"The far-field polarization ellipse passed through this quarter waveplate is different from that of the source"
Isn't this expected? you used a circular polarized source, and after the waveplate it changes to linearly poolarized light as it shuld be. right? do you expect to be the same as the source circular polarization? from your description I am confused.
A1: you get the linear polarization with linear polarized sources. seems without waveplate, right?
A2: the vertical line in the polarization plot means it is a linear polarization but not 45 deg linearly polarization.
I think your results are correct but you need to uderstand them, for example what the theta, phi mean in the plot? what is the difference between phi=-135 and phi=-90?
You already got the linearly polarized results, Then you need to correctly interpret them.
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