I did the EOM sweep measurement. It looks like we are fine above ~30 MHz, but the junk at low frequencies could explain why we had excess RFAM at, say, 18 MHz. The plot and a diagram of the experimental setup are below.
 
The source level was the maximum 15 dBm, the frequency range was 1-100 MHz (linear) over 801 pts (maximum) with 30 averages. The RFAM amplitude is now back below about -80 dBm for the standard DC PD voltage of 100 mV we have been using. Note: the strange ~2 MHz oscillation for low incident power remains...
I also reconfigured the AOM double-pass setup, realigning the polarizing optics and extracting the double-first-order beam. I was able to get ~50% efficiency (~125 mW out / 250 mW in), or a single-pass efficiency of ~71%. Tomorrow I will direct this beam into the cavity and maximize transmission, then continue with the loop measurements.
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Remember that you still have to check the crystal for resonances. Sweep the EOM and look at the CCW PD with the cavity blocked internally. The mechanical Q of the crystal can be ~1000s, so it needs to be a fairly fine sweep.
If there are resonances close to the 33 MHz, you'll have to tune it off a little bit. And where's the sketch for the Pomona matching circuit?
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