Trends in ultrashort and ultrahigh power laser pulses based on optical parametric chirped pulse amplification

Since the proof-of-principle demonstration of optical parametric amplification to efficiently amplify chirped laser pulses in 1992,optical parametric chirped pulse amplification(OPCPA)became the most promising method for the amplification of broadband optical pulses.In the meantime,we are witnessing an exciting progress in the development of powerful and ultrashort pulse laser systems that employ chirped pulse parametric amplifiers.The output power and pulse duration of these systems have ranged from a few gigawatts to hundreds of terawatts with a potential of tens of petawatts power level.Meanwhile,the output pulse duration based on optical parametric amplification has entered the range of fewoptical-cycle field.In this paper,we overview the basic principles,trends in development,and current state of the ultrashort and laser systems based on OPCPA,respectively.     

Coherent Scattering of Light by Bose-Einstein Condensation in a Tight Confinement

We have observed strong scattering of a probe light by dilute Bose-Einstein condensate （BEC） ^87Rb gas in a tight magnetic trap. The scattering light forms fringes at the image plane. It is found that we can infer the real size of the condensation and the number of the atoms by modelling the imaging system. We present a quantitative calculation of light scattering by the condensed atoms. The calculation shows that the experimental results agree well with the prediction of the generalized diffraction theory, and thus we can directly observe the phase transition of BEC in a tight trap.     

Semiconductor-Optical-Amplifier-Based Inverted and Non-Inverted Wavelength Conversion at 40 Gb/s Using a Detuning Optical Bandpass Filter

We experimentally demonstrate 40Gb/s semiconductor-optical-amplifier-based tunable wavelength conversion （WC） using a detuning optical bandpass filter. Both inverted and non-inverted WCs are obtained by shifting the filter central wavelength with respect to the probe wavelength. When the filter is red shifted by 0.4nm or blue shifted by 0.3nm, the WC is non-inverted. However, when the filter is blue shifted by 0.1 nm, the WC is inverted. It is experimentally demonstrated that the WC has a tunable range covering the C-band.     

先进的微生物芯片检测系统及其应用

发展了一种先进的微生物芯片检测方法,并研制用于芯片检测的新型数字化成像扫描检测系统。采用激光诱导荧光的检测原理设计一种新颖的CCD数字化成像扫描检测系统结构,荧光信号采集端的数值孔径NA=0．72,工作距离3．22 mm,系统检测灵敏度小于每平方微米1个荧光分子。以微生物大肠杆菌和黄单胞菌检测为例,设计基因芯片,并应用所研制的芯片检测系统实现了微生物的正确鉴定,提供了一种高效的食品安全检测整体解决方法。实验结果表明两种微生物的芯片检测实验结果稳定可靠,与国外共焦扫描仪检测的结果完全一致。     

All-Optical RZ-to-NRZ Format Conversion with a Tunable Fibre Based Delay Interferometer

All-optical format conversion from return-to-zero （RZ） to non-return-to-zero （NRZ） is demonstrated with temperaturecontrolled all-fibre delay interferometer （DI） at 20 Gb/s. The operation principle is theoretical analysed with the help of numerical simulation and spectra analysis. Theoretical analysis results are consistent well with the experimental results. The format conversion can be achieved with power penalty of 0.54 dB and with output extinction ratio 20 dB.     

Growth and Characterization of A1GaN/A1N/GaN HEMT Structures with a Compositionally Step-Graded A1GaN Barrier Layer

A new A1GaN/A1N/GaN high electron mobility transistor （HEMT） structure using a compositionally step-graded A1GaN barrier layer is grown on sapphire by metalorganic chemical vapour deposition （MOCVD）. The structure demonstrates significant enhancement of two-dimensional electron gas （2DEG） mobility and smooth surface morphology compared with the conventional HEMT structure with high A1 composition A1GaN barrier. The high 2DEG mobility of 1806 cm2/Vs at room temperature and low rms surface roughness of 0.220 nm for a scan area of 5μm×5 μm are attributed to the improvement of interracial and crystal quality by employing the stepgraded barrier to accommodate the large lattice mismatch stress. The 2DEG sheet density is independent of the measurement temperature, showing the excellent 2DEG confinement of the step-graded structure. A low average sheet resistance of 314.5Ω/square, with a good resistance uniformity of 0.68%, is also obtained across the 50 mm epilayer wafer. HEMT devices are successfully fabricated using this material structure, which exhibits a maximum extrinsic transconductance of 218 mS/ram and a maximum drain current density of 800 mA/mm.     

Ab Initio Comparative Study of Zincblende and Wurtzite ZnO

By employing the first-principles pseudopotential plane-wave method, the physical properties of zincblende ZnO are investigated in comparison with those of the common wurtzite structure. Zincblende ZnO is predicted to be a direct gap semiconductor. Compared to the wurtzite structure, the zincblende ZnO is characterized by smaller bandgap and pressure coefficient, larger electron effective mass, increasing static dielectric constants and more covalent bonding. Furthermore, the optical properties including dielectric function and energy loss function of zincblende ZnO were obtained and analysed with some features. These aspects reveal promising applications of zincblende ZnO in optoelectronic devices.     

积分中值ξ=ξ(x)的渐近性

对一类不满足g(n)≠0的函数g讨论了第一积分中值定理中ξ=ξ(x)在x→+∞时的渐近性质,并对第二积分中值定理的中值ξ=ξ(x)的渐近性进行了探讨,给出一些相关的结果.     

MULTIPLE EQUILIBRIA IN BAROCLINIC ATMOSPHERE BY THERMAL FORCING RELATED TO SUBTROPICAL HIGH

By using Lorenz's moist general circulation model, a nonlinear and dissipative system describing atmospheric motion has been obtained in approximation of Low Order.The multiple equilibria and the transformation between the flow patterns of winter and summer, the latitudinal oscillation of subtropical high by thermal forcing and nonlinear interaction of general circulation are studied in this paper.The results show that the transformation of flow patterns is a discontinuous leaping, and is a process of resetting new flow pattern by rapid exchange inflow field.In the corresponding dry model, we cannot find the latitudinal oscillation of the center of subtropical high.In the moist model, after the thermal effect of water vapor is drawn into the model, nonlinear interaction appears between flow and heating fields.This effect helps to bring about the latitudinal oscillation of subtropical high.     

利用Gupta势研究ConCu13-n (n=1～12)混合团簇的基态结构和熔化行为

利用Gupta多体相互作用势结合遗传算法和分子动力学方法模拟研究了ConCu13-n (n=0～13)单质及混合团簇的基态结构和熔化行为,结果表明：ConCu13-n (n=1~12)混合团簇的基态结构均是在单质Co13、Cu13基态二十面体基础之上的畸变,Co原子先占据中心后占据表面,表面上的Co原子总连接在一起,抱团分布;分析二级差分能和混合能发现Co1Cu12、Co7Cu6具有相对高的稳定性,可视为幻数结构团簇;ConCu13-n (n=1~12)混合团簇的熔点均位于Co13、Cu13单质团簇的熔点之间,且随着Co原子数目的增多总体呈上升趋势,但在n=3时出现反常（熔点降低）,这可归因于Co3Cu10的基态与第一激发态之间的能量差远小于Co2Cu11的相应值。