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Entry  Wed Jul 9 21:05:31 2014, manasa, Update, General, AOM and PSL Ringdown  data_code.zipPSL_ringFit.pdfAOMringFit.pdf
    Reply  Thu Jul 10 00:38:20 2014, manasa, Update, General, AOM and PSL Ringdown  
Message ID: 10168     Entry time: Wed Jul 9 21:05:31 2014     Reply to this: 10171
Author: manasa 
Type: Update 
Category: General 
Subject: AOM and PSL Ringdown  

After the fits, here are the numbers!

Component Measured Expected
AOM 85.1 ns 200 ns (spec sheet) 
PMC 164.6 ns  Finesse/(2*pi*FSR)  = 163.4 ns

* We have a huge difference to the AOM switching time that was measured. The spec sheet mentions acoustic velocity in the material to be 4.2 mm/us and the well matched diameter in the AOM to be 1100 um. This would give a switching time ~ 200 ns. We could probably be having a much smaller beam size in the AOM for the measured switching time.

* The PMC  parameters that I had been referring to from the wiki were actually wrong and which was the reason for the mismatch that I was finding. I modified the wiki according to the found references to the actual measurement here: PMC parameters The measured values now and then match pretty well.

* Since the AOM does not change the power of the output beam by very much, what we see is actually a step response. Also, we have a lot of noise in the data obtained at the PD. 

RXA: some more comments...

  1. The fact that the AOM can only modulate the power by a tiny bit means that it is very mis-aligned or that the driver is broken.
  2. You need to take into account the AOM step time in the calculation of the PMC step time. Its not a step response if the input step is not a step, but a exponential.
  3. I wouldn't trust that old John Miller entry for the PMC Finesse. As you can see from his elog, even he didn't trust it.
  4. As we were discussing before, making a little step is not the same as a full ringdown. cf. G000413 and T900007


Attachment 1: data_code.zip  1.542 MB
Attachment 2: PSL_ringFit.pdf  1.393 MB  Uploaded Wed Jul 9 22:12:29 2014  | Hide | Hide all
Attachment 3: AOMringFit.pdf  1.359 MB  Uploaded Wed Jul 9 22:12:53 2014  | Hide | Hide all
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