Optimal conditions for high-speed all-optical SOA-based wavelengthshifting

We analyze the system performance of gain-saturated semiconductor optical amplifier (SOA)-based all-optical wavelength shifting with respect to its dynamic characteristics. When considering the risetime, contrast ratio and intersymbol interference, we find that there exists an optimal probe power and wavelength for high-speed wavelength shifting which reduces the power penalty by 3 dB. The minimum power penalties for the data rates of 10 and 20 Gb/s are 25 and 5 dB, respectively     

Chalcogen-Containing Manganese Carbonyl Clusters: Synthesis and Structural Transformations

Recently, we have developed several synthetic routes to the new classes of chalcogen-containing manganese carbonyl clusters, and the interesting structural transformations and reactivity of the resultant clusters have been investigated as well. In this short review, the syntheses and bonding modes of the sulfur, selenium, and tellurium-containing manganese carbonyl complexes reported by our laboratory will be presented, and the cluster growth and transformation will be systematically compared and discussed.     

Maskless selective diffusion of Si into GaAs

A maskless selective diffusion of silicon into GaAs is achieved by the selective modification of the GaAs surface using low energy Ar sputtering. The Ga rich surface resulting from the Ar sputtering prevents the diffusion of silicon into GaAs.<>     

Self-aligned index-guided multiple quantum well laser by sulphur diffusion-induced disordering

A simple self-aligned fabrication process for sulphur-diffusion disordered AlGaAs/GaAs multiple quantum well (MQW) lasers is described that produces refractive index guiding. However, the gradual profile of sulphur diffusion causes a separation between the disordered/nondisordered interface and the pn junction which leads to a large lateral optical loss of the index-guided mode.<>     

Scalable and lightweight key distribution for secure group communications

Securing group communications in dynamic and large‐scale groups is more complex than securing one‐to‐one communications due to the inherent scalability issue of group key management. In particular, cost for key establishment and key renewing is usually relevant to the group size and subsequently becomes a performance bottleneck in achieving scalability. To address this problem, this paper proposes a new approach that features decoupling of group size and computation cost for group key management. By using a hierarchical key distribution architecture and load sharing, the load of key management can be shared by a cluster of third parties without revealing group messages to them. The proposed scheme provides better scalability because the cost for key management of each component is independent of the group size. Specifically, our scheme incurs constant computation and communication overheads for key renewing. In this paper, we present the detailed design of the proposed scheme and performance comparisons with other schemes. Briefly, our scheme provides better scalability than existing group key distribution approaches. Copyright © 2004 John Wiley & Sons, Ltd.     

Digitally redesigned PAM controller and ideal state reconstructor for input time-delay/nondelay systems with nonsynchronous sampling

This paper develops a new digitally redesigned pulse-amplitude modulated (PAM) controller for a continuous-time input time-delay/nondelay system with nonsynchronous sampling. The concept of the law of the mean from the input integral calculus is utilized for the development of the equivalent digital predictor controllers from the available analog predictor controllers. As a result, the digitally controlled states closely match the original continuous-time states. To implement the developed discrete-time state-feedback PAM controller, this paper also develops an ideal discrete-time state using nonsynchronously sampled input-output data of the continuous-time input delay/nondelay system without establishing a dynamic observer.This work was supported by the National Science Council of the Republic of China under contract NSC-84-2213-E-006-051, the NASA-Johnson Space Center under grant NAG-9-746, and the U.S. Army Research Office under DAAH 04-94-G-0227.     

Observation of Radial Propagation of Electrostatic Fluctuations in Edge Plasma of the Sino United Spherical Tokamak

Radial propagation of electrostatic fluctuations in the edge plasma of Sino-United Spherical Tokamak (SUNIST) has been measured using Langmuir probes. The propagation characteristics of the floating potential fluctuations are analysed by the two-point correlation technique. The results show radially outward propagation of the turbulent fluctuations at all measured radial positions. The power-average wavenumber profile is approximately constant in plasma edge region and suddenly increases to the limiter. These results are in good agreement with the model predictions proposed by Mattor which suggests that the drift wave propagation may be a source of edge turbulence.     

Synthesis and spectroscopic properties of finite Ph2N-containing oligo(arylenevinylene) derivatives that emit blue to red fluorescence

[structure: see text] A series of oligo(phenylenevinylene) (OPV) derivatives with finite conjugation units were prepared in short steps from few building blocks. The central and terminal aryl groups of these OPV dyes contain cyano and Ph(2)N substituents, respectively, which affect color of fluorescence. The wavelength ranges from 472 nm (blue) to 614 nm (red) depending on the position of the cyano group.     

Multi-pumped tellurite-based Raman fiber amplifier based on Gaussian fitting of gain spectrum

Optical and Quantum Electronics - In this paper, we have considered a dual branch with dual hop wireless cooperative communication system which comprises direct radio frequency path as well as...