[Torrey, Ian]
A theory on the poor finesse measured on the OFCs has been that the mirrors are simply dirty. After hearing Hartmut mention that their optics were dirty straight out of the box from the supplier has convinced me to move forward on cleaning the OFC super optics. Koji has kindly agreed to oversee on Monday at 1 PM. In preperation for this I am going to take up to date measurements of the filter cavities to directly compare to after the cleaning. Currently the plan is to take an updated mode scan, ringdown measurement, and power budget (this has some flaws due to the poor lock quality but we will do our best). In addition, a quick inventory check before this happens:
-Fresh First contact - Yes
-Peek Mesh - Yes
-Clean scissors - Can clean a pair ahead of time
-Clean Forcepts/Tweezers - Same as above
-High purity N2 with a regulator - this we do not have. I think this can be purchased on campus and obtained very quickly but would ask Lee's approval.
-Top Gun - Yes.
In terms of data taking:
Cav Scan and updated ringdown measurements can be seen in "Nextcloud\GQuEST\B102\Output Filter Cavities\PreFirstContactData\"
OFC1
-1550 input - 15.6 mW
-1550 trans - 3.7 mW * 2 (through 50:50 BS)
-1550 refl - 5.2mW
I do not think the 1550 path loss is this bad. As previously discussed it is hard to optimize the 1550 output while locked on 775.
-775 input - 50 uW
-775 REFL - 4 +/-1 uW
-775 TRANS 46 uW
Update to this. Koji came into the lab and gave me some useful tips for first contacting. I've also been emailing with Koji and Garilynn. Couple points for everyone:
-AirGas (the vendor) is on techmart, this is who people use to buy high purity N2 for first contact purposes. I've set up an account for the Lee Lab. Should be able to see it on the website later today.
-Conversly Garilynn thinks its probably fine to clean these small mirrors without N2. The point of N2 is when peeling the dried first contact it can cause static build up, this is not as big of a problem with the small mirrors we are using.
-Last point that is worth mentioning is that LIGO "cleans and bakes" the mesh they use to peel FC. Garilynn pointed out an alternate peel method of putting a small drop on the edge of the optic and use this to initiate the peel.