Optical properties of aperiodic metallic photonic crystal structures

In this thesis the linear optical properties of aperiodic metallic photonic crystals are studied. All structures consist of a metal grating on top of a waveguide material. The incident light can excite plasmonic modes in the metal as well as photonic modes in the waveguide underneath. These resonances are coupled to each other. In the first part of the thesis, the samples with a one-dimensional metal grating are studied. The structural arrangement of the metal wires on top of the dielectric waveguide layer is disordered, quasicrystalline, or fractal. For the disorder samples, the experimentally obtained coupling constant shows reduced values for larger disorder amounts. Additionally, the calculated coupling constants are compared to the experimentally obtained Urbach energies. It is found that the relation between these two parameters is dependent on the disorder model as well as on the average grating period. The optical properties of the samples with the quasicrystalline and fractal metal wire arrangement are analyzed with respect to their long, short, and average wire distances. The next part of the thesis deals with two-dimensional metal gratings. The metal disks are arranged in a quasicrystalline fashion with the disks being elliptically shaped and rotated with respect to the sample x axis. It is found that the optical properties of such structures are dependent on the eccentricity of the metal disks as well as on the rotation angle between the short main axis and the sample x axis. Afterwards, a theoretical model is developed in order to describe the optical properties of such structures. With the theoretical approach it is possible to calculate the normal incidence spectra as well as the oblique light incidence spectra. This model is used to predict the absorption enhancement of plasmonic solar cells.