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

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(a)
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(c)
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1.8
1.6
1.4
1.2
1
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0.6
0.4
0.2
0.06
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0.04
0.03
0.02
0.01
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3.2. VECTORIAL MODEL RESULTS
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(b)
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Figure 3.4: Simulation of single particle scattering in both the scalar and the vectorial model. (a) is
calculated using the scalar model, (b), (c) and (d) are the z, x and y component of the field using the
vectorial model, respectively. Parameters of the simulations are λ = 700 nm, εm = εp =-16.5, εr=1,
Rp=50 nm.
3.2.2 Parabolic Nanoparticle Chains for SPP Beam Focusing
By directing an SPP beam towards the opening of a parabolic chain of nanoparticles the SPP
beam can be focused into a small point. The nanoparticles are placed on the parabola with
a constant distance between them. The properties of the beam focusing are determined by
the width of the parabola at the opening, the height of the parabola and the distance between
scatterers. The focal distance of the parabola can be determined by the following expression
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FD = −w2
16h
where h is the height of the parabola and w is the width of the parabola as defined by
y(−w/2) = y(w/2) = −h where y(x) = ax 2 is the expression for the parabola. From this
expression it is seen that the focal distance is negative since h (and w) is a positive number.
Since the parabola has its apex at the origin this means that the focal point lies within the
parabola.
(d)
2
1.8
1.6
1.4
1.2
1
1.4
1.2
1
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0.6
0.4
0.2
0.8
0.6
0.4
0.2
x 10 −4
(3.3)
In Tbl. 3.1 focal distances for a number of combinations of parabola widths and heights are
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