@article{43018,
  author       = {{Alhaddad, Samer and Förstner, Jens and Grynko, Yevgen}},
  issn         = {{0022-4073}},
  journal      = {{Journal of Quantitative Spectroscopy and Radiative Transfer}},
  keywords     = {{tet_topic_scattering}},
  publisher    = {{Elsevier BV}},
  title        = {{{Numerical study of light backscattering from layers of absorbing irregular particles larger than the wavelength}}},
  doi          = {{10.1016/j.jqsrt.2023.108557}},
  volume       = {{302}},
  year         = {{2023}},
}

@article{31574,
  abstract     = {{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.}},
  author       = {{Grynko, Yevgen and Shkuratov, Yuriy and Alhaddad, Samer and Förstner, Jens}},
  issn         = {{0019-1035}},
  journal      = {{Icarus}},
  keywords     = {{tet_topic_scattering}},
  pages        = {{115099}},
  publisher    = {{Elsevier BV}},
  title        = {{{Negative polarization of light at backscattering from a numerical analog of planetary regoliths}}},
  doi          = {{10.1016/j.icarus.2022.115099}},
  volume       = {{384}},
  year         = {{2022}},
}

@inbook{33466,
  abstract     = {{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.}},
  author       = {{Grynko, Yevgen and Shkuratov, Yuriy and Alhaddad, Samer and Förstner, Jens}},
  booktitle    = {{Springer Series in Light Scattering - Volume 8: Light Polarization and Multiple Scattering in Turbid Media}},
  editor       = {{Kokhanovsky, Alexander}},
  isbn         = {{9783031102974}},
  issn         = {{2509-2790}},
  keywords     = {{tet_topic_scattering}},
  publisher    = {{Springer International Publishing}},
  title        = {{{Light Scattering by Large Densely Packed Clusters of Particles}}},
  doi          = {{10.1007/978-3-031-10298-1_4}},
  volume       = {{8}},
  year         = {{2022}},
}

@article{29075,
  abstract     = {{We study a double-scattering coherent mechanism of negative polarization (NP) near opposition that is observed for powder-like surfaces. The problem is solved numerically for absorbing structures with irregular constituents, cubes, spheres, and ellipsoids larger than the wavelength of incident light. Our simulations show that double scattering between two random irregular particles shows weak NP. Adding one more particle significantly increases the relative contribution of double scattering which enhances NP. Simulations with regular shapes and controlled geometric parameters show that the interference mechanism is sensitive to the geometry of the scattering system and can also result in no polarization or even strong enhancement of positive polarization at backscattering.}},
  author       = {{Alhaddad, Samer and Grynko, Yevgen and Farheen, Henna and Förstner, Jens}},
  issn         = {{0146-9592}},
  journal      = {{Optics Letters}},
  keywords     = {{tet_topic_scattering}},
  number       = {{1}},
  pages        = {{58}},
  title        = {{{Numerical analysis of the coherent mechanism producing negative polarization at backscattering from systems of absorbing particles}}},
  doi          = {{10.1364/ol.444953}},
  volume       = {{47}},
  year         = {{2022}},
}

@inproceedings{34136,
  author       = {{Grynko, Yevgen and Shkuratov, Yuriy and Alhaddad, Samer and Förstner, Jens}},
  keywords     = {{tet_topic_scattering}},
  location     = {{Granada, Spain}},
  publisher    = {{Copernicus GmbH}},
  title        = {{{Light backscattering from numerical analog of planetary regoliths}}},
  doi          = {{10.5194/epsc2022-151}},
  year         = {{2022}},
}

