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  • 1
    Electronic Resource
    Electronic Resource
    Control of quantum dynamics by a locally optimized laser field. Application to ring puckering isomerization (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 100 (1994), S. 5646-5655 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We presented a theoretical method for controlling quantum dynamics by locally optimized nonstationary laser fields, within the semiclassical theory of the molecule–radiation field interaction. The external laser field is optimized based on the control theory of a linear time-invariant (LTI) system, so that both the summation of the population of the nontarget states and the total energies of the laser fields are minimized. The optimization procedure involves operation of the so-called feedback gain matrix to the time-dependent state vector. This procedure is carried out at every successive short stage, in which the time-dependent Schrödinger equation can be approximated to the equation of motion of the LTI system. As an example, the control theory was applied to laser-induced ring-puckering isomerization, the dynamics of which can be described as the wave packet in the one-dimensional double minimum potential under locally optimized laser fields. The result indicated that nearly 100% of the population can be transferred to the final product state by irradiation of the optimized laser fields. The optimized laser fields were analyzed to obtain information on the carrier frequencies or the frequency modulation by using the fast Fourier transform method. These results were then compared with the result of isomerization induced by nonoptimized laser fields.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.467132
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  • 2
    Electronic Resource
    Electronic Resource
    Control of a quantum dynamics by a locally optimized laser field. II. Application to a system with dissipation (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 6586-6592 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We present a theory for controlling the dynamics of a dissipative, quantum system with a laser field optimized locally in time. The theory is applicable to both weak and strong field control of the quantum dynamics. The theoretical groundwork is based on the equation of motion of the density matrix in Liouville space. Interactions between the molecules and the heat bath are taken into account within a Markov approximation. The derivation of the locally optimized laser field in a feedback form is based on the local optimization theory in the Hilbert space, proposed in a previous paper [M. Sugawara and Y. Fujimura, J. Chem. Phys. 100, 5646 (1994)]. The theory is applied to a simple, two-level quantum system with a dephasing constant. We present both the calculated time evolution of the off-diagonal density matrix element and that of the population of the states in the optimized laser field. These calculations show that the control of the system by the laser field is sufficient to avoid the dephasing effects. We discuss how the dephasing dynamics affects the optimization of the laser field.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.468353
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  • 3
    Electronic Resource
    Electronic Resource
    Room-temperature exciton optical absorption peaks in InGaAsP/InP multiple quantum wells (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 1353-1355 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We grew In1−xGaxAsyP1−y/InP quantum wells (QWs) by low-pressure metalorganic vapor phase epitaxy. The In1−xGaxAsyP1−y layer was closely lattice matched to InP with a composition of y=0.9 (x=0.47y). We investigated structural imperfections such as composition fluctuations, interface roughness, and nonperiodicity analyzing the low-temperature photoluminescence linewidth. We found that the InGaAsP layer composition fluctuated, causing about 5 meV inhomogeneity in the exciton energy level in QWs wider than about 3 nm. Since we obtained very smooth interfaces with less than one monolayer of fluctuation and excellent periodicity by lowering growth temperature to 570 °C, the inhomogeneity of the exciton energy level could be held at 6 meV for 20-period 10-nm multiple QWs. As a result, despite composition fluctuations, a clear room-temperature exciton optical absorption peak was observed at 1.5 μm for the first time to our knowledge.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.100713
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  • 4
    Electronic Resource
    Electronic Resource
    Analysis of recombination centers in (AlxGa1−x)0.5In0.5P quaternary alloys (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 4946-4949 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We studied nonradiative recombination centers in undoped (AlxGa1−x)0.5In0.5Pgrown by metalorganic vapor phase epitaxy using transient capacitance spectroscopy. We found three deep energy levels, including a mid-gap level. We drew an equation to get a capture cross section for minority carriers, and obtained it using isothermal capacitance transient spectroscopy measurement. The mid-gap level had an electron capture cross section of 2 × 10−10 cm2 and a hole capture cross section of 1 × 10−15 cm2. The time constant of nonradiative recombination through the mid-gap level was found to be comparable to that of radiative recombination. We concluded that the mid-gap level is an effective nonradiative recombination center that reduces photoluminescence intensity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.349041
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  • 5
    Electronic Resource
    Electronic Resource
