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I Using multiple mirrors in Michelson Interferometer

  1. Jul 17, 2017 #1
    The number of mirrors typically used in Michelson Interferometer is 2. I am looking up the respective Wikipedia article and MIT's youtube video.

    I am wondering, for the sake of one of my experiment, whether more than 2 mirrors can be used in the interferometer? I require the traversing mirror to be in a remote location and moving is a non-orthogonal line. I intend to use more mirrors to get the interference pattern. I wish to know if this is feasible.
  2. jcsd
  3. Jul 17, 2017 #2

    Charles Link

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    You can add extra mirrors to the two paths. One thing that I believe is necessary is that the mirrors do need to be optically flat, at least in order to get optimal results.
  4. Jul 17, 2017 #3
    Are you saying that one arm of the interferometer would be significantly longer than the other arm?
  5. Jul 17, 2017 #4
    Yes. More like the image attached.

    Attached Files:

  6. Jul 17, 2017 #5
    You should make sure that the coherence length of the laser is large enough for the distances you are contemplating, otherwise you will not get an interference pattern: https://en.wikipedia.org/wiki/Coherence_length
  7. Jul 17, 2017 #6

    Charles Link

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    There is the requirement that the optical path distances of the two arms do need to be within a coherence length of each other. Depending upon the nature of the source this could place some restrictions on your apparatus, as @pixel has just responded.
  8. Jul 18, 2017 #7
    Thanks for this info. I was not aware of this.
    Is there a way to estimate the coherance length, in case my laser manufacturer does not specify this detail in the specification?
  9. Jul 18, 2017 #8
    Experimentally, I guess you could start with the two arms equal in length and then gradually change the length of one arm. The pattern will change as you do this, but what you want to monitor is the contrast in the pattern. At some point it will get washed out. That will tell you by how much the two arm lengths can differ.
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