@inbook{21587,
  abstract     = {{Solving partial differential equations on unstructured grids is a cornerstone of engineering and scientific computing. Nowadays, heterogeneous parallel platforms with CPUs, GPUs, and FPGAs enable energy-efficient and computationally demanding simulations. We developed the HighPerMeshes C++-embedded Domain-Specific Language (DSL) for bridging the abstraction gap between the mathematical and algorithmic formulation of mesh-based algorithms for PDE problems on the one hand and an increasing number of heterogeneous platforms with their different parallel programming and runtime models on the other hand. Thus, the HighPerMeshes DSL aims at higher productivity in the code development process for multiple target platforms. We introduce the concepts as well as the basic structure of the HighPerMeshes DSL, and demonstrate its usage with three examples, a Poisson and monodomain problem, respectively, solved by the continuous finite element method, and the discontinuous Galerkin method for Maxwell’s equation. The mapping of the abstract algorithmic description onto parallel hardware, including distributed memory compute clusters, is presented. Finally, the achievable performance and scalability are demonstrated for a typical example problem on a multi-core CPU cluster.}},
  author       = {{Alhaddad, Samer and Förstner, Jens and Groth, Stefan and Grünewald, Daniel and Grynko, Yevgen and Hannig, Frank and Kenter, Tobias and Pfreundt, Franz-Josef and Plessl, Christian and Schotte, Merlind and Steinke, Thomas and Teich, Jürgen and Weiser, Martin and Wende, Florian}},
  booktitle    = {{Euro-Par 2020: Parallel Processing Workshops}},
  isbn         = {{9783030715922}},
  issn         = {{0302-9743}},
  keywords     = {{tet_topic_hpc}},
  title        = {{{HighPerMeshes – A Domain-Specific Language for Numerical Algorithms on Unstructured Grids}}},
  doi          = {{10.1007/978-3-030-71593-9_15}},
  year         = {{2021}},
}

@article{24788,
  author       = {{Alhaddad, Samer and Förstner, Jens and Groth, Stefan and Grünewald, Daniel and Grynko, Yevgen and Hannig, Frank and Kenter, Tobias and Pfreundt, Franz‐Josef and Plessl, Christian and Schotte, Merlind and Steinke, Thomas and Teich, Jürgen and Weiser, Martin and Wende, Florian}},
  issn         = {{1532-0626}},
  journal      = {{Concurrency and Computation: Practice and Experience}},
  keywords     = {{tet_topic_hpc}},
  pages        = {{e6616}},
  title        = {{{The HighPerMeshes framework for numerical algorithms on unstructured grids}}},
  doi          = {{10.1002/cpe.6616}},
  year         = {{2021}},
}

@article{17803,
  abstract     = {{We numerically simulate multiple light scattering in discrete disordered media represented by large clusters of irregular non-absorbing particles. The packing density of clusters is 0.5. With such conditions diffuse scattering is significantly reduced and light transport follows propagation channels that are determined by the particle size and topology of the medium. This kind of localization produces coherent backscattering intensity surge and enhanced negative polarization branch if compared to lower density samples.}},
  author       = {{Grynko, Yevgen and Shkuratov, Yuriy and Förstner, Jens}},
  issn         = {{0022-4073}},
  journal      = {{Journal of Quantitative Spectroscopy and Radiative Transfer}},
  keywords     = {{tet_topic_scattering}},
  pages        = {{107234}},
  title        = {{{Light backscattering from large clusters of densely packed irregular particles}}},
  doi          = {{10.1016/j.jqsrt.2020.107234}},
  volume       = {{255}},
  year         = {{2020}},
}

@article{8872,
  abstract     = {{We consider light scattering from a new type of model particle whose shape is represented in the form of a generalized ellipsoid having N foci, where N is greater than two. Such particles can be convex as well as concave. We use the geometrical optics approximation to study the light scattering from 3-foci particles. Non-zero elements of the scattering matrix are calculated for ensembles of randomly oriented independent transparent particles, m = n + i0. Several internal reflection orders are considered separately. It was found that the transmission-transmission (TT) and transmission-reflectance-transmission (TRT) components dominate in the formation of intensity of scattered light at large and small phase angles, respectively. We found a significant role of the total internal reflections of the TRT in the middle portion of the phase angle range. The main factors in the formation of positive linear polarization are the R and TRT component. The TT component is responsible for the formation of negative polarization branch at large phase angles.}},
  author       = {{Stankevich, Dmitriy and Hradyska, Larissa and Shkuratov, Yuriy and Grynko, Yevgen and Videen, Gorden and Förstner, Jens}},
  issn         = {{0022-4073}},
  journal      = {{Journal of Quantitative Spectroscopy and Radiative Transfer}},
  keywords     = {{tet_topic_scattering}},
  pages        = {{49}},
  title        = {{{Light scattering by 3-Foci convex and concave particles in the geometrical optics approximation}}},
  doi          = {{10.1016/j.jqsrt.2019.04.016}},
  volume       = {{231}},
  year         = {{2019}},
}