    Frequency characteristics of the Mn-doped InP p-n junction (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 1961-1963 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Admittance spectroscopy is applied to the analysis of the thermal properties of the Mn acceptor-doped InP grown by liquid-phase epitaxy. The thermal activation energy and capture cross section are determined as ΔET=183 meV and σp=1.8×10−13 cm2, respectively. The cutoff frequency of the emission of holes from the Mn acceptor is 1 GHz at 300 K. It is shown that the small signal frequency characteristic of a buried heterostructure laser is improved at frequencies f〉1 GHz by using the Mn-doped p-InP layer for the current blocking region.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.341094
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  • 6
    Electronic Resource
    Electronic Resource
    Fe-doped semi-insulating InP grown by chloride vapor-phase epitaxy (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 4698-4700 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Fe-doped semi-insulating (SI) InP layers have been grown using chloride vapor-phase epitaxy for the first time. Fe-doping was carried out by introducing FeCl2 to the growth region, bypassing the source region. The FeCl2 was formed by etching a pure metallic Fe source by HCl vapor. The resistivity of the SI-InP epitaxial layers was evaluated by measuring current-voltage characteristics, and a high value of 4×108 Ω cm was obtained. The semi-insulating current blocking was maintained up to an applied voltage of nearly 30 V, even at 110 °C, with a layer 4.3 μm thick.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.338385
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  • 7
    Electronic Resource
    Electronic Resource
    Liquid phase epitaxial growth of Fe-doped semi-insulating InGaAsP lattice matched to InP over the entire composition range (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 53 (1988), S. 574-576 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Fe-doped semi-insulating In1−x Gax Asy P1−y (0≤y≤1, y=2.2x) epitaxial layers lattice matched to InP with nearly intrinsic carrier concentrations have been successfully grown over the entire composition range by liquid phase epitaxy. Maximum resistivities as high as 8×107 Ω cm for InP, 2×105 Ω cm for InGaAsP (y=0.57), and 2×103 Ω cm for InGaAs (y=1) have been achieved. The critical growth temperature necessary to obtain semi-insulating layers significantly decreased as the composition was varied from y=0 to y=1. The Fe doping characteristics are well defined by the composition dependence of the Fe distribution coefficient.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.99861
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  • 8
    Electronic Resource
    Electronic Resource
    Evaluation of exciton absorption peak broadening factors in InGaAsP/InP multiple quantum wells (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 53 (1988), S. 2290-2292 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We evaluated the magnitude of broadening factors of ground-state exciton absorption peaks in In1−xGaxAsyP1−y/InP (x=0.47y) multiple quantum wells (MQW's) with about 10 nm wells. The absorption peaks broadened with a decrease of y. Analyzing the absorption peak broadening with increasing temperature, the thermal broadening factor at 300 K was found to be about 9 meV and composition independent. Analyzing the photoluminescence linewidth at 4.2 K, it was found that composition fluctuations in the well caused an inhomogeneity of the exciton energy level of 4.4 meV for the y=1.0 MQW and 7.5 meV for the y=0.6 MQW, being the greatest contributors to inhomogeneous broadening. We conclude that the exciton absorption peak broadening with a decrease of y is primarily due to the increase of composition fluctuations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.100256
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  • 9
    Electronic Resource
    Electronic Resource
    Exact determination of superlattice structures by small-angle x-ray diffraction method (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 52 (1988), S. 742-744 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The structure of In1−xGaxAsyP1−y/InP superlattices (x=0.27 and y=0.60) is investigated by small-angle x-ray diffraction method. The interference peaks due to the superlattice structure were clearly observed up to the 6th order. The period of the superlattice was determined from the angular positions of the peaks using the modified Bragg's law. By analyzing the diffraction patterns of the first and the secondary peaks according to the optical multilayer theory, the thickness of each component (In1−xGaxAsyP1−y and InP) was uniquely determined within an error of ±1 A(ring). This method can be used to determine any type of superlattice structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.99342
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  • 10
    Electronic Resource
    Electronic Resource
    Effect of spin-orbit split-off band on optical gain in AlGaInP/GaInP strained quantum wells (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 466-468 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The optical gains in AlGaInP/GaInP strained quantum wells using valence band structures by the second-order k⋅p method, with and without spin-orbit split-off (SO) band effect have been calculated. It was easy to overestimate the optical gain without considering the SO-band effect, because a small spin-orbit splitting energy for GaInP makes higher nonparabolicity of the valence bands. The SO-band effect is particularly significant under tensile strain, since the SO band makes the effective mass very large due to the large interaction between the SO and light hole bands. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.114058
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