I'm investigating periodic structures with cross-shape metallic antennas embedded within a dielectric (silicon dioxide). I'm wondering if a Wood's anomoly feature/dip will only occur for when metallic structures are on the boundary between 2 dielectrics or whether there would still exist some periodically related phenomena when these metallic structures are far enough into the thick dielectric layer where they are essentially surrounded by a homogeneous medium. They are being investigated for their absorption properties with the addition of a ground plane.
Let us understand under Wood's anomaly a resonance with a plasmon propagating along a metal-dielectric interface. Such resonance will exist whatever the position of the metal surface. The spectral position of the plasmon resonance (and the corresponding dip) depends however on the plasmon propagation constant and the latter is a function of the thickness of the dielectric layer.
You can find more information about surface plasmons in the following book:
https://openlibrary.org/books/OL2737031M/Surface_plasmons_on_smooth_and_rough_surfaces_and_on_gratings
Normally I would also follow this path, but in the case for this system I am looking at THz resonances of thin, isolated, periodic Aluminium crosses which are sat atop a thick dielectric substrate and surrounded by air (so there is no metal-dielectric border as such). Additionally, I don't think that in this case a (propagating) SPR would be present so I wonder which of the 2 dielectrics I use to calculate the (potential) Wood's anomaly resonance wavelengths. Underneath the thick dielectric substrate is a flat reflective aluminium ground plane to provide a Fabry-Perot type effect.
Working with frequency selective surface (FSS) or metasurface structures with dielectric substrate/superstrate, Wood's anomaly occurs for frequencies higher than the 1st resonant frequency of the structure, (especially when the incident angle change from normal to grazing.) Note Wood's anomaly is not grating lobes. They are caused by the surface wave propagating on the dielectric surface. (please check the FSS Books by Ben Monk and T.K. Wu on this subject).
Three good references on Wood's anomaly;
1) RJ Luebbers and BA Munk, Some effects of dielectric loading on periodic slot arrays, IEEE Trans., vol. AP-26, (4), pp. 536-542, 1978.
2) J. Blick, et. al., Inductive grids in the region of diffraction anomalies, theory, experiment, and applications, IEEE Trans., vol. MTT-28, (10), pp. 1119-1125, 1980.
3) A. Hessel and AA Oliner, A new theory of Wood's anomalis on optical gratings, Appl. Opt., vol. 4, (10) pp. 1275-1297, 1965.
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