@inproceedings{3588,
  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}},
  author       = {{Afzal, Ayesha and Schmitt, Christian and Alhaddad, Samer and Grynko, Yevgen and Teich, Jürgen and Förstner, Jens and Hannig, Frank}},
  booktitle    = {{Proceedings of the 29th Annual IEEE International Conference on Application-specific Systems, Architectures and Processors (ASAP)}},
  isbn         = {{978-1-5386-7479-6}},
  keywords     = {{tet_topic_hpc}},
  pages        = {{49--56}},
  title        = {{{Solving Maxwell's Equations with Modern C++ and SYCL: A Case Study}}},
  doi          = {{10.1109/ASAP.2018.8445127}},
  year         = {{2018}},
}

@inproceedings{4581,
  author       = {{Grynko, Yevgen and Förstner, Jens}},
  booktitle    = {{2018 IEEE 17th International Conference on Mathematical Methods in Electromagnetic Theory (MMET)}},
  isbn         = {{9781538654385}},
  keywords     = {{tet_topic_numerics, tet_topic_shg}},
  publisher    = {{IEEE}},
  title        = {{{Application of the Discontinuous Galerkin Time Domain Method in Nonlinear Nanoplasmonics}}},
  doi          = {{10.1109/mmet.2018.8460261}},
  year         = {{2018}},
}

@article{4324,
  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.}},
  author       = {{Grynko, Yevgen and Shkuratov, Yuriy and Förstner, Jens}},
  issn         = {{0146-9592}},
  journal      = {{Optics Letters}},
  keywords     = {{tet_topic_scattering}},
  number       = {{15}},
  pages        = {{3562}},
  publisher    = {{The Optical Society}},
  title        = {{{Intensity surge and negative polarization of light from compact irregular particles}}},
  doi          = {{10.1364/ol.43.003562}},
  volume       = {{43}},
  year         = {{2018}},
}

@inproceedings{1588,
  abstract     = {{The exploration of FPGAs as accelerators for scientific simulations has so far mostly been focused on small kernels of methods working on regular data structures, for example in the form of stencil computations for finite difference methods. In computational sciences, often more advanced methods are employed that promise better stability, convergence, locality and scaling. Unstructured meshes are shown to be more effective and more accurate, compared to regular grids, in representing computation domains of various shapes. Using unstructured meshes, the discontinuous Galerkin method preserves the ability to perform explicit local update operations for simulations in the time domain. In this work, we investigate FPGAs as target platform for an implementation of the nodal discontinuous Galerkin method to find time-domain solutions of Maxwell's equations in an unstructured mesh. When maximizing data reuse and fitting constant coefficients into suitably partitioned on-chip memory, high computational intensity allows us to implement and feed wide data paths with hundreds of floating point operators. By decoupling off-chip memory accesses from the computations, high memory bandwidth can be sustained, even for the irregular access pattern required by parts of the application. Using the Intel/Altera OpenCL SDK for FPGAs, we present different implementation variants for different polynomial orders of the method. In different phases of the algorithm, either computational or bandwidth limits of the Arria 10 platform are almost reached, thus outperforming a highly multithreaded CPU implementation by around 2x.}},
  author       = {{Kenter, Tobias and Mahale, Gopinath and Alhaddad, Samer and Grynko, Yevgen and Schmitt, Christian and Afzal, Ayesha and Hannig, Frank and Förstner, Jens and Plessl, Christian}},
  booktitle    = {{Proc. Int. Symp. on Field-Programmable Custom Computing Machines (FCCM)}},
  keywords     = {{tet_topic_hpc}},
  publisher    = {{IEEE}},
  title        = {{{OpenCL-based FPGA Design to Accelerate the Nodal Discontinuous Galerkin Method for Unstructured Meshes}}},
  doi          = {{10.1109/FCCM.2018.00037}},
  year         = {{2018}},
}

