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Question on beamsplitter when light is backward-incident

  1. Sep 26, 2015 #1
    Hi all,

    I'm new to this forum and not sure if this is the right place to post this question.

    I know that beamsplitters normally have dielectric coating on one side and AR coating on the other side. I'm looking at this plate beamsplitter specifically: https://www.thorlabs.com/NewGroupPage9.cfm?ObjectGroup_ID=4808

    I want to know what would happen if light is incident inversely, eg, it hits AR coating first then the dielectric coating. Will I get part of the light going downwards and the rest going through the beamsplitter?

    Basically I'm looking for a beamsplitter that only allows on-way transmission.

    Any help is greatly appreciated!
  2. jcsd
  3. Sep 27, 2015 #2


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    One-way transmission violates the second law of thermodynamics, it would allow to reduce entropy. I don't know how this beamsplitter would behave, but there is no one-way-transmission (neglecting exotic non-linear effects that are not relevant here).
  4. Sep 27, 2015 #3


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    It will work the same both ways around. There are no one-way mirrors.
  5. Sep 28, 2015 #4

    Andy Resnick

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