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- Karlsson, Fredrik, 1974-, et al.
(author)
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Optical polarization anisotropy and hole states in pyramidal quantum dots
- 2006
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In: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 89, s. 251113-
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Journal article (peer-reviewed)abstract
- The authors present a polarization-resolved photoluminescence study of single semiconductor quantum dots (QDs) interconnected to quantum wires, measured both in a top geometry, and in a less conventional cleaved-edge geometry. Strong polarization anisotropy is revealed for all observed transitions, and it is deduced that closely spaced QD hole states exhibit nearly pure heavy-or light-hole character. These effects are attributed to the large aspect ratio of the dot shape
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- Karlsson, K Fredrik, et al.
(author)
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Spectral signatures of high-symmetry quantum dots and effects of symmetry breaking
- 2015
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In: New Journal of Physics. - : Institute of Physics Publishing (IOPP). - 1367-2630. ; 17:10
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Journal article (peer-reviewed)abstract
- High symmetry epitaxial quantum dots (QDs) with three or more symmetry planes provide a very promising route for the generation of entangled photons for quantum information applications. The great challenge to fabricate nanoscopic high symmetry QDs is further complicated by the lack of structural characterization techniques able to resolve small symmetry breaking. In this work, we present an approach for identifying and analyzing the signatures of symmetry breaking in the optical spectra of QDs. Exciton complexes in InGaAs/AlGaAs QDs grown along the [111]B crystalline axis in inverted tetrahedral pyramids are studied by polarization resolved photoluminescence spectroscopy combined with lattice temperature dependence, excitation power dependence and temporal photon correlation measurements. By combining such a systematic experimental approach with a simple theoretical approach based on a point-group symmetry analysis of the polarized emission patterns of each exciton complex, we demonstrate that it is possible to achieve a strict and coherent identification of all the observable spectral patterns of numerous exciton complexes and a quantitative determination of the fine structure splittings of their quantum states. This analysis is found to be particularly powerful for selecting QDs with the highest degree of symmetry ( C 3 v and ##IMG## [http://ej.iop.org/images/1367-2630/17/10/103017/njp519062ieqn1.gif] $D_3h$ ) for potential applications of these QDs as polarization entangled photon sources. We exhibit the optical spectra when evolving towards asymmetrical QDs, and show the higher sensitivity of certain exciton complexes to symmetry breaking.
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- Troncale, V., et al.
(author)
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Control of valence band states in pyramidal quantum dot-in-dot semiconductor heterostructures
- 2007
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In: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 91:24
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Journal article (peer-reviewed)abstract
- The character of the hole states in a pyramidal GaAsAlGaAs quantum dot-in-dot (DiD) heterostructure is shown to be controllable by tailoring the confinement potential shape. The change in ground valence band state from heavy hole like to light hole like is demonstrated by side-view polarization resolved photoluminescence measurements. The experimental findings are supported by three-dimensional numerical model calculations. The results are applicable for polarization control in quantum dot photonic devices. © 2007 American Institute of Physics.
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- 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
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In: Nanotechnology. - : Institute of Physics; 1999. - 0957-4484 .- 1361-6528. ; 21:28, s. 285202-
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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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- Troncale, V., et al.
(author)
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Excited excitonic states observed in semiconductor quantum dots using polarization resolved optical spectroscopy
- 2007
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In: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 101, s. 081703-
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Journal article (peer-reviewed)abstract
- We present results on the polarization-resolved photoluminescence emitted from InGaAs/AlGaAs single quantum dots (QDs) grown in inverted tetrahedral pyramids. The emitted light was detected for two mutually perpendicular linear polarization directions in the less conventional cleaved-edge geometry, in addition to the standard top-emission geometry. Whereas the in-plane linear polarization was isotropic, as a consequence of the high symmetry of the system, we found a strong polarization anisotropy of the edge-emitted light revealing QD states of predominantly heavy- or light-hole character. By temperature control of the charge state, several neutral and charged light-hole like exciton complexes were identified. In particular, a biexciton showing a twofold radiative recombination path, leading to two nearly perpendicularly polarized emission multiplets, was identified. These results are also of technological relevance for any design of optoelectronic QD-integrated devices
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