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A Can we make a circular polarization laser directly?

  1. May 30, 2016 #1
    Now,we get the circular polarization photon using 1/4 waveplate, can we make a circular polarization laser directly through Stimulated Emission Radiation?
    or, when a electron transition from one level to another level,what kind of polarization of the photon, linear or circular?
    thank you!
  2. jcsd
  3. May 30, 2016 #2


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    Theoretically you can if you also provide pump light source with circular polarization. But in practice, it may not be that easily realizable. A first obstacle I can identify is the induced birefringence in the gain medium when its temperature starts increasing. Even if the pump source is circularly polarized (or any polarization), the output does not exactly have the same polarization state as the pump due to the modification inside the gain medium itself.
  4. Jun 2, 2016 #3
    thank you,why linear polarization pump don not induced birefringence in the gain medium?
  5. Jun 2, 2016 #4


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    It's the heating procsee induces birefringence, not the polarization. Pump with any polarization will identically cause heating in the gain medium and if this is not mitgated, above certain temperature the birefringence effect will become significant.
  6. Jun 2, 2016 #5


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    Heating effects aside, I don't think using a CP pump has anything to do with the laser output. The pump simply establishes a population inversion. The excited atoms are in a metastable state with a long lifetime, so they store energy that can be put into the output beam through stimulated emission. All memory of the pump process is lost. You would need to find a laser medium that emits a CP wave when it drops to the ground state.

    EDIT: I think that means that the cavity must have resonate with CP, which probably means inserting materials into it that would kill the resonator Q. Probably better to manipulate the output beam.
    Last edited: Jun 2, 2016
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