40m QIL Cryo_Lab CTN SUS_Lab TCS_Lab OMC_Lab CRIME_Lab FEA ENG_Labs OptContFac Mariner WBEEShop
  40m Log  Not logged in ELOG logo
Entry  Mon May 2 17:11:55 2016, rana, Update, COC, RC folding mirrors 
    Reply  Wed May 18 01:10:22 2016, gautam, Update, COC, Finesse modelling arms.pdfPRC.pdfSRC.pdfFinesse_model.zip
       Reply  Tue May 24 22:49:02 2016, gautam, Update, COC, Finesse modelling - mode overlap scans 9x
          Reply  Tue May 24 23:17:37 2016, ericq, Update, COC, Finesse modelling - mode overlap scans 
             Reply  Thu Jun 16 15:57:46 2016, gautam, Update, COC, Contrast as a function of RoC of ETMX contrastDefect.pdffinesseCode.zip
                Reply  Thu Jun 16 18:42:12 2016, rana, Update, COC, Contrast as a function of RoC of ETMX 
                   Reply  Thu Jun 16 23:02:57 2016, gautam, Update, COC, Contrast as a function of RoC of ETMX contrastDefect.pdf
                      Reply  Mon Jun 20 01:38:04 2016, rana, Update, COC, Contrast as a function of RoC of ETMX 
                         Reply  Mon Jun 20 18:07:15 2016, gautam, Update, COC, Contrast as a function of RoC of ETMX contrastDefectComparison.pdf
             Reply  Tue Jun 28 16:06:09 2016, gautam, Update, COC, RC folding mirrors - further checks C1_HOMcurves_Y.pdfC1_HOMcurves_DR.pdf
                Reply  Thu Jun 30 16:21:32 2016, gautam, Update, COC, Sideband HOMs resonating in arms image.jpegC1_HOMcurves_Y.pdfC1_HOMcurves_X.pdf
                Reply  Sat Aug 13 18:25:22 2016, gautam, Update, COC, RC folding mirrors - Numerical review PRX_consolidated.pdfSRX_consolidated.pdfGouy_PRC.pdfGouy_SRC.pdf
                   Reply  Tue Aug 16 11:51:43 2016, gautam, Update, COC, RC folding mirrors - Numerical review PRC_consolidated.pdfSRC_consolidated.pdfGouyPRC.pdfGouySRC.pdf
                      Reply  Tue Aug 16 16:38:00 2016, gautam, Update, COC, RC folding mirrors - Numerical review PRC_consolidated.pdfSRC_consolidated.pdfGouyPRC.pdfGouySRC.pdf
                         Reply  Wed Aug 17 14:37:36 2016, gautam, Update, COC, RC folding mirrors - Numerical review PRG.pdf
                            Reply  Wed Aug 17 16:28:46 2016, Koji, Update, COC, RC folding mirrors - Numerical review 
                            Reply  Mon Nov 21 15:34:24 2016, gautam, Update, COC, RC folding mirrors - updated specs Recycling_Mirrors_Specs_Nov2016.pdf
                               Reply  Thu Feb 23 10:59:53 2017, gautam, Update, COC, RC folding mirrors - coating optimization PR3_R_170222_2006.pdfPR3_123_TOnoise_170222_2203.pdfPR3_123_Layers_170222_2203.pdfPR3AR_R_170222_2258.pdfPR3AR_123_Layers_170222_2258.pdf
                                  Reply  Tue Mar 14 10:56:33 2017, gautam, Update, COC, RC folding mirrors - coating optimization PR3_R_170313_1701.pdfPR3AR_123_Layers_170313_1701.pdfPR3AR_R_170313_1752.pdfPR3AR_123_Layers_170313_1752.pdf
                                     Reply  Mon Apr 10 15:37:11 2017, gautam, Update, COC, RC folding mirrors - v3 of specs uploaded  8x
Message ID: 12413     Entry time: Tue Aug 16 11:51:43 2016     In reply to: 12407     Reply to this: 12414
Author: gautam 
Type: Update 
Category: COC 
Subject: RC folding mirrors - Numerical review 

Summary of roundtable meeting yesterday between EricG, EricQ, Koji and Gautam:

We identified two possible courses of action.

  1. Flip the G&H mirror (PR2/SR2) back such that the (convex) HR face is the right way round. We want to investigate what are the requirements on a new PR3/SR3 optic that will guarantee cavity stability and also give good mode matching.
  2. Order two new sets of mirrors (i.e. replace all 4 folding mirrors). In this case, we want to spec a flat (how flat is reasonable to specify? EricG will update us) PR3/SR3, and design a PR2/SR2 with some concavity that will guarantee cavity stability in the event PR3/SR3 deviates from flatness (but still within what we spec). The choice to make PR3 as close to flat as possible is because the angle of incidence in our arrangement means that any curvature on PR3 dominates astigmatism.

I have done some calculations to evaluate the first alternative. 

  • Based on yesterday's preliminary discussion, we felt it is not reasonable to spec mirrors with RoC > 4km (sag of ~80nm). So I restrict my analyses to the range 300m-4km
  • Koji has a measurement of the phase maps for the G&H mirrors. The measured curvature is ~-500m. In my simulations, I've tried to allow for error in this measurement, so I look at the range -450m to -700m for the G&H mirror.
  • The Gouy phase analysis suggests we should look for an RoC of +500m (concave) for the new PR3/SR3 to have a TMS of ~1.5 MHz. Anything flatter (but still concave) means the TMS gets smaller.
  • The mode-matching in this region also looks pretty good, between 98% and 99%
  • I will post results of the analysis for the second alternative here for comparison

Something else that came up in yesterdays meeting was if we should go in for 1" optics rather than 2", seeing as the beam spot is only ~3mm on these. It is not clear what (if any) advantages this will offer us (indeed, for the same RoC, the sag is smaller for a 1" optic than a 2").


Attachments:

Attachment #1: Mode-matching maps between PRX and Xarm cavities, PRY and Yarm cavities with some contours overlaid.  

Attachment #2: Mode-matching maps between SRX and Xarm cavities, SRY and Yarm cavities with some contours overlaid. 

Attachment #3: Gouy phase calculations for the PRC

Attachment #3: Gouy phase calculations for the SRC

 

Attachment 1: PRC_consolidated.pdf  705 kB  | Hide | Hide all
PRC_consolidated.pdf
Attachment 2: SRC_consolidated.pdf  738 kB  Uploaded Tue Aug 16 15:31:04 2016  | Hide | Hide all
SRC_consolidated.pdf
Attachment 3: GouyPRC.pdf  35 kB  Uploaded Tue Aug 16 15:31:15 2016  | Hide | Hide all
GouyPRC.pdf
Attachment 4: GouySRC.pdf  36 kB  Uploaded Tue Aug 16 15:31:34 2016  | Hide | Hide all
GouySRC.pdf
ELOG V3.1.3-