@article{3523,
  abstract     = {{We numerically simulate the circular polarization ratio of the radar signal backscattered from a large-grain cometary coma and compare the simulation results with the radar measurements for seven comets. We apply the discrete dipole approximation method and a model of random irregular particles. Our results confirm water ice composition of the cm-sized chunks detected by the NASA Deep Impact space probe in the vicinity of the nucleus of Comet 103P/Hartley 2. The index of the power-law size distribution in this case can be constrained to the range n ≈ 3.3–4.3. For the other considered comets the circular polarization ratio can be reproduced with variations of the power index between 2 and 5.}},
  author       = {{Dogra, Shraddha and Grynko, Yevgen and Zubko, Evgenij and Förstner, Jens}},
  issn         = {{0004-6361}},
  journal      = {{Astronomy & Astrophysics}},
  keywords     = {{tet_topic_scattering}},
  pages        = {{A20}},
  publisher    = {{EDP Sciences}},
  title        = {{{Radar backscattering from a large-grain cometary coma: numerical simulation}}},
  doi          = {{10.1051/0004-6361/201730801}},
  volume       = {{608}},
  year         = {{2017}},
}

@inbook{3836,
  abstract     = {{We apply the Discontinuous Galerkin Time Domain (DGTD) method for numerical simulations of the second harmonic generation from various metallic nanostructures. A Maxwell–Vlasov hydrodynamic model is used to describe the nonlinear effects in the motion of the excited free electrons in a metal. The results are compared with the corresponding experimental measurements for split-ring resonators and plasmonic gap antennas.}},
  author       = {{Grynko, Yevgen and Förstner, Jens}},
  booktitle    = {{Recent Trends in Computational Photonics}},
  editor       = {{Agrawal, Arti}},
  isbn         = {{9783319554372}},
  issn         = {{0342-4111}},
  keywords     = {{tet_topic_numerics, tet_topic_shg, tet_topic_meta}},
  pages        = {{261--284}},
  publisher    = {{Springer International Publishing}},
  title        = {{{Simulation of Second Harmonic Generation from Photonic Nanostructures Using the Discontinuous Galerkin Time Domain Method}}},
  doi          = {{10.1007/978-3-319-55438-9_9}},
  year         = {{2017}},
}

@article{35,
  author       = {{Linnenbank, Heiko and Grynko, Yevgen and Förstner, Jens and Linden, Stefan}},
  issn         = {{2047-7538}},
  journal      = {{Light: Science & Applications}},
  keywords     = {{tet_topic_opticalantenna, tet_topic_shg}},
  number       = {{1}},
  pages        = {{e16013}},
  publisher    = {{Springer Nature}},
  title        = {{{Second harmonic generation spectroscopy on hybrid plasmonic/dielectric nanoantennas}}},
  doi          = {{10.1038/lsa.2016.13}},
  volume       = {{5}},
  year         = {{2016}},
}

@article{3834,
  abstract     = {{The problem of light scattering by ice crystals of cirrus clouds is considered in the case of a hexagonal ice plate with different distributions over crystal orientations. The physical-optics approximation based on (E, M)-diffraction theory is compared with two exact numerical methods: the finite difference time domain (FDTD) and the discontinuous Galerkin time domain (DGTD) in order to estimate its accuracy and limits of applicability. It is shown that the accuracy of the physical-optics approximation is estimated as 95% for the averaged backscattering Mueller matrix for particles with size parameter more than 120. Furthermore, the simple expression that allows one to estimate the minimal number of particle orientations required for appropriate spatial averaging has been derived.}},
  author       = {{Konoshonkin, Alexander and Borovoi, Anatoli and Kustova, Natalia and Okamoto, Hajime and Ishimoto, Hiroshi and Grynko, Yevgen and Förstner, Jens}},
  issn         = {{0022-4073}},
  journal      = {{Journal of Quantitative Spectroscopy and Radiative Transfer}},
  keywords     = {{tet_topic_scattering}},
  pages        = {{132--140}},
  publisher    = {{Elsevier BV}},
  title        = {{{Light scattering by ice crystals of cirrus clouds: From exact numerical methods to physical-optics approximation}}},
  doi          = {{10.1016/j.jqsrt.2016.12.024}},
  volume       = {{195}},
  year         = {{2016}},
}

