We used the BeamScan to characterize the divergence of the NPRO laser as a function of distance. Measurements were taken at (1/e^2)*Imax. We then fit the data to the function characteristic of gaussian divergence to find the location and size of the waist. The results are shown graphically in the attached file. Extrapolating, we found that the waist is 21.5 cm behind the laser aperture, and the (virtual, assuming that the laser beam encounters a diverging lens before the aperture) waist size is 124 micrometers.
Here is our data:
The distances, measured in inches from the base of the laser, are
[0 0.5 1 3 5 7 9 11 13 15 17 19 21 23 25]. The distance from the aperture of the laser to the base is 0.75 inches.
The beam sizes, measured in micrometers along one axis, are
[1334 1399 1542 1655 1968 2234 2537 2785 3063 3359 3638 4001 4253 4561 4708]
The directories for each of the Matlab files used to generate a graph of the data and carry out a least-squares regression are