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  • American Institute of Physics (AIP)  (9)
  • Wiley-Blackwell  (6)
  • EMBO Press  (4)
  • Oxford University Press  (3)
  • Blackwell Publishing Ltd  (1)
  • 1995-1999  (23)
  • 1
    Electronic Resource
    Electronic Resource
    Spectroscopic measurement of packaging-induced strains in quantum-well laser diodes (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 1196-1201 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Packaging-induced strain is studied in high-power semiconductor lasers by a noninvasive optical technique. Fourier-transform photocurrent measurements with intentionally strained laser array devices for 808 nm emission reveal spectral shifts of optical transitions within the active region. These shifts by up to 10 meV serve as a measure for the strain status within the active layer of the devices and are compared with model calculations. For different packaging architectures we quantify the strain portion which is transmitted to the optically active region of the semiconductor device. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.370870
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  • 2
    Electronic Resource
    Electronic Resource
    Polarization bistability in strained ridge-waveguide InGaAsP/InP lasers: Experiment and theory (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 6135-6144 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: New experimental and theoretical results on TE/TM bistability in 1.3 μm ridge-waveguide InGaAsP/InP bulk lasers at room temperature are presented. Measured polarization resolved light power–current (P–I) characteristics as well as lateral near- and far-field patterns are compared with results from a theoretical model based on the paraxial wave equations for TE- and TM-polarized modes and the diffusion equation for the carrier distribution. The model was numerically evaluated by use of the beam propagation method. The observed TE/TM bistability is explained by the interplay of three different effects: (i) Tensile stress of about 109 dyn/cm2 promotes the TM gain strongly enough to compete with the TE mode. (ii) Improved TM waveguiding due to an enhancement of the effective refractive index near the beam axis caused by carrier depletion with increasing current leads to the onset of TM lasing and TE/TM switching. (iii) The TE/TM transition is accompanied by an abrupt increase of spatial hole burning in the lateral carrier distribution. Because of this nonlinear effect, a lower current is needed to switch the laser back to TE, giving rise to a hysteresis loop in the P–I characteristics and to TE/TM polarization bistability. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359139
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  • 3
    Electronic Resource
    Electronic Resource
    Control of light polarization in InGaAsP/InP lasers by injection of light pulses (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 2064-2069 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Light emission from a ridge waveguide 1.3 μm InGaAsP/InP semiconductor laser pumped both electrically and optically was analyzed by polarization- and time-resolved measurements. The electric and the optical excitation was realized with a dc-bias current and with 150 ps pulses from a Q-switched Nd-YAG laser at 1.064 μm wavelength, respectively. The pump light was introduced into the InGaAsP/InP laser through a window opened in the substrate gold contact. The steady-state P–I characteristics of the semiconductor laser exhibited a transition from TM- to TE-polarized light emission if the injection current surpasses a certain value that depends on the heatsink temperature. Depending on the dc-bias current and the optical pulse power, a variety of different emission characteristics of the semiconductor laser were observed: pure TE or TM pulsations, in combination with a background cw emission in some cases; simultaneous emission of TE and TM pulses and switching between TM and TE emission states with switching times as short as 30 ps. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.364257
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  • 4
    Electronic Resource
    Electronic Resource
    Time evolution of grating decay during photorefractive fixing processes in LiNbO3 (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 308-312 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Decays of the diffraction efficiency of gratings written in Fe:LiNbO3 have been studied in connection with photorefractive fixing. Measurements have been carried at five different temperatures within the range of interest in photorefractive fixing, 144–168 °C. The decay curves are nonexponential and can be fitted to a sum of three simple exponential components, whose effective activation energies and preexponential factors have been determined. The dependence of the last exponential component on the grating period Λ has been measured and a 1/Λ2 law has been found. The decay constants have also been found to depend on the time the crystal is kept at the setting temperature before writing the grating. The difficulties for establishing a model taking into account the occurrence of several sites for protons in LiNbO3 are discussed. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359393
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  • 5
    Electronic Resource
    Electronic Resource
    Direct spectroscopic measurement of mounting-induced strain in high-power optoelectronic devices (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 3908-3910 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Thermally induced strain caused by device packaging is studied in high-power semiconductor lasers by a noninvasive technique. Fourier-transform photocurrent measurements with intentionally strained laser array devices for 808 nm emission reveal spectral shifts of quantum-confined optical transitions in the optical active region. These shifts by up to 7 meV serve as a measure for strain and are compared with model calculations. For a given packaging architecture, about one quarter of the mounting-induced strain is transferred to the quantum-well region of the device. Spatially resolved measurements demonstrate a lateral strain gradient in the devices. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.122932
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  • 6
    Electronic Resource
    Electronic Resource
