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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 7669-7671 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Studies of superconductivity and flux pinning were carried out on (Bi1.64Pb0.36)Sr2Ca1−xYxCu2O8+y (x=0, 0.05, 0.11, 0.33) single crystals grown by the self-flux method. X-ray diffraction, transport, and magnetic measurements were performed for purposes of characterization. X-ray analysis revealed that the c lattice parameter systemically decreases as the Y doping level increases. The superconducting transition temperature Tc decreases from 80 to 30 K as x increases. A strong annealing effect on Tc and superconducting volume has been observed. Resistance measurements show that x=0.33 samples are semiconductive over a wide temperature range between 4.2 and 300 K for the as-grown state, but become metallic with Tc of 65–70 K after air or oxygen annealing. Flux pinning was studied by measuring the hysteresis loop at different temperatures and different fields. A peak effect was observed in all the codoped samples. Results show that at low temperatures, the peak field is smaller than in solely Pb doped crystals and decreases as x increases (x〉0.1). However, the peak field at high temperature for the x=0.05 sample is higher than in heavily Pb doped Bi2212 crystals, indicative of a strong pinning due to the codoping. © 2001 American Institute of Physics.
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 2048-2050 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effect of growth temperature on the optical properties of self-assembled In0.65Al0.35As/Al0.35Ga0.65As quantum dots is studied using photoluminescence and electroluminescence spectra. With the growth temperature increasing from 530 to 560 °C, the improvement of optical and structural quality has been observed. Furthermore, edge-emitting laser diodes with three stacked InAlAs quantum dot layers grown at different temperature are processed, respectively. For samples with quantum dots grown at 560 °C, the continuous wave operation is obtained up to 220 K, which is much higher than that of ones with InAlAs islands grown at 530 °C and that of the short-wavelength quantum-dot laser previously reported. © 2001 American Institute of Physics.
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 5433-5436 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The size and shape evolution of self-assembled InAs quantum dots (QDs) influenced by 2.0 ML InAs seed layer has been systematically investigated for 2.0, 2.5, and 2.9 ML deposition on GaAs(100) substrate. Based on comparisons with the formation of large incoherent InAs islands on single-layer samples at late growth stage, the larger coherent InAs quantum dots at 2.9 ML deposition has been observed on the second InAs layer. A simple model analysis accounting for the surface strain distribution influenced by buried islands gives a stronger increment of critical QD diameter for dislocation nucleation on the second layer in comparison with the single-layer samples. Additionally, the inhibition of dislocation nucleation in InGaAs/GaAs large islands can also be explained by our theoretical results. © 2000 American Institute of Physics.
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 129-135 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Optical quality SrxBa1−xNb2O6 (SBN) thin films, both undoped and Eu3+-doped, of thickness less than 0.5 μm have been successfully grown on fused quartz substrates using a pulsed laser deposition technique. Optical properties of these films were characterized in high-resolution spectroscopic experiments in time and frequency domains. For undoped SBN thin films, broadband emission in the UV region extending to the visible was observed following excitation at 355 nm. This emission is attributed to exciton luminescence of the SBN film. Nonlinear optical response in the picosecond regime and the third-order nonlinear susceptibility, χ(3), were studied using degenerate four-wave-mixing methods. In transverse alignment, χ(3) is enhanced by two orders of magnitude in comparison with its bulk counterpart. A thermal annealing process, monitored via changes in spectral properties of Eu3+, was employed to convert the as-grown amorphous film into a polycrystalline film. High-resolution spectroscopic measurements in the frequency domain were conducted on a 200-nm-thick film of Eu3+-doped SBN. Our spectroscopic results suggest that Eu3+ ions may substitute for Nb, thereby occupying a normally six-fold coordinated lattice site. At liquid helium temperature, spectral holes in the 7F0–5D0 optical transition were burned in the thermally annealed films. Typical observed hole widths were 70–100 MHz and hole depths were as large as 30% of the peak fluorescence intensity. © 2002 American Institute of Physics.
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 3392-3395 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Optical and structural investigations of InAs quantum dots (QDs) covered by InxGa1−xAs (0≤x≤0.3) overgrowth layer have been systematically reported. The decrease of strain in the growth direction of InAs quantum dots covered by InGaAs layer instead of GaAs is demonstrated by transmission electron microscopy experiments. In addition, the atomic force microscopy measurement shows that the surface of InAs islands with 3-nm-thick In0.2Ga0.8As becomes flatter. However, the InGaAs islands nucleate on the top of quantum dots during the process of InAs islands covered with In0.3Ga0.7As. The significant redshift of the photoluminescence peak energy and reduction of photoluminescence linewidth of InAs quantum dots covered by InGaAs are observed. The energy gap change of InAs QDs covered by InGaAs could be explained in terms of reducing strain, suppressing compositional mixing, and increasing island height. © 2000 American Institute of Physics.
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  • 6
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 81 (2002), S. 978-980 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report experimental results on the injection locking of individual multimode broad-area high-power laser (one-in-a-time) in a linear array bar consisting of 19 lasers driven by a common current source. Each broad-area laser, capable of generating a beam with a power of 1 W, is injection locked to a single-longitudinal and transverse mode with less than 0.5 mW of injection power. The injection-locked broad-area laser shows very narrow linewidth close to the injection laser regardless of the output power. Our research suggests that the matching of the injection wavelength to one of the free-running modes of lasers in the array is the essential condition for achieving coherent operation of the array via injection locking. © 2002 American Institute of Physics.
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  • 7
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 728-730 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An aperiodic optical superlattice is designed. The designing method is universal and can be applied to all frequency conversion processes by using the coupling of quasiphase matching, without any limitations to special materials and to given fundamental wavelengths. © 2001 American Institute of Physics.
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  • 8
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 78 (2001), S. 3580-3582 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An intersubband Raman laser has been realized in an artificial GaAs/AlGaAs three-level quantum-well structure. A CO2 laser in resonance with the one-to-three level transition is used as the pump, while the lasing emission occurs via the three-to-two level transition. The one-to-two level spacing is designed to be in resonance with the AlAs-like longitudinal optical phonon mode, favoring the Raman process. This work presents an alternative mechanism for realizing intersubband lasers and opens up new possibilities in reaching the far infrared region and achieving room-temperature operation. © 2001 American Institute of Physics.
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  • 9
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 78 (2001), S. 2067-2069 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A multicolor infrared photodetector based on the epitaxial integration of an n-type with a p-type GaAs/AlGaAs quantum-well stack is experimentally demonstrated. Additionally, a quantum-well GaAs light-emitting diode is inserted between the stacks to achieve up-conversion of mid-infrared radiation to near-infrared signal. This device shows a remarkable selectivity on wavelength: depending on the bias voltage the peak wavelength detection can be switched on and off between 9.1 and 4.85 μm. © 2001 American Institute of Physics.
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  • 10
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 76 (2000), S. 3741-3743 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Self-organized In0.55Al0.45As/Al0.50Ga0.50As quantum dots are grown by the Stranski–Krastanow growth mode using molecular beam epitaxy on the GaAs(311)A substrate. The optical properties of type-II InAlAs/AlGaAs quantum dots have been demonstrated by the excitation power and temperature dependence of photoluminescence spectra. A simple model accounting for the size-dependent band gap of quantum dots is given to qualitatively understand the formation of type-II In0.55Al0.45As/Al0.50Ga0.50As quantum dots driven by the quantum-confinement-induced Γ→X transition. The results provide new insights into the band structure of InAlAs/AlGaAs quantum dots. © 2000 American Institute of Physics.
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