Light Matter Interaction in Nanostructured Materials
Kremers
Christian
Kremers, Christian
aut
2011-07-08
2014-08-12
de
<p>In this thesis two aspects of electromagnetic wave interaction with nano structured material
are studied.
<br> First, two alternative semi-analytical methods to solve the scattering problem on optical
nanowire antenna are introduced. In order to reduce the general three dimensional
volume integral equation describing the scattering problem to a simple semi-analytical
one dimensional integro-differential equation, both methods utilize solutions of the problem
of plane wave scattering on infinite cylinder. A regularization and discretization
scheme is proposed in order to transform the integro-differential equations into solely
integral equation. This transformation enables to solve the original problem without the
necessity to impose additional boundary conditions at the nanowire edges. Numerical
evaluation of the proposed methods and their comparison with different numerically rigorous
methods is presented for scattering cross-section calculations. Gold nanowires are
analyzed at optical and near-infrared spectral range. The introduced one-dimensional
semi-analytical methods demonstrate good agreement and superior numerical performance
in comparison with rigorous numerical methods.
<br> Second, the radiation of a uniformly moving charge (Cherenkov radiation) inside a
general three dimensional (3D) and two dimensional (2D) periodic dielectric medium is
studied. In particular analytical expressions for the emission spectrum and for the field
distribution in the far-field zone are derived. The obtained formula for the Cherenkov
power emitted per unit length (emission spectrum) of the charge trajectory involves
the calculations of Bloch modes and corresponding group velocities at limited points
of the reciprocal space only. The analysis reveals (i) that the Cherenkov effect exists
for every charge velocity (ii) that the radiation can be suppressed if the coupling of the
current density produced by a moving charge with a Bloch mode is poor and (iii) that an
enhancement of radiated energy is possible if only the component of the group velocity
orthogonal to the trajectory of the charge is small. Additional inside in the Cherenkov
radiation process is gained from the analytical expression for the field distribution in the
far-field zone. It is shown that the far-fieeld radiation can be calculated in a 3D photonic
crystal by a surface integral and in a 2D one by a contour integral over just a small
fraction of the first Brillouin zone. The spatial variation in the far-field intensity is due
to (i) interference of just a few Bloch eigenmodes and (ii) the topological properties of
the k-space surface (3D) or contour (2D). The obtained expressions both for the emission
spectrum and the field distribution are confirmed by comparison with rigorous numerical
calculations. The agreement in both cases is very good where the analytical expressions
are faster and much less demanding on computational resources.
urn:nbn:de:hbz:468-20111108-165121-4
2014-08-12T08:33:12.521Z
2014-08-12T09:20:59.813Z
published
Diss
fbe/elektrotechnik/diss2011/kremers