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1

Digitale Medien

Optical gain and spontaneous emission in InGaAs/GaAs multiple quantum well laser diodes (1996)

Schönfelder, Alexander ; Ralston, John D. ; Czotscher, Konrad ; [weitere]

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 80 (1996), S. 582-584

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: We present gain and spontaneous emission measurements in In0.35Ga0.65As/GaAs multiple quantum well lasers. First, the gain is extracted from measured amplified spontaneous emission through a laser facet. Second, unamplified spontaneous emission is detected through the transparent GaAs-substrate. Taking advantage of the fundamental relationship between gain and spontaneous emission, the separation of the electron and hole quasi-Fermi levels, ΔEF, at various bias currents below laser threshold is accurately determined. Theoretically, ΔEF is calculated utilizing a simple two-subband structure model. Fitting the theoretical predictions to the experimental data allows us to determine the threshold carrier density (nth=2.0×1018 cm−3), the in-plane hole effective mass (mv1=0.21m0), and the amount of band gap shrinkage at threshold (ΔEg,th=33 meV). © 1996 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.362721

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2

Digitale Medien

A new method for the synthesis of magnetoliposomes (1999)

Sangregorio, Claudio ; Wiemann, Joan K. ; O'Connor, Charles J. ; [weitere]

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 85 (1999), S. 5699-5701

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: A new method for the synthesis of magnetoliposomes, i.e., nanosized magnetic particles coated by a phospholipid membrane, is presented. Magnetoliposomes are prepared by directly using the phospholipid vesicles as nanoreactors for the precipitation of the magnetic particles. The magnetoliposomes have been characterized using transmission electron microscopy imaging and x-ray powder diffraction. The magnetic properties of the magnetoliposomes have been investigated with a superconducting quantum interference device magnetometer. Our results indicate that the magnetoliposomes contain approximately spherical maghemite nanoparticles averaging 25 nm in diameter. The occurrence of a phospholipid bilayer surrounding the magnetic particles is confirmed both by transmission electron micrographs of samples negatively stained with uranyl acetate and by digital fluorescence imaging microscopy measurements of magnetoliposomes labeled with fluorescein. The temperature dependence of the zero field cooled and field cooled susceptibilities of the magnetoliposomes is consistent with their expected superparamagnetic nature. © 1999 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.370256

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3

Digitale Medien

Analytical criteria for nonlinear instability of thermal structures (1995)

Ibañez S., Miguel H. ; Rosenzweig, Patricia

[S.l.] : American Institute of Physics (AIP)

Physics of Plasmas 2 (1995), S. 4127-4133

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ISSN: 1089-7674

Quelle: AIP Digital Archive

Thema: Physik

Notizen: Analytical criteria for supercritical and asymptotic stability and for subcritical and superexponential instability are obtained for slab-like, spherical, and cylindrical thermal structures. It is assumed that both, the thermal conductivity κ(T) and the gain/loss function Q(T), can be written as continuous functions of the temperature and they have continuous derivatives. Conditions on κ and Q under which the symmetry of the structure determines the kind of instability (or stability) are obtained. Additionally, it is found that the response of the structure not only depends on the amplitude of the disturbance, but also on whether the disturbance increases or decreases the initial steady temperature. In particular, the threshold value for the amplitude of the disturbances beyond which a linearly stable configuration destabilizes, and explicit conditions for catastrophic heating or cooling are obtained. Applications to structures constituted by atomic and molecular gas are outlined. © 1995 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.871036

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4

Digitale Medien

Structural and carrier density dependence of carrier lifetime in InGaAs/GaAs multiple-quantum-well lasers (1996)

Czotscher, K. ; Weisser, S. ; Larkins, E. C. ; [weitere]

Woodbury, NY : American Institute of Physics (AIP)

Applied Physics Letters 69 (1996), S. 3158-3160

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ISSN: 1077-3118

Quelle: AIP Digital Archive

Thema: Physik

Notizen: The carrier lifetime in undoped and p-doped mesa and ridge waveguide In0.35Ga0.65As/GaAs multiple-quantum-well lasers is extracted from the frequency response of the spontaneous emission. The radiative recombination coefficient is found to be the same for mesa and ridge waveguide lasers, and is nearly independent of the doping level. For ridge waveguide lasers, a simple method is proposed to obtain the lateral broadening of the active region due to carrier diffusion. When the corrected active region width is considered, the threshold carrier densities for both undoped and p-doped lasers are independent of the lateral structure and cavity width. Further, the surface recombination velocity in mesa lasers is determined. © 1996 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.116814

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5

Digitale Medien

Carrier profile for In0.35Ga0.65As/GaAs multiquantum well lasers from capacitance–voltage measurements (1996)

Arias, J. ; Esquivias, I. ; Ralston, J. D. ; [weitere]

Woodbury, NY : American Institute of Physics (AIP)

Applied Physics Letters 68 (1996), S. 1138-1140

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ISSN: 1077-3118

Quelle: AIP Digital Archive

Thema: Physik

Notizen: The carrier profile for MBE grown In0.35Ga0.65As/GaAs multiquantum well laser structures with nominally undoped and beryllium-doped active regions was determined by using the capacitance–voltage (C–V) technique at room temperature. A simple theoretical model was used to extract the impurity concentration and the quantum-well carrier density from the experimental profiles. We obtained a high carrier concentration in nominally undoped devices caused by a strong growth temperature dependent Be diffusion from the p-cladding layer, and no difference between doped samples with different nominal dopant location. © 1996 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.115738

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