非对称量子阱中非线性光学吸收系数的计算

非对称量子阱中的非线性光学效应因其潜在的实用价值而引起人们的广泛关注,而量子阱内带间的光学吸收问题对研究远红外光学探测器件具有重要的理论指导意义.以Pschl-Teller势阱为例研究了影响非对称量子阱中的非线性光学吸收系数的因素.考虑到带间的电子弛豫,用量子力学中的密度矩阵算符理论导出了Pschl-Teller势阱中的线性与三阶非线性光学吸收系数的表达式.因该势阱中有两个可调参数,通过调节系统的参数,发现该系统的非线性光学吸收系数呈规律性的变化.以典型的GaAs/AlGaAs非对称量子阱为例作了数值计算,通过调节系统的参数,数值计算结果表明,入射光强以及系统的非对称性对量子阱的非线性光学吸收系数有较大的影响,从而为实验上研究非对称量子阱的非线性光学效应提供了必要的理论依据.     

激光捕获技术及其发展

激光捕获技术是利用光辐射力来捕捉、移动和操纵微粒的先进技术。光镊即单光束梯度力光阱是通过在高度会聚的激光束束腰附近所产生的极高的场强梯度来形成皮牛顿量级的力,可以三维地捕获和操纵微小粒子。阐述了激光捕获技术的模型和原理以及系统的基本结构;追踪了激光捕获技术的最新研究进展;介绍了非高斯型光阱、光纤光阱和全息光镊等几种特殊形式,并分析了每种形式的特点。展望了激光捕获技术的发展前景。     

Novel model of FM-noise conversion in a UMZI using RF external phase modulation of lasers: Theoretical and experimental results

In this paper, we propose and demonstrate a new and original model for theoretical calculation and experimental measurement of the noise power spectral density (NPSD) in phase-modulated optical links. The phase modulation is operated in the RF frequency range by an external phase modulator. The NPSD is derived for the first time in interferometric systems, by considering all effects such as the 1/f FM noise of the laser and white noise applied to light from a 1550 nm DFB laser, with phase modulation. The results show for the first time the influence of the phase modulation index, modulation frequency and interferometric delay in the phase-to-intensity noise conversion. The experimental and simulation results of conversion of FM-noise to intensity noise in an optical link by considering the external RF phase modulation are shown with good agreement.     

在BEPC上建造γ束线站的分析

考虑电子的反冲并利用康普顿散射,研究了激光同步辐射光源(LSS)辐射的光子波长、光子能量。结果表明,对于不同的γ,LSS辐射的光子波长和能量有不同的近似公式。当γ<<λ1/4λe时,LSS辐射的光子波长λ2≈λ1/4γ2,能量(εc2≈4γ2εc1;当γ>>λ1/4λe时,LSS辐射的光子波长λ2≈λe/γ,能量cε2≈m0γc2;结果表明,LSS辐射的条件是种子激光的波长λ1大于电子的物质波波长λm;LSS辐射的极值波长是λ2m ax=h/m0γv,极值能量是cε2m ax=βeε;本文后半部分提出了利用北京正负电子对撞机的强流高亮度电子束与激光的康普顿背散射产生单色γ射线的建议。     

SiN团簇光电子能谱的指认

应用含时密度泛函理论研究了SiN团簇低能激发态的性质.将计算结果与前人已有的计算结果进行了比较，此外还根据计算得到的低能激发能对SiN^-阴离子的光电子能谱进行了理论指认.研究表明，SiN^-阴离子的基态为¹Σ态，而光电子能谱上的X峰和A峰分别对应于¹Σ→²Σ和¹Σ→²Π的跃迁.研究结果还表明，用含时密度泛函的方法来处理激发态的问题是成功的. 关键词： 团簇 光电子能谱 基态 激发态     

