Polarimetric Imaging: From Optical Coherent Tomography to Laser Radar

Polarization, the term used to describe the complex direction of the electric field vector, plays an essential role in the interaction of light and matter. Polarimetric imaging technique takes advantage of the fact that a given object emits/scatters light uniquely depending on its properties, which allows us to distinguish objects with similar reflectivity but different polarimetric features. By breaking down the light into independent polarization components, one can often reveal occluded information from the intensity-based images.;The subject of this thesis is polarimetric imaging. It addresses the science of acquiring, processing, and analyzing the polarization states of images. Any arbitrary polarization state of the light can be represented by the well-known Stokes Vector, with each of the four parameters of the vector being real observable quantities expressed in terms of polarization states. It represents both polarized and unpolarized light in a very succinct vector form. The thesis focuses on mapping the full Stokes vector of different scenarios for different applications under different constrains. We first demonstrate an inline automated Stokesmeter architecture that circumvents the speed limit of the conventional Stokesmeter and integrate it with Laser Radar (LADAR). The polarization-sensitive LADAR is applied to various scenes and found to detect information indiscernible to a conventional, intensity-based LADAR. Then we demonstrate theoretically and experimentally the first polarization-sensitive OCT (PSOCT) system capable of capturing the full Stokesmetric information of the biological sample reflection with the interferometry of unpolarized light using a combination of heterodyning and filtering techniques. In order to incorporate the superb optical sectioning ability of the PSOCT into the LADAR, we investigate a data buffering system making use of a pair of white light cavities (WLC). We study the possibilities of constructing the WLC based on two different mechanisms: negative dispersion medium and linearly chirped Bragg grating (LCBG). The analysis shows that WLC is achievable with the negative dispersion medium. In the case of LCBG, we find that the accumulated effect of multiple scatterings at different position inside the LCBG produces a positive group delay, which is contradictory to conventional notion about the LCBG, thus preventing the WLC from being realized.