Biomedical Engineering Reference
In-Depth Information
strongest excitations for the
x
-oriented EHD are those just outside
the CNPs.
TherelativeinsensitivityoftheverylargeNRRvaluestotheEHD
location in the interior and the immediate exterior of the super-
resonant CNPs indicates that they would be good candidates for a
highly localized nano-sensor. By having the CNP tuned to a dipole
sourceneartoit,thepowerreachingthefarfieldwillbesignificantly
amplified. Moreover, the large field localization near to the CNP, cf.,
Fig. 14.11a and 14.11b, indicates that its performance as a nano-
antennais very good.
Although the work in this section was devoted to active CNPs
consisting of a 24 nm radius silica nano-core radius covered
with a 6 nm thick silver nano-shell, the overall conclusions on
their performance characteristics qualifying them as elements for
localized nano-sensors and nano-antennas also hold true for a
number of other active CNP configurations. As a brief illustration
of this point, we note that two additional active Ag-based CNP
configurations were studied: one in which the silica nano-core
radius was set to 16 nm, with the plasmonic layer thickness being
set to 4 nm, and the other in which the silica nano-core radius was
set to 8 nm, with the plasmonic layer thickness being set to 2 nm. In
bothcases,theparameter
κ
wastunedtoachievethemaximumNRR
values, and it was found that they both lead to approximately the
same peak NRR values as the currently examined 6 nm thick silver
nano-shell. Nonetheless, as one might expect, the optimal value of
the parameter
κ
leading to the super-resonant behavior was found
to increase as the active CNP size was decreased, that is, more gain
isneededtoachievethesuper-resonantstateforsmalleractiveCNP
configurations.
14.3.5
Jamming Effects of Active CNPs for Single and
Multiple EHD Excitations
Apartfromtheabove-reportedsuper-resonantpropertiesofspecific
active CNPs, in which the power radiated by the EHD is significantly
enhanced, there are additional interesting results when the EHD is
locatedoutsidetheCNPs.In[14],itwasdemonstratedthatidentical
CNPs can lead to large enhancements as well as to large reductions
