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  • 1
    Electronic Resource
    Electronic Resource
    Characterization of geometric effects for the guide/antiguide intensity modulator (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 4455-4457 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The characteristics of geometric dimensions, such as the modulation length L, the central guide width W, and the gap G between the central guide and antiguide regions for the performance of the guide/antiguide intensity modulator have been examined. Both theoretical predictions and experimental measurements are reported here.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352186
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  • 2
    Electronic Resource
    Electronic Resource
    Effect of layer thickness variations on the performance of asymmetric Fabry–Perot reflection modulators (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 855-860 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present a study of the effect of the active cavity layer thickness variations on the operating characteristics of normally on low voltage high performance asymmetric Fabry–Perot modulators. For a modulator consisting of 25.5 periods of 100 A(ring) GaAs quantum wells confined by 45 A(ring) (GaAs/AlAs) short period superlattices with 5 pairs and 20.5 pairs of top and bottom quarter-wave stacks, respectively, and assuming only layer thickness variation caused by Ga flux nonuniformity, the shift of the Fabry–Perot mode wavelength with respect to the fractional change of GaAs thickness inside the active cavity is ∼6 times that of the quantum well heavy hole exciton. This affects the relative distance between the wavelengths of the quantum well exciton and the Fabry–Perot resonance, and hence the performance of the modulators. Also, the tolerable percentage change of the Fabry–Perot mode wavelength should be less than 0.13% in order that such modulator arrays have at least 10:1 contrast ratios at a fixed optimum operating wavelength. This defines the epitaxial growth tolerance and precision with which we can obtain a desired operating wavelength, and the uniformity requirement on the two-dimensional arrays of such kind of modulators.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351758
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  • 3
    Electronic Resource
    Electronic Resource
    Analysis and optimization of quantum-well thickness for GaAs/AlGaAs and InGaAs/GaAs/AlGaAs quantum-well lasers (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 5047-5054 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The gain-current coefficient and current density at transparency of GaAs/AlGaAs and InGaAs/GaAs/AlGaAs quantum-well (QW) laser structures have been calculated as a function of the QW thickness by a straightforward numerical calculation. The optimum QW thicknesses are determined to be 100 and 105 A(ring) for typical GaAs/AlGaAs and InGaAs/GaAs/AlGaAs QW laser structures, respectively, using the widely accepted semilogarithmic expression for threshold current density of QW lasers. These calculated optimum QW thicknesses agree with the reported experimental data very well. The reduction of the laser threshold current density as a result of using the optimum QW thickness is estimated to be 15% typically.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352033
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  • 4
    Electronic Resource
    Electronic Resource
    Asymmetric Fabry–Perot reflection modulators using red- and blue-shifted electroabsorption effects (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 875-877 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Applying electric fields along the quantum-confined direction of superlattices generates either red-shift (quantum-confined Stark effect) or blue-shift (field-induced Stark localization in superlattices) electroabsorption effects, and the dominating effect changes from a blue-shift to a red-shift as the superlattice period increases from small values. Both effects are utilized in asymmetric Fabry–Perot structures to implement high-contrast electro-optic modulators. In comparison, the red shift provides lower insertion loss while the blue shift provides lower operating voltage swings.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.346775
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  • 5
    Electronic Resource
    Electronic Resource
    Analysis and optimization of graded-index separate-confinement heterostructure waveguides for quantum well lasers (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 2857-2861 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Waveguide structures for quantum well (QW) lasers are analyzed numerically by a straightforward 2×2 matrix approach. It is shown that this approach is capable of analyzing separate-confinement heterostructure (SCH) waveguides, having any arbitrarily graded-index (GRIN) profile in the waveguide layers and any number of QWs in the active layer, to any desired level of accuracy. Using this waveguide analysis, general GRIN-SCH waveguide structures of QW lasers can be optimized for maximum confinement factors. It is estimated that the laser threshold current density can be reduced typically by 10% as a result of this waveguide optimization.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.348593
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  • 6
    Electronic Resource
    Electronic Resource
    Simultaneous gain and phase-shift enhancements in periodic gain structures (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 4387-4389 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The recently proposed concept of periodic gain, i.e., dividing the active region into segments placed at optical electric-field standing wave maxima, has been shown to greatly reduce the threshold gain requirement of the active media by up to a factor of 2 in high-finesse vertical cavity surface-emitting lasers. The lasing wavelength is determined by the period of the standing wave; however, previous analyses of these structures have failed to show that a similar enhancement effect occurs for the index shift resulting from the active segments as well. In this communication, we show that effects on both gain and index can be rigorously derived from conventional transmission scattering theory.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.344912
