I am thinking about centimeter band radiation and parallel wire filters as a specific example. Suppose there is a regular series of parallel wire filters every fraction of a wavelength for a full wavelength or more. The angular orientation of each filter is rotated by the same constant fraction of a full circle from the orientation of the previous filter.

Will this series of rotating linear filters pass circularly polarized radiation of the proper wavelength and handedness?

If so, does it make a difference if the filters are every quarter of a wavelength, every tenth of a wavelength, or even every one one-hundredth of a wavelength?


Everytime you go from one linear filter to another, you will project the linearly polarized light onto the direction of the next filter to get a linearly polarized light rotated by a small angle and with a slightly lower amplitude. In the end, you would still have a linearly polarized light, so the answer to your question is no.

To be more quantitative, assume you start with a linearly polarized light of amplitude $A$ and that each of the filters is rotated of a angle $\delta \theta$ with respect to the previous one. After passing through $N$ of these filters, you get a light of amplitude $A \cos (\delta \theta)^N$, linearly polarized, and whose plane of polarization is rotated of an angle $N \delta \theta$ with respect to the original plane of polarization.

  • $\begingroup$ Note that the OP specified filters 'every fraction of a wavelength' - not independent linear polarizers, and asked if it would pass circularly polarized light. In fact, that is what such filters are designed to do. $\endgroup$
    – Jon Custer
    Sep 7 '16 at 14:52
  • $\begingroup$ Thanks for a very clear specific answer. I was afraid something like this was true. Jim Graber $\endgroup$
    – Jim Graber
    Sep 7 '16 at 15:56
  • $\begingroup$ @Jon Custer I'm not sure what you mean, maybe I missed something. Could you explain a bit more in a comment or a new answer ? $\endgroup$
    – Dimitri
    Sep 7 '16 at 16:29
  • 1
    $\begingroup$ @Dimitri - turn it around - why are certain molecules chiral, and how do they affect light propagation? One example is sugar in water. Yet sugar molecules are sub-wavelength. $\endgroup$
    – Jon Custer
    Sep 7 '16 at 18:29

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