In this thesis we investigate theoretically various types of sculptured thin film (STF) envisioned as platforms for optical sensing. A STF consists of an array of parallel nanowires which can be grown on a substrate using vapour deposition techniques. Typically, each nanowire has a diameter in the range from ~ 10-300 nmwhile the film thickness is ~<1μm. Through careful control of the fabrication process, both the optical properties and the porosity of the STF can be tailored to order. These abilities make STFs promising for optical sensing applications, wherein it is envisaged that the material to be sensed infiltrates the void region in between the parallel nanowires and hence changes the optical properties of the STF. Various homogenization formalisms can be used to estimate the constitutive parameters of the infiltrated STFs. In this thesis two different homogenization formalisms were used: the Bruggeman formalism (extended and non–extended versions) and the strong-permittivityfluctuation theory (SPFT). These were used in investigations of the following optical–sensing scenarios: (i) Electromagnetic radiation emitted by a dipole source inside an infiltrated chiral STF. The effects of using the extended Bruggeman homogenization formalism, which takes into account the nonzero size of the component particles,were studied. (ii) Surface–plasmon– polariton waves on ametal–coated, infiltrated columnar thin film. The influences of using the extended SPFT formalism, which takes into account the nonzero size of the component particles and their statistical distributions, were explored. (iii) A metal-coated infiltrated chiral STF which supports both surface-plasmon-polariton waves and the circular Bragg phenomenon. The possibility of using in parallel both surface-plasmon-polariton waves and the circular Bragg phenomenon was investigated using the non–extended Bruggeman formalism. Our numerical studies revealed that the design performance parameters of the infiltrated STF are bode well for these optical–sensing scenarios. The use of inverse Bruggeman formalism was also investigated: this was found to be problematic in certain constitutive parameter regimes, but not those for optical–sensing scenarios considered in this thesis.

In this work samples with silver nanocolumnar structures were successfully fabricated by glancingangle deposition. From SEM investigations of the samples it is concluded that distinct andseparated nanocolumns can be grown without pre-patterned substrates using this method (givensuitable deposition conditions). The sample that exhibits the most distinct and well separatedcolumns was modelled using HFSS with optical properties of silver in nanocolumns obtained bymeasurements on the samples grown by glancing angle deposition, thin enough to not havedeveloped columns. From numerical calculations it was shown that the unit cell arrangement of thecolumns has a large influence on the optical characteristics. It was found that a diamond-like unitcell designed as two identical square lattices shifted by half the lattice spacing in one direction and2-1/2 times the lattice spacing of the other direction gives the best and a fair agreement to theexperimental ellipsometry data. Based on this model calculations were made to determine thewavelength dependent average local current exhibited in the columns as well as the currentdensity. This study showed the occurrence of broadbanded plasmon resonances of longitudinalmode at λ=1363 nm and of transverse mode at λ=545 nm. It was also shown that the opticalcharacteristics are strongly polarization dependent as is expected for such anisotropic samples.

In this work columnar nanospirals of AlInN were grown on top of TiN-coated sapphire substrates by magnetron sputtering. A variety of samples with different growth parameters were fabricated and investigated. The main objectives in this work were to optimize the degree of circular polarization and to control the active wavelength region for where this polarization effect occurs. Attempts were made to achieve a high degree of circular polarization in both reflected and transmitted light. It is shown that for reflected light it is possible to achieve a high degree of circular polarization within the visible wavelength regions. For transmitted light the concept of achieving circularly polarized light is proven.