@article{4551, abstract = {{An intentional positioning of optically active quantum dots using site-selective growth by a combination of molecular beam epitaxy (MBE) and focused ion beam (FIB) implantation in an all-ultra-high-vacuum (UHV) setup has been successfully demonstrated. A square array of periodic holes on GaAs substrate was fabricated with FIB of 30 keV ions followed by an in situ annealing step. Subsequently, the patterned holes were overgrown with an optimized amount of InAs in order to achieve site-selective growth of the QDs on the patterned holes. Under well-optimized conditions, a selectivity of single quantum dot growth in the patterned holes of 52% was achieved. Thereafter, carrier injection and subsequent radiative recombination from the positioned InAs/GaAs self-assembled QDs was investigated by embedding the QDs in the intrinsic part of a GaAs-based p–i–n junction device. Electroluminescence spectra taken at 77 K show interband transitions up to the fifth excited state from the QDs.}}, author = {{Mehta, Minisha and Reuter, Dirk and Melnikov, Alexander and Wieck, Andreas D. and Michaelis de Vasconcellos, Steffen and Baumgarten, Tim and Zrenner, Artur and Meier, Cedrik}}, issn = {{1386-9477}}, journal = {{Physica E: Low-dimensional Systems and Nanostructures}}, keywords = {{Molecular beam epitaxy, Focused ion beam, Self-assembled quantum dot, Electroluminescence}}, number = {{10}}, pages = {{2749--2752}}, publisher = {{Elsevier BV}}, title = {{{Intentionally positioned self-assembled InAs quantum dots in an electroluminescent p–i–n junction diode}}}, doi = {{10.1016/j.physe.2009.12.053}}, volume = {{42}}, year = {{2010}}, } @article{4552, abstract = {{Here we report on investigations on CdSe quantum dots incorporated in ZnSe based Schottky photodiodes with near-field shadow masks. Photoluminescence and photocurrent of individual quantum dots were studied as a function of the applied bias voltage. The exciton energy of the quantum dot ground state transition was shifted to the excitation energy by using the Stark effect tuning via an external bias voltage. Under the condition of resonance with the laser excitation energy we observed a resonant photocurrent signal due to the tunnelling of carriers out of the quantum dots at electric fields above 500 kV/cm.}}, author = {{Panfilova, M. and Michaelis de Vasconcellos, S. and Pawlis, A. and Lischka, K. and Zrenner, Artur}}, issn = {{1386-9477}}, journal = {{Physica E: Low-dimensional Systems and Nanostructures}}, keywords = {{CdSe/ZnSe quantum dots, Photodiode, Quantum confined Stark Effect, Photocurrent, II–VI Semiconductors}}, number = {{10}}, pages = {{2521--2523}}, publisher = {{Elsevier BV}}, title = {{{Resonant photocurrent-spectroscopy of individual CdSe quantum dots}}}, doi = {{10.1016/j.physe.2010.01.013}}, volume = {{42}}, year = {{2010}}, } @article{6619, abstract = {{Strömungsbasierte Mischprozesse sind grundlegender Bestandteil vieler chemischer Prozesse. Realisierbare Mischzeiten reichen von einigen Millisekunden bis zu Sekunden, wobei die vollständige Homogenisierung oft nicht sichergestellt ist. Werden kinetische Parameter chemischer Reaktionen dieses Zeitskalenbereichs ohne Berücksichtigung der Mischprozesse bestimmt, sind sie mischungsmaskiert und geben die inhärente chemische Kinetik nicht wieder. In dieser Arbeit wird die Validierung und Anwendung einer Methode zur Bestimmung inhärenter chemischer Kinetiken von in Flüssigphase ablaufenden chemischen Reaktionen im stationären, laminaren Flachbettmikroreaktor vorgestellt. Der verfolgte Ansatz basiert auf der mechanistischen Modellierung der Molmengen unter Berücksichtigung von Konvektion, Diffusion und Reaktion und der Bestimmung der unbekannten Parameter durch Anpassung des Modells an experimentell ermittelte Konzentrationsverläufe.