The above is a beam that has been sliced in the x and y directions. Pictures of this beam has been taken at different spots through its focus (after a lens of course). The plots below show the distance from the center of the beam to the spot where the intensity of the beam is about 16% (1/e^2) of the overall intensity. This spot is called the 1/e^2 spot size.
This program is funded by the National Science Foundation through grant number PHY-1157044. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.