| 51. |
- Atlasov, K.A., et al.
(author)
-
Wavelength and loss splitting in directly coupled photonic-crystal defect microcavities
- 2008
-
In: Optics Express. - 1094-4087. ; 16:20, s. 16255-16264
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Journal article (peer-reviewed)abstract
- Coupling between photonic-crystal defect microcavities is observed to result in a splitting not only of the mode wavelength but also of the modal loss. It is discussed that the characteristics of the loss splitting may have an important impact on the optical energy transfer between the coupled resonators. The loss splitting - given by the imaginary part of the coupling strength - is found to arise from the difference in diffractive outof-plane radiation losses of the symmetric and the antisymmetric modes of the coupled system. An approach to control the splitting via coupling barrier engineering is presented. © 2008 Optical Society of America.
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| 52. |
|
|
| 53. |
|
|
| 54. |
|
|
| 55. |
- Gallo, P., et al.
(author)
-
Integration of site-controlled pyramidal quantum dots and photonic crystal membrane cavities
- 2008
-
In: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 92, s. 263101-
-
Journal article (peer-reviewed)abstract
- The authors demonstrate the deterministic coupling between a single, site-controlled InGaAs/GaAs pyramidal quantum dot (QD) and a photonic crystal membrane cavity defect. The growth of self-ordered pyramidal QDs in small (300 nm base side) tetrahedral recesses etched on (111)B GaAs substrates was developed in order to allow their integration within the thin GaAs membranes. Accurate (better than 50 nm) positioning of the QD with respect to the optical cavity mode is achieved reproducibly owing to the site control. Coupling of the dot emission with the cavity mode is evidenced in photoluminescence measurements. The deterministic positioning of the pyramidal QDs and the control of their emission spectrum opens the way for devices based on QDs integrated with coupled nanocavities.
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| 56. |
|
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| 57. |
|
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| 58. |
|
|
| 59. |
- Karlsson, Fredrik, 1974-, et al.
(author)
-
Electroluminescence and photoluminescence excitation study of asymmetric coupled GaAs/AlxGa1-xAs V-groove quantum wires
- 2004
-
In: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 70:4
-
Journal article (peer-reviewed)abstract
- We have studied systems of asymmetric coupled GaAs V-groove quantum wires p-i-n diodes, in which the electrons and holes are injected into different wires. Despite the use of a 7 nm thick AlGaAs tunnel barrier, and although we demonstrate that holes tunnel more slowly than electrons, we observe a very efficient and fast tunneling between the quantum wires (QWR's). We attribute this to the achievement of a resonance between hole levels in the two QWR's. Photoluminescence excitation experiments are compared with accurate calculations of the excitonic absorption yielding a level of carrier transfer of nearly 100%. Temperature-dependent electroluminescence exhibits clear effects of tunneling up to room temperature but cannot distinguish separate electron/hole tunneling from exciton tunneling.
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| 60. |
- Karlsson, Fredrik, 1974-, et al.
(author)
-
Electrolummescence of asymmetric coupled GaAs/AlGaAs V-groove quantum wires
- 2003
-
In: Institute of Physics Conference Series. - 0951-3248 .- 2154-6630. ; 174, s. 183-186
-
Journal article (peer-reviewed)abstract
- We have studied systems of asymmetric coupled GaAs V-groove quantum wires, in which the electrons and holes are injected into different wires. Our experimental results indicate efficient electron and hole tunneling, despite a 7 nm thick AlGaAs tunnel barrier. Temperature dependent electroluminescence exhibit clear effects of tunneling up to room temperature but cannot distinguish electron/hole tunneling from exciton tunneling.
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| 61. |
|
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| 62. |
|
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| 63. |
- Karlsson, Fredrik, 1974-, et al.
