I and koji setup the measurement of the QPD response to the pitch and yaw displacements of the beam spot.
We did this using a 100mW 1064nm laser. Its power was attenuated to ~ 1.9mW, and the spot size at the QPD position was 6000-7000 um .
The QPD was put on a translation stage, using which, the center of teh QPD wrt the beam spot could be moved in pitch and yaw.
Following are the measurements :
The slope of teh linear region is -8356 /inch
The slope of the linear region in this is 9085/inch