Matt, Lisa

We spent the afternoon assembling the green QPD sled in the new EY lab.  Our reference design comes from G1100129.

The first picture is of the EY clean lab, in its current disorganized state.  For the record, the particle counter reads 0 except when we are near it, in which case it may reach ~50 particles/CF.

The second picture shows the input green laser (~2mW of green, collimated at w ~ 2mm), arranged to send a beam across the class A sled to the beam scan.  The 2" converging lens (L1, ROC = 154.5mm), the 50/50 beam-splitter, and the first 1" diverging lens (L2, ROC = -25mm) are in place, but the first HR mirror is absent to allow the beam to exit onto the beam scan.

The third picture is of the same setup.  Yes, the laser is on.  Yes, it is visible light.  No, you can't see it on any of the clean optics, or in the air.  Only the dirty fiber collimator shows some light.

While in this configuration, we adjusted the position of L2 until we got something we liked (based on quick beam scanning), and then we took some beam scan data.  In the last 2 columns, I've divided the 36.8% data by sqrt(2) to convert it to beam waist radius, and then taken the mean of these data with the 60.7% data.

The last picture is of the final assembly, with all mirrors, lenses and QPDs in place.  The black glass beam dumps are AWAL.