Sculptured thin films (STFs) are nano-engineered materials whose columnar morphology is designed to elicit a desired optical response. The objective of this thesis is the development of a microscopic-to-macroscopic model to obtain a quantitative understanding of the response of a locally biaxial chiral STF that is infiltrated with a chiral fluid. This objective is achieved in two parts. The first part is the development of a microscopic-to-continuum model which can incorporate the structurally induced biaxiality of chiral STFs with non-circular columns. The second part is the solution of a boundary value problem for the optical response of a planewave-illuminated chiral STF whose nonhomogeneous constitutive properties have been obtained in the first part of the model. Studies implementing the model would open the door to the development of technological applications such as chiral-STF-based optical glucometers, switches, and tunable optical filters.; First, a Bruggeman formalism for the homogenization of dielectric-in-dielectric composites is developed. This formalism is applied to percolation in metal-dielectric composites. Percolation is found to be direction-dependent.; Next, the formalism for electromagnetic planewave propagation through a dielectric chiral STF when axially excited is given. The solution of a boundary value problem for a dielectric chiral STF slab when axially excited is then given. The response depends largely on the shape of the columns, the porosity of the film, and the local morphological angle of elevation of a column. Different regions in the parameter space exist where optical activity can be maximized (or minimized), thus providing insight for device design.; The model is further developed for an axially excited chiral STF infiltrated with a chiral fluid. The Bruggeman formalism is generalized so as to determine the constitutive properties of a composite material comprising isotropic dielectric and isotropic chiral ellipsoids. A boundary value problem is set up and solved for an axially excited chiral STF layer infiltrated with a chiral fluid. The presence of the fluid can either cause a blue- or red-shift of the center-wavelength of the Bragg regime, depending on the chirality of the fluid. It can also enhance or decrease the bandwidth of the Bragg regimes as well as other optical response properties. These results suggest the usefulness of chiral STFs as optical sensing components of medical patches, particularly for optical glucometry. Possible use of a chiral fluid to enhance the efficiency of circular polarization filters is also suggested.; Next, a boundary value problem for a non-axially excited chiral STF infiltrated with a chiral fluid is solved. Two prominent Bragg regimes are observed, one exhibiting selective reflection and the other non-selective reflection. A chiral fluid can modify the optical response of the chiral STF in both Bragg regimes. The non-selective Bragg regime is far less sensitive to the chirality of the fluid.; Finally, calibration of the model against measured transmittance data for an axially excited chiral STF is presented. Two distinct regions in the parameter space where calculated and measured transmittance data match within the Bragg regime are found. The ambiguity which arises can be lifted though non-axial excitation of the chiral STF. As an alternative to non-axial excitation, infiltration of the chiral STF with a chiral fluid can lift the ambiguities. For this, optical properties other than the transmittances and reflectances are found to be better suited.
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