缓冲层生长温度对In0.82Ga0.18As 薄膜结构及电学性能的影响

采用低压金属有机化学气相沉积(LP-MOCVD)技术,两步生长法在InP衬底上制备In_0.82Ga_0.18As材料。研究缓冲层的生长温度对In_0.82Ga_0.18As薄膜的结构及电学性能的影响。固定外延薄膜的生长条件,仅改变缓冲层生长温度(分别为410,430,450,470 ℃),且维持缓冲层其他生长条件不变。用拉曼散射研究样品的结构性能,测量四个样品的拉曼散射光谱,得到样品的GaAs的纵向光学(LO)声子散射峰的非对称比分别为1.53,1.52,1.39和1.76。测量样品的霍耳效应表明,载流子浓度随缓冲层生长温度变化而改变,同时迁移率也随缓冲层生长温度变化而改变。通过实验得出:缓冲层的生长温度能够影响In_0.82Ga_0.18As薄膜的结构及电学性能。最佳的缓冲层生长温度为450 ℃。     

热解温度对酚醛树脂焦的微观结构和还原NO反应性的影响

利用傅立叶变换红外光谱(FTIR)、X射线衍射(XRD)和Raman光谱研究了热解温度(500～900℃)对酚醛树脂焦炭微观结构的影响.使用热重分析仪(TGA)研究了酚醛树脂焦还原NO的反应性.结果表明,随着热解温度升高,苯环、酚羟基、脂肪亚甲基等官能团含量降低.衍射实验表明存在(002)峰、(10)峰和(11)峰.随着热解温度升高,焦炭微晶尺寸增大,微晶结构逐渐趋向有序.酚醛树脂焦的Raman光谱分析与XRD分析存在较好的关联性.反应性实验表明焦炭还原NO的反应性没有随热解温度呈现规律性的变化.     

卡文迪什实验室建设方针演进的启示

从卡文迪什实验室建设指导思想和办室方针的演进史料的分析入手,剖析了卡文迪什实验室的成功与建设方针演进的内在联系,总结了卡文迪什实验室建设方针的演进对我国不同类型高校、不同研究水平的实验教学示范中心的建设工作的现实指导意义.     

Study of nucleon resonances in a chiral quark model via η productions

In this report we investigate η-meson productions on the proton via electromagnetic and hadron probes in a chiral quark model approach. The observables, such as, differential cross section and beam asym-metry for the two productions are calculated and compared with the experiment. The five known resonances S_(11)(1535), S_(11)(1650), P_(13)(1720), D_(13)(1520), and F_(15)(1680) are found to be dominant in the reaction mech-anisms in both channels. Significant contribution from a new S_(11) resonances are deduced. For the so-called "missing resonances", no evidence is found within the investigated reactions. The partial wave amplitudes for π~-p→ηn are also presented.     

基于流场模拟的涡旋压缩机涡齿应力变形分析

为了更准确地计算涡旋压缩机涡旋齿的应力和变形,提出一种基于流场模拟的应力变形计算方法。通过对涡旋压缩机工作过程进行气体流动的数值模拟,得到其压力场和温度场分布。将流场分布作为载荷边界条件进行涡旋齿的受力变形计算,得到涡旋齿在气体压力、热载荷及其同时作用下的应力分布和变形规律。分析了涡旋齿的径向变形和轴向变形,讨论了不同主轴转角下的涡旋齿应力和变形,比较了动涡旋齿和静涡旋齿的变形。结果表明:在压缩结束时刻动涡旋齿的应力和变形最大,最大应力位于齿头根部,最大变形位于齿头顶部。     

椭圆柱形光学黑洞红外辐射特性分析

本文主要采用时域有限差分(FDTD)方法计算了二维椭圆柱形光学黑洞的红外辐射特性。并且采用几何光学近似(GOA)对椭圆柱形的光学黑洞的光线入射轨迹进行分析和比较。研究结果表明,FDTD计算的光学黑洞内的能流分布结果与GOA计算的光学黑洞内的光线入射轨迹结果相吻合,椭圆柱形光学黑洞的红外辐射特性主要受折射率梯度和入射波长的影响。     

天然竹红菌素粗品的光物理特性及机理分析

用SP-2558型光谱实验系统测得了天然竹红菌素粗品的三维荧光光谱,给出其随样品浓度变化的规律,进而利用软件和理论分析提出,天然竹红菌素粗品荧光光谱主要是竹红菌甲素（HA）和竹红菌乙素（HB）荧光光谱的贡献,HA的荧光光谱受其他成分影响较大,造成了短波峰的蓝移和长波峰的红移;HA与HB之间的辐射能量转移导致其荧光光谱中长波成分增加,从而形成较宽的谱段;由分子间氢键形成的多聚体会导致天然竹红菌素粗品溶液的发射峰随浓度的增加而红移,因而通过对天然竹红菌素粗品的浓度调控,可以在一定的范围内实现对发射光波段的调控,这对指导临床上的应用具有较高的参考价值。     

High speed and wide temperature range uncooled 1.3-μm ridge waveguide DFB lasers

A 1.3-μm wavelength vertical-mesa ridge waveguide mulitple-quantum-well （MQW） distributed feedback （DFB） laser with high directly modulated bandwidth and wide operation temperature range is reported. With the optimization of the strained-layer MQWs in the active region, the surrounding graded-index separated-confinement-heterostructure waveguide layers, together with the optimization of the detuning and coupling coefficient of the DFB grating, high directly modulation bandwidth of 16 GHz at room temperature and wide working temperature range from -40 to 85 ℃ are obtained. The mean time to failure （MTTF） is estimated to be over 2×10^6 h. The device is suitable as light source of high-bit-rate optical transmitters with small size and reduced cost.     

Dual-channel phase-shifting interferometry for microscopy with second wavelength assistance

Dual-channel phase-shifting interferometry for simultaneous phase microscopy is presented. Red and blue light beams are used for microscope illumination. A 45 tilted beamsplitter replicates the object and reference waves in red light together with the object wave in blue light into two parallel beams. The two resulting quadrature phase-shifting interferograms in red light and the object waves in blue light are generated in the two channels. The two interferograms are recorded simultaneously by a color charge-coupled device (CCD) camera, and can be separated via RGB components of the recorded color patterns without crosstalk. As a result, the phase of tested specimen can be retrieved. The feasibility of the proposed method is demonstrated by test performed on a microscopic specimen.     

High-efficiency continuous-wave and Q-switched operation of a resonantly pumped Ho:YAP ring laser

We demonstrated continuous-wave (CW) and Q-switched operation of a room-temperature Ho:YAP ring laser that is resonantly end-pumped by a diode-pumped Tm:YLF laser at 1.91 ??m. Continuous wave output power of 3 W at 2119 nm is obtained under the absorbed pump power of 10.17 W, corresponding to a slope efficiency of 60%. For the Q-switched regime the maximum pulse energy of 1.58 mJ and the minimum pulse width of 590 ns at the repetition rate of 1 kHz are achieved.