(author)
-
Fractional-dimensional excitonic absorption theory applied to V-groove quantum wires
- 2004
-
In: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 70:15
-
Journal article (peer-reviewed)abstract
- A fractional-dimensional approach is applied to a realistic V-groove quantum wire in order to calculate the excitonic absorption spectrum. An excellent agreement is obtained with much more computationally demanding models as well as with experimental photoluminescence excitation data. However, comparison with a full excitonic calculation reveals situations were the concept of fractional dimensions to some extent fails.
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| 64. |
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| 65. |
- Karlsson, Fredrik, 1974-, et al.
(author)
-
Strongly reduced exciton transfer between parallel quantum wires
- 2007
-
In: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 90:10, s. 101108-101108-3
-
Journal article (peer-reviewed)abstract
- Exciton transfer between two parallel GaAs V-groove quantum wires or two planar quantum wells separated by AlGaAs barriers ranging from 5.5 nm to 20 nm thickness is studied by photoluminescence and photoluminescence excitation spectroscopy. It is found that the transfer is strongly reduced between the widely spaced quantum wires as compared with quantum wells. This observation is supported by model calculations, which yield strong dimensionality dependence of the photon-exchange transfer.
|
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| 66. |
|
|
| 67. |
- Lazarev, M., et al.
(author)
-
Parabolic tailored-potential quantum-wires grown in inverted pyramids
- 2015
-
In: Journal of Crystal Growth. - : Elsevier. - 0022-0248 .- 1873-5002. ; 414, s. 196-199
-
Journal article (peer-reviewed)abstract
- Quasi-one-dimensional AlGaAs quantum wires (QWRs) with parabolic heterostructure profiles along their axis were fabricated using metallorganic vapor phase epitaxy (MOVPE) On patterned (111)B GaAs substrates. Tailoring of the confined electronic states via modification in the parabolic potential profile is demonstrated using model calculations and photoluminescence spectroscopy. These novel nanostructures are useful for studying the optical properties of systems with dimensionality between zero and one. (C) 2014 Elsevier B.V. All rights reserved.
|
|
| 68. |
|
|
| 69. |
|
|
| 70. |
|
|
| 71. |
- Palmgren, Susanna, 1969-, et al.
(author)
-
Polarization-resolved optical absorption in single V-groove quantum wires
- 2006
-
In: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 89, s. 191111-
-
Journal article (peer-reviewed)abstract
- Optical transitions associated with all three linear polarization directions were investigated in single GaAs V-groove quantum wires of different wire thicknesses. This was accomplished by combining absorption measurements in V-groove waveguide geometry with surface-excited photoluminescence excitation spectroscopy. The observed transitions were identified with the aid of model calculations. It is shown that excitonic intersubband coupling should be accounted for in order to explain the optical transitions associated with confined light-hole-like states. The results are relevant for the design of efficient quantum wire waveguide modulators and lasers.
|
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| 72. |
- Sagalowicz, L., et al.
(author)
-
Defects, structure, and chemistry of InP-GaAs interfaces obtained by wafer bonding
- 2000
-
In: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 87:9, s. 4135-4146
-
Journal article (peer-reviewed)abstract
- We have examined the crystallographic structure of GaAs/InP interfaces obtained by wafer fusion following different procedures. Plan-view and cross-sectional transmission electron microscopy reveal that the interface is not only composed of a regular array of two sets of edge dislocations and is more complex than generally supposed. If a twist is created due to misalignment of the two substrates, the dislocations are not edge dislocations but also have a screw component. Dislocations for which the Burgers vectors have a component normal to the interface are also present. Those dislocations probably result from steps and some of them accommodate the tilt between the two substrates. Inclusions and voids as well as a low number of volume dislocations are present in all the samples. The observed volume dislocation density near the interface lies in the 10(5)-10(7) cm(-2) range and these volume dislocations may be associated with thermal mismatch. The origin of all these defects is discussed.
|
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| 73. |
|
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| 74. |
- Szeszko, J., et al.
