Biomedical Engineering Reference
In-Depth Information
Figure 14.10
The NRR as a function of the wavelength,
λ
, for the spherical
Ag-basedpassive(a)andsuper-resonant(b)CNP.Theresultsareshownfor
both
z
-and
x
-orientedEHDs,andinallcases,theEHDislocatedinthesilica
nano-core at 12 nm along the positive
x
-axis.
the investigations, the EHD was taken to be either
z
or
x
-oriented,
and is placed along the positive
x
-axis with the coordinates (
r
s
,
θ
s
=
90
◦
,
φ
s
=
0
◦
). Moreover, the magnitude of the dipole moment was
setequalto
p
=
5nA-m.Thepresentresultsrepresentasummaryof
[14-16]; for further details please refer to these works.
14.3.4.1 NRR results
λ
Figure 14.10 shows the NRR as a function of the wavelength,
,for
the Ag-based CNP for (a)
κ
=
0 (corresponding to a lossless and
passiveCNP)and(b)
κ
=−
0.245 (correspondingtoanactiveCNP).
In both of the cases, the results for the two EHD orientations are
shown, and the EHD is located in region 1 at
r
s
=
12 nm.
For a given value of
κ
, identical NRRs result in the depicted
wavelength range for the two EHD orientations. For the active CNP,
κ
=−
0.245wasfoundtoleadtothelargestNRRvalue(around72.5
dB at 502.1 nm) for both EHD orientations. This enhanced behavior
corresponds to the super-resonant state found in the plane wave
case, in which the NRR values are significantly increased and the
intrinsic plasmonic losses are vastly overcome, relative to the case
of the corresponding passive Ag-based CNP for which largest NRR
is around 17 dB (at 502.7 nm), see Fig. 14.10a. Thus, as in the case
of a plane wave excited CNP discussed previously, the gain inclusion
helpsovercomingthelossesintheCNPwhenitisexcitedbyanEHD.
In addition, it thus leads to enhanced resonance phenomena with
