Camilla, Ryan C., Dhruva

Yesterday, we tried to move the crystal position on the OPO to try and optimize non-linear gain but we had no luck. Sending movement commands through the PI870 driver seemed to do something because we saw the OPO getting kicked. However, the NLG didn't seem to change at all. Our fear is that maybe the wiring was wrong and we were actually moving the lens instead but there shouldn't be any reason for that to have happened. 

I decided to go ahead and try to characterize the OPO as is and took measurments of the following at different pump powers

OPO Fiber Launch, OPO Refl (Locked), OPO Refl (Unlocked), OPO Trans and NLG. 

All powers seemed to vary linearly with each other which makes sense. One exception is the Unlocked OPO Refl power which seems to saturate at high pump powers. From the NLG, I also backed out the internal squeeze factors in the OPO at the various pump powers, using the expression 

NLG = (1-r1/(exp(-z)-r1) )^2

Where r1 = sqrt(.935) is the input mirror reflectivity in the OPO. Threshold is achieved when z = -ln(r1)

The internal squeeze factor z should be proportional to the amplitude of the pump field circulating inside the cavity. Plotting the calculated values of z against the square root of the OPO Trans power and OPO Fiber Launch showed a linear relation which is good evidence that the math is correct, and that the OPO works like we should expect it to. Plugging in the conditions for threshold tells us that we should expect to see it at an OPO trans power of 0.223mW (Launch = 26.01mW)