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We discuss the wafer design and fabrication process for the 1.3-μm-wavelength AlGaInAs/InP transistor lasers, and the structural dependence of lasing and the electrical characteristics are shown. We particularly focus on the base structure, and the thickness and width dependence are numerically and experimentally analyzed. A thicker base layer resulted in lower optical confinement factor in the quantum wells (QWs), higher optical loss, and lower current gain. In addition, a wider base width caused leak current recombination outside the QWs. By modifying the structure of an n-p-n TL, it was possible to simultaneously realize room-temperature continuous-wave lasing and transistor operation. [ABSTRACT FROM PUBLISHER]

Finding damage inside pipes is important for the inspection of complex pipes used in nuclear power plants and chemical plants. A number of studies have investigated the mechanisms of an actuator with an electric cable to provide locomotion through various devices in complex pipes. An in-pipe robot capable of movement in narrow complex pipes has not yet been developed. In the present paper, we propose a globular magnetic actuator group that exhibits a very high thrust force and is capable of free reversible motion in complex pipes. Two actuators of the same size and characteristics are coupled by the magnetic connection method, which generates almost no mechanical loss. The globular magnetic actuator group capable of reversible motion through elongation and contraction of eight shape-memory-alloy (SMA) coils was fabricated. Experimental results indicate that the prototype actuator group is able to climb at a rate of 29 mm/s in a straight pipe while pulling a load mass of 48 g. [ABSTRACT FROM AUTHOR]

This paper proposes a globular magnetic actuator of a new type that exhibits a very high thrusting force and is capable of a reversible motion in a complex pipe. The globular magnetic actuator of the reversible type due to opening and closing of a compound material by using elongation and contraction of four shape-memory-alloy (SMA) coils was fabricated. The globular magnetic actuator moves by difference in frictional force between forward and backward supporting force of the compound material. Experimental result shows that the prototype actuator was able to climb at 18 mm/s in the straight pipe when pulling the load mass of 24 g. In addition, the measurement of an average speed carried out for two patterns of movement in a complex pipe with many curved parts and step parts. The prototype actuator was able to move in the complex pipe over the average speed of 35 mm/s. This actuator has many possible applications, including small pipe inspection and maintenance. [ABSTRACT FROM AUTHOR]

Room-temperature continuous-wave operation of a 1.3-\mum npn-AlGaInAs/InP transistor laser is successfully achieved for the first time. A threshold current of 39 mA and an external differential quantum efficiency of 13% are obtained under common base operation, while simultaneous transistor action is achieved with a current gain \beta of 0.02. [ABSTRACT FROM PUBLISHER]