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Entry  Wed Apr 21 10:09:23 2010, kiwamu, Update, Green Locking, waist positon of Gaussian beam in PPKTP crystals focal_positin_edit.png
    Reply  Tue Apr 27 14:18:53 2010, kiwamu, Update, Green Locking, waist positon of Gaussian beam in PPKTP crystals mode_in_PPKTP.png
       Reply  Thu Jul 29 21:13:39 2010, Dmass, Update, Green Locking, waist positon of Gaussian beam in PPKTP crystals 
          Reply  Thu Jul 29 22:58:25 2010, kiwamu, Update, Green Locking, waist positon of Gaussian beam in PPKTP crystals 
             Reply  Fri Jul 30 00:02:15 2010, Dmass, Update, Green Locking, waist positon of Gaussian beam in PPKTP crystals 
                Reply  Fri Jul 30 09:51:58 2010, kiwamu, Update, Green Locking, Re: waist positon of Gaussian beam in PPKTP crystals efficiency_waist_edit.pngPPKTPmode.pngPSL_doubling.pngmode_in_PPKTP.png
Message ID: 3325     Entry time: Thu Jul 29 21:13:39 2010     In reply to: 2850     Reply to this: 3327
Author: Dmass 
Type: Update 
Category: Green Locking 
Subject: waist positon of Gaussian beam in PPKTP crystals 

Quote:

The mode profile of Gaussian beams in our PPKTP crystals was calculated.

I confirmed that the Rayleigh range of the incoming beam (1064 nm) and that of the outgoing beam (532 nm) is the same.

And it turned out that the waist postion for the incoming beam and the outgoing beam should be different by 13.4 mm toward the direction of propagation.

These facts will help us making optical layouts precisely for our green locking.


(detail)

The result is shown in the attached figure, which is essentially the same as the previous one (see the entry).

The horizontal axis is the length of the propagation direction, the vertical axis is the waist size of Gaussian beams.

Here I put x=0 as the entering surface of the crystal, and x=30 mm as the other surface.

The red and green solid curve represent the incoming beam and the outgoing beam respectively. They are supposed to  propagate in free space.

And the dashed curve represents the beams inside the crystal.

A trick in this calculation is that: we can assume that  the waist size of 532 nm is equal to that of 1064 nm divided by sqrt(2) . 

If you want to know about this treatment in detail,  you can find some descriptions in this paper;

"Third-harmonic generation by use of focused Gaussian beams in an optical super lattice" J.Opt.Soc.Am.B 20,360 (2003)"

If I understand your elog, you are just calculating the the offset in position space that you get by having a refractive index.

Did you end up changing the mode matching so that the rayleigh range (which changes with refractive index) was confocally focused inside the crystal (e.g. Zr = 15 mm?

 

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