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  • 1
    Publication Date: 2017-10-17
    Description: Atmospheric black carbon (BC) absorbs solar radiation, and exacerbates global warming through exerting positive radiative forcing (RF). However, the contribution of BC to ongoing changes in global climate is under debate. Anthropogenic BC emissions, and 5 the resulting distribution of BC concentration, are highly uncertain. In particular, long range transport and processes affecting BC atmospheric lifetime are poorly understood. Here we discuss whether recent assessments may have overestimated present day BC radiative forcing in remote regions. We compare vertical profiles of BC concentration from four recent aircraft measurement campaigns to simulations by 13 aerosol 10 models participating in the AeroCom Phase II intercomparision. An atmospheric lifetime of BC of less than 5 days is shown to be essential for reproducing observations in remote ocean regions, in line with other recent studies. Adjusting model results to measurements in remote regions, and at high altitudes, leads to a 25% reduction in AeroCom Phase II median direct BC forcing, from fossil fuel and biofuel burning, over 15 the industrial era. The sensitivity of modeled forcing to BC vertical profile and lifetime highlights an urgent need for further flight campaigns, close to sources and in remote regions, to provide improved quantification of BC effects for use in climate policy.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
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  • 2
    Publication Date: 2022-05-25
    Description: Author Posting. © American Meteorological Society, 2012. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Bulletin of the American Meteorological Society 93 (2012): 1547–1566, doi:10.1175/BAMS-D-11-00201.1.
    Description: The Geostationary Coastal and Air Pollution Events (GEO-CAPE) mission was recommended by the National Research Council's (NRC's) Earth Science Decadal Survey to measure tropospheric trace gases and aerosols and coastal ocean phytoplankton, water quality, and biogeochemistry from geostationary orbit, providing continuous observations within the field of view. To fulfill the mandate and address the challenge put forth by the NRC, two GEO-CAPE Science Working Groups (SWGs), representing the atmospheric composition and ocean color disciplines, have developed realistic science objectives using input drawn from several community workshops. The GEO-CAPE mission will take advantage of this revolutionary advance in temporal frequency for both of these disciplines. Multiple observations per day are required to explore the physical, chemical, and dynamical processes that determine tropospheric composition and air quality over spatial scales ranging from urban to continental, and over temporal scales ranging from diurnal to seasonal. Likewise, high-frequency satellite observations are critical to studying and quantifying biological, chemical, and physical processes within the coastal ocean. These observations are to be achieved from a vantage point near 95°–100°W, providing a complete view of North America as well as the adjacent oceans. The SWGs have also endorsed the concept of phased implementation using commercial satellites to reduce mission risk and cost. GEO-CAPE will join the global constellation of geostationary atmospheric chemistry and coastal ocean color sensors planned to be in orbit in the 2020 time frame.
    Description: Funding for GEO-CAPE definition activities is provided by the Earth Science Division of the National Aeronautics and Space Administration.
    Description: 2013-04-01
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: application/pdf
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 518-523 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A symmetric coupled double-quantum-well (CDQW) structure in InGaAs/InAlAs lattice matched to InP can give enhanced Stark effects for electroabsorption modulation near 1.3 μm. The optical features of this material are the dramatic quenching of the heavy-hole exciton and the simultaneous emergence of the normally forbidden higher-order transitions. An effective-mass model for the double-quantum-well structure yields predictions in good agreement with experimental results. The model can be used to predict the optical properties of not only symmetric CDQWs but also asymmetric structures as well.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 759-761 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the generation of short optical pulses from novel monolithic colliding-pulse mode-locked quantum well lasers. Transform-limited pulses with durations of 1.4 ps at a repetition rate of 32.6 GHz have been achieved, with nearly 100% intensity modulation depth and a peak optical power of 10 mW. This is the shortest transform-limited pulse directly generated from monolithic mode-locked lasers (time-bandwidth product =0.3).
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 1253-1255 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ultrafast subpicosecond optical pulse generation is achieved by passive colliding-pulse mode locking of monolithic multiple quantum well InGaAsP semiconductor lasers. Transform-limited optical pulses with durations of 1.1, 0.83, 1.0, and 0.64 ps are achieved at repetition rates of 40, 80, 160, and 350 GHz, respectively, without using any external ac sources.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 53 (1988), S. 1297-1298 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A phase comparator based on two cascaded semiconductor electroabsorption waveguide modulators is demonstrated for the first time. The operation principle of this device is derived and experimentally confirmed.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 65 (1994), S. 3167-3169 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report our experiment on the use of a double-disk structure to couple light output from a microdisk laser which allows us to maintain a high Q value of the microdisk resonator. The small photon leakage rate from the lower lasing disk to the top waveguiding disk can be carefully controlled by choosing the distance between the two disks. Various structures can be fabricated on the top disk to couple the light out. In this letter, a simple opening in the top disk is used for output coupling. © 1994 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 62 (1993), S. 2950-2952 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Electromigration of hydrogen inside polycrystalline silicon (polysilicon) has been observed for the first time. Experiments were conducted on polysilicon emitter (poly emitter) n-p-n transistors with and without atomic hydrogen inside polysilicon. The current gain (β) of n-p-n was selected to monitor electromigration of hydrogen during current stress because of its high sensitivity to hydrogen passivation of dangling bonds. The major characteristics of hydrogen electromigration are shown in this letter.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 60 (1992), S. 598-600 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Organometallic vapor phase epitaxy was used to grow a novel periodic index separate confinement heterostructure (PINSCH) InGaAs/AlGaAs multiple quantum well (MQW) laser. Secondary ion mass spectrometry and transmission electron microscopy were used to characterize the structure. The performance of the PINSCH laser was compared with that of a graded index separate confinement heterostructure (GRINSCH) MQW laser grown under similar conditions. The PINSCH laser uses cladding layers comprised of periodic semiconductor multilayers (Al0.4Ga0.6As/GaAs) which provide both optical and electrical confinement. Since the optical field decays over several multilayers, and therefore is far less tightly confined than in the GRINSCH structure, a significant reduction of the transverse far-field angle occurs. Comparing the performance of 5×750 μm self-aligned ridge waveguide InGaAs/AlGaAs lasers emitting at 980 nm, the PINSCH structure exhibits a transverse far-field angle of 23° compared to 46° for the GRINSCH. This is obtained at the expense of a modest increase in threshold current (19 mA vs 10 mA).
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 59 (1991), S. 2781-2783 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on the first room-temperature operation of aluminum-free In0.2Ga0.8As/GaAs/ In0.49Ga0.51P multiple-quantum-well lasers grown by gas-source molecular beam epitaxy. These lasers have low threshold current density Jth of 177 A/cm2, high internal quantum efficiency of 91%, and low internal waveguide loss of 9.1 cm−1. The characteristic temperature T0 is 150 K, which is the highest value ever reported. These results demonstrate that gas-source molecular beam epitaxy is suitable for growing high-quality In0.2Ga0.8As/GaAs/In0.49Ga0.51P lasers.
    Type of Medium: Electronic Resource
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