Based on the effective mass approximation and envelope function theory, the exciton binding energy in a single InAs / InxAl1 − xAs quantum well is calculated by the variational method under the applied electric field and laser field. The effects of material composition, well width, laser parameters, and electric field intensity on the exciton binding energy are calculated. The results show that the confinement potential is distorted by the laser field and the barrier is tilted by the electric field. The exciton binding energy is reduced by the presence of laser field or electric field. It is also shown that the exciton binding energy increases with the decrease of the indium component within a certain range. In addition, the effect of the well width on the exciton binding energy is not linear, and the exciton binding energy increases to a maximum first and then decreases with the decrease of the well width. The binding energy of excitons depends on the interaction of several parameters.
In the framework of effective mass envelope function approximation, the impurity states in GaN / AlxGa1 − xN spherical quantum dot (QD) are calculated by plane-wave expansion method. The binding energies of the impurity in 1s and 2p± states and the transition energy between 1s state and 2p± state are calculated and analyzed in detail. Several critical influencing factors of impurity states, including geometry, impurity position, material composition, and applied electric field, are considered in the calculation. The effects of QD radius, the impurity position, and the electric field strength on binding energies of 1s state and 2p± state are different. However, the effect of Al component on binding energies of 1s state and 2p± state is consistent. The transition energy is strongly dependent on the QD radius, impurity position, Al composition, and electric field strength. The change trend of transition energy is similar to that of binding energy in 1s state.
In the framework of effective mass envelope function approximation, the impurity states are calculated in InGaAsP/InP core–shell quantum dots by plane wave expansion method, and the effect of electric field is considered. The impurity binding energies in 1s and 2p ± states, and the impurity transition energy between 1s state and 2p ± state are calculated and analyzed in detail with the change of shell thickness, core radius, impurity position, and electric field strength. The results show that the impurity states in the core are stable when the shell thickness is more than 0.4a * . The binding energies and transition energies decrease with the increase of core radius. The applied electric field destroys the symmetrical distribution of binding energy and transition energy about the core center. The increase or decrease of the binding energy and transition energy depend upon the position of impurity and the direction of electric field.
Silicon photonics attracted much attention in past decades, but it is challenging for silicon laser source because of its indirect bandgap. The long-wavelength InAs/GaAs quantum dot (QD) laser monolithically grown on Ge substrate has been reported. Promising performance was reported by solid source molecular beam epitaxy (MBE). In this paper, gas source MBE was tried for the growth of InAs QD lasers on Ge. InAs QD laser is demonstrated in continuous wave mode at room temperature, with wavelengths covering 1.0-1.3 microns. The lowest threshold current density was obtained as 48 A/cm2 with an output power of several tens of mW.
Within the framework of effective mass approximation, the binding energy of a hydrogenic donor impurity in
zinc-blende GaN/AlxGa1-xN spherical quantum dot (QD) is investigated using the plane wave basis. The
dependencies of the binding energy on electric field, magnetic field, QD radius and impurity position are obtained.
The maximum of impurity binding energy is shifted from the centre of QD and the degenerating energy located for
symmetrical positions with respect to the centre of QD are split in presence of the external electric field. The
binding energy increases with the increases of magnetic field when the impurity located at the centre of QD. In the
presence of electric and magnetic field simultaneously, an increase in the electric field strength leads to a decrease
of the maxima of binding energy with an increase in magnetic field.
KEYWORDS: Network architectures, Optical networks, Networks, Mobile communications, Computer architecture, Interfaces, Data modeling, Switches, Global system for mobile communications, General packet radio service
To compare with the 2G mobile communication, 3G technologies can supply the perfect service scope and performance. 3G is the trend of the mobile communication. So now to build the transmission network, it is needed to consider how the transmission network to support the 3G applications. For the 3G network architecture, it include the 2 part: Utran access network and core network. So the metro optical network should consider how to build the network to adapt the 3G applications. Include the metro core and access layer. In the metro core, we should consider the network should evolved towards the Mesh architecture with ASON function to realize the fast protection and restoration, quick end-to-end service provision, and high capacity cross-connect matrix etc. In the access layer, the network should have the ability to access the 3G services such as ATM interface with IMA function. In addition, the traffic grooming should be provided to improve the bandwidth utility. In this paper, first we present the MCC network situation, the network planning model will be introduced. Then we present the topology architecture, node capacity and traffic forecast. At last, based on our analysis, we will give a total solution to MCC to build their metro optical network toward to the mesh network with the consideration of 3G services.
