Biomedical Engineering Reference
In-Depth Information
Figure 4.2
The schematic image of chiral meta-atoms used to fabricate
chiral metamaterials: (a) the cylindrical spirals, (b) the rings with
orthogonal linear ends (
particles), and (c) the broken wires with linear
parts along the coordinate axes. The signs “
+
”and“
−
” denote the right and
left chiral elements, correspondingly [43].
rings with linear horns directed normally to the ring plane but in
oppositedirections.Theelementsdifferbythehornsbenddirection
at the split of the ring. When moving along the wire upwards, in the
first element, the right rotation takes place by passing the ring, and
inthesecondelement,theleftrotationdoes.Linearpartsofthethird
pair of the chiral particles (Fig. 4.2a) are directed along the axes
of the left and right Cartesian coordinate system, correspondingly.
These elements are further simplification of previous ones and can
have asimpler technological realization.
To understand the optics of chiral particles, let us now consider
(seee.g.[19])whathappensifanelectromagneticwaveincidentson
a small conducting spiral (Fig. 4.2a). Let the field in the area of the
spiralhasthecomponents
E
z
and
H
z
,alongthespiralaxis.Then,the
longitudinal (along the spiral axis) component of the electric dipole
moment
d
z
is formed both by the component
E
z
of the electric field
producing current along the spiral axis and the component
H
z
of
the magnetic field penetrating the spiral rings and inducing the ring
current with longitudinal component. Thus,
d
z
=
α
EE
E
z
+
α
EH
H
z
,
(4.8)
where
α
EE
is the regular electric polarizability of the spiral, and
α
EH
is so-called electromagnetic cross-polarizability of the particle.
Analogously, the longitudinal component of the spiral magnetic
dipole moment
m
z
is formed by the ring electric current produced
by the magnetic field penetrating the spiral and the ring current
