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Entry  Wed Jan 30 11:16:32 2013, Jenne, Update, Locking, Mode spacing calc 
    Reply  Wed Jan 30 15:45:09 2013, Zach, Update, Locking, Mode spacing calc HOM11.pngHOM55.png
       Reply  Thu Jan 31 14:30:50 2013, Jenne, Update, Locking, Mode spacing calc Half_PRC_Configs.pdf
          Reply  Thu Jan 31 15:20:46 2013, Zach, Update, Locking, Mode spacing calc 
Message ID: 7966     Entry time: Wed Jan 30 15:45:09 2013     In reply to: 7961     Reply to this: 7973
Author: Zach 
Type: Update 
Category: Locking 
Subject: Mode spacing calc 

Quote:

Thus, the modes should be well separated

=>  spacing is 4.3 MHz while FWHM is 0.311 MHz  (cavity fsr = 34.5 MHz)

Something looks fishy. I calculate a transverse mode spacing of 2.21 MHz---is there a factor of two missing somewhere in your analytical calculation?

delta_f = (1/2/pi) * w01 - w00 = (1/2/pi) * acos(±sqrt(0.96)) /pi *2 * pi * c /2 /L = 2.21 MHz

I guess that's still OK, but if you are using 11-MHz sidebands, there is a n+m=5 mode within one linewidth of resonance. Can you use 55?

-------------

May I suggest my arbcav() tool for things like this? I think it's pretty handy for just this sort of calculations. I'm actually hoping to revamp the I/O to make it much cleaner and more intuitive.

>> T = [0.055 20e-6];

>> L = [4.34 4.34];

>> RoC = [115.5 1e10];

>> theta = [0 0];

>> fmod = 11e6;

>> lambda = 1064e-9;

>> num_pts = 1000;

>> loss = 50e-6;

>> [fin,coefs,df] = arbcav(T,L,RoC,theta,fmod,loss,lambda,num_pts);

>> fmod = 55e6;

>> [fin,coefs,df] = arbcav(T,L,RoC,theta,fmod,loss,lambda,num_pts);

 

HOM11.png HOM55.png

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