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  • 1995-1999  (13)
  • 1990-1994  (11)
  • 1
    Electronic Resource
    Electronic Resource
    Facet and bulk heating of GaAs/AlGaAs high-power laser arrays studied in spatially resolved emission and micro-Raman experiments (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 5559-5563 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Temperature profiles in the bulk and at the front facet of a 20 emitter GaAs/AlGaAs double-quantum-well laser array are studied by spatially resolved luminescence and micro-Raman spectroscopy. For optical output powers of about 1 W, the facet temperature of the individual emitters differs by up to 90 K. In contrast, the temperature distribution inside the resonator is highly uniform with temperature differences of less than 2 K. The facet temperature distribution correlates with the near-field intensity pattern of the laser array. Reabsorption of laser emission close to the facet and subsequent surface recombination of the photogenerated carriers represent the main heating mechanism. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363606
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Picosecond time-resolved luminescence of tetracene thin films (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 5192-5194 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The energy relaxation of excitons in the organic semiconductor tetracene (film thickness 160 nm) is studied by photoluminescence from 15 to 300 K using time-correlated single-photon counting. The well-known relaxation of triplet excitons with time constant ∼7 ns is accompanied by a faster relaxation process with time constants ranging from 260 ps to 1.2 ns, depending on temperature and wavelength. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359757
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Femtosecond fifth-order nonlinear response of nuclear motion in liquids investigated by incoherent laser light. Part I. Theory (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 108 (1998), S. 4159-4172 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The fifth-order nonlinear response is analyzed applying incoherent broadband laser light with femtosecond autocorrelation time under nonresonant conditions. Raman-like excitation is performed combining the broadband incoherent laser with a quasi-cw narrow-band laser with a frequency difference of both lasers tuned to match the frequency of a nuclear mode. The pulsed broadband laser is split into three identical beams allowing application of two different time delays between them. Similar to experiments with single fs pulses, Raman double excitation allows to discern homogeneous and inhomogeneous broadening of the nuclear response. The separation of the broadening contributions, however, demands careful analysis of the signal dependence on delay time in the tail of the observed peaks. Particular features of the experiment, which is described in the second part of this paper, as interferences with cascading of third-order processes and a deconvolution procedure to extract the molecular parameter from the experimental data are theoretically discussed. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.475814
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  • 4
    Electronic Resource
    Electronic Resource
    Femtosecond fifth-order nonlinear response of nuclear motion in liquids investigated by incoherent laser light. Part II. Experiment (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 108 (1998), S. 4173-4182 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A setup for detection of a fifth-order nonlinear Raman process based on incoherent laser light is developed, enabling the introduction of two independent delay times. Depending on phase matching conditions, interference of nonlinear processes of third- and fifth-order or a dominance of one of these processes can be obtained. Possibilities to distinguish between them are discussed and signals of fifth-order Raman-type processes are identified. Regarding the chosen time variable the delay curves are symmetric. Because the correlation time of the incoherent radiation is in the order of magnitude of the fast dephasing time in the liquids, a necessary deconvolution procedure is developed and applied to extract molecular data. A fast dephasing time obtained for nitrobenzene agrees with published data. In mixtures of nitrobenzene with trifluoroethanol the dephasing time decreases, additional excitation of an intramolecular vibration causes an increased effective dephasing times. Both effects could be simulated by independent molecular responses for both kinds of molecules or independent relaxation mechanisms, respectively. From the dependence of the measured FWHM times on the delay time between the two excitations, relations of two relaxation times can be deduced. This information is going beyond that obtainable from third-order coherent techniques. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.475815
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  • 5
    Electronic Resource
    Electronic Resource
