# Polarization Measurement

Assume having a laser beam which is horizontal linear polarized. As one measure the sqrt(intensity) transmitted through a rotatable linear polarizer its pattern corresponds to a cosine. Plotting this in a polar coordinate system results in the so called "polarization ellipse". But the result is far away from being a (more or less) horizontal line.

But what does the polarization ellipse tell me?

My problem is that from the polar plot one may interpret that the original beam has E-Field components also in non-horizontal direction. But this is (ideally) not true. But only the polarizator has (excepted for the vertical position) components in horizontal direction leading to a transmitted field.

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 And how is the plot called one obtains by means of the measurement ("transmitted intensity of a linear polarized laser beam through a step-wise rotated linear polarizator") described above? – Fred Feb 17 at 17:58

The polarization ellipse is not defined as the plot in polar coordinates. The polarization ellipse has $E_x$ and $E_y$ (if $z$ is the axis of propagation) as abscissa and ordinate.