Low-Threshold High-Temperature Operation of ～7.4μm Quantum Cascade Lasers

We report low-threshold high-temperature operation of 7.4#m strain-compensated InGaAs/lnAIAs quantum cascade lasers （QCLs）. For an uncoated 22-μm-wide and 2-mm-long laser, the low-threshold current densities, i.e. 0.33kA/cm^2 at 81 K in pulsed mode and 0.64kA/cm^2 at 84K in cw mode, are realized. High-temperature operation of uncoated devices, with a high value of 223K, is achieved in cw mode.     

Teleportation of an n-bit one-photon and vacuum entangled GHZ cavity-field state

A scheme for teleporting an arbitrary n-bit one-photon and vacuum entangled Greenberger-Horne-Zeilinger （GHZ） state is proposed. In this scheme, the maximum entanglement GHZ state is used as a quantum channel. We find a method of distinguishing four Bell states just by detecting the atomic states three times, which is irrelevant to the qubit number of the state to be teleported.     

Switching and Self-trapping Dynamics of Dark Solitons in a Two-Component Bose-Einstein Condensate

Two coupled dark solitons are considered in a two-component Bose-Einstein condensate, and their dynamics are investigated by the variational approach based the renormalized integrals of motion. The stationary states as physical solutions to the describing equations are obtained, and the dynamic mechanism is demonstrated by performing a coordinate of a classical particle moving in an effective potential field. The switching and selftrapping dynamics of the coupled dark vector solitons are discussed by the evolution of the atom population transferring ratio.     

质量起源——量子色动力学与质量起源

 ……有读者可能会问：我们是不是离题了？既然量子色动力学中的胶子是无质量的，而夸克虽然有质量，但其质量是不可约化的。那么，量子色动力学与质量起源这一主题又能有什么关系呢？应该说，这是一个很合理的疑问。但量子色动力学的奇妙之处就在于，它形式上异常简洁，内涵却惊人地丰富。它宛如一坛绝世的佳酿，越品就越是回味无穷。在谈论质量起源问题的时侯，人们往往把注意力放在包含希格斯机制的电弱统一理论上，因为希格斯机制在登场伊始就打出了质量产生机制的响亮广告。但事实上我们将会看到，看似与质量起源问题无关的量子色动力学对这一问题有着非常独特而精彩的回答，从某种意义上讲，这一回答才是标准模型范围内的最佳回答。……     

干涉条纹边缘检测方法的比较与改进

研究了干涉条纹边缘检测中的Sobel算子和Laplacian算子,针对二者使干涉条纹变粗和模糊的现象,提出了改进的Laplacian算子。该改进算子先对干涉条纹利用Gauss函数进行平滑,然后再作Laplacian变换。实验结果表明,改进的Laplacian算子克服经典算子的不足,获得清晰的条纹边缘,满足了干涉条纹后续处理要求。     

Spatial coherences of the sound pressure and the particle velocity in underwater ambient noise

The spatial coherences were investigated between the sound pressure and the three orthogonal components of the particle velocity in underwater ambient noise. Based on the ray theory, integral expression was derived for the spatial coherence matrix of the sound pressure and the particle velocity in a stratified ocean with dipole noise sources homogenously distributed on the surface. The integrand includes a multiplying factor of the vertical directivity of the noise intensity, and the layered ocean environment affects the spatial coherences via this directivity factor. For a shallow water environment and a semi-infinite homogenous medium, the coherence calculation results were given. It was showed that the sound speed profile and the sea bottom could not be neglected in determining the spatial coherences of the ambient noise vector field.     

Audio watermarking based on psychoacoustic model and critical band wavelet transform

Watermark embedding algorithm based on critical band wavelet transform of digital audio signal is proposed in this paper. The masking threshold for each audio signal segment was calculated on the basic of psychoacoustic model. According to the similarity between critical band of human auditory system and critical band wavelet transform, a watermark was embedded into the low-band and mid-band coefficients of digital wavelet. The embedding strength was adaptively controlled by the masking threshold. The experiment results show that the embedded watermark signal is inaudible, and the watermarked audio signal has good robustness against many attacks such as compression, noise, re-sampling, low-pass filtering.     

高能p-A碰撞Drell-Yan过程中的初态核效应

核遮蔽和能量损失效应是p-A碰撞中两种重要的初态核效应. 本文利用从轻子-原子核深度非弹性散射实验数据中抽取的束缚核子的部分子分布函数, 在色弦模型中研究了Drell-Yan双轻子对产生过程中的能量损失效应. 通过对FNAL E772和E866实验数据的χ²分析, 得到夸克在冷核中的能量损失率为－dE/dz=2.06GeV/fm. 这和该模型理论预言的结果(－dE/dz～2GeV/fm)一致. 通过将理论计算结果与实验数据进行比较, 发现考虑到能量损失后能很好的解释实验现象.     

MOSFET辐照诱生界面陷阱形成过程的1/f噪声研究

基于界面陷阱形成的氢离子运动两步模型和反应过程的热力学平衡假设,推导了金属-氧化物-半导体-场效应晶体管(MOSFET)经历电离辐照后氧化层空穴俘获与界面陷阱形成间关系的表达式.利用初始1/f噪声功率谱幅值与氧化层空穴俘获之间的联系,建立了辐照前的1/f噪声幅值与辐照诱生界面陷阱数量之间的半经验公式,并通过实验予以验证.研究结果表明,由于辐照诱生的氧化层内陷阱通过与分子氢作用而直接参与到界面陷阱的建立过程中,从而使界面陷阱生成数量正比于这种陷阱增加的数量,因此辐照前的1/f噪声功率谱幅值正比于辐照诱生的界面陷阱数量.研究结果为1/f噪声用作MOSFET辐照损伤机理研究的新工具,对其抗辐照性能进行无损评估提供了理论依据与数学模型.     

光纤型宽带可调连续波差频产生中红外激光器

报道一种新型光纤化宽带可调连续波中红外激光器系统,该激光系统采用准相位匹配(QPM)的差频产生(DFG)技术,非线性晶体为多周期的周期性极化掺镁铌酸锂晶体(PPMgLN),掺镱光纤激光器(YDFL)用作抽运光源,可调激光器经掺铒光纤放大器(EDFA)功率提升后作为信号光源。利用建立的准相位匹配-差频产生系统,获得了连续波中红外差频光输出;实验发现,温度导致相位失谐的半峰全宽(FWHM)为4.5℃;通过优化选择晶体周期,并结合调节信号光波长和控制温度,该准相位匹配-差频产生系统可在3.1~3.6μm内连续调谐。