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  • 7
    Electronic Resource
    Electronic Resource
    Evaluating the effects of optical and carrier losses in etched-post vertical cavity lasers (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 5871-5875 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We demonstrate the combined effects of optical scattering loss and surface recombination (or carrier diffusion) on the performance and scalability of etched-post vertical cavity lasers (VCLs). The size dependence of optical losses and threshold gain are determined from pulsed measurements of external quantum efficiency. Deeper etch depths result in a stronger radial dependence of the threshold gain, which quickly increases the threshold current density. With optical loss accounted for, pulsed threshold current density measurements give the extra information needed for evaluating carrier loss. Surface recombination or carrier diffusion also results in threshold current density increases, but scalability is ultimately limited by the ability of the active region to provide enough gain for smaller size, higher optical loss devices. Even with these losses, three-quantum-well VCLs with shallow etches have threshold currents as low as 420 μA. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360588
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  • 8
    Electronic Resource
    Electronic Resource
    Effects of surface recombination on carrier distributions and device characteristics (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 3208-3215 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We calculate the effects of surface recombination on carrier distributions and device characteristics. The conventional approach assumes a constant surface recombination velocity in the calculation of the surface recombination current and carrier distributions. In this paper, we use the Shockley–Reed–Hall recombination mechanism to calculate the surface recombination rate without resorting to the use of a surface recombination velocity. The current continuity equation and Poisson's equation are solved simultaneously for the carrier distributions, current density, and electric field in the bulk. The effects of surface recombination and surface charged states are included explicitly in the boundary conditions and charge neutrality equation. As a result of the inclusion of the surface charged states in the calculation, acceptor, donor, and compensating surface trap states can easily be included in our model. We calculate the influence of surface recombination on the performance of ridge-type devices and show that appropriate surface delta doping can be used to effectively reduce the surface recombination current for an uncompensated surface. We also compare our results to those obtained from a simple model which is based on a constant surface recombination velocity. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360009
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  • 9
    Electronic Resource
    Electronic Resource
    Lateral carrier diffusion and surface recombination in InGaAs/AlGaAs quantum-well ridge-waveguide lasers (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 4479-4487 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We measured the increase in threshold currents due to lateral carrier diffusion in InGaAs/AlGaAs quantum-well ridge-waveguide laser diodes. The ridge stripes were fabricated by using both in situ monitored pure Cl2 reactive ion etching and selective wet etching to completely eliminate the spreading current in the conductive upper cladding layer while keeping the ridge sidewalls straight. After comparing the threshold data with a theoretical model, the ambipolar diffusion coefficient is found to be 22 cm2/s in the population-inverted InGaAs layer. This model is based on the calculated optical gain curve and the ambipolar carrier transport in the quantum-well and waveguiding layers. The dependence of carrier lifetime on the local carrier concentration is included in the calculation. Moreover, from another set of devices with the portions of the active layer outside the ridge stripes etched away, the surface recombination velocity is found to be around 1–2×105 cm/s.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357279
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  • 10
    Electronic Resource
    Electronic Resource
    High-efficiency and low-threshold InGaAs/AlGaAs quantum-well lasers (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 3932-3934 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: High-efficiency and low-threshold InGaAs/AlGaAs quantum-well laser structures have been grown by molecular beam epitaxy. Material characterization was performed on polyimide-planarized ridge-waveguide lasers. The measured material gain data are compared to theoretical calculations that include the valence-band mixing effects. Total injection current densities of 84 and 60 A/cm2 have been measured from 50-μm-wide laser diodes with cavity lengths of 2850 μm (from a double-quantum-well sample) and 1770 μm (from a single-well sample), respectively. Moreover, we have also obtained a cw threshold current as low as 2.1 mA from a 1.7-μm-wide and 140-μm-long as-cleaved ridge-waveguide device. In addition, the lateral current leakage for the double-quantum-well sample is found to be twice that of the single-well one.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357408
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