Abe, Aritomi, Marc

Previously we were using the pinhole to characterize the beams.

We found out that this technique is heavily dependent on the alignment on the pinhole and that the power fluctuations affect strongly the quality of the measurement.

Also, as the translationStage.v3.vi that allows to automatically perform many scans along the Z direction is now available, we switched to using the razorblade with this vi.

The 2 lenses have been moved so that L1 (closest to the periscope) and L2 (closest to the imaging unit) are now respectively :

L1->L2 = 21.2 cm

L2-> z=0 of translation stage = 23.4 cm

With this configuration, we characterized the red and ir beams when cutting the beam vertically. For this, we placed the razor blade as close as possible to the 2" holder at the edge towards the lenses.

The measurement and fit are presented figure 1 (red := red beam, black := ir beam) where the z position corresponds to the real one (ie the half width of the 2" holder (9 mm) has been substracted)

It gives :

ir : waist size = 37.5 um at z=38mm

red : waist size = 76.6 um at z=42.8 mm

During the week-end, we started several measurement of the red and ir beams with the blade at the edge of the 2" holder towards the imaging unit (ie 1.8cm closer to the imaging unit than the measurement presented in this entry). This will allow to check the crossing point of these 2 beams.

We should get all the required measurements on Monday.

Note that the height of the ir beam has been corrected following this measurement as shown in elog2444.