University of Paderborn

About: University of Paderborn is a education organization based out in Paderborn, Nordrhein-Westfalen, Germany. It is known for research contribution in the topics: Control reconfiguration & Software. The organization has 6684 authors who have published 16929 publications receiving 323154 citations.

From quantum pulse gate to quantum pulse shaper-engineered frequency conversion in nonlinear optical waveguides

Abstract: Full control over the spatiotemporal structure of quantum states of light is an important goal in quantum optics, to generate, for instance, single-mode quantum pulses or to encode information on multiple modes, enhancing channel capacities. Quantum light pulses feature an inherent, rich spectral broadband-mode structure. In recent years, exploring the use of integrated optics as well as source engineering has led to a deep understanding of the pulse-mode structure of guided quantum states of light. In addition, several groups have started to investigate the manipulation of quantum states by means of single-photon frequency conversion. In this paper, we explore new routes towards complete control of the inherent pulse-modes of ultrafast pulsed quantum states by employing specifically designed nonlinear waveguides with adapted dispersion properties. Starting from our recently proposed quantum pulse gate (QPG), we further generalize the concept of spatiospectral engineering for arbitrary ?(2)-based quantum processes. We analyse the sum-frequency generation-based QPG and introduce the difference-frequency generation-based quantum pulse shaper (QPS). Together, these versatile and robust integrated optical devices allow for arbitrary manipulations of the pulse-mode structure of ultrafast pulsed quantum states. The QPG can be utilized to select an arbitrary pulse mode from a multimode input state, whereas the QPS enables the generation of specific pulse modes from an input wavepacket with a Gaussian-shaped spectrum.

Solving nonlinear equations for selective harmonic eliminated PWM using predicted initial values

Abstract: The authors report novel methods for determining switching angles for selective-harmonics-eliminated pulse-width modulation (SHE PWM) inverters. Such switching angles are defined by a set of nonlinear equations, and to solve these equations a predicting algorithm is used to calculate initial values which are first-order approximations of the exact solutions. With these predicted initial values, the Newton algorithm can be used to find the solutions within usually only one or two iterations. The authors also suggest another approach for solving the SHE PWM problem: an ordinary differential equations approach. The advantages of this approach are discussed, and its applications are demonstrated by some examples. >

Symmetry-Selective Third-Harmonic Generation from Plasmonic Metacrystals

Abstract: Nonlinear processes are often governed by selection rules imposed by the symmetries of the molecular configurations. The most well-known examples include the role of centrosymmetry breaking for the generation of even harmonics, and the selection rule related to the rotational symmetry in harmonic generation for fundamental beams with circular polarizations. While the role of centrosymmetry breaking in second harmonic generation has been extensively studied in plasmonic systems, the investigation of selection rules pertaining to circular polarization states of harmonic generation is limited to crystals, i.e., symmetries at the atomic level. In this Letter we demonstrate the rotational symmetry dependent third harmonic generation from nonlinear plasmonic metacrystals. We show that the selection rule can be imposed by the rotational symmetry of metacrystals embedded into an isotropic organic nonlinear thin film. The results presented here may open new avenues for designing symmetry-dependent nonlinear optical responses with tailored plasmonic nanostructures.

Process mining framework for software processes

Abstract: Software development processes are often not explicitly modelled and sometimes even chaotic. In order to keep track of the involved documents and files, engineers use Software Configuration Management (SCM) systems. Along the way, those systems collect and store information on the software process itself. Thus, SCM information can be used for constructing explicit process models, which is called software process mining. In this paper we show that (1) a Process Mining Framework can be used for obtaining software process models as well as for analysing and optimising them; (2) an algorithmic approach, which arose from our research on software processes, is integrated in the framework.