We present a method that improves the emission efficiency of InAs quantum dots (QDs) fabricated by antimony surfactant-mediated metal organic chemical vapor deposition. This process consists of removing the excess segregated antimony from the surface of InAs/Sb:GaAs QDs by applying a high arsenic pressure before capping. In such a way, one benefits from the advantages of InAs/Sb:GaAs QDs (high density, low coalescence) without the formation of antimony-induced nonradiative defects. Finally, we show that this better QD interface quality results in a strong decrease of the threshold current densities of InAs/Sb:GaAs QD lasers in the 1.3 μm band.
Abmmf-Autonomous Underwater Vehicles (AWs) are suitable for condition SUNV of artillcial sbocinres such as pillars and caissons in harbors. This paper describes a method to trace the structure's surface using a iight-section p m w g system. This proliling system determines the continuous shape of the target objects over a wide area by the light sectioning method The vehicle navigates referencing the principal shape of the stlpcture, tracing its surface while taking video images. This method dso enables threedimenslond mapping oftraced structures and the seabed The method is implemented using testbed A W "Tri-Dog 1" and vedied by tank tests. The AUV navigate robustly against Mvid objects such as small obstades and Uoating particles. Precise depth mapping of the tank botlom Is carried out.
I. JNTRODIJCITONAutonomous Underwater Vehicles (AWs) are suitable for ocean observation since they can swim k l y without the restriction imposed by an umbilical cable. It can be said &at A W s are increasingly finding practical applications worldwide [1][2][3][4][5]. Commercial obsemtion of the seabed, for investigation of underwater oilfields and resources, has already been executed by A W s using side scan sonar, mdtibeam sonar, sub-bottom profiler etc [6].There is a great demand for A W s not only for wide area survey but also for condition survey of artificial underwater structures such as pillars and caissons in harbors, dams, bodies of ships, and installations of deepsea oilfields. Such structures require periodic inspection. These task are typically carried out by human divers and Remotely Operated Vehicles (ROVs). However the use of buman divers carries an inherent risk and is not applicable at great depth. ROVs require an umbilical cable that restricts their movement. The demand for development of highly intelligent A W s that can undertake such missions is expected to increase greatly over the next few years.Intelligent behavioral control, sensing, navigation and motion control are essential to accomplish autonomous observation of underwater structures using A W s . In an underwater environment, it is especially difficult to detect obstacles (sensing) and to obtain precise position data (navigation). The authors have proposed the autonomous observation method using A W s that can overcome these challenges [7][8]. The method has been implemented by detecting the target objects, localizing them, and then approaching them by taking video images while closely tracing their shape. A laser ranging system consisting of laser pointing devices and a CCD camera was introduced for sensing. The system was shown to provide precise distance to the target object so that the vehicle could trace its shape vhile maintaining a constant distance and attitude to it. This method is hown as relative navigation. The method wa8 implemented using the testbed A W 'Tri-Dog 1" 191 and has been proved experimentally by tank tests. Sea trials were also carried out at Kamaishi port in Japan [IO].
The A W performed observation of breakwater caissons.D...
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