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  • 1
    Electronic Resource
    Electronic Resource
    Band parameters for III–V compound semiconductors and their alloys (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 5815-5875 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present a comprehensive, up-to-date compilation of band parameters for the technologically important III–V zinc blende and wurtzite compound semiconductors: GaAs, GaSb, GaP, GaN, AlAs, AlSb, AlP, AlN, InAs, InSb, InP, and InN, along with their ternary and quaternary alloys. Based on a review of the existing literature, complete and consistent parameter sets are given for all materials. Emphasizing the quantities required for band structure calculations, we tabulate the direct and indirect energy gaps, spin-orbit, and crystal-field splittings, alloy bowing parameters, effective masses for electrons, heavy, light, and split-off holes, Luttinger parameters, interband momentum matrix elements, and deformation potentials, including temperature and alloy-composition dependences where available. Heterostructure band offsets are also given, on an absolute scale that allows any material to be aligned relative to any other. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1368156
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  • 2
    Electronic Resource
    Electronic Resource
    Changes in soil chemistry and aggregate stability induced by fertilizer applications, burning and trash retention on a long-term sugarcane experiment in South Africa (2002)
    Oxford, UK : Blackwell Science Ltd
    European journal of soil science 53 (2002), S. 0 
    Details
    ISSN: 1365-2389
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Throughout the world there is a trend towards retaining crop residues rather than burning them. For this reason, changes in soil chemistry and aggregation in a Vertisol induced by 59 years of burning or green cane harvesting with or without annual fertilizer applications were investigated. Crop residues were either burnt prior to harvest with the harvest residues raked off (R1), burnt prior to harvest with the harvest residues left on the soil surface (R2), or left unburnt with all the trash left on the soil surface (R3). Concentrations of organic C in the surface 10 cm of soil increased with fertilizer applications and with increasing amounts of crop residue returned in the order R1 〈 R2 〈 R3. Fertilizer applications caused an accumulation of residual P in both inorganic (Pi) and organic (Po) forms. A sequential P fractionation showed that fertilizer P accumulated in both labile and recalcitrant Pi and Po forms, and trash retention caused an accumulation of recalcitrant Po. Concentrations of K decreased in the unfertilized R1 and R2 treatments because K reserves were depleted. By contrast, there was an increase in the concentrations of K in the fertilized R3 treatment. The soil became more acid on the fertilized and, to a lesser extent, trash retention plots. We attribute this to nitrification and subsequent nitrate leaching. Acidification resulted in a loss of exchangeable Ca and Mg, a decrease in ECEC, and an increase in the concentrations of total and monomeric Al in soil solution, in exchangeable Al3+ and in the buffering reserve of non-exchangeable Al associated with organic matter. Aggregate stability was increased by increasing crop residues but decreased by fertilizer applications. The decrease was attributed to an increase in the proportion of exchangeable cations present in monovalent form due to applications of fertilizer K and leaching of Ca and Mg. We conclude that trash retention and annual fertilizer applications have substantial long-term effects on both organic matter status and soil pH and therefore on other soil chemical and physical properties.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2389.2002.00472.x
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  • 3
    Electronic Resource
    Electronic Resource
    Far-field characteristics of mid-infrared angled-grating distributed feedback lasers (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 6997-7005 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The far-field emission characteristics of mid-infrared angled-grating distributed-feedback (α-DFB) lasers with W active regions are calculated using a self-consistent beam-propagation formalism that is more general than previous analyses. The theoretical projections are compared with the results of an experimental study of optically pumped α-DFB devices. Near-diffraction-limited beam quality is obtained both theoretically and experimentally for pump stripes ≤50 μm wide. While simulations employing the theoretical linewidth enhancement factor of 1.7 for the homogeneously-broadened W-laser gain spectrum predict that the good beam quality should be retained for stripes as wide as (approximate)200 μm, the data indicate a much more rapid degradation. That finding can be reproduced only by assuming that inhomogeneous broadening increases the structure's linewidth enhancement factor to (approximate)5. The experiments and theory also yield a steering of the output beam to off-normal angles as large as 6° when temperature tuning shifts the gain peak away from the grating resonance. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1326858
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  • 4
    Electronic Resource
    Electronic Resource
    Continuous-wave operation of λ=3.25 μm broadened-waveguide W quantum-well diode lasers up to T=195 K (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 76 (2000), S. 256-258 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Mid-infrared (λ=3.25 μm) broadened-waveguide diode lasers with active regions consisting of 5 type-II "W" quantum wells operated in continuous-wave (cw) mode up to 195 K. At 78 K, the threshold current density was 63 A/cm2, and up to 140 mW of cw output power was generated. A second structure with ten quantum wells operated up to 310 K in pulsed mode. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.125739