双色激光场中1维共线氢分子离子的经典动力学研究

 运用经典理论方法，并采用辛算法数值求解了双色激光场作用下1维共线氢分子离子(H₂⁺)的哈密顿正则方程，得到了氢分子离子在激光场下的经典轨迹。计算了单色场和双色场下氢分子离子(H₂⁺)的存活几率、电离几率、解离几率、库仑爆炸几率随时间的演化，分析了双色场的相位、强度、强度比及倍频的变化对氢分子离子动力学行为的影响,并给出了相应的物理解释。     

High pressure X-ray diffraction study of CdAl2Se4 and Raman study of AAl2Se4 (A=Hg, Zn) and CdAl2X4 (X=Se, S)

We report the results of an X-ray diffraction study of CdAl₂Se₄ and of Raman studies of HgAl₂Se₄ and ZnAl₂Se₄ at room temperature, and of CdAl₂S₄ and CdAl₂Se₄ at 80 K at high pressure. The ambient pressure phase of CdAl₂Se₄ is stable up to a pressure of 9.1 GPa above which a phase transition to a disordered rock salt phase is observed. A fit of the volume pressure data to a Birch-Murnaghan type equation of state yields a bulk modulus of 52.1 GPa. The relative volume change at the phase transition at ∼9 GPa is about 10%. The analysis of the Raman data of HgAl₂Se₄ and ZnAl₂Se₄ reveals a general trend observed for different defect chalcopyrite materials. The line widths of the Raman peaks change at intermediate pressures between 4 and 6 GPa as an indication of the pressure induced two stage order-disorder transition observed in these materials. In addition, we include results of a low temperature Raman study of CdAl₂S₄ and CdAl₂Se₄, which shows a very weak temperature dependence of the Raman-active phonon modes.     

Structural and electronic properties of graphite layers grown on SiC(0 0 0 1)

Photoelectron spectroscopy, low-energy electron diffraction, and scanning probe microscopy were used to investigate the electronic and structural properties of graphite layers grown by solid state graphitization of SiC(0 0 0 1) surfaces. The process leads to well-ordered graphite layers which are rotated against the substrate lattice by 30°. On on-axis 6H-SiC(0 0 0 1) substrates we observe graphitic layers with up to several 100 nm wide terraces. ARUPS spectra of the graphite layers grown on on-axis 6H-SiC(0 0 0 1) surfaces are indicative of a well-developed band structure. For the graphite/n-type 6H-SiC(0 0 0 1) layer system we observe a Schottky barrier height of ?_B,n = 0.3 ± 0.1 eV. ARUPS spectra of graphite layers grown on 8° off-axis oriented 4H-SiC(0 0 0 1) show unique replicas which are explained by a carpet-like growth mode combined with a step bunching of the substrate.     

Diode-pumped 671 nm laser frequency doubled by CPM LBO

A design of diode-pumped high-efficiency Nd:YVO₄/LBO red laser is reported. Using critical phase-matching (CPM) LBO, 671 nm red laser was obtained from 1342 nm light by intracavity frequency doubling. With an incident pump laser of 800 mW, using type-I and type-II CPM LBO, 97 and 52 mWTEM₀₀ mode red laser outputs were obtained, with optical-to-optical conversion efficiencies of up to 12.1% and 6.5%, respectively.     

复合体系方法测量液体力学谱

本文介绍了采用复合体系，测量得到凝聚态物质从固态到液态连续变化力学谱的一种新的实验方法。以簧振动为例，给出了解析的计算公式，以及应用条件。通过进一步综合分析，得到具有更广应用范围的近似公式，可以近似应用于其他不同的振动模式，如低频扭摆。应用新的测量方法，给出了典型小分子玻璃材料甘油和碳酸丙稀从玻璃态到液态的力学谱，观察到甘油和碳酸丙稀玻璃化转变、碳酸丙稀的再结晶、熔化和挥发的过程；测量得到挥发过程中水的质量随时间精确变化的曲线。最后，本文给出了新方法的一些应用展望。