TABLE OF CONTENTS Polarimeters are devices used to measure the polarization state of light after sample interaction; useful in characterizing interactions beyond absorption, transmission, and reflectance. Polarimetry is often used in conjunction with spectroscopy to more fully assess material properties. While liquid crystal materials are commonly imaged and characterized using polarimeters and polarization microscopy, they may also be integrated as components of these devices, enabling rapid scanning and robust polarimetric analysis.
Polarimeters can be used to probe a variety of material properties which affect the polarization state, including linear birefringence, linear dichroism, circular birefringence, circular dichroism, and scattering coefficients. Birefringence in biological specimens is caused by a preferential long range biomolecular order (anisotropy) in a tissue or group of cells, as opposed to a random distribution of molecular alignment (isotropic). As a result, biological specimens possesing birefringence include filamentous proteins, fibers, cholesterol, and other structures polymericinnature. Theanisotropyin biomolecular order induces a different refractive index depending on the input polarization direction, in turn causing a phase lag between orthogonal polarization states and changing the polarization state of the light propogating through the sample; analogous to a liquid crystal molecule or other birefringent crystals. Because of the birefringence induced retardance and polarization variation, biostructural features can be imaged using polarimetry or polarization microscopy. In a configuration with a birefringent sample between crossed polarizers and analyzer, the output will show brighter regions where the polarization state has rotated and dark states...
