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sheila.dwyer@LIGO.ORG - posted 00:39, Friday 26 January 2018 - last comment - 08:10, Friday 26 January 2018(40284)
fiber collimators

Terry, Sheila

We seem to have a mix up with our fiber collimators.  We measured the beam profile out of our 532 nm collimator this afternoon, because our mode matching into the OPO is very poor, and found it to be 52 um.  This afternoon Terry and I measured the waist out of both of our collimators for both wavelengths. 

  532 nm horizontal waist 532 nm vertical waist 1064 nm horizontal waist 1064 vertical waist
collimator supposedly for 532 (SN4) 52um @ 0.11m 53 um @ 0.10m 256um @ 0.27m 253um @ 0.27m
collimator supposeldy for 1064 209um @0.22m 255um @ 0.33m 155um @ -0.22m 156um @ -0.23m

The 532 collimator that we have is SN4.  Maggie sent a link to a git where she has measured data from SN4 for 532nm, this data shows that the waist is 264 um 0.6 meters from the collimator.  I am not sure right now what the serial number of our 1064 collimator is, but the data on the git says SN01 has a waist of around 280um @0.3 meters while SN17 and 18 have waists around 315/320um.  

It seems like the most plausible explanation is that we have the collimators swapped somehow even though we have been careful not to do that since taking them out of the bag.  If the one that we think is the 532nm SN4 is really 1064nm SN01, these measurements aren't as crazy, although there is still a discrepancy between the waist position of the 1064 beam coming out of our SN4 collimator and what Maggie measured for SN01.  

The data for all four of the measurements that Terry and I took this afternoon are in the comments in the attached script. 

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Comments related to this report
lisa.barsotti@LIGO.ORG - 08:10, Friday 26 January 2018 (40285)
The collimators can be (quite easily, I would say) distinguished by looking at them, if you know the "color code".

The 1064nm ones have a milky looking color, while the 532nm ones have a pink-ish color. 

Hope this helps to confirm your theory..


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