Excitation of bound plasmons along nanoscale stripe waveguides: a comparison of end and grating coupling techniques

In this paper we excite bound long range stripe plasmon modes
with a highly focused laser beam. We demonstrate highly confined
plasmons propagating along a 50 μm long silver stripe 750 nm wide and 30
nm thick. Two excitation techniques were studied: focusing the laser spot
onto the waveguide end and focusing the laser spot onto a silver grating. By
comparing the intensity of the out-coupling photons at the end of the stripe
for both grating and end excitation we are able to show that gratings provide
an increase of a factor of two in the output intensity and thus out-coupling
of plasmons excited by this technique are easier to detect. Authors expect
that the outcome of this paper will prove beneficial for the development of
passive nano-optical devices based on stripe waveguides, by providing
insight into the different excitation techniques available and the advantages
of each technique.