Participaint: Aritomi, Chienming, Eleonora, Shurong and Yuhang

At the beginning, we want to do like this. Scanning green beam phase with a 1Hz, 1.5Vpp ramp signal. Then adjusting MZ offset to have different power going to OPO. Lock p-pol and adjust PLL to make both p and s-pol resonant. Locking OPO by p-pol. Sending green. Measuring OPO s-pol(BAB) transmission DC to see the parametric amplification and de-amplification. 

1. Today's change: For making sure we are locking OPO at resonance. We set up a DC/RF photo detector for OPO s-pol transmission.

2. Lock OPO with p-pol, found demodulated s-pol transmission RF oscillating at 1Hz. The RF signal before demodulation oscillates at 15MHz with an amplitude modulated at 1Hz.

3. The green injection changes the co-resonant condition. We guess this is because of temperature change. See attached picture 1.

We did like this finally. Manually put the transmission of the seed beam on maximum pk-pk. Don't use p-pol lock and PLL. For different pump power, we measured the amplification and deamplification. See attached figure 2. We did the fit and found the threshold now should be around 140mW.

Since we know the green changed the temperature of OPO crystal, we also checked the temperature influence. For a green power of 60mW, we changed temperature from 6.9kOm to 7.2kOm. Now the optimal temperature seems to be 7.06kOm, which is 0.04kOm far from previous optimal temperature 7.02kOm. However, the influence of temperature change caused by green power seems not crucial. In any case, the non-linear crystal is still working in the broad optimal region.

However, we decided to check the matching.