The metro network has experienced three generations periods. First-generation one is a traditional SDH-based network, the second-generation metro network is SDH-based and Ethernet integrated multi-service transport platforms (MSTPs) to transmit voice and data service, the third-generation SDH-based multi-service transport platforms (MSTPs) with MPLS and RPR combined to guarantee the QoS. However traditional SDH network has many disadvantages so the 4G MSTP appears, which is favored for intelligent function to realize the end-to-end service provision., intelligent control plane with GMPLS, Virtual concatenation, LCAS traffic engineer, Grooming and Switching etc. It was developed with the objective of dynamic bandwidth adjustment, protection and restoration, high network utility rate, low time delay to transport the data traffic and improve the capability of the bandwidth management, SLA (Service Level Agreement). At the same time, it can introduce the new service to make the carriers competitive. In this paper, first we present the carrier network situation, then we give the network architecture with intelligent function. At last, we analysis the performance enhancement the GMPLS MSTP bring to.
Wavelength Division Multiplexed (WDM) networks that route optical connections using intelligent optical cross-connects (OXCs) is firmly established as the core constituent of next generation networks. Rapid failure recovery is fundamental to building reliable transport networks. Mesh restoration promises cost effective failure recovery compared with legacy ring networks, and is now seeing large-scale deployment. Many carriers are migrating away from SONET ring restoration for their core transport networks and replacing it with mesh restoration through “intelligent” O-E-O cross-connects (XC).
The mesh restoration is typically provided via two fiber-disjoint paths: a service path and a restoration path. this scheme can restore any single link failure or node failure. And by used shared mesh restoration, although every service route is assigned a restoration route, no dedicated capacity needs to be reserved for the restoration route, resulting in capacity savings.
The restoration approach we propose is Centralized Pre-computing, Local Distributed Optimization, and Shared Disjoint-backup Path. This approach combines the merits of centralized and distributed solutions. It avoids the scalability issues of centralized solutions by using a distributed control plane for disjoint service path computation and restoration path provisioning. Moreover, if the service routes of two demands are disjoint, no single failure will affect both demands simultaneously. This means that the restoration routes of these two demands can share link capacities, because these two routes will not be activated at the same time. So we can say, this restoration capacity sharing approach achieves low restoration capacity and fast restoration speed, while requiring few control plane changes.
In the last five years, the traffic growth rate in China has been extremely fast. By 2005, the number of wired telephone customers is estimated to reach 220 to 260 million, while the number of expected cellular customers will reach 260 to 290 million. To meet these challenges, we will continue evolving with more wavelengths and higher speed. By evolving point-to-point WDM systems to OTN/ASON systems, we can eliminate the throughput bottleneck of network nodes caused by electronics, provide optical-layer bandwidth- management capability, provide scalability (which allows continuous traffic growth and network expansion), and provide reconfigurability (which allows semi-dynamic and dynamic optical networking). We can also simplify and speed up provisioning of high-speed circuits and services and offer fast network protection and restoration on the order of tens or hundreds of milliseconds to guarantee excellent network and service survivability. The CMCC (China Mobile Communication Company) will build its OTN network towards the ASON. The CMCC’s long-haul national network utilizing OXC has clearly becomes an intelligent network. It offers end-to-end point-and-click provisioning, shared mesh restoration with a few tens to a couple of hundred msec restoration times, re-provisioning of connections in the event of double failures and network capacity that is not optimally used. In this paper, first we present the CMCC network situation, The network planning tool will be introduced, Then we compare ring with mesh solution in terms of the cost, network performance, protection and restoration, network re-optimization. At last we derive a desired conclusion.
In this paper proposed a novel approach integrated recent advances in MPLS traffic engineering with wavelength switching/routing technologies to achieve optical interconnect for IP-centric Data Networks. In it, digital wrapper replaces SDH/SONET function block, so the IP layer can be placed directly over the optical layer. By outlined how the MPLS Traffic Engineering could be used on the wavelength switching network and how to design new network node to achieve optical interconnect. Furthermore, have shown an approach to dynamically interconnect routers via wavelength, including a bypass routing in the node, new wavelengths may easily be introduced to the network at a reasonable cost and to better support various classes of traffic.
In this letter, we report the MBE growth of GRIN-SCH ALGaAs single quantum well lasers. In order to obtain high quality laser materials, superlattice among GaAs buffer and n-AlGaAs cladding layer was incorporated. Reduced Be dopant concentration in the p-AlGaAs cladding layer near the GRIN region was adopted, which is believed to be benefit to the control of p-n junction places and reduction of the oxygen incorporation. High power broad-area lasers were fabricated. The typical threshold current density is 300A/cm2 and the minimum threshold current density is 220A/cm2 for the 500 micrometers cavity length lasers. High slope efficiency of 1.3W/A for 1000 micrometers cavity length lasers was obtained, recorded CW output power at room temperature has reached 2.3W. The measured characteristics temperature T(subscript 0$. is as high as 185K.
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