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Dr. Xavier Porte

Dr. Xavier Porte is working on external quantum control of photonic nanostructures. He is interested in chaotic dynamics, chaos synchronization, and complex networks with time delayed couplings in mesoscopic systems. His research is located at the crossroads between nonlinear dynamics, nanophotonics and quantum information technology (QIT). Particularly focusing at the edge of the non-classical regime where quantum fluctuations govern the nonlinear dynamics of externally-coupled microlasers. First experimental studies on this field included polarization-mode chaos in microscopic semiconductor lasers induced by cavity QED enhanced fluctuations and injection locking of cavity QED enhanced lasers operating in the quantum regime.
Xavier Porte studied physics at Universitat de les Illes Balears (Spain) and did his Master and PhD degrees at Instituto de Física Interdisciplinar y Sistemas Complejos (Spain) under the supervision of Prof. Dr. Ingo Fischer. During his PhD studies, he did a research stay at the Technische Universität Darmstadt (Germany), under the supervision of Prof. Dr. Wolfgang Elsässer. Xavier is a member of the Optical Society of America (OSA) and of the German Physical Society (DPG).

PhD students

Steffen Holzinger, M.Sc.

Steffen Holzinger is working on the demonstration of non-linear dynamics and chaos in feedback-coupled quantum-dot (QD) microlasers in the quantum limit. Hereby, the impact of non-linear dynamics and cavity quantum electrodynamics effects is explored beyond the description of the Lang-Kobayashi model for classical semiconductor lasers. This includes the systematic study of micropillar lasers subject to self-feedback with different β-factors (controlled by the quality-factor) and different number of QDs contributing to the lasing mode under variation of feedback strength and the length of the external cavity. Due to their slightly elliptical cross-section QD-micropillars exhibit two linear, orthogonally polarized lasing modes which compete using a common gain medium. By applying polarized external feedback a strong change in the intensity and the dynamics of the modes is investigated.
Steffen Holzinger did his B.Sc. and M.Sc. in nanotechnology at Julius-Maximilians-Universität Würzburg. His master study was focused on semiconductor physics and finalized by a master thesis on “Spectroscopy of polaritons in photonic wires” in the group of Prof. Martin Kamp in 2014.
Steffen Holzinger is a member of the German Physical Society (DPG) and the School of Nanophotonics (Research Training group of the CRC 787).
Elisabeth Schlottmann, M.Sc.

Injection locking of standard semiconductor lasers, where the slave adapts to the master laser’s frequency is well known and widely applied e.g. for laser stabilization. We go beyond the classical injection locking by exploring the quantum limit of injection locking by using a microscopic quantum dot micropillar laser as a slave. This device with a high quality factor and a low mode volume exhibits high spontaneous emission enhancement due to the Purcell effect, enabling stable lasing at intra-cavity photon numbers as low as a few tens.
In these microlasers we will inject classical lasers with low intensity as well as other microlasers or single photon sources. With high resolution spectra and time-resolved measurements we will investigate the slave laser´s dynamics.
Elisabeth Schlottmann studied physics at the Technische Universität Berlin specialized in experimental and theoretical solid state physics and optics. Within the scope of her Clara von Simson Prize-winning master thesis she studied single semiconductor quantum dots, particularly the fine structure splitting and the generation of entangled photon pairs in the group of Prof. Reitzenstein. Elisabeth Schlottmann is a member of the German Physical Society (DPG) and the School of Nanophotonics (Research Training group of the CRC 787).
Arsenty Kaganskiy, M.Sc.

Arsenty Kaganskiy is working on the development of a complementary fabrication technology platform for deterministic micropillar lasers with site-controlled QDs in the active layer. The advantage of the used technique should be a possibility of control the number of QDs in the active layer. Spectral resonance will be achieved by determine the wavelength of target QDs in the single QD regime or the center wavelength of small ensembles of site-controlled QDs before patterning micropillar lasers with adjusted diameter. In the case of small ensembles, the non-resonant coupling mechanism will ensure effective gain-contributions also from detuned QDs within the inhomogeneously broadened ensemble of site-controlled QDs. Thus it will be possible to realize QD-microcavities for the study of lasing with a pre-determined number of QDs in order to reach the single-QD regime of feedback-coupled lasing in a controlled way.
Arsenty Kaganskiy did his M. Sc. at Technical University Berlin after he had got his B. Sc. at South Federal University in Rostov on Don (Russia). The master thesis “Development of deterministic quantum dot nanostructures for generation of entangled photon pairs” was done in the workgroup of Professor Stephan Reitzenstein in 2014. In 2015 Arsenty Kaganskiy was awarded with the Study Award in Physics for his Master thesis from the Physics Society of Berlin. Arsenty Kaganskiy is a member of the German Physical Society (DPG) and the School of Nanophotonics (Research Training group of the CRC 787).
Sören Kreinberg, M.Sc.

Sören Kreinberg is working on mutual coupling and synchronization of the aforementioned microlasers to study their correlated dynamics down to the regime of ultra-low light levels where individual photons are exchanged between the microlasers. His work adresses the question of the cause of isochronal synchronization of two chaotic devices separated by distances larger than their coherence time.
Sören Kreinberg studied physics at TU Dortmund University. During the research for his master's thesis in the group of Prof. Bayer he investigated transient optical phenomena in semiconductors, using ultrafast laser spectroscopy. Sören Kreinberg is a member of the German Physical Society (DPG) and the School of Nanophotonics (Research Training group of the CRC 787).

Bachelor and Master students

Marlon Placke, B.Sc.

In optical spectroscopy the emission properties of the systems under investigation depend on their excitation. Besides the usually considered spectral width and partial coherence of the excitation light field, its quantum statistics must also be taken into account. We study the sensitivity of quantum emitters such as microlasers or quantum dots to the statistics of the excitation field and investigate applications to external quantum control of photonics devices.
Marlon Placke studied physics at the University Bremen and at the Technical University Berlin with a focus on solid state and applied physics.
He is currently writing his master thesis on excitation statistics dependent spectroscopy in the group of Stephan Reitzenstein.

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