P7 – Scattering of Surface Plasmon Polaritons by Gold ... - repetit.dk

(a) (b)
3.2. VECTORIAL MODEL RESULTS
Figure 3.2: Numerical results from the scalar model showing reflection of SPPs off a mirror structure.
In both images the SPP is incident from the left with a wavelength of 700 nm. Fig. 3.2(a) is a mirror
structure with lattice constant 700 nm, and Fig. 3.2(b) is a mirror structure with lattice constant 200
nm.
scatterers. For certain combinations of SPP wavelength and configuration of scatterers, SPP
propagation is inhibited inside the array. In Fig. 3.3(a) a periodic array of 20×30 scatters
with a scatterer distance of 300 nm is shown. The plasmon is incident from the left with a
wavelength of 685 nm. It is seen that the array block SPP propagation, the intensity on the
right side of the array is very weak. The SPP is almost completely reflected and the intensity
decreases inside and along the array. In Fig. 3.3(b) the same structure is shown but with three
rows missing. Here it is seen that there is still a large reflection, but that SPPs are also guided
through the channel. The highest intensity is found just outside the end of the channel.
For the waveguide to guide the light only through the channels, it is necessary that the wavelength
of the incident SPP lies somewhere in the SPP bandgap (SPPBG) of the array. If this
is not the case, the SPP will propagate through and inside the structure even if there are no
missing rows.
3.2 Vectorial Model Results
In the last section the results from the scalar model were presented. In this section the results
from the vectorial model are shown. The results are based on the theory described in Sec. 2.4.
As in the last section all images have the origin in the middle of the image, the positive x-axis
is directed to the right and the positive y-axis is directed upwards. In all images the SPP is
incident from the left.
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