10
1 Introduction
Fig. 1.3 Parameterisation of the polarisation state of an electromagnetic wave, using the ellipticity
angle χ and orientation angle ψ. The polarisation ellipse (blue curve) is the projection of the
oscillation of the electric field onto a plane perpendicular to the direction of propagation
the major axis of the polarisation ellipse away from the x-axis of the lab coordinate
system. A positive orientation angle is defined by the angle formed by an anticlockwise rotation of the polarisation state relative to the x-axis, e.g. ψ = +45
◦ occurs in
the top right-hand quadrant of the polarisation ellipse as displayed in Fig. 1.3.
1.2.2 Alternative Descriptions of the Polarisation State
1.2.2.1 Ellipsometric Parameters
The ellipsometric parameters are an alternate parameterisation of the polarisation
ellipse. Rather than taking into account the half-lengths of the polarisation ellipse,
the ellipsometric paramaters consider the s- and p-polarised components of the electromagnetic wave that form the polarisation state. In terms of these components the
polarisation state is parameterised by