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Gaussian beam passing through a circular aperture

  1. Feb 14, 2010 #1
    Hi all,

    when I have a Gaussian beam passing through a circular aperture:
    What should be the far field (Fraunhoffer's) distribution?

    Thanks in advance,
  2. jcsd
  3. Feb 14, 2010 #2

    Andy Resnick

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    The far-field diffraction pattern is the Fourier transform of the field at the aperture. So, it depends on how over- or under-filled the aperture is by the beam. If the beam size is much larger than the aperture, the far-field pattern is close to an Airy function. If the beam severely underfills the aperture, the far-field pattern is nearly a Gaussian. Intermediate cases will present intermediate results- the transform of circ(r/D)*Gaus(ar) = Somb(D*u) # Gaus(u/a), where '#' is the convolution operator, etc.
  4. Feb 14, 2010 #3
    Thank you!

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