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  Thu Dec 1 20:20:15 2016, gautam, Update, IMC, IMC loss measurement plan IMG_3471.JPG
    Reply  Fri Dec 2 16:40:29 2016, gautam, Update, IMC, 24V fuse pulled out 
       Reply  Mon Dec 5 01:58:16 2016, gautam, Update, IMC, IMC ringdowns IMCringdown.pdfIMCringdown_2.pdf
          Reply  Mon Dec 5 15:55:25 2016, gautam, Update, IMC, IMC ringdowns 7x
             Reply  Mon Dec 5 19:29:52 2016, gautam, Update, IMC, IMC ringdowns REFLanomaly.pdf
                Reply  Tue Dec 6 00:43:41 2016, gautam, Update, IMC, more IMC ringdowns 
                   Reply  Wed Dec 7 11:52:48 2016, ericq, Update, IMC, Partial IMC ringdowns IMCpartial.pngIMCpartial.zip
                      Reply  Thu Dec 8 19:01:21 2016, rana, Update, IMC, Partial IMC ringdowns 
                   Reply  Sun Dec 2 17:26:58 2018, gautam, Update, IMC, IMC ringdown fitting tauTheoretical.pdfringdownFit.pdfringdownScatter.pdfcavPole.pdf
                      Reply  Fri Dec 7 12:51:06 2018, gautam, Update, IMC, IMC ringdown fitting time_reflAndTrans.pdfcorner_transOnly.pdfcorner_reflAndTrans.pdf
Message ID: 12672     Entry time: Wed Dec 7 11:52:48 2016     In reply to: 12667     Reply to this: 12675
Author: ericq 
Type: Update 
Category: IMC 
Subject: Partial IMC ringdowns 

The transients are likely due to doppler interference due to the input laser frequency sloshing due to errant control signals after the IMC unlock. I performed a few "partial" ringdowns by reducing the power by about 80% while keeping the IMC servo locked. (Function generator at 0.5Vpp square wave, 0.25V offet. Turned IMC boosts off to increase the stable range of the servo).

I need to work out how to extract the loss from this, I think having a partial ringdown may change the calculations somewhat; the time constants in the trans and refl signals are not identical.

Thanks to Gautams nice setup, it was very easy to take these measurements. Thanks! Code and data attached.

Attachment 2: IMCpartial.zip  11 kB
ELOG V3.1.3-