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Entry  Thu Aug 28 17:36:03 2014, Evan, DailyProgress, optic, Mode-matching solution for north cavity ctn_algaas_alm.pdfctn_algaas.zip
    Reply  Thu Aug 28 19:10:40 2014, Evan, DailyProgress, optic, Mode-matching solution for north cavity 
Message ID: 1488     Entry time: Thu Aug 28 17:36:03 2014     Reply to this: 1489
Author: Evan 
Type: DailyProgress 
Category: optic 
Subject: Mode-matching solution for north cavity 

Current configuration:

  • Target waist: 180 µm, z = 0 mm
  • Lens 1: 140 mm focal length, z = −711 mm (24″ from center of vacuum chamber + 4″ through periscope)
  • Lens 2: 84 mm focal length, z = −991 mm (11″ further behind lens 1)
  • Seed waist = ??

Since we know we were mode-matched fairly well into the 180 µm waist of the silica/tantala cavity (>93% visibility), I asked alm to propagate this waist backward through the lenses in order to find a seed waist. It reports a waist of 161 µm at z = −1373 mm.

I asked alm for a new configuration using the same two lenses. The best configuration (mode overlap = 1) is as follows:

  • Seed waist: 161 µm at z = −1373 mm
  • Lens 1: 140 mm focal length, z = −743 mm
  • Lens 2: 84 mm focal length, z = −1023 mm
  • Target waist: 215 µm, z = 0 mm

So we should move lens 1 back by 32 mm (=1.3″), and move lens 2 back by the same amount.

Attachment 1: ctn_algaas_alm.pdf  30 kB  Uploaded Fri Aug 29 10:39:33 2014  | Hide | Hide all
ctn_algaas_alm.pdf
Attachment 2: ctn_algaas.zip  1 kB  Uploaded Fri Aug 29 10:39:45 2014
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