RIght! Overview out of the way - now comes the trivial first bit

Step 1: Beam out of the laser - this will be tricky, but we'll see what we can actually measure in this set-up. Can't get the Beamscan head any closer to the laser and using a lambda/2 plate + polariser to control power until the Faraday isolator is in place. Using 1 inch separation holes as reference points for now - need better resolution later, but this is fine for now and gives an idea of where things need to go on the bench. The beam is aligned to the 3rd row up (T) for all measurements, the Beamscan spits out diameters (measuring only the 13.5% values) so convert as required to beam radius and the beam is checked to ensure a reasonable Gaussian profile throughout.

Position A1_13.5%_width A2_13.5%_width

(bench) (um mean) (um mean)

32 2166.1 1612.5

31 2283.4 1708.3

30 2416.1 1803.2

29 2547.5 1891.4

27 2860.1 2070.3

26 2930.2 2154.4

25 3074.4 2254.0

24 3207.0 2339.4

OK. As expected, this measurement is in the linear region of the beampath - i.e. not close to the  waist position and beyond the Rayleigh length) so it pretty much looks like two straight lines. There's no easy way to get into the path closer to the laser, so reckon we'll just need to infer back from the waist after we get a lens in there. Attached the plot, but about all you really need to get from this is that the beam out of the laser is very astigmatic and that the vertical axis expands faster than the horizontal.

Not terribly exciting, but have to start somewhere.