Contrast Defect Ratio at 2 W = 8.4 +- 0.2 ppm

Contrast Defect is as follows: 



The electric fields associated with this equation are shown in the fourth attachment.

When DARM is locked on RF at 2 watts and the OMC is locked, we get about 11.8 mA, or 14.0 mW of power on the OMC DCDPs.  This means the DARM offset is around 29 pm according to this plot.
During this measurement, we move the DARM offset from 29 to -29 pm and see what happens.

Procedure:
1) Lock OMC while DARM is locked on RF
2) Zero the QPD offsets for OMC ASC by switching to OMC dither alignment, zeroing, and moving back to QPD control
3) Zero the OMC LSC dither control signal by offloading to PZT2, then stop the feedback, parking the OMC on the carrier fringe
4) Change DARM1 TRAMP to 120 seconds
5) Move DARM1 OFFSET through zero (in this case from 9e-5 cts to -9e-5 cts)
6) Re-engage OMC LSC by stopping input, clearing history, unholding output, and restarting input.  This will find the fringe again quickly for the next measurement.

Parameters during measurement:
            Input Power  = 1.89 W
     PRG at 0 pm Offset  = 46.8 +- 0.1
      DCPD Responsivity  = 0.858 A/W
DCPD Quantum Efficiency  = 0.98
   OMC DCPD Dark Offset  = 7.2e-5 +- 3e-5 mW  (Found at the last time the IMC was OFFLINE)
      OMC DCPD NULL/SUM  = 0.0060 +- 0.0015
   Measurement GPS Time  = 1229475480


Differences between 0 and 29 pm DARM offset:
Value         29 pm     0 pm    29 pm/0 pm
------------------------------------------
PRG            46.5     47.0         0.99
TRX [cts]    1502.    1518.          0.99
TRY [cts]    1555.    1572.          0.99

Assumed to be one:
- IMC Transmission
- Input Faraday Transmission
- Output Faraday Transmission
- OMC Transmission
- Mode Matching

Not yet considered:
- RF45 Transmission through the OMC
- Source of contrast (differential lens)

Dark Port alogs:
45753 DARM offset calibration
45734 OMC DCPD Sum/Null Matrix