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Homework Help: Converting laser fwhm bandwidth in m to hz

  1. Apr 9, 2010 #1
    hi, pls can someone help me with converting FWHM bandwidth of a laser from metres to hertz
  2. jcsd
  3. Apr 9, 2010 #2


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    Just from the dimensions
    frequency (1/s)= speed (m/s) / wavelength (m)
  4. Apr 9, 2010 #3
    thank you but i didn't think you could directly convert fwhm bandwidth just using that, when i did it i got a bandwidth of region 10E17 Hz -does that seem a bit high from a ruby laser cavity length 0.1m?

    If i post the whole question it might help. Also should i include the refractive index of the medium ie c/n=f lambda, if this is the right way to do it?

    for the 0.1m cavity, n =1.8, FWHM gain bandwidth is 2E-9m
    qu is: what is the longitudinal mode spacing and the number of lasing modes? i could give the spacing in either freq or wavelength but its easier to do i think in freq that's why i wanted to convert. many thanks if you can help.
  5. Apr 10, 2010 #4
    you can use the following formula

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