Biomedical Engineering Reference
In-Depth Information
Figure 14.14
Single/multipleelectricHertziandipoles(EHDs)illumination
of a CNP. The EHDs are outside the CNP and are represented by the black-
colored circles. Three excitation cases are considered: Case 1 (EHD A), Case
2(EHDA
+
C), and Case 3 (EHD A
+
B
+
C
+
D). Please see the main text for
further explanations.
originofthesecoincidewiththecenteroftheCNP.TheexcitingEHDs
are located symmetrically at positions in the
xy
-plane outside the
CNP,thatis,EHDsAandCareonoppositesidesoftheCNPalongthe
x
-axis,whereasEHDsBandDareonoppositesidesalongthe
y
-axis.
The coordinates of the observation point are (
r
,
θ
,
φ
). The locations
of the EHDs are specified by (
r
s
,
θ
s
=
π/
2) and
φ
s
=
0(EHD
A
),
π/
2(EHD
B
),
π
(EHD
C
)and3
π/
4(EHD
D
).
14.3.5.2 Far-field results
For the following discussion, the EHDs in any of the three excitation
cases, Case 1, 2, or 3, were taken to be
z
-oriented, and the
magnitudes of their dipole moments were assumed identical and
equalto
p
=
5nA-m.TheEHDsarelocatedattheirrespectiveplaces
in the
xy
-plane at a radial distance of
r
s
=
40 nm, see Fig. 14.14 and
the end of Section 14.3.5.1. The quantity NRR from (14.7) has been
generalized to handle the multiple-EHD excitation and will be used
currently to illustrate thefar-field results.
As noted in the beginning of Section 14.3.5 above, the so-called
super-resonant state, which leads to large radiated powers, was
found for
κ
=−
0.245 in the Case 1 excitation [14, 56] (this
likewise being in line with the results reported in Section 14.3.4).
The response of the super-resonant state is illustrated in Fig. 14.15
in which the NRR is shown as a function of the excitation
for
the super-resonant Ag-based CNP. The resonance, resulting in the
λ
