The interactions of silver nanorings with polarized optical wave are numerically studied. If the resonant conditions are
tuned, the polarization of incident field, inside the nanoring hole, will be reversed by the single silver nanoring due to the
surface plasmon resonance, thus, the nanoring hole becomes a region of which permittivity is negative. Put two identical
silver nanorings closely, there are two nodes happened between nanorings. It indicates that there is a very steep gradient
of electric field and quasi-standing waves exist between nanorings. If many silver nanorings are lined up, the holes of the
nanorings will form a negative permittivity chamber. The more close to the center of the chamber, the more ideal the
polarization is reversed.
Single silver nanorod (the size is much less than the optical wavelength) is an excellent surface plasmon generator.
Under the interaction with a polarized optical wave, the s1ilver nanorod behaves like a funnel of the electromagnetic
field, the gathered electromagnetic fields (surface plasmons) surround the nanorod. Due to the effect of the localization,
the surface plasmons are highly enhanced in comparison with the incident wave. Consider a hexagonal nanocrystal
which is constructed by identical silver nanorods, and the nanorods are embedded in a silica block. As a polarized optical
wave illuminates on the crystal, a nanoimage is formed by the coupling of surface plasmons below the crystal.
Interestingly, the nanoimage is dependent on the direction of the polarization, that is, the nanoimages are varied with the
rotation of the polarization. On the other point of view, the nanocrystal is like a nano-kaleidoscope. The intensity of the
nanoimage is higher than the incident wave, if the patterns of the nanoimages can be controlled, the applications of the
nanoimages will never to be overlooked.
There are two modes of surface plasmon, radiative and nonradiative. Theoretically, the evanescent surface electric fileds (nonradiative surface plasmon) have their maximum on the surface and exponentially decaying field perpendicular to it. Though the evanescent surface wave can not radiate, the enhancement of the surface electric field has become an important feature in plasmonics. Especially, if one can control the enhancement factor of a plasmonic device, that is, if the intensity of the optical near field which is excited on a plasmonic object can be adjusted exactly, there will be many novel applications implemented. Based on three-dimensional finite-difference time-domain method, we analyze the interactions of the two identical spherical silver particles with optical wave. Our results show that the electric amplitudes at the midpoint of the two particles are dependent on the direction of the alignment. We convince that by changing the angle between the alignment of the particles and the polarization, the local electric intensity would be tuned well.