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Does the NA value in “use thin lens” in the beam options refer to the real NA ?

    • M Z

      Dear all,

      Does the NA value in "use thin lens" in the beam options of FDTD refer to the real NA in experiment ?

      And what does the distance from focus refer to ?


    • Guilin Sun
      Ansys Employee

      Yes, you are right that NA means numerical aperture of the objective lens used to produce such a beam.

      Please refer this article: 

      The distance from foucs is the ditance of the injection plane to the focus plane.

      Please write post in the dedicated Photonics forum:

      Photonics (

      Photonics – Chinese (

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