Temperature delocalization of charge carriers in semiconductor lasers

The temperature dependences of emission characteristics are investigated for laser diodes based on asymmetric separate-confinement heterostructures with a broadened waveguide. It is established that an increase in the charge-carrier concentration in the waveguide layer is the basic mechanism of saturation in the light-current characteristic with increasing temperature in the CW mode. It is experimentally shown that the temperature delocalization of charge carriers leads to increasing internal optical losses and decreasing external differential quantum efficiency. It is shown that the degree of delocalization of charge carriers depends on the charge-carrier temperature distribution, the threshold concentration, and the quantum-well depth. The effect of thickness and energy depth of the quantum well on the temperature sensitivity of the threshold current and output optical power is considered.     

“太阳神2A”升空

2004年12月18日，一枚欧洲“阿丽亚娜-5”型运载火箭将法国一颗“太阳神2A”军事侦察卫星送入了太空轨道，“太阳神2A”军事侦察卫星进入距地面435英里的同步轨道。箭上另外六颗小型科学卫星也已经顺利进入预定轨道。这是11年来“阿丽亚娜”系列火箭首次进行“一箭七星”的发射任务。     

低频无线Mesh系统解决方案投入市场

由美国Strix系统有限公司研发的低频无线网络网格（Mesh）通信产品——UItraMANET自组网无线设备正式投入行业市场。     

Formation of WO<Subscript> <Emphasis Type="Italic">x</Emphasis> </Subscript>–ZrO<Subscript>2</Subscript> isomerization catalysts from anion-modified zirconium hydroxide

The formation of zirconia-based isomerization catalysts during thermal conversions of hydroxide modified with different amounts of tungstate groups has been studied by differential scanning calorimetry and X-ray diffraction analysis. The mechanism of formation of tungstated zirconia from a hydroxide precursor has been formulated.     

Pulsed semiconductor lasers with higher optical strength of cavity output mirrors

Asymmetric heterostructures with an ultrathick waveguide based on an AlGaAs/GaAs alloy system that allow lasing at a wavelength of 905 nm have been developed and fabricated by hydride metalorganic vapor-phase epitaxy. The internal optical loss and internal quantum efficiency of semiconductor lasers based on such structures were 0.7 cm^-1 and 97%, respectively. It is shown that the highest output optical power of laser diodes with antireflecting (SiO₂) and reflecting (Si/SiO₂) coatings deposited on untreated Fabry-Perot cavity facets obtained by cleaving in an oxygen atmosphere reached 67 W in the pulsed mode and is limited by mirror damage. Treatment of Fabry-Perot cavity facets by etching in argon plasma and the formation of coatings with passivating and oxygen-blocking GaN and Si₃N₄ layers allowed an increase in the maximum output optical power to 120 W. Mirror damage was not observed at the attained output optical power.     

Diffusion, perfusion, and T2 magnetic resonance imaging of anti-intercellular adhesion molecule 1 antibody treatment of transient middle cerebral artery occlusion in rat

The effect of anti-intercellular adhesion molecule-1 (anti-ICAM-1) antibody treatment of transient (2 h) middle cerebral artery (MCA) occlusion in the rat was measured using diffusion (DWI)-, T2 (T2I)- and perfusion (PWI)-weighted magnetic resonance imaging. Rats were treated upon reperfusion with an anti-ICAM-1 monoclonal antibody (n=11) or a control antibody (n=7). DWI, T2I and PWI were performed before, during, and after induction of focal cerebral ischemia from 1 h to 7 days. In both groups, the apparent diffusion coefficient of water (ADCw) and cerebral blood flow (CBF) values in the ischemic region significantly declined from the preischemic ADCw values (p<0. 05). The post ischemic increase in T2 of the control group was significantly higher at 48 h than in the anti-ICAM-1 treated group (p<0.05). CBF was not significantly different between the two groups. The temporal profiles of MRI cluster analysis, which combines ADCw and T2 maps into a single image, was significantly different between groups. These data suggest that the neuroprotective effect of anti-ICAM-1 antibody treatment is reflected in reductions of T2 and lesion growth during reperfusion and may not be associated with increased cerebral perfusion.