Causality Implications for Absorption by EM Metasurfaces

A causal electromagnetic (EM) metasurface is backed by a lossless substrate and partially absorbs obliquely incoming rays. The integral of the absorbed power along the entire frequency axis is analytically evaluated, and the obtained sum rules indicate the global absorption by such a generic configu...

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Bibliographic Details
Published inNanomaterials (Basel, Switzerland) Vol. 15; no. 11; p. 793
Main Author Valagiannopoulos, Constantinos
Format Journal Article
LanguageEnglish
Published Switzerland MDPI AG 25.05.2025
MDPI
Subjects
Absorption
Boundary conditions
Causality
Damping
Electromagnetism
Interfaces
Inverse design
Lorentz oscillator
Magnetic fields
metasurface
Metasurfaces
Planar structures
Plasma frequencies
Sum rules
Wave propagation
Lorentz oscillator
absorption
causality
metasurface
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Summary:A causal electromagnetic (EM) metasurface is backed by a lossless substrate and partially absorbs obliquely incoming rays. The integral of the absorbed power along the entire frequency axis is analytically evaluated, and the obtained sum rules indicate the global absorption by such a generic configuration. The beneficial influence of the plasma frequency and damping factor on the total absorbance score as well as the opposite effect of the angle of excitation, is noted. An overall lossless behavior at the incidence direction where the propagating waves into the substrate turn into evanescent is identified, once the magnetic field is parallel to the interface. The reported results can be useful in the tailoring of spectrally dependent absorption by a whole class of planar structures and, accordingly, in the forward and inverse design of lossy photonic metasurface setups.
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ISSN:2079-4991
2079-4991
DOI:10.3390/nano15110793