(author)
-
Exciton confinement and trapping dynamics in double-graded-bandgap quantum nanowires
- 2012
-
In: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 100:21
-
Journal article (peer-reviewed)abstract
- We fabricate and study quantum dot structures incorporating quasi-one-dimensional excited states. The structures are realized by graded bandgap GaAs/AlGaAs quantum wires self-formed inside inverted tetrahedral pyramids. The ground state transitions exhibit typical characteristics of fully confined excitons, including single photon emission. Efficient carrier thermalization and relaxation, as well as correlated photon emission is observed also among the excited states, indicating the formation of quasi-one-dimensional multi-exciton states. These structures offer interesting possibilities for collecting and directing charge carriers towards heterostructured potential traps.
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| 75. |
- Troncale, V., et al.
(author)
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Dynamic switching of hole character and single photon polarization using the quantum confined Stark effect in quantum dot-in-dot structures
- 2010
-
In: Nanotechnology. - : Institute of Physics; 1999. - 0957-4484 .- 1361-6528. ; 21:28, s. 285202-
-
Journal article (peer-reviewed)abstract
- The engineering of the three-dimensional (3D) heterostructure potential in GaAs/AlGaAs pyramidal quantum dot-in-dots (DiDs) provides control over the valence band symmetry and hence on the polarization of the emitted photons. We propose a technique for dynamic switching of hole character and photon polarization in DiDs by means of an applied electric field. The structural parameters required for producing this effect are discussed. Asymmetric DiDs are found to be particularly suitable for obtaining switching with fields smaller than 1 kV cm(-1). The proposed device enables generation of single photons with dynamic control on the photon polarization, with potential applications in quantum information technology.
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| 76. |
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| 77. |
- Weman, Helge, 1960-, et al.
(author)
-
High internal quantum efficiency, narrow linewidth emission InGaAs/GaAs/AlGaAs quantum wire light-emitting diode
- 2002
-
In: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 81:15, s. 2839-2841
-
Journal article (peer-reviewed)abstract
- High internal quantum efficiency (similar to60%), narrow linewidth (as narrow as 14 meV) exciton emission at room temperature has been obtained using strained InGaAs V-groove quantum wire (QWR) light-emitting diodes (LEDs). The high efficiency is achieved with the aid of selective carrier injection through self-ordered AlGaAs vertical quantum wells (VQWs), where the VQWs are separated from the InGaAs QWRs by thin GaAs spacer layers in order to reduce nonradiative recombination and inhomogeneous alloy broadening. Evidence for excitonic recombination in these LEDs up to RT is provided by measurements of the emission energy shifts at high magnetic fields.
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| 78. |
|
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| 79. |
- Weman, Helge, 1960-, et al.
(author)
-
Semiconductor Quantum-Wires and Nano-Wires for optoelectronic Applications
- 2009
-
In: Journal of materials science. Materials in electronics. - : Springer Science and Business Media LLC. - 0957-4522 .- 1573-482X. ; 20:1, s. S94-S101
-
Journal article (peer-reviewed)abstract
- Exciton transfer between two parallel GaAs V-groove quantum wires (QWRs) or two planar quantum wells (QWs) separated by AlGaAs barriers ranging from 5.5 nm to 20 nm thickness is studied by photoluminescence (PL) and PL excitation (PLE) spectroscopy. It is found that the transfer is strongly reduced between the widely spaced QWRs as compared with QWs. We have also investigated the optical absorption in single QWRs embedded in an AlGaAs V-shaped channel waveguide. Using a combination of PLE and absorption measurements we construct the full dependence of absorption spectra on the linear polarization. Our studies reveal the importance of inter-subband mixing in determining the energies of the light-hole-like transitions and thus the QWR absorption. Finally we present recent results on the fabrication and structural characterization of GaAs and GaP nanowires (NWs) grown by molecular beam epitaxy (MBE) on GaAs(111)B and Si(111) substrates, using Au-catalyzed vapor–liquid–solid growth technique. It is shown that, apart from optimizing the NW growth parameters, substrate material and the procedure for preparing the substrate before the MBE growth play an important role in controlling the NWs.
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