    Adjustment of the critical current in a Nb–InxGa1−xAs/InP Josephson contact by light exposure (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 75 (1999), S. 391-393 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The critical current of a Nb–InGaAs/InP Josephson junction is increased stepwise by light exposure. Shubnikov–de Haas effect measurements under illumination show that the increase of the critical current originates from photogenerated electrons in the quantum well. A further enhancement of the critical current is gained under continuous illumination. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.124385
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  • 7
    Electronic Resource
    Electronic Resource
    Icosahedra of icosahedra: The stability of (C60)13 (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 6088-6089 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The relative stability of clusters of fullerenes has been investigated. By heating the clusters before ionization we have obtained mass spectra where only the monomer and (C60)13 are present in significant amounts. An approximately 20% increase of the activation energy for evaporation of a monomer from (C60)13 compared to that from (C60)14 explains the experimental results. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.472448
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  • 8
    Electronic Resource
    Electronic Resource
    High-resolution ultraviolet laser spectroscopy on jet-cooled benzene molecules: Ground and excited electronic state polarizabilities determined from static Stark effect measurements (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 110 (1999), S. 10393-10402 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Static electric polarizabilities of the S0(1A1g) ground electronic and the vibronically excited 61 S1(1B2u) state of benzene were measured by applying ultraviolet (UV) laser Stark spectroscopy. The experimental setup consisted of a frequency doubled tunable narrow-band continuous wave (cw) laser system operating at 259 nm, a molecular beam apparatus, and a capacitor capable of generating strong static and homogeneous electric fields up to 250 kV/cm. Experimental linewidths of less than 30 MHz were achieved for the rotational transitions, and Stark displacements of typically several 10 MHz could be detected. Stark patterns of 16 rotational lines were recorded and analyzed under different field strengths. Validity of second-order perturbation theory was confirmed by the observed effects, and the diagonal components of the polarizability tensors could be adjusted by a weighted least-squares technique. Results were applied to calculating Stark spectra and comparing them to experimental data. Good agreement could be found, except for an obscure singular perturbation within one rotational line. The new polarizabilities were compared to both experimental and theoretical results in the literature. Ground state data are in general agreement, whereas no comparable experimental work addressing the excited electronic state exists. Finally, polarizabilities of the beginning five polyacenes were compiled and compared with the benzene data. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.478971
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  • 9
    Electronic Resource
    Electronic Resource
    Laser spectroscopy of free pentacene molecules (I): The rotational structure of the vibrationless S1←S0 transition (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 906-911 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The rotational structure of the vibrationless S1←S0 transition of pentacene has been investigated using a strongly collimated seeded supersonic argon beam. Because single rotational lines could not be completely resolved, a band contour analysis was performed. The rotational constants of the electronic ground state X 1A1g were found to be under the asymmetric rotor approximation A″=1320.6(9), B″=117.97(9), C″=108.28(15) MHz, whereas the differences to the first electronic excited state A 1B2u are ΔA=A′−A″=13.2(3), ΔB=−0.764(45), ΔC=−0.54(6) MHz. A new value of the band origin was determined to be ν00=18 648.996(4) cm−1 and the band type was confirmed to be of type b as proposed by symmetry arguments. Good agreement between observed and calculated spectra was obtained assuming planarity in both ground and excited state. From the fit procedure a rotational temperature of about 7 K was deduced. The nuclear statistical weights of the electronic ground state are reported. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.476631
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  • 10
    Electronic Resource
    Electronic Resource
    Diel and seasonal patterns of food intake and prey selection by Coregonus sp. in re-oligotrophicated Lake Lucerne, Switzerland (1998)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 52 (1998), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Feeding intensity by whitefish Coregonus sp., in oligotrophic Lake Lucerne in Switzerland was high during dusk when the bulk of potential prey items were in the depth zone occupied by the fish. Diet composition was fairly uniform throughout the day but changed substantially over the seasons. The fish fed opportunistically; differences between seasons reflected changes in prey availability. During the intensive feeding and growing period (May-September), fish were found in the upper 20 m of the lake feeding primarily on cladocerans. Large and non-evasive species, Daphnia spp. and Bythotrephes longimanus, were the most numerous and frequent organisms in the diet during the major part of the growing season. Smaller (Bosmina spp.) as well as evasive species (cyclopoid copepods) were consumed in large numbers when larger, non-evasive species were rare in the lake. The fish showed strong preference for the least abundant crustacean, B. longimanus, while the most abundant crustaceans, calanoid copepods, were rare in the diet. The fish not only selected particular species but, within each species, selected the larger individuals. Diel vertical migration of the prey items in this lake could be, at least in part, attributed to fish predation pressure. The observed selectivity patterns shown by the fish are explained in terms of prey visibility, escape ability, the overlap in distribution of predators and prey in time and space, the profitability of the prey and the present trophic state of the lake.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1095-8649.1998.tb02009.x
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