Mueller Matrix Imaging and Spectroscopy

Abstract

This thesis presents experimental work on the following topics in Mueller matrix polarimetry; instrument design and implementation, and selected applications of liquid crystal based Mueller matrix polarimeters (MMP) and spectroscopic Mueller matrix ellipsometry (MME).

In particular MMPs were designed using ferroelectric liquid crystals (FLC) and liquid crystal variable retarders (LCVR) as polarization changing components. The polarimeters were optimized by using genetic algorithms with the system matrix condition numbers as figures of merit. A calibration routine was adapted to calibrate an overdetermined MMP based on LCVRs. The temporal response of the FLC based MMP was studied in order to investigate its potential as a high speed MMP.

The FLC based MMP was implemented as an imaging MMP. Applications studied with the imaging MMP were strain mapping in multi crystalline silicon, directional mapping of collagen fibers, polarizing properties of an anisotropic plasmonic polarizer and nematic textures in colloidal dispersions of synthetic clay.

Spectroscopic MME was used to study two types of nanopatterned plasmonic samples. Optical and structural properties of biaxial in plane gold nanowires were found through parametrization of the dielectric tensor of the layer. Strong localized surface plasmon resonances (LSPR) were found in the plane normal to the wires and in the plane along the wires. A small resonance was also found in the out of plane direction. The ellipsometric modelling allowed for determining parameters of the local geometry. Anisotropic Cu nanoparticles embedded in mixed oxide (Cu2O and SiO2) nanopillars were also studied using MME. Cu nanoparticles were localized as discs on the top, as droplets inside and as needles on the side of the nanopillars. MME allowed for detecting the splitting of the modes in wavelength and in p− and s−polarized modes originating from the nanoparticle shapes.

Finally, measurement and modeling of GaSb nanopillars using spectroscopic MME allowed for the determination of small tilt angles of only a few degrees.