Influence of Deviation on Optical Transmission through Aperiodic Superlattices

We propose a deviation model and study the influences of the relative error and sensitivity of a machine on the transmission coefficients （TCs） of Fibonacci superlattices. It is found that for a system with fewer layers, the influence of deviation can be ignored. When superlattices become more complicated, they may be fabricated by a machine with suitable relative error and possess the designed value of TO. However, when the number of system layers exceeds some critical value, superlattices should be manufactured only by precise machines. The influence of the sensitivity is also discussed.     

不同环境温度下工艺参数对扩散吸收式制冷机的性能影响

外界环境温度对扩散吸收制冷循环有重要影响,以四台相同结构的扩散吸收式制冷机为基础,用实验的手段研究了不同环境温度下,氨水溶液灌装浓度、充注压力、输入功率等工艺参数对扩散吸收式制冷机性能的影响。得出了实验样机在各工况下的最优工艺参数;研究发现随环境温度的升高,样机的最佳灌装浓度下降,而最佳输入功率和最适宜充注压力升高。可为扩散吸收式制冷机根据环境温度选择各工艺参数提供一定的依据。     

Holographic behavior of a photopolymer at high thicknesses and high monomer concentrations: mechanism of photopolymerization

One of the main problems involved in the development of holography is that of the recording material used. In this study the behavior of a photopolymer is analyzed when thicknesses greater than 100 μm are used. The photopolymer is made up of acrylamide as monomer, triethanolamine as radical generator, yellowish eosin as sensitizer and polyvinyl alcohol as binder. The main problem is that an increase in thickness produces more scattering and consequently a decrease in the diffraction efficiency. In this study we analyzed the influence of the concentration of monomer on scattering and found that an increase in the concentration reduces scattering. The behavior of the material varies as the concentration of acrylamide is increased. Two polymerization mechanisms compete and so the behavior of the photopolymer is not linear, the reaction is slower and the expected maximum efficiency is not reached. It has been demonstrated experimentally that when the recording intensity is reduced the photopolymer behaves in a linear way. Received: 28 January 2000 / Revised version: 25 July 2000 / Published online: 13 December 2000     

Influence of auxiliary violet light on holographic kinetics at low and high recording intensities in bacteriorhodopsin film

The photochromic bacteriorhodopsin (BR) film can be used as a rewritable holographic recording medium. Due to the saturation absorption and the scattering and reflecting lights from the BR film, the grating contrast-ratio of the hologram is diminished during the hologram recording. When the intensity of the recording light is low, the influence of the saturation absorption and the scatter and reflection of BR film on the grating contrast-ratio is weak. But for the case of intense recording light, this influence is more serious. It is found that the influence of the auxiliary violet light on the holographic kinetics of diffraction efficiency is distinct under different recording intensities. At the low recording light intensity, the steady diffraction efficiency is increased and the peak diffraction efficiency is suppressed by the auxiliary violet light. But for intense recording light, the steady diffraction efficiency and the peak diffraction efficiency are both increased by the auxiliary violet light. Based on the two-state model of BR photochromism, we give a good theoretical explanation to the above phenomena.     

Efficiency of autonomous soft nanomachines at maximum power

We consider nanosized artificial or biological machines working in steady state enforced by imposing nonequilibrium concentrations of solutes or by applying external forces, torques, or electric fields. For unicyclic and strongly coupled multicyclic machines, efficiency at maximum power is not bounded by the linear response value 1/2. For strong driving, it can even approach the thermodynamic limit 1. Quite generally, such machines fall into three different classes characterized, respectively, as "strong and efficient," "strong and inefficient," and "balanced." For weakly coupled multicyclic machines, efficiency at maximum power has lost any universality even in the linear response regime.     

Morphology of carbon nanostructures and their electrochemical performance for lithium ion battery

A comparative study has been carried out on anodes made from carbon nanostructures of five different morphologies—single walled, double walled and multiwalled carbon nanotubes (with two different diameters), and carbon nanofibers. The specific area of the samples of these carbon nanostructures has been determined and their structure and morphology have been characterized by microscopy, X-ray diffraction and Raman spectroscopy. Depending on the morphology and the size of the nanostructures in the anode, the reversible capacity obtained ranges from 450 to 600 mAh g⁻¹ and the coulombic efficiency is in the range of 85–98% after 12 cycles. Increasing the surface area, both inside and outside for the tubes of a nano-size, gives rise to increased number of surface sites, which may be intercalated reversibly leading to increased specific charge capacity. Formation of the solid electrolyte interface layer covers a part of these surface sites as well as results in capacity fading, which also increases with increasing surface area. Increased defect sites responsible for elastic scattering in Raman spectra do not appear to have deciding influence on either enhanced capacity or capacity fading. Nano-sized constituent in the electrode appears to improve mechanical characteristics ensuring good mechanical integrity on cycling and high coulombic efficiency.     

