Comparative study on the power scaling performance of three different coherent polarization beam combination system structures

Coherent polarization beam combination (CPBC) is a new kind of coherent beam combination configuration with high combining efficiency and excellent beam quality. In order to extend the CPBC system to a large scale, we provide a comparative study on the power scaling performance of three different coherent polarization beam combination system structures. It is found that the pairwise structure has high tolerance to aberrations and has the potential to extend to a large scale with high combining efficiency. In consideration of all the aberrations, the combining efficiency of the pairwise structure can be attained as high as 90% when the combined beams are more than 200. Some instructive suggestions are given to extend the CPBC system to a large scale.     

Thermodynamics Properties of Oxymatrine in NaCl Solution

The enthalpies of dissolution of oxymatrine in 0.9%NaCl solution were measured using a RD496-2000 Calvet Microcalorimeter at 309.65 K under atmospheric pressure. The differen-tial enthalpy and molar enthalpy of oxymatrine dissolution in the 0.9%NaCl solution of were determined. The corresponding kinetic equation that described the dissolution process was elucidated. Moreover, the half-life, molar entropy, molar enthaply, and Gibbs free energy of the dissolution process were also obtained.     

The 260-W coherent beam combining of two compact fibre amplifier chains

Coherent beam combining of two fibre amplifier chains with a total power of 260 W in a compact system using the stochastic parallel gradient descent (SPGD) algorithm is demonstrated. A 150 MHz linewidth fibre laser is built and introduced for high-power amplification to mitigate stimulated Brillouin scattering (SBS). Compact high-power amplifier chains are built with low power all-fibre system and high-power bulk free-optics fibre amplifiers. When the total power is about 260 W, active phase-locking of two high-power amplifiers is demonstrated using the SPGD algorithm. In closed-loop, the power in the main lobe increases 1.68 times, the visibility is increased from 0 to 0.62, and the phase residual error is less than λ/10.     

位点可控的二乙氧磷酰化壳寡糖的合成

以壳寡糖(COS)为原料, 二乙基亚磷酸酯(DEPH)为磷酰化试剂, 通过改变反应体系中三乙胺(TEA)的用量控制二乙基磷酰基的进攻位点, 实现了2-N和3,6-O位点二乙基亚磷酰化壳寡糖衍生物的合成, 制备了N-二乙氧磷酰化壳寡糖及N,O,O-二乙氧磷酰化壳寡糖, 并采用单一变量法对合成条件进行了优化, 用³¹P NMR对产物进行了跟踪分析. 合成N-二乙氧磷酰化壳寡糖的最优反应条件为2 g COS, n_COS∶n_TEA=1∶6, n_COS∶n_DEPH=1∶3, 滴加DEPH和CCl₄的时间为2 h, 低温反应2 h, 在该优化条件下产物的磷含量为1.50%(质量分数). 合成N,O,O-二乙氧磷酰化壳寡糖的最优反应条件为2 g COS, n_COS∶n_TEA=1∶6, n_COS∶n_DEPH=1∶5, 滴加DEPH和CCl₄ 的时间2 h, 低温反应4 h, 常温反应8 h, 在该优化条件下产物的磷含量为3.42%. 对合成反应的可能机理进行了推测.     

Lens axicon illuminated by polychromatic Gaussian beams for generating uniform focal segments

In this paper, we investigate a lens axicon, which actually is a lens with spherical aberration, illuminated by a polychromatic Gaussian beam for producing an extended axial line image of a desired length and nearly uniform intensity. A numerical calculation is performed to investigate the dependence of the axial intensity distribution of the focal segment on the parameters of the incident polychromatic Gaussian beam. It is shown that, compared with monochromatic Gaussian beam illumination, the illumination of the polychromatic Gaussian beam may improve the uniformity of the distribution of the axial intensity, and this improvement in the uniformity of the axis intensity is strongly dependent on the spectral width of the incident Gaussian beam. Moreover, apodization with annular super-Gaussian amplitude distribution is employed to reduce the undesired oscillation of the axial intensity.     

Time-resolved spectral wing emission kinetics and optical imaging of human cancerous and normal prostate tissues

Time-resolved polarization-dependent kinetics of near infrared (NIR) spectral wing (SW) emission from human cancerous and normal prostate tissues was investigated. The differences between the temporal profiles, intensities and polarization properties of SW emission from cancerous and normal prostate tissues were observed. The intensity of SW emission from cancerous prostate tissue at peak position was found ∼2 times stronger than the normal prostate tissue indicating changes of fluorophores contained in the cancerous tissue compared with normal tissue. The decay time of anisotropy of SW emission from cancerous tissue was found ∼1.4 times longer than that of normal tissue reflecting changes of the micro-environment of fluorophores in the cancerous tissue as compared with the normal tissue. The stronger intensity of SW emission from cancerous tissue was used to image and identify cancerous areas surrounded by normal tissue.     

Focus shaping of cylindrically polarized vortex beams by a high numerical-aperture lens

The focus-shaping technique of a cylindrically polarized vortex beam by a high numerical-aperture lens is reported. Such a polarized vortex beam is decomposed into radial and azimuthal polarization. It is shown that the total intensity distribution in the focal region is dependent not only on the numerical-aperture maximal angle and the polarization rotation angle but also on the topological charge. By choosing the proper combination of parameters, the adjustably confined flat-topped focus and focal hole can be obtained. The focus-shaping technique may find wide applications, such as optical tweezers, laser printing and material processing.     

随机并行梯度下降算法模拟两路光纤放大器相干合成与实验研究

对利用随机并行梯度下降(SPGD)算法对多路光纤放大器相干合成进行了数值模拟,并进行了两路瓦级光纤放大器相干合成的实验.实验结果表明,SPGD算法能够有效控制各路光纤激光的相位,系统闭环将目标圆孔内的能量提高了1.57倍;并使得目标圆孔内能量大于理想值80%的概率从27.7%提升到了70.3%.取得了较为明显的相干合成效果.对算法用于多路高功率光纤放大器相干合成的可行性进行了探讨.     

Electrochemical characteristics of sulfur composite cathode for reversible lithium storage

The electrochemical characteristics of the sulfur composite cathode for reversible lithium storage were investigated. The sulfur composites showed novel electrochemical characteristics as well as high specific capacity and good cycleability. The sulfur composite presented the average discharge voltage of 1.9 V, which was just the half of conventional LiCoO₂ cathode materials, indicating that the double cells in series presented the same working voltage as conventional LiCoO₂ cells and meaning that the sulfur composite cells will have good interchangeability with conventional LiCoO₂ cells. The overcharge test showed that the sulfur composite cell cannot be charged over 5.0 V, indicating that the sulfur composite cell presented the intrinsic safety for overcharge. Overcharge can cause serious problems for the conventional Li ion cells. The overcharge test also showed that the sulfur composite cell was destroyed when the cell was charged over 4.0 V, resulting in that the cell cannot normally be discharged again. It is found, however, that the sulfur composite cell can be discharged again at very low current density of a 0.002-C rate after the cell was overcharged. Being much safer than lithium metal anode, the graphite anode was used to fabricate sulfur composite/graphite lithium ion cells with a prelithiated sulfur composite cathode, which was produced by electrochemical lithiation. The charge/discharge and cycling characteristics of the sulfur composite/graphite cell was investigated. The result showed that the sulfur composite/graphite cells can be normally cycled and showed the different voltages from that of the cell with the lithium metal anode. This paves the effective way to fabricate safer sulfur composite/graphite lithium ion cells.