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Brewster's Angle in lasers

  1. May 20, 2016 #1
    1. The problem statement, all variables and given/known data
    Fresnel losses occur between two different media that have different refractive indices. To reduce these losses we can change the angle of incidence to brewster's angle. At this angle, the amount of reflective loss is minimized for p-polarized light.

    Do we assume that laser light is p-polarised to begin with? Is the flashlamp / flashtube p-polarised? After population inversion and electron's giving off photons, they do so in a p-polarised way?
     
  2. jcsd
  3. May 20, 2016 #2

    blue_leaf77

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    The light can come in any polarization direction. Since E field is a vector, it can be decomposed into components. In the case of refraction and reflection at the interface, one typically consider the so-called P and S polarization direction. These directions are mutually perpendicular. The incoming light can then be decomposed into components along these two directions. When the light is incident at the Brewster angle, however, there is no reflection for the P component, i.e. all portion in the P direction gets transmitted. But the other component, the S component, still gets reflected.
     
  4. May 20, 2016 #3

    Charles Link

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    I think I have seen the Brewster angle used in design of a HeNe laser where left and right outside face of the discharge tube are at the Brewster angle and the mirrors that complete the cavity are outside of the discharge tube. The resulting laser will then be very much p-polarized because the cavity Q wouldn't be high enough to have lasing properties for the s-polarization because of the reflective losses across the glass discharge faces. The p-polarization meanwhile has nearly 100% transmission across these faces.
     
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