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  • 5
    Electronic Resource
    Electronic Resource
    Low-threshold optically pumped λ=4.4 μm vertical-cavity surface-emitting laser with a PbSe quantum-well active region (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 78 (2001), S. 3770-3772 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report pulsed emission from an optically pumped lead-salt vertical-cavity surface-emitting laser with a PbSe/PbSrSe quantum-well active region. The lasing wavelength of λ=4.44 μm is nearly constant over the temperature range 200–280 K, and the threshold is only 10.5 kW/cm2 at 260 K, where the gain peak and cavity mode are in resonance. Over 330 mW of peak power is emitted at 260 K, into a circular beam whose divergence angle increases with pump intensity. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1378808
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  • 6
    Electronic Resource
    Electronic Resource
    Virtual mesa and spoiler midinfrared angled-grating distributed feedback lasers fabricated by ion bombardment (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 78 (2001), S. 3394-3396 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: It is demonstrated that the suppression of parasitic Fabry–Perot-like lasing modes substantially enhances the beam quality and brightness of wide-stripe angled-grating distributed feedback lasers emitting in the midwave infrared. The direct facet-to-facet gain path is blocked by loss regions that are created by ion bombardment with 900 keV silicon ions. Both virtual mesa structures, in which loss regions bound both sides of the 300-μm-wide angled gain path, and spoiler structures, in which loss is induced only near the facets, decrease the etendue of the output by nearly an order of magnitude, and increase the brightness by up to a factor of 3. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1377044
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  • 7
    Electronic Resource
    Electronic Resource
    HgCdTe photodetectors with negative luminescent efficiencies 〉80% (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 78 (2001), S. 3082-3084 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have characterized the negative luminescent properties of photovoltaic HgCdTe detector structures with a room-temperature cutoff of 4.2 μm. Using an optical modulation method to directly measure the emittance as a function of applied bias and temperature, the blackbody signal at 295 K is found to be suppressed by a factor of 5.6. The negative luminescence efficiency of 82% and the apparent blackbody temperature change of (approximate)−35 K are nearly independent of heatsink temperature over the range 265–305 K. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1370539
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  • 8
    Electronic Resource
    Electronic Resource
    Photonic-crystal distributed-feedback lasers (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 78 (2001), S. 1475-1477 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The far-field emission characteristics and spectral purity of photonic-crystal distributed-feedback (PCDFB) lasers, in which the grating is defined on a two-dimensional lattice that is tilted with respect to the facets, are analyzed using a self-consistent time-domain simulation. It is shown that both conventional DFB and angled-grating DFB devices are special cases of the PCDFB laser, which combines and enhances the best features of each. The simulations project both high beam quality and high spectral purity out to pump stripes of width (very-much-greater-than)100 μm. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1355670
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  • 9
    Electronic Resource
    Electronic Resource
    Mid-infrared angled-grating distributed feedback laser (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 76 (2000), S. 3164-3166 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report near-diffraction-limited output from an angled-grating distributed feedback type-II W laser emitting near 3.4 μm. For pulsed optical pumping of a 50-μm-wide stripe at 78 K, the far-field beam divergence angle was only 1.4°. The slope efficiency was 64% of that for a conventional Fabry–Pérot laser on the same bar. However, the spectral linewidth decreased by only a factor of 2. The beam quality was substantially better than that for the Fabry–Pérot laser out to stripe widths of at least 800 μm. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.126617
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  • 10
    Electronic Resource
    Electronic Resource
    Mid-infrared photonic-crystal distributed-feedback laser with enhanced spectral purity and beam quality (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 3221-3223 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report a photonic-crystal distributed-feedback (PCDFB) laser with an antimonide type-II "W" active region. Optical lithography and dry etching were used to pattern the two-dimensional rectangular lattice with a second-order grating tilted by 20° relative to the facet normal. For pulsed optical pumping, the emission line centered on λ=4.6–4.7 μm is considerably narrower (7–10 nm) than for Fabry-Pérot and angled-grating DFB (α-DFB) lasers fabricated from the same wafer. The PCDFB beam quality is also substantially enhanced, e.g., by a factor of 5 compared with the α-DFB at a pump-stripe width of 200 μm. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1418445
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