Environmental Engineering Reference
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Fig. 7.13 The spectral enhancement factor comparisons. The enhancement factor by the cavity
(Cav) coupled with the DC-MS sphere is drawn with red straight line. The algebraic summation
of the enhancement factor by the uncoupled single cavity and that by the uncoupled single DC-
MS sphere is plotted with black dash line. The near-field distributions at the wavelengths denoted
with the green arrows are shown in the inset. The metal dissipation ratio of the cavity is defined
as the metal loss of the coupled cavity over that of the uncoupled one. Likewise, the metal
dissipation ratio of the DC-MS sphere is defined as the metal loss of the coupled DC-MS sphere
over that of the uncoupled one. 2011 OSA; Ref. [ 33 ]
observably smaller than the enhancement factor by the cavity coupled with the
DC-MS sphere at long wavelengths ranging from 620 to 800 nm. The coherent
interplay between the cavity and the DC-MS sphere is undoubtedly confirmed by
the result. Then, we analyze the metal dissipation ratio defined as the metal loss of
the coupled concentrator over that of the uncoupled one. The inset of Fig. 7.13
shows that the metal dissipation ratio of the DC-MS sphere is substantially larger
than that of the cavity. The evanescent SPPs from the inner surface of metallic
cavity sufficiently penetrate the DC-MS sphere inducing stronger local plasmon
resonance as well as larger metallic loss. Thus, the DC-MS sphere becomes more
effective concentrator when it is coupled with the cavity. Finally, we discuss the
coupling modes in the hybrid plasmonic system. Calculated by Eq. ( 7.37 ),
Fig. 7.14 depicts a polarization charge distribution on the surface of the cavity,
indicating a bonding and antibonding coupling modes in the hybrid system. The
bonding modes at 620 and 750 nm have a denser charge distribution if the distance
between the cavity and the shell surfaces becomes closer. However, the anti-
bonding mode at 650 nm reverses the polarity of the polarization charge when the
face-to-face distance approaches the minimum. The near fields of the bonding
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