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TE / TM polarization of a Laser Diode

  1. Oct 8, 2011 #1
    I am working with a Laser Diode and I need to observe the intensity of the diode in TE and TM polarizations. the Diode is polarized in the horizontal axis (linear polarization). Is it sufficient to use a half wave plate and rotate it by 90 degrees to observe TE and TM modes?

    Also, what kind of output should i expect while using a half wave plate in front of a linearly polarized source? Will I get maxima at pi/2 angles of the plate and minima at pi/4 angles?

    Thanks for the help!
  2. jcsd
  3. Oct 13, 2011 #2

    Claude Bile

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    Science Advisor

    If I understand your post correctly, it is not sufficient simply to put a half-wave plate in front of the laser to detect the (say) TM mode as all you're doing is rotating the (say) TE output by 90 degrees and detecting it again.

    Assuming the laser initially emits primarily off the TE polarization, the first solution would be to simply use a polarizer to filter out the TE mode and attempt to detect a residual TM mode. The second solution would be to use an external cavity with a polarizer to suppress the TE mode and attempt to excite the TM mode. Keep in mind though that using an external cavity will affect the output mode.

    A half-wave plate will rotate the linear polarization and as such will not give intensity minima and maxima (unless a polarizer is placed in between the output and the detector of course).

    Last edited: Oct 13, 2011
  4. Oct 14, 2011 #3
    Thanks so much for the help Claude! I will try using the polarizer method which you suggested.
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