@inproceedings{3840,
  abstract     = {{In the problem of light scattering by ice crystals of cirrus clouds, two exact methods (FDTD – finite difference time domain and DGTD – discontinuous Galerkin time domain) and the physical-optics approximation are used for numerical calculations of the Mueller matrix in the case of ice hexagonal plates and columns. It is shown that for the crystals larger than 10 μm at the wavelength of 0.532 μm the exact methods and physical-optics approximation closely agreed within three diffraction fringes about the centers of the diffraction patterns. As a result, in the case of random orientation of these crystals, the physical-optics approximation provides accuracy 95% for the averaged Mueller matrix.}},
  author       = {{Konoshonkin, Alexander V. and Kustova, Natalia V. and Borovoi, Anatoli G. and Okamoto, H. and Sato, K. and Ishimoto, H. and Grynko, Yevgen and Förstner, Jens}},
  booktitle    = {{22nd International Symposium on Atmospheric and Ocean Optics: Atmospheric Physics}},
  editor       = {{Matvienko, Gennadii G. and Romanovskii, Oleg A.}},
  keywords     = {{tet_topic_scattering}},
  publisher    = {{SPIE}},
  title        = {{{Comparison between the physical-optics approximation and exact methods solving the problem of light scattering by ice crystals of cirrus clouds}}},
  doi          = {{10.1117/12.2248409}},
  year         = {{2016}},
}

@article{3843,
  abstract     = {{We simulate light scattering by random irregular particles that have dimensions much larger than the wavelength of incident light at the size parameter of 𝑋=200 using the discontinuous Galerkin time domain method. A comparison of the DGTD solution for smoothly faceted particles with that obtained with a geometric optics model shows good agreement for the scattering angle curves of intensity and polarization. If a wavelength-scale surface roughness is introduced, diffuse scattering at rough interface results in smooth and featureless curves for all scattering matrix elements which is consistent with the laboratory measurements of real samples.}},
  author       = {{Grynko, Yevgen and Shkuratov, Yuriy and Förstner, Jens}},
  issn         = {{0146-9592}},
  journal      = {{Optics Letters}},
  keywords     = {{tet_topic_scattering}},
  number       = {{15}},
  pages        = {{3491--3493}},
  publisher    = {{The Optical Society}},
  title        = {{{Light scattering by irregular particles much larger than the wavelength with wavelength-scale surface roughness}}},
  doi          = {{10.1364/ol.41.003491}},
  volume       = {{41}},
  year         = {{2016}},
}

@article{3849,
  abstract     = {{The physical optics approximations are derived from the Maxwell equations. The scattered field equations by Kirchhoff, Stratton-Chu, Kottler and Franz are compared and discussed. It is shown that in the case of faceted particles, these equations reduce to a sum of the diffraction integrals, where every diffraction integral is associated with one plane–parallel optical beam leaving a particle facet. In the far zone, these diffraction integrals correspond to the Fraunhofer diffraction patterns. The paper discusses the E-, M- and (E, M)-diffraction theories as applied to ice crystals of cirrus clouds. The comparison to the exact solution obtained by the discontinuous Galerkin time domain method shows that the Kirchhoff diffraction theory is preferable.}},
  author       = {{Konoshonkin, Alexander V. and Kustova, Natalia V. and Borovoi, Anatoli G. and Grynko, Yevgen and Förstner, Jens}},
  issn         = {{0022-4073}},
  journal      = {{Journal of Quantitative Spectroscopy and Radiative Transfer}},
  keywords     = {{tet_topic_scattering}},
  pages        = {{12--23}},
  publisher    = {{Elsevier BV}},
  title        = {{{Light scattering by ice crystals of cirrus clouds: comparison of the physical optics methods}}},
  doi          = {{10.1016/j.jqsrt.2016.05.006}},
  volume       = {{182}},
  year         = {{2016}},
}