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Fachgebiet Theoretische Elektrotechnik (TET)
Prof. Dr. Jens Förstner

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: ThemenPublikationenTeam

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Light backscattering from numerical analog of planetary regoliths

Y. Grynko, Y. Shkuratov, S. Alhaddad, J. Förstner. Light backscattering from numerical analog of planetary regoliths. In: 16th Europlanet Science Congress 2022, Granada, Spain, 2022.


Far-field Calculation from magnetic Huygens Box Data using the Boundary Element Method

C. Marschalt, D. Schroder, S. Lange, U. Hilleringmann, C. Hedayat, H. Kuhn, D. Sievers, J. Förstner, in: 2022 Smart Systems Integration (SSI), IEEE, 2022

In this publication a novel method for far-field prediction from magnetic Huygens box data based on the boundary element method (BEM) is presented. Two examples are considered for the validation of this method. The first example represents an electric dipole so that the obtained calculations can be compared to an analytical solution. As a second example, a printed circuit board is considered and the calculated far-field is compared to a fullwave simulation. In both cases, the calculations for different field integral equations are under comparison, and the results indicate that the presented method performs very well with a combined field integral equation, for the specified problem, when only magnetic Huygens box data is given.


Light Scattering by Large Densely Packed Clusters of Particles

Y. Grynko, Y. Shkuratov, S. Alhaddad, J. Förstner, in: Springer Series in Light Scattering - Volume 8: Light Polarization and Multiple Scattering in Turbid Media, Springer International Publishing, 2022

We review our results of numerical simulations of light scattering from different systems of densely packed irregular particles. We consider spherical clusters, thick layers and monolayers with realistic topologies and dimensions much larger than the wavelength of light. The maximum bulk packing density of clusters is 0.5. A numerically exact solution of the electromagnetic problem is obtained using the Discontinuous Galerkin Time Domain method and with application of high- performance computing. We show that high packing density causes light localization in such structures which makes an impact on the opposition phenomena: backscattering intensity surge and negative linear polarization feature. Diffuse multiple scattering is significantly reduced in the case of non-absorbing particles and near-field interaction results in a percolation-like light transport determined by the topology of the medium. With this the negative polarization feature caused by single scattering gets enhanced if compared to lower density samples. We also confirm coherent double scattering mechanism of negative polarization for light scattered from dense absorbing slabs. In this case convergent result for the scattering angle polarization dependency at backscattering can be obtained for a layer of just a few tens of particles if they are larger than the wavelength.


Negative polarization of light at backscattering from a numerical analog of planetary regoliths

Y. Grynko, Y. Shkuratov, S. Alhaddad, J. Förstner, Icarus (2022), 384, pp. 115099

We model negative polarization, which is observed for planetary regoliths at backscattering, solving a full wave problem of light scattering with a numerically exact Discontinuous Galerkin Time Domain (DGTD) method. Pieces of layers with the bulk packing density of particles close to 0.5 are used. The model particles are highly absorbing and have irregular shapes and sizes larger than the wavelength of light. This represents a realistic analog of low-albedo planetary regoliths. Our simulations confirm coherent backscattering mechanism of the origin of negative polarization. We show that angular profiles of polarization are stabilized if the number of particles in a layer piece becomes larger than ten. This allows application of our approach to the negative polarization modeling for planetary regoliths.


Broadband optical Ta2O5 antennas for directional emission of light

H. Farheen, L. Yan, V. Quiring, C. Eigner, T. Zentgraf, S. Linden, J. Förstner, V. Myroshnychenko, Optics Express (2022), 30(11), pp. 19288

Highly directive antennas with the ability of shaping radiation patterns in desired directions are essential for efficient on-chip optical communication with reduced cross talk. In this paper, we design and optimize three distinct broadband traveling-wave tantalum pentoxide antennas exhibiting highly directional characteristics. Our antennas contain a director and reflector deposited on a glass substrate, which are excited by a dipole emitter placed in the feed gap between the two elements. Full-wave simulations in conjunction with global optimization provide structures with an enhanced linear directivity as high as 119 radiating in the substrate. The high directivity is a result of the interplay between two dominant TE modes and the leaky modes present in the antenna director. Furthermore, these low-loss dielectric antennas exhibit a near-unity radiation efficiency at the operational wavelength of 780 nm and maintain a broad bandwidth. Our numerical results are in good agreement with experimental measurements from the optimized antennas fabricated using a two-step electron-beam lithography, revealing the highly directive nature of our structures. We envision that our antenna designs can be conveniently adapted to other dielectric materials and prove instrumental for inter-chip optical communications and other on-chip applications.


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Prof. Dr. Jens Förstner

Theoretische Elektrotechnik (TET)

Jens Förstner
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