Partially Polarized Physical Optics and the Impact of Degree of Polarization on Parameter Estimation

Kurzfassung

When an electromagnetic wave propagates through a medium, it can experience different types of natural or artificially introduced effects. One possible type of impact is the gradual loss of intensity (referred to as attenuation). A medium cannot only attenuate the electromagnetic wave, it can also influence its degree of polarization (DOP). The degree of polarization of an electromagnetic wave denotes the relationship between the (averaged) intensity of the polarized portion of the electromagnetic wave to its total (averaged) intensity. What will happen if a fully polarized electromagnetic wave (DOP equals to one) is sent to an object, which partially or fully depolarizes the incoming wave (DOP smaller than one up to maximum zero), but the sensor is only able to receive one particular polarization? To address this question, we first need the ability to model a complex valued partially polarized electromagnetic wave. This is achieved by applying the recently developed bi-spinorial representation of electromagnetic waves (BRS) to the theory of Physical Optics (PO). The BRS is a formalism that can represent all cases of coherent, non-coherent, fully polarized and partially polarized electromagnetic waves. It can further describe them in such a way that the principles of energy conservation and conservation of an incoming polarization state are already manifested in the equations. This is not the case for Stokes or Jones calculus. In addition, the classical PO was extended with the so called Grassmann algebra to increase its computational efficiency. It is important to mention that the application of the Grassmann algebra was enabled by the application of BRS, which adds another novelty to our research.