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Message ID: 845     Entry time: Thu Jul 1 17:47:19 2010
Author: Jenna 
Type: Laser 
Category: GYRO 
Subject: Mode Matching Solution 

Here is the spherical lens solution that doesn't take into account the astigmatism of the cavity. All of these values were calculated using the programs that I posted in my earlier mode matching post.

The required beam waist size for the cavity at the input mirror is 931µm. I got this number by calculating the X and Y components of the waist separately and then averaging them. 

The mode matching solution I get from the program is to use a 125mm and a 175mm lens. The 125mm lens should be located 232.292mm from the mirror in the corner of the table (at 4W2L), and the 175mm lens 337.616mm from that.  This lens solution gives a beam waist size of exactly 931µm, and an offset from the input mirror of 1.7µm. Taking into account the astigmatism of the cavity, this gives an overlap function value of η=.9910.

This eta value is still very high even with the astigmatism of the cavity, and doesn't change much until you move the lenses dramatically. I need to modify one of my programs to plot the eta value as the lens position changes, and I'll add a plot once I get that written to better quantify this. 



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