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  • 1
    Electronic Resource
    Electronic Resource
    Gain-switched semiconductor laser amplifier as an ultrafast dynamical optical gate (1988)
    Springer
    Applied physics 46 (1988), S. 69-77 
    Details
    ISSN: 1432-0649
    Keywords: 42.55.Px ; 42.60.Da ; 85.60.Jb
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A gain-switched semiconductor laser is shown to act as an optical gate with picosecond resolution and amplification for light pulses from another laser source. The amplification mechanism and the gate width change qualitatively when the gate laser undergoes a transition from a pumping rate slightly below the dynamic laser threshold to slightly above the dynamic threshold. If the gate laser is pumped below but close to its dynamical threshold, unsaturated amplification of an external signal pulse occurs over a delay time range between the external optical pulse and the electrical driving pulse of about 100–200 ps which is equivalent to the optical gate width. The signal amplification is observed to increase by two orders of magnitude and the gate width decreases by one order of magnitude if the gate laser is pumped slightly above the dynamical threshold. Amplification then occurs for input signals injected much earlier. A detailed theory of coherent, time-dependent amplification including the nonlinear dynamics of the semiconductor laser is shown to account for the observations. Both amplification regimes, below and above threshold, are reproduced in the numerical simulations. The extremely short and highly sensitive gate range above threshold is identified as being due to the gain maximum related with the first relaxation oscillation of the laser.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00698655
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  • 2
    Electronic Resource
    Electronic Resource
    Avalanche generator triggered picosecond light pulses from unbiased V-groove GaAs/GaAlAs lasers
    Amsterdam : Elsevier
    Physica B+C 129 (1985), S. 469-472 
    Details
    ISSN: 0378-4363
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0378-4363(85)90625-4
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  • 3
    Electronic Resource
    Electronic Resource
    Turn-on delay time fluctuations in gain-switched AlGaAs/GaAs multiple-quantum-well lasers (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 2469-2471 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The turn-on delay time jitter in unbiased gain-switched AlGaAs/GaAs multiple-quantum-well lasers is determined by measuring the transient fluctuations of the total emitted power with the use of a fixed-time sampling technique with a picosecond temporal resolution. The turn-on jitter is found to decrease significantly with increasing pumping rate, particularly when the lasers are operated at an excitation level at which only the first relaxation oscillation is emitted. The root-mean-square jitter of the emitted optical pulses decreases from about 20 ps just above the laser threshold to a value of 14 ps at the threshold for the appearance of the second relaxation oscillation. These results demonstrate that an accurate adjustment of the pumping rate is essential for a low-jitter single-pulse operation of the gain-switched lasers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.341025
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  • 4
    Electronic Resource
    Electronic Resource
    Picosecond spectra of gain-switched AlGaAs/GaAs multiple quantum well lasers (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 53 (1988), S. 2263-2265 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The temporal waveform of the single longitudinal modes emitted by gain-switched AlGaAs/GaAs multiple quantum well lasers is analyzed by means of a synchroscan streak camera system coupled to a spectrograph. It is found that only 50% of the number of the longitudinal modes contributing to the time-averaged spectrum are present during the first relaxation oscillation. The time-dependent shift of the envelope of the mode spectrum is quantitatively explained by a spectral shift of the gain maximum as a function of the time-varying charge carrier density. The results demonstrate that, for the analysis of transient multimode spectra of gain-switched injection lasers, inclusion of the energy dependence of the gain and gain compression is mandatory.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.100248
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  • 5
    Electronic Resource
    Electronic Resource
    Palliativtherapie bei gastrointestinaler Obstruktion (1999)
    Springer
    Der Chirurg 70 (1999), S. 1397-1401 
    Details
    ISSN: 1433-0385
    Keywords: Key words: Intestinal obstruction ; Cancer ; Surgical therapy. ; Schlüsselwörter: Ileus ; Malignom ; palliative Operation.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung. Die gastrointestinale Obstruktion stellt bei Tumorpatienten eine häufige Notsituation dar. Neben einem Tumorrezidiv, einem Zweittumor oder einer intraperitonealen Tumorausbreitung können auch im fortgeschrittenen Tumorstadium benigne Veränderungen (radiogene Stenosen, Briden) ursächlich sein. Im Vordergrund der Therapie steht der Versuch, durch operative Maßnahmen die Darmobstruktion zu beseitigen. Ist dies bei fortgeschrittener intraabdomineller Tumorausbreitung nicht möglich, stehen eine Reihe endoskopischer interventionell radiologischer und medikamentöser Maßnahmen zur Verfügung, die individuell und abhängig von der jeweiligen Erfahrung zur Anwendung kommen mit dem Ziel, eine Linderung der Beschwerden zu erreichen.
    Notes: Summary. Gastrointestinal obstruction is a frequently observed emergency with tumor patients. In addition to tumor relapse, the development of a second tumor or intraperitoneal tumor spreading, and benign alterations in advanced tumor stages (radiogenic stenosis, adhesions) may also be the cause for the obstruction. The main objective of therapy is an attempt to eliminate the intestinal obstruction through surgery. If this is not possible because of advanced intra-abdominal tumor expansion, several endoscopic or interventional radiology methods, and drugs are available, that are used on an individual basis and based on prevailing experience to relieve the patient's condition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001040050077
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