Exploring the interaction of light with materials periodically structured in space and time is intellectually rewarding and, simultaneously, a computational challenge. Appropriate computational tools are urgently needed to explore how such upcoming photonic materials can control light on demand. Here, we introduce a semi-analytical approach based on the transition matrix (also known as T-matrix) to analyze the optical response of a spatiotemporal metasurface. The metasurface consists of a periodic arrangement of time-varying scattering particles. In our approach, we depart from an individual scatterer's T-matrix to construct the effective T-matrix of the metasurface. From that effective T-matrix, all observable properties can reliably be predicted. We verify our semi-analytical approach with full-wave numerical simulations. We demonstrate a speed-up with our approach by a factor of more than 500 compared to a finite-element simulation. Finally, we exemplify our approach by studying the effect of time modulation on a Huygens' metasurface and discuss some emerging observable features.
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http://dx.doi.org/10.1364/OE.476035 | DOI Listing |
Heliyon
August 2024
Department of Mathematics, Bangabandhu Sheikh Mujibur Rahman Science and Technology University, Gopalganj 8100, Bangladesh.
This paper revisits the distribution of thermodynamic variables within initial protoplanets formed via gravitational instability (GI) across a broad mass spectrum ranging from (where denotes 1 Jupiter mass, equal to g), using the Homotopy Analysis Method (HAM), a novel approach in this context. Concerning heat transfer within the protoplanets, consideration is given to the convective mode. Our findings reveal a noteworthy alignment between the results obtained via the HAM, utilizing only the first four terms (third approximation), and numerical outcomes.
View Article and Find Full Text PDFSensors (Basel)
December 2024
School of Instrumentation Science and Engineering, Harbin Institute of Technology, Harbin 150001, China.
The magnetic acceleration noise (MAN) that stems from the eddy current dissipation of a test mass (TM) serves as an important source of noise for space inertial sensors. Given the problem that the eddy current dissipation magnetic acceleration noise (ECDMAN) of a cubic TM defies analytical solutions, an analytical model of ECDMAN for a spherical TM, which has the same volume as the cubic TM, is systematically derived on the basis of the principles of electromagnetism and the fluctuation-dissipation theorem, and this model can be used as an approximate analytical model for the evaluation of this noise term. Based on the approximate analytical model, with the TM of the LISA Pathfinder (LPF) as the research object, this paper obtains a modification coefficient using the approach of combining the analytical method with the finite element method (FEM), and establishes a semi-analytical model of ECDMAN for the cubic TM.
View Article and Find Full Text PDFMicroscopes generally achieve better 2D imaging compared to 3D, and super-resolution microscopes often aggravate such axial-lateral resolution mismatch. A prime example is vortex phase-based stimulated emission depletion (STED) fluorescence microscopy, which only narrows the point-spread function laterally, thereby increasing the point-spread function (PSF) anisotropy. In this study, we developed a semi-analytical theory based on the Nijboer-Zernike expansion, developed a set of metrics and performed experiments to establish the merits of the alternative, bivortex phase-based, coherent-hybrid STED.
View Article and Find Full Text PDFEnviron Sci Technol
December 2024
Department of Geosciences, University of Tübingen, Schnarrenbergstraße 94-96, Tübingen 72076, Germany.
Redistribution of pollutants between different solid phases occurs frequently in field and laboratory settings. Examples include the input of urban particles carrying pollutants into soils or rivers with suspended particles or passive sampling. Since multiple mass transfer mechanisms are involved and natural particles typically are very heterogeneous, modeling of sorption/desorption kinetics is challenging.
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