I finished the configuration of the optical setup for our hemispherical scatterometer Yesterday.
The beam of the new laser is now focussed to a beam diameter of ca. 0.32 mm at the sample's surface.

However, I think there are still things that need to be done:

A diagram of measurements of the beam's profile is shown in the attachment. It shows the measured values of the profile without a focussing lens (circles) and with a lens at 430 mm distance to the collimator (stars). The actual distance of the lens in the setup is, however, 490 mm. Due to a small mistake, I underestimated the distance to the sample a little bit and had to readjust the positionof the lens.
Anyway, as can be seen, the measured values are in consistence with the calculated ones (dotted curves) only until the waist has been reached. With increasing distance again, there is a considerable difference between measured and theoretical value of the beam's radius*.
I think I have to measure again and try to find out the reason of the difference.

*The values are related to a Gaussian fit of the beam's cross-sectional intensity and represent the diameter of a Gaussian curve.