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Entry  Thu Jun 3 00:52:37 2010, tarac, Laser, Laser, Aligning AOM 97-02848-01r0.pdf
    Reply  Thu Jun 3 08:42:44 2010, Frank, Laser, Laser, Aligning AOM AOM3080-194.JPG
       Reply  Thu Jun 3 14:47:58 2010, Frank, Laser, Laser, Aligning AOM 
          Reply  Thu Jun 3 15:45:39 2010, Frank, Laser, Laser, Aligning AOM 
             Reply  Thu Jun 3 22:00:21 2010, Frank, Laser, Laser, Aligning AOM 
                Reply  Fri Jun 4 00:03:17 2010, Jenne, Computing, Environment, Spam 
                   Reply  Sat Jun 5 16:17:05 2010, Koji, Computing, Environment, Spam 
Message ID: 144     Entry time: Thu Jun 3 22:00:21 2010     In reply to: 143     Reply to this: 146
Author: Frank 
Type: Laser 
Category: Laser 
Subject: Aligning AOM 

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 I'm aligning the AOM and maximizing the diffracted beam's power by positioning the AOM and adjusting the beam size by moving the lens.

For single pass, the maximum efficiency I could get is only ~60%, so for double pass, the power will be down to 36%, but for now I'll settle with this number.

I could not find the manual for Crystal technology AOM 3080-194. The closest one is model 3080-197 which is attached below.

I'm not sure what is the difference between the two model, but 3080-197 has 70% diffraction efficiency.

Because of adjusting the lens, the RefCav's beam path also changes, now I have to realign RefCav again.

 

  Another step for AOM alignment is adjusting the mirror that reflects the transmitted beam back to the AOM again.

The distance between the mirror and the center of the AOM should be the same as ROC of the mirror.

After this I should be able to start locking ACav.

 did you measure the power of the vco? How much is it if you tune it to maximum?

Here a copy of a general datasheet for the 3080-194. maximum efficiency is ~80% @2W RF power. You should ask peter about the detailed datasheet which comes with each AOM and contains measured values for the one you are using. Measured values depend on the beam size and RF power. Typical values are 87% in reality.

AOM3080-194.JPG

 Oh, I see, the beam diameter is 1100 um, I use 150um. I'll try changing the beam size and see what happens. Thanks Frank. I'll measure the power of the VCO too.

 have a look into the datasheet which came with the AOM. Don't make it too large. Clear aperture is about 1.7mm max. You can also have a look into the manual of the 35W laser (ATF lab). It contains a copy of one of these datasheets as well (with the graph of efficiency vs beam size). You don't need more than 60%, but you should try to get around 50% for the double-passed beam as we don't have so much laser power in total available. Assuming the original 15mW on the RF detector you need about 45mW for the acav now and 15mW for the refcav, so 60mW total after the PMC. With the current 95mW out of the laser it should be no problem( in principle). After the isolator and EOM you might have something about 85mW upstream of the PMC which means you need 70% transmission through the PMC. Anyway, a larger beam size gives you better eff.  If you make it 500um or so you should get 50% in the double-passed configuration.

 I manage to get 70% efficiency from P wave. When I try S wave, I get 78% which is close to the specified value. So for double pass, the efficiency should be upto 50%. The beam size is ~550 um.  I redo the mode matching calculation for the AOM (and also RefCav and ACav) and move the beam a bit to the side of the table so that the insulation box won't get in the way.

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