}}, author = {{Warnecke, H.-J. and Bothe, D. and Zrenner, Artur and Berth, Gerhard and Hüsch, K.-P.}}, issn = {{0009-286X}}, journal = {{Chemie Ingenieur Technik}}, number = {{3}}, pages = {{251--258}}, publisher = {{Wiley}}, title = {{{Modellbasierte Bestimmung lokal gültiger Kinetiken chemischer Reaktionen in Flüssigphase mittels Flachbettmikroreaktor*}}}, doi = {{10.1002/cite.200900169}}, volume = {{82}}, year = {{2010}}, } @article{4547, abstract = {{The coherent state manipulation of single quantum systems is a fundamental requirement for the implementation of quantum information processors. Exciton qubits are of particular interest for coherent optoelectronic applications, in particular due to their excellent coupling to photons. Until now, coherent manipulations of exciton qubits in semiconductor quantum dots have been performed predominantly by pulsed laser fields. Coherent control of the population of excitonic states with a single laser pulse, observed by Rabi oscillations, has been demonstrated by several groups using different techniques1,2,3. By using two laser pulses, more general state control can be achieved4, and coupling of two excitons has been reported5,6. Here, we present a conceptually new approach for implementing the coherent control of an exciton two-level system (qubit) by means of a time-dependent electric interaction. The new scheme makes use of an optical clock signal and a synchronous electric gate signal, which controls the coherent manipulation.}}, author = {{Michaelis de Vasconcellos, S. and Gordon, S. and Bichler, M. and Meier, Torsten and Zrenner, Artur}}, issn = {{1749-4885}}, journal = {{Nature Photonics}}, number = {{8}}, pages = {{545--548}}, publisher = {{Springer Nature}}, title = {{{Coherent control of a single exciton qubit by optoelectronic manipulation}}}, doi = {{10.1038/nphoton.2010.124}}, volume = {{4}}, year = {{2010}}, } @article{4553, abstract = {{We present results on ferroelectric micro-domains obtained by confocal second harmonic microscopy. The high potential of this technique is demonstrated by imaging periodic ferroelectric domain structures in the surface of planar X-cut lithium niobate (LN) and in the body of ridges fabricated by plasma etching on X-cut LN as well. In both cases the measured second harmonic signal reveals a strong contrast between inverted and non-inverted domain sections. This enabled a depth-resolved non-destructive tomography of micro-domains in ridge structures in all three dimensions.}}, author = {{Berth, Gerhard and Wiedemeier, Volker and Hüsch, Klaus-Peter and Gui, Li and Hu, Hui and Sohler, Wolfgang and Zrenner, Artur}}, issn = {{0015-0193}}, journal = {{Ferroelectrics}}, keywords = {{Nonlinear microscopy, ferroelectric micro-domains, confocal imaging, LiNbO3}}, number = {{1}}, pages = {{132--141}}, publisher = {{Informa UK Limited}}, title = {{{Imaging of Ferroelectric Micro-Domains in X-Cut Lithium Niobate by Confocal Second Harmonic Microscopy}}}, doi = {{10.1080/00150190902993267}}, volume = {{389}}, year = {{2009}}, } @article{4554, abstract = {{We have investigated the properties of neutral and charged excitons in single CdSe/ZnSe QD photodiodes by μ-photoluminescence spectroscopy. By applying a bias voltage, we have been able to control the number of electrons in a single QD by shifting the energy levels of the QD with respect to the Fermi level in the back contact. Also the quantum-confined Stark effect was observed as a function of the applied electric field.}}, author = {{de Vasconcellos, S. Michaelis and Pawlis, A. and Arens, C. and Panfilova, M. and Zrenner, Artur and Schikora, D. and Lischka, K.