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Group velocity dispersion

  1. Sep 1, 2010 #1
    Hey ppl,
    I have a question for you.

    For the case of light propagation in the air the the group-velocity dispersion parameter D is infinity because the derivative of the group velocity should be a zero (group velocity is constant ; w=ck and Vgroup=dw/dk). Who can explain me this? dispersion parameter is infinity meaning that the pulse will spread very fast. I never thought about that question but maybe I'm wrong. Plz clarify me that point.

    formula for D parameter you can find here:
    http://en.wikipedia.org/wiki/Dispersion_(optics)
     
  2. jcsd
  3. Sep 1, 2010 #2
    the question is solved. you can't not turn upside down the second derivative. i.e

    a=(Dispersion parameter)=(approx) d2(k)/d2(w)[tex]\neq[/tex]1/d2(w)/d2(k). here was the problem. in the case of light propagation through the air a should equal to zero.


    d2()-second derivative=[tex]\partial[/tex]2

    d2(k)/d2(w)=[tex]\partial[/tex]2k/[tex]\partial[/tex]2w
     
    Last edited: Sep 1, 2010
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