Biomedical Engineering Reference
In-Depth Information
exceed absorption. The contribution from
CD
sca
becomes significant
at electrodynamic resonances. In an isotropic chiral molecular
medium, the constitutiverelations are [40]:
D
=
ε
E
+
i
ξ
B
,
(1.2)
B
H
=
μ
+
i
ξ
E
.
(1.3)
where
ξ
is introduced as a chiral parameter. Solving the coupled
Maxwell's equations with constitutiverelations of achiral medium,
c
∂
B
1
∇×
E
=−
∂
t
,
c
∂
D
1
∇×
H
=
∂
t
,
∇·
D
=
0,
∇×
B
=
0,
(1.4)
weobtain
E
H
E
H
.
=
i
c
−
i
ξ
1
∇×
(1.5)
2
−
ε
−
ξ
−
i
ξ
We will see that the degeneracy between RCP and LCP is broken by
finding eigenvalues of the matrix in Eq. (1.5),
k
k
−
ξ
+
ε
+
ξ
=
c
2
.
(1.6)
−
ξ
+
ε
+
ξ
2
Therefore, those light beams will propagate with different propaga-
tion constants. The difference between the propagation constants,
k
+
and
k
−
, results from the chiral parameter
ξ
of a chiral medium.
Generally speaking, it will shift electromagnetic resonances and
influence the strength of absorption and scattering. A CD signal
with an electrodynamic origin can be identified from the spectra.
This process is an interplay strongly dependent on the geometric
parameters such as the size of the structure and the thickness
of shells, and the dielectric functions of component materials. In
Section 1.4, a Mie solution incorporating a chiral parameter will be
used to solve the light scattering problem of multilayer core-shell
structures [6]. Multipole vector harmonics are included to address
this scattering problem [7].