}}, issn = {{0026-2692}}, journal = {{Microelectronics Journal}}, keywords = {{CdSe quantum dots, Photodiode, Stark effect}}, number = {{2}}, pages = {{215--217}}, publisher = {{Elsevier BV}}, title = {{{Exciton spectroscopy on single CdSe/ZnSe quantum dot photodiodes}}}, doi = {{10.1016/j.mejo.2008.07.055}}, volume = {{40}}, year = {{2008}}, } @article{4555, abstract = {{Semiconductor microdiscs are promising for applications in photonics and quantum-information processing, such as efficient solid-state-based single-photon emitters. Strain in the multilayer structure of those devices has an important influence on their optical properties. We present measurements of the strain distribution in ZnMgSe/ZnSe microdiscs by means of micro-photoluminescence and micro-Raman imaging. Photoluminescence measurements of microdiscs reveal substantially broadened emission lines with a shift to lower energy at the undercut part of microdiscs, indicating local relaxation in this area. The distribution of the strain in the microdiscs is obtained from an imaging micro-Raman analysis, revealing that the freestanding part of the microdiscs is free of defects.}}, author = {{Panfilova, M. and Pawlis, A. and Arens, C. and de Vasconcellos, S. Michaelis and Berth, Gerhard and Hüsch, K.P. and Wiedemeier, V. and Zrenner, Artur and Lischka, K.}}, issn = {{0026-2692}}, journal = {{Microelectronics Journal}}, keywords = {{Raman, Photoluminescence, Microdisc, ZnSe}}, number = {{2}}, pages = {{221--223}}, publisher = {{Elsevier BV}}, title = {{{Micro-Raman imaging and micro-photoluminescence measurements of strain in ZnMgSe/ZnSe microdiscs}}}, doi = {{10.1016/j.mejo.2008.07.056}}, volume = {{40}}, year = {{2008}}, } @article{4557, abstract = {{The optical properties of semiconductor quantum dots are in many respects similar to those of atoms. Since quantum dots can be defined by state-of-the-art semiconductor technologies, they exhibit long-term stability and allow for well-controlled and efficient interactions with both optical and electrical fields. Resonant ps excitation of single quantum dot photodiodes leads to new classes of coherent optoelectronic functions and devices, which exhibit precise state preparation, phase-sensitive optical manipulations and the control of quantum states by electrical fields.}}, author = {{Zrenner, Artur and Ester, P and Michaelis de Vasconcellos, S and Hübner, M C and Lackmann, L and Stufler, S and Bichler, M}}, issn = {{0953-8984}}, journal = {{Journal of Physics: Condensed Matter}}, number = {{45}}, publisher = {{IOP Publishing}}, title = {{{Coherent optoelectronics with single quantum dots}}}, doi = {{10.1088/0953-8984/20/45/454210}}, volume = {{20}}, year = {{2008}}, } @article{4556, abstract = {{Very clean single photon emission from a single InGaAs/GaAs quantum dot is demonstrated by the use of a coherent optical state preparation. We present a concept for single photon emission, which uses p-shell Rabi-flopping followed by a sequence of relaxation and recombination. The proof of the (clean) single photon emission is performed by photon correlation measurements.}}, author = {{Ester, P. and Lackmann, L. and Hübner, M.C. and Michaelis de Vasconcellos, S. and Zrenner, Artur and Bichler, M.}}, issn = {{1386-9477}}, journal = {{Physica E: Low-dimensional Systems and Nanostructures}}, keywords = {{Antibunching, Single photon emission, Rabi oscillation, Coherent manipulation}}, number = {{6}}, pages = {{2004--2006}}, publisher = {{Elsevier BV}}, title = {{{p-Shell Rabi-flopping and single photon emission in an InGaAs/GaAs quantum dot}}}, doi = {{10.1016/j.physe.2007.09.129}}, volume = {{40}}, year = {{2007}}, }