Sheila, Camilla

The NLG vs OPO trans powers in 82202 didn't make sense. We thought it could be pump depletion from a high seed so we reduced Seed from 0.6 to 0.2mW. NLG measured following 76542.

125uW for NLG of 80 seemed much more sensible but when we increased the seed back to 0.6uW we got the same NLG so were not seeing pump depletion.

Plot attached shows the power in and refl off OPO, we are happy with the current OPO position and don;t think that the crystal has more losses yet.

Looking at the old data, NLGs measured on Thursday 09 January 2025:

• For 140uW, NLG was 15.8. But we are seeing pump depletion, as as soon as the Seed is injected, the OPO trans drops form 140uW to 100uW and becomes noisy, plot attached. Seed injected was 0.61.
• For 120uW, NLG was 13.3.  But we are seeing pump depletion, as as soon as the Seed is injected, the OPO trans drops form 120uW to 90uW and becomes noisy, plot attached. Seed injected was 0.61.
• The same pump depletion did NOT happen today when we had 125mW and an NLG of 80 measured, plot attached. With Seed at 0.51mW.

Next time we take NLG data, we should make sure that the seed power is low enough that the OPO trans power is steady at the requested power,  so the OPO is not experiencing pump depletion.