Sub-Wavelength Focusing in Inhomogeneous Media with a Metasurface Near Field Plate

Overcoming the diffraction limit, which enables focusing much less than the wavelength, requires tailoring the evanescent spectrum of an aperture’s field distribution. We model and simulate a corrugated near field plate, which can generate a sub-wavelength focus in inhomogeneous background media. Al...

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Bibliographic Details
Published in:Sensors (Basel, Switzerland) Switzerland), 2019-10, Vol.19 (20), p.4534
Main Authors: Strikwerda, Andrew C., Sleasman, Timothy, Anderson, William, Awadallah, Ra’id
Format: Article
Language:English
Subjects:
Ablation
Corrugated plates
corrugated surface
Design
diffraction limit
evanescent spectrum
finite element method
Geometry
Inhomogeneous media
Magnetic fields
Magnetic resonance imaging
metasurface
Metasurfaces
near field plates
Near fields
sensing
sub-wavelength focusing
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Summary:Overcoming the diffraction limit, which enables focusing much less than the wavelength, requires tailoring the evanescent spectrum of an aperture’s field distribution. We model and simulate a corrugated near field plate, which can generate a sub-wavelength focus in inhomogeneous background media. All reactive coupling, between the metasurface near field plate and the focusing domain and among the corrugations in the metasurface, is taken into consideration with the finite element method, which we solve in combination with a constraint to generate a desired focus. Various geometries for the near field plate are considered and we demonstrate that the proposed method can effectively create a deeply sub-wavelength focus within a layered medium having properties resembling brain tissue. Such a device could find use as a detector of biological signals or for hyperthermic treatment near the skin surface.
ISSN:1424-8220
1424-8220
DOI:10.3390/s19204534