So for my experimental optics class, I had to create a device that would emit horizontally polarized light such that its intensity is independent of an incoming linearly polarized beam of arbitrary polarization direction. What would be the most efficient method?

I thought of using an xy analyser which would split the beam into two orthogonal beams, and use two quarter wave plates to turn the vertical beam into a horizantal one whilst the total intensity is still constant. Then I would just reflect both beams and since they are both horizontal now, they could superimpose with the same total intensity as the original beam.

  • $\begingroup$ Why do you need "the most efficient method" for "experimental optics class"? Why don't you just use a polarizer?:-) $\endgroup$
    – akhmeteli
    Oct 19, 2013 at 6:46
  • $\begingroup$ you can't make the output polarization axis independent of the input polarization axis. they are related by Malus' Law $\endgroup$
    – gregsan
    Oct 19, 2013 at 7:42

1 Answer 1


The easiest way is to feed it through a circular polarizer, and then a horizontal polarizer. The input beam will always be reduced in intensity by 50% on its pass through the circular polarizer regardless of orientation, and then the circular light will be converted to horizontal with 50% loss by the horizontal polarizer.

It requires no beam separation and beam recombination, the beam doesn't have to be bent or reflected anywhere, and it just needs two sequential components.

  • $\begingroup$ Wouldn't you need a quarter wave plate to turn linearly polarized light to circular which requires the incoming beam to be at 45 degrees $\endgroup$
    – user31283
    Oct 19, 2013 at 17:21
  • $\begingroup$ I believe there exist plain circular polarizers which are not sensitive to the incoming beam polarization, such as these: edmundoptics.com/optics/polarizers/circular-polarizers/… $\endgroup$ Oct 19, 2013 at 18:28
  • $\begingroup$ However, I haven't bought or used them, so if someone has used them and knows otherwise, it'd be great to hear the specifics. And of course your original method works, so if worst comes to worst you can always use that. $\endgroup$ Oct 19, 2013 at 18:30
  • $\begingroup$ A third way would be to use a thin-film reflectance polarizer. The horizontal would be reflected, and the vertical would be transmitted (depending on the geometry of your setup). The vertical could be rotated, and then combined with the horizontal. This is similar to your original statement, of course. $\endgroup$ Oct 19, 2013 at 18:35
  • $\begingroup$ How exactly do you combine the two horizontal beams such that intensity would combine? Would you simply use a convex lens? $\endgroup$
    – user31283
    Oct 20, 2013 at 1:01

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