A rate equation model is introduced to theoretically analyze the results obtained in the experiment, in which the Gaussian spatial distribution of the intracavity photon density is taken into account. The numerical solutions of the rate equations agree with the experimental results.     

A singularly perturbed nonlinear traction problem in a periodically perforated domain: a functional analytic approach

We consider a periodically perforated domain obtained by making in a periodic set of holes, each of them of size proportional to ε. Then, we introduce a nonlinear boundary value problem for the Lamé equations in such a periodically perforated domain. The unknown of the problem is a vector‐valued function u, which represents the displacement attained in the equilibrium configuration by the points of a periodic linearly elastic matrix with a hole of size ε contained in each periodic cell. We assume that the traction exerted by the matrix on the boundary of each hole depends (nonlinearly) on the displacement attained by the points of the boundary of the hole. Then, our aim is to describe what happens to the displacement vector function u when ε tends to 0. Under suitable assumptions, we prove the existence of a family of solutions {u(ε, ? )}_{ε ∈ ]0,ε ′ [} with a prescribed limiting behavior when ε approaches 0. Moreover, the family {u(ε, ? )}_{ε ∈ ]0,ε ′ [} is in a sense locally unique and can be continued real analytically for negative values of ε. Copyright © 2013 John Wiley & Sons, Ltd.     

1560nm激光经PPLN和PPKTP晶体准相位匹配倍频研究

将1560nm光栅反馈复合腔半导体激光器产生的连续激光注入掺铒光纤放大器,放大至约5 W,分别采用周期极化铌酸锂(PPLN)和周期极化磷酸氧钛钾(PPKTP)晶体单次穿过进行准相位匹配倍频,对应获得约336mW和210mW的780nm激光输出,倍频效率约为7%和4.4%。通过监视倍频光纵模,显示其具有良好的单频输出特性。此外,还扫描测得了Rb原子D2线的吸收光谱,表明780nm激光的频率调谐范围大于10GHz。采用无调制偏振光谱技术将1560nm半导体激光器频率锁定至87 Rb 5S1/2(Fg=2)-5P3/2(Fe=3)超精细跃迁线上。相对于自由运转450s内1560nm激光频率起伏约4MHz,锁定后可将残余频率起伏压低至1.5MHz左右。