多波长泵浦宽带拉曼放大器功率增益研究

受激拉曼散射（SRS）的Stokes波谱线型比较复杂,本文分别用Gauss线型和Lorentz线型,研究多波长泵浦宽带Raman放大器的增益特性,提出宽带增益平坦的多波长泵浦方案,研究表明增益平坦程序与泵清波频率间隔密切相关。对G．652、G．653、G．655光纤和新型大有效面积非零色散平坦光纤的Raman放大增益分别进行了研究,结果表明Raman增益与光纤种类和光纤传输性有关,特别是随光纤有效纤芯面积的增大而明显减小。     

Electronic density oscillations in gold atomic chains assembled atom by atom

Linear Au chains two to 20 atoms long were constructed on a NiAl(110) surface via the manipulation of single atoms with a scanning tunneling microscope. Differential conductance (dI/dV) images of these chains reveal one-dimensional electronic density oscillations at energies 1.0 to 2.5 eV above the Fermi energy. The origin of this delocalized electronic structure is traced to the existence of an electronic resonance measured on single, isolated Au atoms. Variations in the wavelength in dI/dV images of an eleven-atom chain taken at different energies revealed an effective electronic mass of 0.4+/-0.1 times the mass of a free-electron.     

On the Momentum,Mass and Energy Transport for Transverse Wave Packets in Warm Plasmas,with Applications to Solitons

The energy-mass equation has been formulated for transverse wave packets of an arbitrary form propagating in warm plasmas and then it has been applied to solitons. In contradistinction to a soliton mass given by Klein [7], the mass defined here cannot be chosen arbitrarily.     

Studies of Ziegler-type catalysts for the polymerization of ethylene and propylene II The polymerization of ethylene with VOCl3-Et3Al2Cl3 (chlorinated activator) catalysts

VOCl₃-Et₃Al₂C1₃(chlorinated activator) catalysts have been employed for the polymerization of ethylene at T between 15 and 85° in n-hexane. Using butylperchlorocrotonate as the activator, the following catalyst efficiencies (g polymerization, hr, atmosphere ethylene in the cap gas) were achieved: 10^6,1 MFI = 0-00; 10^5,8, e.g. MFI = 1 0 (with 9 per cent H₂ present in the cap gas) and 10^6–9 MFI = 0?4 (with 44 mmole/1 styrene in the hexane medium). Reactions between the aluminium alkyl and the activator molecules produced other chlorinated species of high average activator effectiveness. The catalyst system could be reactivated by further additions of Et₃Al₂Cl₃. The minimum value of the polymerization propagation rate constant is estimated to be 10¹²²?6x10,461 cm³/mole sec.     

Doped semiconductors in an inhomogeneous magnetic field

We show that a potential difference is generated across a semiconductor sample containing free carriers when the sample is in a magnetic field gradient in the direction of the field. A measurement of the potential difference can give direct information concerning the effective mass and effective g-factor of the free carriers.     

Distance dependence of the interaction between single atoms: gold dimers on NiAl(110)

The importance of substrate-mediated adsorbate-adsorbate interactions on electronic states has been demonstrated for Au dimers on NiAl(110) with a scanning tunneling microscope and density functional calculations. An unoccupied resonance observed in single Au atoms splits into a doublet in Au dimers. The energy splitting depends inversely on the distance between the two adatoms, revealing the relative importance of direct and substrate-mediated interactions. Spatially resolved conductance measurements of Au dimers reveal the symmetric and antisymmetric characters of the doublet states.     

Time-Resolved Temperature Measurement of AlGaN/GaN Electronic Devices Using Micro-Raman Spectroscopy

We report on the development of time-resolved Raman thermography to measure transient temperatures in semiconductor devices with submicrometer spatial resolution. This new technique is illustrated for AlGaN/GaN HFETs and ungated devices grown on SiC and sapphire substrates. A temporal resolution of 200 ns is demonstrated. Temperature changes rapidly within sub-200 ns after switching the devices on or off, followed by a slower change in device temperature with a time constant of ~10 and ~140 mus for AlGaN/GaN devices grown on SiC and sapphire substrates, respectively. Heat diffusion into the device substrate is also demonstrated     

Heterogeneous InSb quantum well transistors on silicon for ultra-high speed, low power logic applications

The heterogeneous integration of InSb quantum well transistors onto silicon substrates is investigated for the first time. 85 nm gate length FETs with f_T = 305 GHz at V_ds = 0.5 V and DC performance suitable for digital logic are demonstrated on material with a buffer just 1.8 mum thick. An initial step towards integrating InSb FETs with mainstream Si CMOS for high-speed energy-efficient logic applications has been achieved.     

Low-leakage InGaAs photodiodes grown on gaAs substrates using a graded strained-layer superlattice

InxGa1?xAs layers with In concentrations up to 35% have been grown on GaAs substrates by MOCVD using a GaAs/InxGa1?xAs superlattice with graded layer thicknesses to accommodate the lattice mismatch. 105 ?m-diameter PIN diodes fabricated from this material have leakage currents below 1 nA at ? 10 V, comparable to devices from lattice-matched material on InP substrates.