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  • 1
    Electronic Resource
    Electronic Resource
    Temperature dependence of the lasing wavelength of InGaAs quantum dot lasers (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 4859-4861 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We observe that the emission wavelength of edge-emitting InGaAs quantum dot lasers has a much weaker temperature dependence (0.6 Å K−1) than equivalent quantum well devices (3 Å K−1). Measured gain and absorption spectra show that the gain peak wavelength due to dot states is almost independent of temperature for a given value of peak gain whereas the absorption edge shifts at a rate of about 2 Å K−1. Above 100 K the occupancy of dot states can be described by Fermi functions and on this basis we find that the measured gain and absorption spectra are in excellent quantitative agreement. Although the band edge energy reduces with increasing temperature, this analysis shows that the energy distribution of dot states matches the evolution of the Fermi functions such as to leave the quasi Fermi level separation and the wavelength of the gain peak unchanged as a function of temperature for a given value of peak gain. This energy distribution is a consequence of the dot size distribution so the match to the Fermi functions is probably fortuitous. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1402666
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  • 2
    Electronic Resource
    Electronic Resource
    Measurement of true spontaneous emission spectra from the facet of diode laser structures (2002)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 80 (2002), S. 1-3 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Measurement of the spontaneous emission and gain spectra provides a complete characterization of a semiconductor gain medium, however, this requires the observation of emission in two directions to avoid amplification of the spontaneous emission spectrum. We show that both the gain spectrum and the true spontaneous emission spectrum can be obtained from amplified spontaneous emission (ASE) spectra measured from the end of a segmented-contact device. The spontaneous emission spectra agree with spectra measured through a top contact window. If the carrier populations are fully inverted at low photon energy, it is possible to convert the ASE-derived spontaneous emission into real units. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1428774
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  • 3
    Electronic Resource
    Electronic Resource
    Modal gain and internal optical mode loss of a quantum dot laser (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 77 (2000), S. 163-165 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The modal gain spectra and internal optical mode loss of a semiconductor laser structure containing a single layer of InGaAs quantum dots have been measured independently and directly as a function of current density. The quantum dot gain exhibits no obvious polarization dependence. The maximum modal gain of (11±4) cm−1 obtained from the ground state of a single layer of quantum dots is in this case insufficient for lasing operation since the internal optical mode loss measured on the same sample is (11±4) cm−1. As expected laser emission is not observed from the dot ground state, but from the excited dot state or from the wetting layer depending on device length. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.126911
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  • 4
    Electronic Resource
    Electronic Resource
    Comparison of experimental and theoretical gain-current relations in GaInP quantum well lasers (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 76 (2000), S. 1522-1524 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We compare the results of a microscopic laser theory with gain and recombination currents obtained from experimental spontaneous emission spectra. The calculated absorption spectrum is first matched to that measured on a laser, ensuring that the quasi-Fermi levels for the calculation and the experiment (spontaneous emission and gain) are directly related. This allows us to determine the inhomogeneous broadening in our experimental samples. The only other inputs to the theory are literature values of the bulk material parameters. We then estimate the nonradiative recombination current associated with the well and waveguide core from a comparison of measured and calculated recombination currents. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.126083
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  • 5
    Electronic Resource
    Electronic Resource
    Direct monitoring of thermally activated leakage current in AlGaInP laser diodes (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 74 (1999), S. 2540-2542 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Using specially prepared structures, we have observed emission from a layer of direct-gap "monitor" material placed between the p-contact layer and p-cladding layer of a conventional 670 nm GaInP laser diode at room temperature. This observation provides direct evidence for electron leakage through the p-cladding layer in these devices. Furthermore, although emission from the quantum well and waveguide core both pin above threshold, indicating that the Fermi levels clamp throughout the active region, the monitor emission continues to rise above threshold. This is characteristic of a drift component to the leakage current, which we have confirmed by a simulation of the carrier transport processes through the cladding layer with and without drift. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.123891
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  • 6
    Electronic Resource
    Electronic Resource
    Measurement of optical mode loss in visible emitting lasers (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 71 (1997), S. 1975-1977 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We describe a technique for direct measurement of the passive optical mode loss of a semiconductor laser or similar semiconductor waveguide structure, based upon measurement of the attenuation of optically excited luminescence in the guided mode as a function of distance traveled along the passive guide. A spectrometer is used to select luminescence in the low energy tail of the spectrum which is subject to very little reabsorption. We have applied the method to a series of highly strained GaInP quantum well laser structures and observe an increase in the mode loss from 9.9 cm−1 for 1% strain to 46 cm−1 for 1.7% strain. This correlates with the appearance of clustered regions in the highly strained wells observed by transmission electron microscopy (TEM). © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.119759
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  • 7
    Electronic Resource
    Electronic Resource
    Threshold current temperature dependence of GaInP/(AlyGa1−y)InP 670 nm quantum well lasers (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 1265-1267 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The temperature dependence of threshold current of (AlyGa1−y)InP/GaInP quantum well lasers (y=0.3, 0.4, and 0.5) has been investigated and used to characterize thermally activated loss mechanisms above room temperature. We show good agreement between activation energies measured by Arrhenius analysis and those expected for the loss of electrons from the well to the X-conduction band minima in the barrier. Our analysis uses measured band gaps of the actual structures, avoiding assumptions about the alloy compositions, spontaneous emission data to subtract radiative and other direct gap processes, and recent band gap data for this alloy system. This provides convincing experimental confirmation of the loss of electrons from the indirect minima as the preferred process causing the rise in current at high temperature in these lasers. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.114392
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  • 8
    Electronic Resource
    Electronic Resource
    Fermi level pinning and differential efficiency in GaInP quantum well laser diodes (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 70 (1997), S. 1073-1075 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Analysis of spontaneous emission spectra of GaInP quantum well laser diodes above and below threshold show that the quasi-Fermi level separation pins within the quantum wells but not throughout the whole device structure. By reproducing the temperature and cavity length dependence of the external differential efficiency using these measurements it is shown that a value of internal differential efficiency which is nonunity is due to current spreading and incomplete carrier injection and that the temperature dependence is due to the temperature dependence of the efficiency with which carriers are injected into the quantum well.© 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.118488
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  • 9
    Electronic Resource
    Electronic Resource
    On the determination of internal optical mode loss of semiconductor lasers (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 70 (1997), S. 2365-2367 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Use is made of a numerical simulation of the light—current characteristic to examine the errors which may arise in the determination of the optical mode loss (αi) from the cavity length dependence of the external differential efficiency (ηextd). In particular, we focus on the effects of incomplete Fermi level pinning and carrier leakage, and show that αi can only be determined correctly if ηextd is determined under conditions where it is invariant both with current level and temperature. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.118875
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  • 10
    Electronic Resource
    Electronic Resource
    Optical mode loss and gain of multiple-layer quantum-dot lasers (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 78 (2001), S. 2629-2631 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Using an electrically pumped multisection technique, we have directly measured the internal optical mode loss of semiconductor-laser structures containing 1, 3, 5, and 7 layers of uncoupled InGaAs quantum dots. The optical loss does not increase with the number of dot layers so higher net modal gain can be achieved by using multiple layers. The maximum modal gain obtained from the ground state increases with dot layer number from 10±4 cm−1 for a single layer to 49±4 cm−1 for the 7 layer sample, which is typical of the threshold gain requirement of a 350 μm long device with uncoated facets. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1366652
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