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Calculate focused spot size - Gaussian FWHM

  1. Sep 28, 2011 #1

    Does anyone know how they calculate the spot size (Gaussian FWHM) at this website?

    For a plane wave, the focused spot size it approx=2*wavelength*f/(pi*d0)
    f=focal length of lens
    d0=collimated beam diameter before lens

    but how do you calculate the spot size of a gaussian?
  2. jcsd
  3. Sep 28, 2011 #2
    If you're asking how to derive the formulas used on the website, you'll have to look it up and wade through the details on your own - laser optics textbooks often go through it, and I bet it's in Born and Wolfe in one form or another, but generally it's a relatively simple and approximate formula that you just use.
  4. Sep 30, 2011 #3
    Anyone else have a more detailed answer?
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