Comprehensive modeling of diffused quantum-well vertical-cavity surface-emitting lasers

A numerical model for investigating the thermal, electrical, and optical characteristics of vertical-cavity surface-emitting: lasers (VCSELs) with a diffused quantum-well (QW) structure is presented. In the model, the quasi-three-dimensional (quasi-3-D) distribution of temperature, voltage and optical fields as well as the quasi-two-dimensional (quasi-2-D) diffusion and recombination of carrier concentration inside the QW active layer are calculated in a self-consistent manner. In addition, the quasi-3-D distribution of implanted ions before and after thermal annealing are computed. The variation of electrical conductivity and absorption loss as well as the influence of impurity induced compositional disordering on the optical gain and refractive index of the QW active layer are also taken into consideration. Using this model, the steady-state characteristics of diffused QW VCSELs are studied theoretically. It is shown that significant improvement of stable single-mode operation can be obtained using diffused QW structure.published_or_final_versio

Active anti-guide vertical cavity surface emitting lasers with diffused quantam wells structure

The enhancement of single transverse mode operation in vertical cavity surface emitting lasers by using interdiffused quantum wells is proposed and analyzed. It is observed that the influence of self-focusing (arising from carrier spatial hole burning and thermal lensing) on the profile of transverse modes can be minimized by introducing a step diffused quantum wells structure inside the core region of quantum-well active layer. Stable single-mode operation in vertical cavity surface emitting lasers can also be maintained.published_or_final_versio

Effect of non-uniform distribution of electric field on diffusedquantum well lasers

The influence of non-uniform distribution of electric field on the steady state and dynamic behavior of diffused quantum well lasers is studied by a self-consistent model. The energy band structure of the quantum well can be distorted significantly by the non-uniform distribution of electric field, especially for devices with diffused quantum well structure. Hence, the evaluation on the optical gain as well as the modulation responses of diffused quantum well lasers using flat band approximation can be deviated significantly with nonuniform distribution of electric field taken into consideration.published_or_final_versio

电脑辅助及远程认知康复的发展与应用

2003-2004 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Feasibility investigation of cognitive rehabilitation service after traumatic brain injury in community

2003-2004 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

TARP γ-7 selectively enhances synaptic expression of calcium-permeable AMPARs

Regulation of calcium-permeable AMPA receptors (CP-AMPARs) is crucial in normal synaptic function and neurological disease states. Although transmembrane AMPAR regulatory proteins (TARPs) such as stargazin (γ-2) modulate the properties of calcium-impermeable AMPARs (CI-AMPARs) and promote their synaptic targeting, the TARP-specific rules governing CP-AMPAR synaptic trafficking remain unclear. We used RNA interference to manipulate AMPAR-subunit and TARP expression in γ-2–lacking stargazer cerebellar granule cells—the classic model of TARP deficiency. We found that TARP γ-7 selectively enhanced the synaptic expression of CP-AMPARs and suppressed CI-AMPARs, identifying a pivotal role of γ-7 in regulating the prevalence of CP-AMPARs. In the absence of associated TARPs, both CP-AMPARs and CI-AMPARs were able to localize to synapses and mediate transmission, although their properties were altered. Our results also establish that TARPed synaptic receptors in granule cells require both γ-2 and γ-7 and reveal an unexpected basis for the loss of AMPAR-mediated transmission in stargazer mice

认知障碍的远程康复进展

2003-2004 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe