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  • 1
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 1437-1439 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Laser-assisted atomic layer epitaxy (LALE) is used to locally deposit device-quality material for the first time, as demonstrated by successfully fabricating broad-area lasers with a GaAs quantum well grown in this way. By hybridizing LALE with conventional metalorganic chemical vapor deposition epitaxy, heterostructures are grown which allow characterization of material quality by photoluminescence and capacitance-voltage measurements. In addition, graded-index separate-confinement heterostructure lasers with threshold current densities of 650 A/cm2 for 580-μm-long devices were made using the LALE quantum well deposit, while devices made away from the deposit did not lase.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 56 (1990), S. 2487-2489 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An experimentally verified model for threshold current in GaAs/AlGaAs quantum well laser diodes has been extended to calculate for the first time the dependence of threshold current on stripe width. The lowest possible threshold is shown to occur when the lateral confinement factor is in the range of 55–60% for typical devices, a value that is not affected by mirror reflectivity or lateral index step. A simple, generalized optimization scheme for obtaining the unique width/length combination that results in lowest threshold is presented, and predicts potential as-cleaved threshold currents as low as 0.5 mA.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 105-107 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A new technique is demonstrated for the formation of narrow active regions in quantum well lasers. In temperature engineered growth (TEG), the substrate temperature is varied during the growth of epitaxial layers by metalorganic chemical vapor deposition (MOCVD) on nonplanar substrates, allowing two-dimensional control of device features. Buried heterostructure designs with submicron active region stripe widths are obtained without the need for fine process control of lateral dimensions. The contact area above the active region is coplanar with the surrounding surface and wide enough to allow easy contacting and heat sinking. Carrier confinement is accomplished by lateral thickness variation of the quantum well active region resulting in a local strip of minimum band gap. Lasers grown in this manner exhibit cw threshold currents as low as 3.8 mA (3.4 mA pulsed), having an as-grown active region width of 0.5 μm. The near-field optical profile indicates stable, single transverse mode operation and minimal current leakage in these devices.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 52 (1988), S. 767-769 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A novel monolithic coupling scheme in which three or four active waveguides interact interferometrically to form a multicavity semiconductor laser is demonstrated. The coupling between perpendicular waveguides is obtained by an integrated beamsplitter. Frequency selection, tunability, and single mode operation are demonstrated.
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  • 5
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 556-558 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A monolithically integrated array of InGaAs/AlGaAs flared amplifiers driven by a single DBR laser through a power splitter network and individually addressed phase modulators is described. Phase adjustment of (approximately-greater-than)2π per element by free-carrier effects is verified by monitoring the interference pattern of all four emitters, and typically requires 〈15 mA of current to obtain a 2π phase shift. Phase matching is achieved among all four diffraction-limited emitters at a pulsed output power of (approximately-greater-than)5 W, and, combined with the proper external lensing, could therefore result in an ultranarrow, single-lobed far-field pattern whose width is determined by the extended aperture of the array. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 62 (1993), S. 175-177 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The temperature sensitivity of both strained and lattice-matched 1.5 μm quantum well lasers has been studied. From a complete experimental investigation of the temperature behavior of carrier lifetime, gain, and internal loss, it is found that Auger recombination is not the dominant factor in affecting the temperature sensitivity of threshold currents in 1.5 μm lasers. Instead, the dominant contribution to the temperature dependence of threshold currents in 1.5 μm lasers is the change in differential gain with temperature—a characteristic not improved by strain.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 749-761 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Multi-cavity transfer molding is an important process step in several electronic and photonic technologies. In some applications, uniform filling of the cavities of the mold, or mold balancing, is required. A semi-empirical flow model to predict mold filling patterns was developed. The algorithm is a one-dimensional network flow simulation that uses experimental pressure drop data to determine the volumetric flow rate through the gates and runners. A comprehensive experimental program was undertaken to determine these hydraulic resistances for different flow rates and mold geometries. A theoretical treatment is also described to compute hydraulic resistance from gate geometry. Uniform gate resistances provide unbalanced filling and higher velocities in the cavities. Balanced filling can significantly reduce the molding compound velocity and the flow induced stresses, but imperfect balancing compromises the benefits. Experimental filling patterns were obtained for two sets of gates. The agreement between the model and the experiments was satisfactory, and the discrepancies were attributed to correctable phenomena.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 1796-1796 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 23 (1983), S. 756-762 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The interest in reaction injection molding of urethane and non-urethane resins has generated a need for a greater understanding of the molding behavior of these reactive systems. The kinetics and rheology of a given resin must therefore be well characterized in order to understand and model the molding process. This often requires semi-empirical correlations rather than strict theoretical considerations. A method of fully characterizing such systems by combining adiabatic reactor and IR studies with viscometer data is therefore described. This results in time-temperature-conversion-viscosity correlations which can be directly utilized in molding studies. Such methods are applied to polyurethane and epoxy systems in the work presented here. It was found that very different activation energies are obtained for the same epoxy-amine system using different kinetic characterization techniques.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Reactive polymer processing is the combined polymerization and processing of reactive prepolymers in a single operation. It encompasses a wide variety of processing methods including Reaction Injection Molding (RIM), a relatively new and growing fabrication method. Reaction Injection Molding utilizes impingement mixing of low viscosity fluids, injection of the reactive mixture into a mold, and polymerization therein to enable the molding of large plastic items. Polyurethane is currently the most commercially utilized RIM material although a number of other systems such as epoxy, nylon, and polyester are also suitable. Non-urethane systems such as epoxy are often not as amenable to the process, however, since they are slower reactions and have a potentially damaging exotherm. A comprehensive analysis was developed to determine if a molding system is processable by RIM. Criteria for processability were established and include the ability to mix on impingement, fill large molds characteristic of the process, and provide a short cycle time without promoting a damaging exotherm. The treatment, consisting of both experimental and numerical techniques, was applied to identify potential epoxy molding systems, establish their processing window, and conduct an optimization of the process parameters to evaluate productivity. The analysis and its conclusions are applicable to most reactive polymer processing operations that employ a rapid, exothermic, polymerization reaction.
    Additional Material: 19 Ill.
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