Infrared optical properties of porous nanoantennas – This work is
concerned with the acquisition of infrared (IR) transmission spectra of single wires
with lengths of a few micrometers, which show resonant excitations in the Infrared.
The measurements were done using a Bruker Hyperion 1000 IR-microscope, which
was not designed for the analysis of small samples; the IR beam was hard to
adjust and the light, which is used for finding the sample, heated the microscope
up, causing a strong shift of the position of the beam. In order to improve the
adjustability a new holder for the condenser was designed, with which a positioning
with a precission of 1 μm is possible. By using an LED lightsource, the heating
and thus the movement of the beam could be greatly reduced. Unfortunately, it
was only after the measurements that both improvements could be accomplished.
The spectra of single and double porous wires were compared, whereby it could be
shown that there is only an increase of the extinction cross section of double wires
and no other significant differences between the spectra. In addition to that, smooth
and porous wires were compared. It turned out that the resonance wavelengths and
the extinction cross sections of smooth wires are higher than those of porous wires.
Also, it seems that the rate of spectra, where the second order of the oscillation
can be identified, is increased. Porous wires seem to have a slightly increased full
width at half maximum. However, the number of the wires that were analysed in
this work is not sufficiently high to allow reliable statements.