Biomedical Engineering Reference
In-Depth Information
Figure 4.3
Planar chiral metamaterial made of 3D gold nanohelices. (A)
Focused-ion-beam(FIB)cutofapolymerstructurepartiallyfilledwithgold
by electroplating. (B) Oblique view of a left-handed helix structure after
removal of the polymer by plasma etching. (C) Top-view image reveals the
circular cross-section of the helices and homogeneity on a larger scale. The
lattice constant of the square lattice is
a
=
2
μ
m. Reprinted from Ref. [23]
with permission from AAAS.
helical cavities in a photoresist with subsequent deposition of gold
insidethese holes.
In any case, known mixing rules (see, e.g., [53, 71]) can be
usedtoelaboratethemacroscopicdescriptionfromthemicroscopic
one.
The application of this procedure to chiral metamaterials with
chaotically situated nanoparticles, with taking (4.10) into account,
results in the followingconstitutiveequations:
D
=
ε
E
+
i
κ
H
,
B
=
μ
H
−
i
κ
E
,
(4.12)
where
κ
is the chirality parameter,
ε
is the permittivity, and
μ
is the
permeability of a chiral medium. Often, the constitutive Eqs. (4.12)
are written as
=
ε
E
rot
E
,
B
=
μ
H
rot
H
,
˜
˜
+
β
+
β
D
(4.13)
