Dhruva, Nutsinee

Now that we are able to sqz with 40 times more CLF power than before we did a "quick" seeding measurement again. First we went out to measure seeing with a 1611 and saw nothing. We then repeated the measurement that was done in alog67050. The steps are

1) offset SQZ laser VCO by -1000 Hz
2) Demodulate LO with 3.124 or 3.126 MHz. This requires switching out RF output in the CER using the IFR set to 12dBm. 
3) Unplug the RF output that is in the rack left to the IFR, U4 channel 1. Send the new RF demod into ISC SQZ 30.
4) Back in the control room. Lock LO loop. 
Note that this is a Homodyne measurement.

On Friday we didn't see anything. Later I realized we could have lowered CLF power by half at the time so I cranked in back up on Monday to 0.7 mW on the CLF launch and repeated the test. The result was we saw 36 nW of seeing at 0.7 mW CLF output measured after AOM2. The plot attached is in V/sqrt(Hz). Shotnoise ~10^-7 V/sqrt(Hz) corresponds to 0.5mW of LO per PD. The seeding peak at 1 kHz measured 2.78*10^-6 V/sqrt(Hz). Solve for current then use the responsivity of 0.8 A/W to get 36nW. 

Attached the plot and a Mathematica notebook for more detailed calculations. Daniel suggested there shouldn't be a sqrt(2) in the seed power calculation but maybe a factor of 2. Seeding might be slightly higher or lower. Will update this alog again once I've done the math.