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Entry  Mon Mar 6 12:34:30 2017, johannes, Summary, ASS, ASS light injection scenarios 
    Reply  Mon Aug 21 20:11:25 2017, johannes, Summary, General, Loss measurements plan 
       Reply  Mon Aug 21 21:26:41 2017, gautam, Summary, General, Loss measurements plan 
          Reply  Tue Aug 22 16:56:54 2017, johannes, Summary, General, AS laser existing components inventory 
             Reply  Mon Aug 28 23:22:56 2017, johannes, Update, PSL, PSL table auxiliary NPRO aom_switching_zoomin.pngaom_switching_zoomout.pngaom_switching_mini_zoomin.pngaom_switching_mini_zoomout.png
                Reply  Tue Aug 29 20:04:09 2017, rana, Update, PSL, PSL table auxiliary NPRO 
                   Reply  Tue Aug 29 21:36:59 2017, johannes, Update, PSL, PSL table auxiliary NPRO isomet_mini_1st_zoomout.pngisomet_mini_0th_zoomout.png
                      Reply  Tue Sep 5 23:13:44 2017, johannes, Update, PSL, PSL table auxiliary NPRO PSL_IR.pdfpsl_aux_laser.pdf
                         Reply  Thu Sep 7 23:09:00 2017, johannes, Update, PSL, PSL table auxiliary NPRO 3200-1113_200_switching_PD10A_zoomin.png3200-1113_200_switching_PD10A_zoomout.png
                            Reply  Mon Sep 11 12:40:32 2017, johannes, Update, PSL, PSL table auxiliary NPRO psl_aux_laser2.svg.pngPSL_IR2.png
Message ID: 12869     Entry time: Mon Mar 6 12:34:30 2017     Reply to this: 13235
Author: johannes 
Type: Summary 
Category: ASS 
Subject: ASS light injection scenarios 

What we want from the light source for the AS port light injection:

  • Frequency control for locking and maintaining known offset from arm cavity resonances -> see below
  • Fast extinguishing light in the IFO -> AOM first order switching

We have four possible laser sources that we can use for the injection of 1064 nm from the back:

  • There are ~65 mW of IR power coming from the PSL doubling oven, of which ~2mW are used for the fiber beat box. The remaining light is currently dumped on the PSL table and would be available. It is picked off after the PMC and does not have any of the sidebands.
  • There is a ~200 mW Lightwave NPRO on the PSL table that is currently unused.
  • Koji said he has a ~500mW NPRO in the OMC lab that has no PZT actuation. I contacted a couple companies about fiber-coupled variable AOM frequency shifters that we can pair with this laser.
  • I don't think using the high power beam of the PSL itself is a good idea, especially if we want to map the loss on the optics, because' we'll need it for the dither locking

I think for maximum flexibility it's best to fiber-couple whichever source we choose on the PSL table and then just collimate it out of a fiber on the AS table. This way if we want to add fiber-coupled modulators of any kind it's a plug-and-play modification.

Different frequency control schemes are:

  • Modulate sidebands on the light and stabilize directly to the arm, using POX/Y or back-reflection at AS
    • Free-space resonant EOM
    • Free-space broadband EOM with Rich's resonant amplifier attachment
    • Fiber-coupled EOM
  • Offset phaselock:
    • PSL IR: Transfer mode-cleaner stability
      • Can lock arms while measurement in progress, but will have PSL IR light on PDs
    • Green from the end;
      • Broadly tunable laser frequency and no interference from IR.

Either way we'll need a few things:

  • Faraday Isolator
    • required for PDH locking, optional if we phaselock instead
  • AOM
    • We have free-space available, looking into fiber-coupled ones with frequency tuning
    • Fast switching electronics
  • Various fiber stuff
    • We have enough to set up the fiber coupling of one light source. I'm starting with the 200 mW NPRO but this is technically interchangable.

I'm working on how to best set this up at the AS port and interfere with normal operation as little as possible. Ideally we use a Faraday just like for squeezed light injection, but this requires some modification of the layout, although nothing that involves mode-matching.



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