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Willkommen im Fachgebiet Theoretische Elektrotechnik (TET)

Unser Forschungsgebiet ist die theoretische Beschreibung von photonischen und optoelektronischen Systemen wie optischen Nanoantennen, dielektrischen Wellenleitern, photonischen Kristallen, Metamaterialien, plasmonischen Systemen, oder biologischen/biomimetischen photonischen Strukturen. Unsere Stärke liegt in der Kombination von hochentwickelten Materialmodellen mit modernsten numerischen Methoden zur Simulation elektromagnetischer Felder.

Forschung: ÜberblickPublikationenTeam

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The five most recent publications


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Unveiling and Imaging Degenerate States in Plasmonic Nanoparticles with Nanometer Resolution

V. Myroshnychenko, N. Nishio, F.J. García de Abajo, J. Förstner, N. Yamamoto, ACS Nano (2018), pp. 8436-8446

DOI
Abstract

Metal nanoparticles host localized plasmon excitations that allow the manipulation of optical fields at the nanoscale. Despite the availability of several techniques for imaging plasmons, direct access into the symmetries of these excitations remains elusive, thus hindering progress in the development of applications. Here, we present a combination of angle-, polarization-, and space-resolved cathodoluminescence spectroscopy methods to selectively access the symmetry and degeneracy of plasmonic states in lithographically fabricated gold nanoprisms. We experimentally reveal and spatially map degenerate states of multipole plasmon modes with nanometer spatial resolution and further provide recipes for resolving optically dark and out-of-plane modes. Full-wave simulations in conjunction with a simple tight-binding model explain the complex plasmon structure in these particles and reveal intriguing mode-symmetry phenomena. Our approach introduces systematics for a comprehensive symmetry characterization of plasmonic states in high-symmetry nanostructures.


Ultrafast electric phase control of a single exciton qubit

A. Widhalm, A. Mukherjee, S. Krehs, N. Sharma, P. Kölling, A. Thiede, D. Reuter, J. Förstner, A. Zrenner, Applied Physics Letters (2018), pp. 111105

DOI
Abstract

We report on the coherent phase manipulation of quantum dot excitons by electric means. For our experiments, we use a low capacitance single quantum dot photodiode which is electrically controlled by a custom designed SiGe:C BiCMOS chip. The phase manipulation is performed and quantified in a Ramsey experiment, where ultrafast transient detuning of the exciton energy is performed synchronous to double pulse p/2 ps laser excitation. We are able to demonstrate electrically controlled phase manipulations with magnitudes up to 3p within 100 ps which is below the dephasing time of the quantum dot exciton.


Intensity surge and negative polarization of light from compact irregular particles

Y. Grynko, Y. Shkuratov, J. Förstner, Optics Letters (2018)

DOI
Abstract

We study the dependence of the intensity and linear polarization of light scattered by isolated particles with the compact irregular shape on their size using the discontinuous Galerkin time domain numerical method. The size parameter of particles varies in the range of X = 10 to 150, and the complex refractive index is m = 1.5 + 0i. Our results show that the backscattering negative polarization branch weakens monotonously, but does not disappear at large sizes, up to the geometrical optics regime, and can be simulated without accounting for wave effects. The intensity backscattering surge becomes narrower with increasing particle size. For X = 150, the surge width is several degrees.


Tailored UV Emission by Nonlinear IR Excitation from ZnO Photonic Crystal Nanocavities

S.P. Hoffmann, M. Albert, N. Weber, D. Sievers, J. Förstner, T. Zentgraf, C. Meier, ACS Photonics (2018), pp. 1933-1942

DOI

Solving Maxwell's Equations with Modern C++ and SYCL: A Case Study

A. Afzal, C. Schmitt, S. Alhaddad, Y. Grynko, J. Teich, J. Förstner, F. Hannig, in: Proceedings of the 29th Annual IEEE International Conference on Application-specific Systems, Architectures and Processors (ASAP), 2018, pp. 49-56

DOI
Abstract

In scientific computing, unstructured meshes are a crucial foundation for the simulation of real-world physical phenomena. Compared to regular grids, they allow resembling the computational domain with a much higher accuracy, which in turn leads to more efficient computations.<br />There exists a wealth of supporting libraries and frameworks that aid programmers with the implementation of applications working on such grids, each built on top of existing parallelization technologies. However, many approaches require the programmer to introduce a different programming paradigm into their application or provide different variants of the code. SYCL is a new programming standard providing a remedy to this dilemma by building on standard C ++17 with its so-called single-source approach: Programmers write standard C ++ code and expose parallelism using C++17 keywords. The application is<br />then transformed into a concrete implementation by the SYCL implementation. By encapsulating the OpenCL ecosystem, different SYCL implementations enable not only the programming of CPUs but also of heterogeneous platforms such as GPUs or other devices. For the first time, this paper showcases a SYCL-<br />based solver for the nodal Discontinuous Galerkin method for Maxwell’s equations on unstructured meshes. We compare our solution to a previous C-based implementation with respect to programmability and performance on heterogeneous platforms.<br


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Gruppenleitung

Prof. Dr. Jens Förstner

Theoretische Elektrotechnik (TET)

Jens Förstner
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+49 5251 60-3013
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