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Abnormal enhancement of electric field inside a thin permittivity-near-zero object in free space
It is found that the electric field can be enhanced strongly inside a
permittivity-near-zero object in free space, when the transverse cross section
of the object is small and the length along the propagation direction of the
incident wave is large enough as compared with the wavelength. The physical
mechanism is explained in details. The incident electromagnetic energy can only
flow almost normally through the outer surface into or out of the
permittivity-near-zero object, which leads to large energy stream density and
then strong electric field inside the object. Meanwhile, the magnetic field
inside the permittivity-near-zero object may be smaller than that of the
incident wave, which is also helpful for enhancing the electric field. Two
permittivity-near-zero objects of simple shapes, namely, a thin cylindrical
shell and a long thin rectangular bar, are chosen for numerical illustration.
The enhancement of the electric field becomes stronger when the
permittivity-near-zero object becomes thinner. The physical mechanism of the
field enhancement is completely different from the plasmonic resonance
enhancement at a metal surface
Squeezing electromagnetic energy with a dielectric split ring inside a permeability-near-zero metamaterial
A novel electromagnetic energy squeezing mechanism is proposed based on the
special properties of permeability-near-zero metamaterials. Nearly no energy
stream can enter a conventional dielectric region positioned inside a
permeability-near-zero material. When a source is surrounded by a dielectric
split ring (encloser with a gap opened), the electromagnetic energy generated
by the source is forced to propagate through the gap. When the gap is narrow,
the energy stream density becomes very large and makes the magnetic field
enhanced drastically in the gap. The narrow gap can be long and bended. This
provides us a method to obtain strong magnetic field without using resonance
enhancement.Comment: 17pages, 4 figure
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