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Aufsatz
Vesicle motion during sustained exocytosis in chromaffin cells
(PLoS, 2015)
Chromaffin cells release catecholamines by exocytosis, a process that includes vesicle docking, priming and fusion. Although all these steps have been intensively studied, some aspects of their mechanisms, particularly those regarding vesicle transport to the active sites situated at the membrane, are still unclear. In this work, we show that it is possible to extract information on vesicle motion in Chromaffin cells from the combination of Langevin simulations and amperometric measurements. We developed a numerical ...
Aufsatz
Beating the limits with initial correlations
(2017-11-28)
Fast and reliable reset of a qubit is a key prerequisite for any quantum technology. For real world open quantum systems undergoing non-Markovian dynamics, reset implies not only purification, but in particular erasure of initial correlations between qubit and environment. Here, we derive optimal reset protocols using a combination of geometric and numerical control theory. For factorizing initial states, we find a lower limit for the entropy reduction of the qubit as well as a speed limit. The time-optimal solution ...
Dissertation
High-Speed 1.55 µm Quantum Dot Lasers with Electronically Coupled Quantum Well - Dot Active Regions
(2019-07-31)
The expansion of long-distance data communication at a wavelength of 1.55 µm calls for larger data transfer rates. Consequently, an improvement of emission and modulation properties of lasers emitting in this wavelength region is of high interest. The utilization of so-called tunnel-injection (TI) structures in InP-based quantum dot (QD) lasers is promising to fulfill this task. The aim of this thesis was the realization and analysis of TI structures in the lattice matched InP material system and incorporation into ...
Dissertation
1.55 μm Quantum Dot Lasers for Telecommunication
(2019)
The thesis at hand investigates the suitability of quantum dot (QD) material for use in long-distance coherent communication. The thesis was written in the frame of the SASER project MONOLOP that is aiming for a compact, monolithically integrated light source with a tunable wavelength covering the C+-band and narrow spectral linewidth below 500 kHz.
The thesis reviews the theoretical background of quantum dot material based on the InP material system and distributed feedback (DFB) lasers with lateral gratings as ...
Dissertation
Quantum optimal control theory of photoelectron spectroscopy
(2018)
The object of this doctoral thesis is two-fold and can be classified into two, but intrinsically related categories: (i) development of theoretical models for the simulation of electron dynamics and in parallel to this, (ii) method development of efficient numerical algorithms for ad hoc control of photoelectron and photoion-related observables. The first category primarily focuses on the development of a variety of theoretical models describing the interaction of light and matter for the extraction and control of ...
Dissertation
Gold Surface Nanostructuring with Ultrashort Laser Pulses - Study of Non-equilibrium Effects
(2019)
Laser material interaction and structure formation in metals under controlled ultrashort laser pulse conditions are discussed in this work. A novel approach is presented describing the exact amount of energy deposited by a laser pulse in a gold surface, applicable under a variety of structuring conditions. The presented model is validated by a new introduced broad-band pump-probe reflectivity measurement method. A technique also applicable to investigate other phenomenas where 20 fs resolution combined with an octave ...
Dissertation
Ab-initio analysis of the structural response of solids after femtosecond-laser-pulse excitation
(2019)
After an intense femtosecond-laser excitation extreme non-equilibrium conditions are induced in materials. The high photon density in such an ultrashort-laser pulse interacts directly with the electronic system of the material. By absorbing the photon energy the electrons are excited in high energy states, where they form a non-equilibrium distribution shortly after the excitation. Due to fast electron-electron scattering and cascading processes equilibrates the electronic system within several femtoseconds to a ...
Dissertation
InP - based quantum dots for telecom wavelengths ranges
(2019-12)
Long-distance quantum communication applications require sources of single photons, emitting at telecom wavelengths (around 1550 nm) with minimum attenu-ation losses of silica fiber.
Semiconductor self-assembled InAs/InP-based quantum dots (QDs) are possible candidates to
reach this spectral region. One of the challenges on the way is a QD asymmetry, which limits the fidelity of entangled photons. Therefore, morphological and optical properties of QDs should be improved in order to achieve the necessary quality and ...
Dissertation
Abhängigkeit des Exchange-Bias Feldes und des Koerzitivfeldes von der mittels Röntgendiffraktometrie gemessenen Kornvolumenverteilung des Antiferromagneten in Exchange-Bias Schichtsystemen
(2019-10-02)
Der Exchange-Bias Effekt wird in vielen technischen Anwendungen, wie z.B. in magnetischen Speichermedien oder in Magnetsensorköpfen zum Pinnen der Magnetisierungsrichtung der Referenzelektrode, eingesetzt. Dieser Effekt tritt ausschließlich in dünnen Schichtsystemen, in denen sich ein dünner Ferromagnet mit einem dünnen Antiferromagneten in Kontakt befindet, auf und bewirkt eine Verschiebung der Hysteresekurve entlang der Magnetfeldachse. Solche Exchange-Bias Schichtsysteme können mittels Ionenbeschuss, d.h., leichte ...