Photorefractive optical properties of volume phase gratings induced in sillenite crystals, when the grating vector lies on the (111) plane

We study the diffraction efficiency of volume phase gratings in Bi₁₂GeO₂₀, when the grating vector, lying on a (111) plane, is at an angle with respect to the crystallographic direction. An external bias field parallel to the direction is applied during recording, thus, the recording conditions depend on the grating vector orientation. The basic parameters determining the diffraction efficiency are the grating vector orientation, the rotatory power and the field-induced linear birefringence (primary and secondary). Analytic expressions for the diffraction efficiency have been obtained by taking into account all the above-mentioned parameters, provided that linearly polarized light is incident on the crystal. In this configuration, the influence of the secondary electro-optic effect (inverse piezoelectric and photoelastic effects) to the diffraction efficiency is actually stronger than the influence of the primary effect. Experimental results are given. Received: 3 January 2000 / Revised version: 6 June 2000 / Published online: 13 September 2000     

赫兹对阴极射线的实验研究及其重要影响

根据赫兹的日记、书信、文集及相关文献,对赫兹所进行的阴极射线的实验研究工作进行了仔细考察,指出他对阴极射线的一系列实验研究为揭示阴极射线的全部特性奠定了重要基础,对勒纳德和汤姆孙在这一领域的研究产生了直接影响．     

Analysis of reflection speckle holograms in a BSO crystal

A theoretical and experimental study of speckle registering in photorefractive BSO crystals through reflection hologram geometry is implemented. The three-dimensional speckle nature is considered in the diffraction efficiency calculations. The interference process produces index-of-refraction gratings in the speckle volume via the photorefractive effect. It is demonstrated that the coupled-wave theory for reflection geometry allows explaining the diffraction efficiency behavior when the interaction length is properly taken into account. It means that the speckle depth is related with the interaction length. The speckle depth can be controlled by the imaging system pupil aperture diameter. Under this condition, the influence of the speckle depth on the diffraction efficiency is analyzed. An agreement between the numerical model based on the coupled-wave theory and the experimental results is obtained.     

Theory of photoinduced charge separation in solids

We discuss photoinduced ionization and charge separation kinetics in solutions as a way to conserve and utilize light energy. Our interest is in the secret of the high efficiency of reaction centers and the fast and irreversible separation of ions involved in reduction and oxidation reactions in the macromolecule. We present a new theory of reversible charge transfer, which shows high efficiency of charge separation: the charge's recombination has a weak influence on the donor cation-state probability's maximum value but a large effect on its long-time behavior. We give the comparison of new results with recently published ones on charge separation kinetics in condensed media. We use the methods of independent reaction “vessels” and “conditional concentrations”. The influence of back charge transfer is essential for long-time tail of the cation-state probability; its action on the cation-state probability's maximum value grows weak with an increase of forward rate constants and acceptor's concentration.     

Transmission second harmonic generation in CdTe at 1.064 μm

Transmission geometry measurements of the efficiency of second harmonic generation in various thicknesses of CdTe samples were made to determine the conversion efficiency dependence on material thickness. Neglecting pump depletion, it is found that for samples of well-defined symmetry, the second harmonic conversion efficiency scales with film thickness, with no observed enhancement owing to coherence length effects. The angular dependence of the observed second harmonic light in films of well-defined symmetry is consistent with second harmonic generation originating in the bulk.     

Effect of Media on the Electric Field of a Rhombic Nanostructure Array

Electric field distribution is an important parameter for nanostructure arrays in nanobiosensing appfications. It can influence the sensitivity and the resolution of nanobiosensors. We focus on the effect of media on the electric field distribution of a rhombic silver nanostructure array. The finite-difference time-domain algorithm- based numerical calculation method is used to monitor the electric field distribution of the silver nanostructures when the refractive index of the medium around the nanostructure array is changed. The calculated results show that tuning the refractive index of the medium around silver can have a considerable influence on the electric field distribution in the reflection and transmission directions. This effect can be used to increase the extinction efficiency and to improve the resolution of the spectra for nanobiosensing.     

Cathode-lifetime and stability problems in arc-dischargetype heavy ion sources

The last few years have seen ion implantation become a widely used industrial method. This has resulted in increasing importance being attached to the reliability of implanters and to a satisfactory working time/maintenance relation and other factors which are in some way connected with reproducibility and homogeneity. With these viewpoints in mind, ion sources seem to be the most sensitive components of implanters. Besides the normal ion source operations such as changing feeding material or gas, etc., ion sources need care in the maintenance. Ion source lifetime and reliability problems are of special consequence in the case of heavy-current machines. The excellent, mechanically scanned target chambers have made possible the use of higher and higher currents, but at the same time these currents can cause lifetime problems which affect the profit of expensive high current machines.     