    Raman spectroscopic characterization of KrF-laser-irradiated silicon (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 2472-2477 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: High-fluence KrF-laser-irradiated silicon wafers exhibit a wealth of surface structures, which are different depending on the medium present above the surface during treatment with ultraviolet light. A special surface feature, appearing after treatment under water and in air, is analyzed with a Raman microprobe spectrometer. It is found to consist of leaflike formed silicon structures located above but still attached to the treated surface. During Raman scattering measurements the temperature of these morphological peculiarity rises considerably even at low cw probe laser powers because of geometrically limited thermal conductivity. It is shown that the temperatures, which were derived from the Stokes–to–anti-Stokes scattering intensity ratio are more reliable than those extracted from line shifts since the stress developing inside the Raman laser-heated leaflike microstructures is not known. A Raman microprobe scan of a damage spot, generated by UV treatment under water, reveals in the most cases an enhanced Raman intensity (factor of 10) in comparison with untreated areas. This enhancement is even larger at surface spots of smaller (≤1 μm) sizes and is attributed to the field enhancement of the incident and scattered radiation field caused by geometrical resonances.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351593
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Compressional oscillation frequency of an anharmonic oscillator: The spherical non-neutral plasma (1994)
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 35 (1994), S. 2349-2356 
    Details
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: The physics of ultrahigh density compressional oscillations of a non-neutral plasma has already been discussed. Here, one technical facet will be analytically plumbed; namely the frequency of such oscillations. These oscillations are governed by differential equations whose solutions involve elliptic integrals of the third kind. Nevertheless, without studying the properties of these integrals, a procedure is demonstrated which permits the development of an analytic formula for the frequency of these anharmonic oscillations. This frequency is shown to be proportional to the cyclotron frequency ωc with a constant of proportionality that depends on the ratio of the difference between the radii of the outer and inner turning points divided by the sum of the radii of the two turning points. These radii, in turn, depend on two constants of integration that represent the energy of the compressional oscillations and the amount of charge in the plasma cloud. The final result of the analysis is that the frequency varies only from ωc/(square root of)2 when the above ratio is small to (2/3)1/2ωc when the ratio is large. These limits are also obtained intuitively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.530557
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  • 7
    Electronic Resource
    Electronic Resource
    Identities in Stone-Cech Compactifications of Semigroups (1999)
    Springer
    Semigroup forum 59 (1999), S. 415-417 
    Details
    ISSN: 1432-2137
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002339900060
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  • 8
    Electronic Resource
    Electronic Resource
    New time-resolved CARS arrangements (1992)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 14 (1992), S. 1023-1032 
    Details
    ISSN: 0392-6737
    Keywords: Stimulated Raman scattering and spectra ; CARS ; Ultrafast optical techniques
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary Two techniques, using incoherent radiations of ns- or ps-pulse durations, respectively, used to obtain subps-time resolutions are described. Their advantages and limits are discussed. As a result both techniques should be used in addition to real fs-methods, because of their more simple arrangements and because of the possibility to determineT 2-times of vibrations even if more than one vibration is simultaneously excited.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02455364
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  • 9
    Electronic Resource
    Electronic Resource
    Thermal Raman shift of the C60 tangentialA g mode (1995)
    Springer
    Applied physics 61 (1995), S. 171-175 
    Details
    ISSN: 1432-0630
    Keywords: 07.65 ; 65.00
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Fullerence C60 exhibits a continuous and reversibleA g (2) mode softening from 1469 to 1459 cm−1, which is linear with laser power up to 21.9 kW/cm2 for C60 crystals under vacuum. Model calculations taking into account the temperature distribution that is induced by the Gaussian intensity profile of the laser beam reproduce the measured frequency shifts. A thermal conductivity of microcrystalline fullerene of 0.27(±0.03) W/mK is derived from this numerical analysis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01538385
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  • 10
    Electronic Resource
    Electronic Resource
    Thermal Raman shift of the C60 tangential Ag mode (1995)
    Springer
    Applied physics 61 (1995), S. 171-175 
    Details
    ISSN: 1432-0630
    Keywords: PACS: 07.65; 65.00
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract.  Fullerene C60 exhibits a continuous and reversible A g (2) mode softening from 1469 to 1459 cm-1, which is linear with laser power up to 21.9 kW/cm2 for C60 crystals under vacuum. Model calculations taking into account the temperature distribution that is induced by the Gaussian intensity profile of the laser beam reproduce the measured frequency shifts. A thermal conductivity of microcrystalline fullerene of 0.27(±0.03) W/mK is derived from this numerical analysis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003390050186
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