Evan, Elli
A 1611 photodiode has been added to ISCT1 in preparation for a schnupp asymmetry measurment.
The new 1611 photodiode sits between the Refl Air A and Refl Air B photodiodes (see table layout D1201103). An AR optic is placed before Refl Air B as a pickoff to divert a small amount of power to the 1611PD. 29mW of power was going toward Refl Air B, of which 0.4mW of power is now diverted to the 1611PD. The beam is slightly larger that the PD area- we could focus the beam to get more power if needed.
The PD is powered by a +/-15V power supply which we placed on top of ISCT1. The cables for the PD are coming out through a patch panel on the left hand side of the table. Evan has made a longer power cable in order to reach the power supply.
Tomorrow we plan to lock PRMI to the sideband and take a preliminary set of measurements for the schnupp asymetry.
Hey, you probably already accounted for this, but you may need to realign the beam onto REFL AIR B since the transmission through the AR window will have translated the beam somewhat. I guess REFL AIR B DC out is acquired somewhere and can be used to optimize the alignment.
We didn't think of that before, but today we touched up the alignment.
We haven't had much success locking the auxiliary laser with the PLL today. It looked like it would lock to the VCO, but the error signal didn't make sense when viewed with an oscilloscope. The beat note also looked very noisy when the PLL was engaged. The PLL didn't lock at all when using the network analyser to sweep the Aux laser offset. We checked the alignment of the beam on the 1611 PD, and did a 64-67MHz sweep using 801 points.