Tell me more ×
Physics Stack Exchange is a question and answer site for active researchers, academics and students of physics. It's 100% free, no registration required.
up vote 0 down vote favorite

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.

share|improve this question
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

2 Answers

up vote 0 down vote

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.

share|improve this answer
up vote 0 down vote

I'm not sure, if I understand your question. Please elaborate a bit further. For starters, this demonstration at wolfram.com may be of help http://demonstrations.wolfram.com/VariableStatesOfPolarizationIncidentOnAWavePlate/.

If you're actually making polarization measurements and are confused by what it all means, check this out: Rotating Quarter-Wave-Plate Stokes Polarimeter.

possibly you may also want to look up the stokes parameters of polarization on Wikipedia,

share|improve this answer
Usually, your are measuring the intensity of the laser beam that is modulated (altered) by the wave plate with a photo diode. therefore in your plot you would have the intensity of the laser beam in volts as a function of the rotation angle of the wave plate. – sebastian Feb 17 at 19:58
The difference between linear horizontal polarized and linear vertical polarized is that you either have a sine or cosine intensity profile. which one you get depends on how you define the angles of the axes of your wave plate in the actual set-up – sebastian Feb 17 at 20:00
So which information actually contains the "intensity over polarizator angle" polar plot? – Fred Feb 17 at 20:52
Did you actually visit any of the links I posted earlier? There are some examples of measurements in the Rotating Quarter Wave Plate Stokes Polarimeter link. The information in that is contained in this plot is the very polarization of your laser beam, i.e. the quantity you wanted to measure in the first place, if i understood correctly. – sebastian Feb 17 at 21:20

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.