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Message ID: 1287     Entry time: Wed Aug 7 20:55:47 2013
Author: Evan 
Type: DailyProgress 
Category: optic 
Subject: Preparing the EOAM 

In preparation for getting the ISS up and running, Tara and I have been fooling around with the EOAM and associated half waveplates. Additionally, Tara inserted a quarter waveplate (mounted horizontally, for space reasons) after the EOAM in order to get linear amplitude modulation. The HWP before the EOAM is at 99 degrees and the QWP after the EOAM is at 51 degrees.

There's currently 8.0 mW going into the EOAM and 4.0 mW coming out after the EOAM + QWP + PBS. When 10 V dc is applied to the EOAM, the power drops to 3.7 mW. This gives a conversion factor of 3.0×10−5 W/V. The value expected from the manual is (π/2)(8 mW / 300 V) = 4×10−5 W/V, so we're not too far off. 

For those who prefer the status quo, the original HWP angles are as follows. The HWP after the PMC was at 336 degrees, the HWP before the EOAM was originally at 150 degrees, and the HWP before the cavity (which Erica is using as a pickoff for her fiber) was at 236 degrees. Restoring these angles will not restore the previous power configuration unless the quarter waveplate is removed.
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