Several documents that are usefull references for the VIP build are collected in the dcc here: D1500302

Summary of what has already been done, for reference:

• Coupling of Prometheus into in air fibers: 
  • First using thorlabs fiber for 532 57169 
  • 532 path re-arranged with diamond in air fiber 57758. 
• Removing O3 Faraday, which is stored in blue bin in my office for now
• Swap of OPO mirrors: 57350
• recabling
  • lens translation stage 58076
  • note about PZT range which is restored to what it should be with OPO in the optics lab while it was smaller than it should have been in the chamber: 57304
  • OPO PZTs 57459, including another note about PZT range issue
• Measurement of escape efficency after OPO mirror swap: 57445
• G path (green pump to OPO):
  • coupling of green from diamond fiber which is not class A (failed RGA) to OPO 57906. This alog includes a photo of how to mount the collimator for the diamond fiber, and a description of how the collimator was adjusted by pointing the beam off the platform.  There are spare collimators in the white bin in the optics lab.  This procedure will need to be repeated when we get the final fiber.
  • In the alog above, I mentioned that I still needed to set the angle of the green polarizer.  I did check this, and the rejection isn't very sensitive to the angle of the polarizer.
  • Mode measurement and lens placement for green pump reflected off OPO towards SQT7 58323  If you want to use these mode matching notebooks, you can get Nic Smith's code a la mode here: https://github.com/nicolassmith/alm
• F path (CLF to OPO):
  • This path had to be re-arranged, although in the original plan we thought we could leave it.  The 1064 collimators are all slightly different, so I set the lens in this path differently than the desgin before O3 to get better mode matching, but this meant that the lens was blocking the beam from SFI1 towards the filter cavity once that path was installed. 
  • This alog has information about the mode matching 57906, this alog descirbes the rearrangement 57960
• Set up of PDH locking of CLF to OPO, to allow us to use beam transmitted by the OPO for mode matching measurements 57638
  • note about this PDH:  It isn't a terribly robust lock, but it is good enough for our purposes.  Keita has seen the locking process.  I use a beamsplitter on the OPO transmitted beam after the A path to look at the transmitted power and set a cursor at the peak height while scanning the PZT.  It is good to check that the PDH signal doesn't have an offset while the cavity is scanning here.  Sometimes we get an offset that could be from RFAM. 
• A path (SQZ from OPO to filter cavity, through SFI1 (Squeezer Faraday Isolator 1):
  • First set up of A path to SFI1, ran into problem with F path interference 57906
  • Further information about A path set up, including description of appertures placed 58076.  The lenses have changed since what is described in this alog.
  • Temperature control of SFI1 and transmission measurement: 58076
  • SFI1 isolation measurement: 58126
  • Note, these transmission and isolation measurements were intended to just check that the performance of the SFI didn't degrade in the process of shipping and installing them.  If you are looking for transmission or isolation measurements, it would be best to use the results from the test report for this Faraday from Florida: T2100094
  • A path mode matching, this was a little bit of a journey:
    • First effort: 58207 see comments for checking if there was an error in lens ROC and an unsucsesfull attempt to measure the mode out of the OPO with no lenses installed.
    • Lee's updated model and two options for new mode matching solutions: 58342 (we opted for option 2 because of space near A:M2)
    • Keita and I noticed that when I walked the beam to align through the Faraday appertures when first setting up the path, I moved the beam well off center on A:M2, so we moved A:M2 to have the beam closer to centered.  We also made a more careful set of measurements of the distances in this path, ands implemented Lee's option two 58426
    • Lee suggested a final nudge to the mode matching, 58474 Keita and implemented this and posted measurements in 58515
    • While this gave us good mode matching going toward the filter cavity, we struggled to get the beam retro reflected back through the apperture on the other side of SFI1 (the side where the beam is transmitted by the TFP towards SFI2).  Keita wrote an explanation of the method used to get the beam retro reflected in 58667
    • Since we moved the lens in and out of the beam several times in the process of trying to get the retro-reflection right, we remeasured the mode matching, including the beam heading towards SFI2 this time in 58663

Things that still need to be done:

• B path (beam returning from filter cavity transmitted by SFI1, through SFI2 toward OFI)
  • Lee is working on recalculating the mode matching for this path, which will need to change after the changes to the A path mode matching.  The lens and mirror B:M1 and B:L1 are on the platform but not aligned, once we place the lens according to the new mode matching we can measure the resulting beam parameter by projecting the beam off the back side of the platform (ie, moving aside B:M2)
  • We have had a few conversations with Paul and Ryan at Florida about how to align SFI2 and the off sled KTP wedge, and Camilla, Georgia and I tried a couple of approaches.  Keita, Georgia Camilla and I just had a conversation where I think we came up with a better plan, I will add a comment to 58707, describing our new idea for this alignment.
  • Once we have SFI2 aligned, we can move the temperature control from SFI1 to SFI2 in order to measure the SFI2 isolation as described in the assembly google doc pages 22-23.
  • Measure SFI2 transmission with OPO transmitted beam, also using temperature controller.
  • Finish alignement and mode matching placing B:L2 (which is currently roughly placed to give a small beam size from the fiber).
• H path:
  • Camilla and I started to set this up using the green fiber which failed it's RGA test, but we now have the first of the fibers that will be finally installed in the chamber. 
  • Start by adjusting the collimator in the way that was described for the G path.  Then we will have to compare the mode coming out of the fiber to the mode matching solution in Figure 25 of T1900649, to see what adjustments to the lens placements might be needed. 
  • H:M2 needs to be a pico mirror, but it isn't currently set up that way.  Corey and Keita have been communicating with Rich and company about these picos.
  • Once the H paht lenses are set, we will want to co-align the green beam with the OPO trans beam on A:DC2, we can project these beams off the platform to co-align them.
• Fiber replacement for G path:
  • When the second class A diamond fiber arrives, we will have to set the collimator for it and realign into the OPO.  Hopefully we do not need to redo the mode matching, if the beam parameter comes out close enough.
• Aperture stops: 
  • There are two apperture stops shown in this drawing of the VIP D2000021 which aren't asociated with a lens, one between the Faraday and polarizer for each of SFI1+2.  We have the aperture stop that should go between SFI1 and the KTP wedge (B:P1) mounted and on the table, although we will need to re-arrange dogs to fit it in.  The stop which goes on the SFI1 sled needs a different height post, the post is in clean and bake at LLO and will arrive soon.
• Overall transmission measurement:
  • I would suggest that once the optical paths are complete, as a final check we measure the transmission of the OPO beam from right out of the OPO (before A:DC1) until the beam directed towards the OFI (ie after B:M4).  If we only set up temperature control on one of the SFIs, the uncontrolled one will have a bit lower transmission, but that can be measured and accounted for.  A measurement like this would have saved us some trouble in O3, because we would have caught the extra loss from the dichroic which was installed backwards.  Doing a similar measurement in chamber would also be a good idea, inlcuding as much of the path as is reasonable.
• Cable routing:
  • Camilla has a bag of parts that can be used to attach cables to the OPO lid. 
• Suspension Balancing
  • There are many balance masses that were removed from the O3 platform in the white bin in the optics lab, and new ones in the bottom of the blue bin.