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Entry  Mon May 10 20:03:22 2010, Kevin, Update, Green Locking, Green Laser Beam Profile vbp.jpgvbp_residuals.jpghbp.jpghbp_residuals.jpg
    Reply  Mon May 10 22:25:03 2010, Koji, Update, Green Locking, Green Laser Beam Profile 
       Reply  Tue May 11 14:39:17 2010, Aidan, Update, Green Locking, Green Laser Beam Profile P5110057_beams.jpg
       Reply  Tue May 11 17:02:43 2010, Kevin, Update, Green Locking, Green Laser Beam Profile vbp.jpgvbp_residuals.jpghbp.jpghbp_residuals.jpg
          Reply  Wed May 12 03:42:38 2010, Koji, Update, Green Locking, Green Laser Beam Profile 
             Reply  Fri May 14 16:14:37 2010, Kevin, Update, Green Locking, Green Laser Beam Profile profile.pngresiduals.png
Message ID: 2933     Entry time: Fri May 14 16:14:37 2010     In reply to: 2916
Author: Kevin 
Type: Update 
Category: Green Locking 
Subject: Green Laser Beam Profile 

Quote:

Strange. I thought the new result became twice of the first result. i.e. w0=32um or so.

Can you explain why the waist raidus is estimated to be three times of the last one?
Can you explain why the measured radius @~70mm is not 0.8mm, which you told us last time,
but is 0.6mm?

The measurements have been done at the outside of the Rayleigh range.
This means that the waist size is derived from the divergence angle

theta = lambda / (pi w0)

At the beginning you used diameter instead of radius. This means you used twice larger theta to determine w0.
So if that mistake is corrected, the result for w0 should be just twice of the previous wrong fit.

 

 

I was off by a factor of sqrt(2). The correct fit parameters are

for the vertical beam profile:

reduced chi^2 = 3.28

x0 = (-87 ± 1) mm

w0 = (32.59 ± 27) µm

for the horizontal beam profile

reduced chi^2 = 2.02

x0 = (-82 ± 1) mm

w0 = (32.23 ± 20) µm

In the following plots * denotes vertical data points and + denotes horizontal data points. The blue curve is the fit to the vertical data and the purple curve is the fit to the horizontal data.

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