Why aren't interference filters also polarizers?

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Discussion Overview

The discussion revolves around the relationship between interference filters and their potential to act as polarizers. Participants explore the mechanisms of light interaction with these filters, particularly in terms of polarization effects, and the conditions under which these effects may or may not be significant.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant suggests that un-passed light reflects off a medium with a definite index of refraction, implying a potential for polarization.
  • Another participant proposes that significant polarization may not occur because light strikes the polarizing filter near the normal angle.
  • A different viewpoint notes that interference filters are polychromatic and vary with viewing angle, but do not significantly polarize light.
  • One participant mentions that dichroic filters exhibit different efficiencies based on the polarization of incident light, indicating some capacity for polarization, albeit lower than dedicated polarizers.
  • It is suggested that filters can be designed to have high pass efficiencies for both s- and p-polarizations, which would minimize polarization effects.

Areas of Agreement / Disagreement

Participants express differing views on the extent to which interference filters can polarize light, indicating that multiple competing perspectives exist without a clear consensus.

Contextual Notes

Some claims depend on specific conditions such as the angle of incidence and the design of the filters, which may not be fully explored in the discussion.

Neo_Anderson
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After all, the un-passed light reflects off a transparent medium with a definite index of refraction, right?
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I think the only reason that you don't get significant polarisation is that the light strikes a polarising filter very near the Normal.
 
...Well, I did get one answer...

Interference filters are poly chromatic, depending on viewing angle. Polychromatic, but not polarizing in any significant way.

Anyone else?
 
The filters I use (dichroics) have different efficiencies depending on the polarization of the incident light (s- or p- polarization), so I expect they can indeed polarize the incident light somewhat. The polarizing efficiency of the dichroic filter is much lower than a polarizer, tho.

It's possible to design filters to have very high pass efficiencies for both the s- and p- states, so they would not induce any large amount of polarization.
 

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