Biomedical Engineering Reference
In-Depth Information
Figure 12.4
(a) Vortex-EELS scattering spectrum for a split ring resonator
structure in gold at the point of maximum scattering in the middle of the
ring. (b-d) Vortex-EELS map of the same split ring resonator at the energy
values marked in part (a).
12.4.4
Probing the Magnetic Plasmon
The generation of vortex electron beams opens up exciting
possibilities in probing the magnetic response of nanostructures,
with the goal of improving our understanding of microscopic
magnetic contributions to their optical response. Figure 12.4 shows
an example calculation given for a split ring resonator structure
in gold, with the same dimensions as Figure 12.3. As expected,
the center of the ring, with the highest magnetic contribution to
the local density of optical states, shows the greatest scattering at
the magnetic plasmon resonance of 0.863 eV. This scattering profile
was calculated in the same way as Figure 12.3, except for the use of
a lineof magnetic dipole sources insteadof electric dipole sources.
From a practical point-of-view, it is interesting to note that
the scattering probability seen here is comparable in magnitude
to that of regular EELS featured in Figure 12.3. Therefore, it is
reasonable to expect that vortex-EELS may be demonstrated in
