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: https://optics.ansys.com/hc/en-us/articles/360034382854-Sources-Plane-wave-and-Beam 

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

Please write post in the dedicated Photonics forum:

Photonics (ansys.com)

Photonics – Chinese (ansys.com)