COHERENT MODEL FOR RESONANT-TUNNELING OF ELECTRONS IN DOUBLE-QUANTUM WELLS UNDER ELECTRIC-FIELDS

Taking the inhomogenous broadening of the electron energy levels into account, a coherent model of the resonant tunneling (RT) of electrons in double quantum wells is presented. The validity of the model is confirmed with the experiments [M. Nido et al., Proc. SPIE 1268, 177 (1990)], and shows that the tunneling process can be explained by the simple coherent theory even in the presence of the carrier scattering. We have discussed the dependence of resonant tunneling on the barrier thickness L(B) by introducing the contrast ratio LAMBDA and the full width at half depth of the RT valley, and found that LAMBDA first increases with increasing barrier thickness, reaches a maximum, and then decreases with a further increase of L(B), in striking contrast to the Fabry-Perot model where a monotonic increase of the peak-to-valley ratio is predicted. We attribute the reduction of LAMBDA with large L(B) to the energy broadening resulting from the carrier scattering. A monotonic decrease of the full width at half depth of the RT valley with an increase of L(R) is also found.

Quantum coherent networks: A theoretical study

Electron transport in quantum coherent networks (interacting quantum waveguide arrays) is investigated theoretically with use of the scattering-matrix method. The scattering matrix for the basic unit of networks, the cross junction with Square or rounded corners, is derived using the mode-matching technique, The overall scattering matrix for the network is obtained by the composition of the scattering matrices associated with each unit of the network, For a uniform network, the transmission spectra are calculated in the single-mode regime and an found notably dependent on the junction geometry. Small reflection for the input terminal and uniform output for some output ports are obtained, which means that the quantum coherent network can be used as a distributing net for the electron waves. Cross junctions with rounded corners of large radii are found to play a negative role in the device application of quantum coherent networks. (C) 1997 American Institute of Physics.

用于WDM系统的垂直腔可调谐光电器件

从理论模型出发分析了实现垂直腔光电器件可调谐的方法，讨论了静电激励的1／3原则，及其对调谐性能的影响，从国内外几个有代表性的研究小组的工作出发，介绍了最新的研究进展。

利用WDM光纤耦合器的光纤光栅传感解调技术

根据WDM光纤耦合器波长解调方案的工作原理、偏振特性以及影响系统波长分辨力的因素,提出一种改进的利用WDM光纤耦合器的光纤光栅传感解调技术.该技术在原技术的基础上,采用偏振控制器控制入射光偏振状态,提高了解调的精度和稳定性.对WDM光纤耦合器的多次波长扫描结果表明,采用偏振控制器后,其波长误差可减小到5pm左右.实验采用1540/1560nm的WDM光纤耦合器对单点光纤光栅应变传感器进行静态解调,结果表明:按此技术开发的解调系统具有0.01nm波长分辨力和10nm的波长线性解调范围.

Investigation on integrated high speed DFB light source and narrow bandwidth RCE photodetector for WDM fiber communication network application

Electroabsorption (EA) modulator integrated with partially gain coupling distributed feedback (DFB) lasers have been fabricated and shown high single mode yield and wavelength stability. The small signal bandwidth is about 7.5 GHz. Strained Si1-chiGechi/Si multiple quantum well (MQW) resonant-cavity enhanced (RCE) photodetectors with SiO2/Si distributed Bragg reflector (DBR) as the mirrors have been fabricated and shown a clear narrow bandwidth response. The external quantum efficiency at 1.3 mum is measured to be about 3.5% under reverse bias of 16 V. A novel GaInNAs/GaAs MQW RCE p-i-n photodetector with high reflectance GaAs/ALAs DBR mirrors has also been demonstrated and shown the selectively detecting function with the FWHM of peak response of 12 nm.

Size and shape evolution of self-assembled coherent InAs/GaAs quantum dots influenced by seed layer

The size and shape Evolution of self-assembled InAs quantum dots (QDs) influenced by 2.0-ML InAs seed layer has been systematically investigated for 2.0, 2.5, and 2.9-ML deposition on GaAs(1 0 0) substrate. Based on comparisons with the evolution of InAs islands on single layer samples at late growth stage, the bimodal size distribution of InAs islands at 2.5-ML InAs coverage and the formation of larger InAs quantum dots at 2.9-ML deposition have been observed on the second InAs layer. The further cross-sectional transmission electron microscopy measurement indicates the larger InAs QDs: at 2.9-ML deposition on the second layer are free of dislocation. In addition, the interpretations for the size and shape evolution of InAs/GaAs QDs on the second layer will be presented. (C) 2001 Elsevier Science B.V. All lights reserved.

基于WDM模型的PCI卡驱动程序设计

基于WDM模型的PCI卡驱动程序设计,是建立Windows操作系统下数据采集系统面临的关键问题。详细分析了WDM驱动程序的工作原理。以PCI9113A数据采集卡为例,提出了利用Microsoft公司的DDk实现Windows2000操作系统下驱动程序的有效开发方法。讨论了驱动程序的测试和封装。

WDM驱动程序在HIRFL-CSR电源控制系统中的应用

为解决基于Web多层架构的HIRFL-CSR电源控制系统的可靠性和实时性差的问题,利用直接在WDM驱动程序中处理被控设备异常的方法来提高控制系统的可靠性和实时性, WDM驱动程序利用WMI主动向应用程序报告被控设备的异常,简化了控制系统的软件结构,从而进一步提高控制系统的实时性和控制效率。

Windows2000的管理机制(WMI)和WDM驱动程序的研究与应用

主要介绍了一种新型的企业管理和设备测试系统。首先描述了WMI的优点及其体系结构。然后介绍怎样把WMI机制和WDM驱动程序结合起来。最后给出一个访问WMI的标准的方法。