Polarized light assessment of multiply scattering heterogenous birefringent media

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Light provides us with much useful information about our surroundings. In addition to its wavelength (colour) and intensity, another useful property of an optical beam is its polarization state, or the orientation of the electric field vector perpendicular to the propagation direction. When light interacts with an object, its polarization state will be changed. Hence the properties of the object can be obtained by measuring this change.Polarization measurements have long been used in TRANSPARENT media or thin materials (thin films) to probe the details of their structure and composition. The proposed work is novel in its use of polarized light for quantifying optically thick TURBID media. The numerous deflections experienced by the light in such materials will significantly scramble its polarization. However, we and others have shown that a surprising amount of useful polarization information can still be retained even after a significant number of (multiple) scattering events. Sensitive measurement and accurate quantification of this surviving polarization signal then yields unique characteristics and "signatures" of the interrogated material. The proposed methodology will thus further optimize measurements and analysis of polarization effects in such interesting but technically challenging turbid media. The long-term goal of the research is to perform accurate polarized light assessment of biological tissues. Although not explicitly pursued here, the developed polarized methods may also find applications in non-biological domains such as remote sensing of turbulent flows and planetary atmospheres, underwater characterization of objects, and inspection in harsh (e.g., radiation damage) environments. The proposed scientific and technical developments will thus (1) optimize polarimetric imaging methods as a rapid guidance technology for accurate assessment of tissue pathology (e.g., tumour margin detection via polarimetrically-guided mass spectrometry during cancer surgery), (2) report on tissue functional status and viability in difficult-to-reach body locations (e.g., inside of the bladder wall in urology), and (3) enable further understanding of linear and non-linear polarized light turbid media (biological tissue) interactions for improved tissue microscopy. Overall, this research program will further advance the promising optical technology based on the unique strengths and information content of polarized light, towards enabling a variety of exciting and important biomedical applications.