Dynamics of Efficiency Change by Temperature in Diode Pumped Nd：YAG Heat Capacity Laser

We investigate the influence of temperature on the efficiency of diode pumped Nd：YAG heat capacity laser is studied. It is shown that the efficiency of such a laser system is greatly reduced at higher temperature. This bad behaviour is mainly caused by the doped-ion redistribution among various Stark levels of the ground state, and by a thermal equilibrium between the upper laser level and the pump level. Meanwhile, the thermal excitations from the ground state to the lower laser level also play a role. We derive a model to describe those effects, with the considerations of emission spectrum of laser diodes, the subtle Stark structures and the linewidth of absorption and of simulated-emission.     

Third-harmonic generation in cylindrical parabolic quantum wires with static magnetic fields

The third-harmonic generation (THG) and its conversion efficiency in Al_xGa_1-xAs/GaAs cylindrical parabolic quantum wires with static magnetic fields are studied in detail. The calculated results show that the parabolic confining potential and the static magnetic field have evident influence on the THG and its conversion efficiency. In addition, the conversion efficiency of the THG is also related to the input optical intensity. It is noted that very high conversion efficiency of the THG can be obtained by increasing properly the input optical intensity and choosing an optimized parabolic confining potential and applied static magnetic field.     

Effect of different conductivity between the spin polarons on spin injection in a ferromagnet/organic semiconductor system

Spin injection across ferromagnet/organic semiconductor system with finite width of the layers was studied theoretically considering spin-dependent conductivity in the organic-semiconductor. It was found that the spin injection efficiency is directly dependent on the difference between the conductivity of the up-spin and down-spin polarons in the spin-injected organic system. Furthermore, the finite width of the structure, interfacial electrochemical-potential and conductivity mismatch have great influence on the spin injection process across ferromagnet/organic semiconductor interface.     

Influence of spatial mode matching in end-pumped solid state lasers

We present investigations on the influence of mode matching on the efficiency of longitudinally pumped solid state lasers. In a theoretical part we enhance an existing model for four level lasers from idealized cylindrical modes to arbitary pump and laser modes in a random relative position thereby neglecting beam deformation due to thermal effects. The theoretical predictions were confirmed experimentally with an end-pumped Nd:YAG rod operated at 1064 nm. To investigate the effect of misalignment on the efficiency we used a Ti-Sapphire pump laser which was displaced relative to the laser beam. To establish the influence of arbitary pump modes on laser performance a diode laser equipped with coupling optics served as pump source for the same resonator. The resulting decrease in slope efficiency compared to the Ti-Sapphire pumped system could be explained in terms of limited mode overlap due to the characteristic pump field distribution produced by the diode coupling optics.     

Enhanced Laser Cooling of Rare-Earth-Ion-Doped Composite Material

We predict enhanced laser cooling performance of rare-earth-ions-doped glasses containing nanometre-sized ultrafine particles, which can be achieved by the enhanucement of locai field around rare earth ions, owing to the surface plasma resonance of small metallic particles. The influence of energy transfer between ions and the particle is theoretically discussed. Depending on the particle size and the ion emission quantum efficiency, the enhancement of the absorption is predicted. It is concluded that the absorption are greatly enhanced in these composite materials, the cooling power is increased as compared to the bulk material.     

Photorefractive properties of (1-10) and (111)-cut sillenite crystals when external electric field is applied along the direction of the optimum diffraction efficiency

We study the influence of the application of an external electric field on the grating formed in (1-10) and (111)-cut photorefractive sillenite crystals. Optimum conditions for application of the bias field are examined, taking into account the shift of the grating orientation for maximum diffraction efficiency along the crystal depth. The contribution of the piezoelectric effect is considered both in the electro-optic tensor and space charge field calculations. An analysis on the diffractive properties under these optimum conditions shows an increase of 30% in maximum diffraction efficiency in Bi₁₂GeO₂₀, and experimental verification for this is provided. Received: 5 November 2001 / Revised version: 18 April 2002 / Published online: 8 August 2002     

绿色陶瓷厚膜电致发光器件研究

报道了采用高介电常数的陶瓷厚膜作绝缘层、ＺｎＳ：Ｅｒ,Ｃ１作为发光层的绿色薄膜电致发光器件（ＣＴＦＥＬ）。器件结构为陶瓷基片／内电极／陶瓷厚膜／发光层（ＺｎＳ：Ｅｒ,Ｃ１）／透明电极（ＺｎＯ：Ａ１）。制备的器件在市电频率驱动下发出明亮的绿光,测量了器件的电致发光（ＥＬ）光谱和亮度－电压曲线,研究了发光机理和效率－电压等特性。